2011-Ctv046 Heating Ventilation and Air Conditioning
Content
Technology overview
Heating, ventilation and air conditioning
Saving energy without compromising comfort
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Heating, ventilation and air conditioning
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Preface
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Reducing energy use makes perfect business sense; it saves money, enhances corporate reputation and helps everyone in the fight against climate change. The Carbon Trust provides easiest effective advice to help businesses take action to reduce carbon emissions, and the easiest way to do this is to use energy more efficiently. This overview of heating, ventilation and air conditioning introduces the main energy saving opportunities for businesses and demonstrates how simple actions save energy, cut costs and increase profit margins.
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Introduction
Heating, ventilation and air conditioning (HVAC) systems control the temperature, humidity and quality of air in buildings to a set of chosen conditions. To achieve this, the systems need to transfer heat and moisture into and out of the air as well as control the level of air pollutants, either by directly removing them or by diluting them to acceptable levels.
Heating systems increase the temperature in a space to compensate for heat losses between the internal space and outside. Ventilation systems supply air to the space and extract polluted air from it. Cooling is needed to bring the temperature down in spaces where heat gains have arisen from people, equipment or the sun and are causing discomfort. Heating, ventilation and air conditioning systems vary widely in terms of size and the functions they perform. Some systems are large and central to the building services – these were probably designed when the building was originally commissioned and use ventilation to deliver heating and cooling. Other systems may provide heating through boilers and radiators, with some limited ventilation to provide fresh air or cooling to certain parts of the building such as meeting rooms. In some cases, individual comfort cooling units have been added to a building to overcome a specific overheating problem that had not been thought of at the time of the original design.
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So if heating, ventilation and air conditioning can be separate systems, why consider them holistically? The answer lies in the interaction of these services with each other and with the building. By considering HVAC systems as individual elements rather than as an interacting system, it would be easy to overlook a major area of energy wastage – that one component might impact on another. For example, it would be wasteful to increase heating inside a building while the cooling system is fighting to reduce temperatures. It is therefore useful to look at how the elements of an HVAC system interact with each other and fine tune each part to save energy and money.
Did you know?
The true definition of an ‘air conditioning system’ is one which has the ability to control temperature, humidity and air quality within precise limits, yet the term is often applied to systems which simply cool the space. These cool air systems are more correctly referred to as ‘comfort cooling’.
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Energy consumption
Heating, ventilation and air conditioning can account for the majority of money spent by an organisation on energy. Even small adjustments to these systems can significantly improve the working environment and at the same time, save money.
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How much energy do HVAC systems use?
There are five important factors that determine the energy use of an HVAC system: • The design, layout and operation of the building – this affects how the external environment impacts on internal temperatures and humidity; • The required indoor temperature and air quality – more extreme temperatures, greater precision and more refined air quality consume more energy; • The heat generated internally by lighting, equipment and people – all of these have an impact on how warm your building is; • The design and efficiency of the HVAC plant – provides heat, cooling and moisture control exactly where it is needed in the building; • The operating times of the HVAC equipment and ability of the controls – these limit operation to exactly when it is needed.
Making savings
• Reducing the need – The design and specification of buildings and HVAC systems have a big impact on energy use and hence, energy spend. Sometimes natural ventilation provides the best solution to HVAC needs – see page 7 to find out more. • Changing staff behaviour – The way occupants use a building and its HVAC systems plays a big role in how a building performs. See page 9 for tips on how staff can learn to control their environment efficiently. • Understanding and using controls – Most HVAC systems are fitted with controls. Learning how to set and regulate these can provide substantial savings and enhance comfort conditions for building occupants. See page 11 for more information. • Maintaining existing systems – Regular maintenance is vital for maximising energy savings and avoiding costly breakdowns, as explained on page 14.
Heating 46%
• Hardware opportunities – If you are considering upgrading or refurbishing your HVAC systems, there are some good opportunities for energy saving. Page 16 shows how new, efficient equipment can often pay back its costs very quickly. Total carbon emissions from energy use in public and commercial buildings 2008
Other Catering 6% 6%
Computing 8% Cooling and ventilation 7% Hot water 6%
Lighting 21%
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Technology overview
Identify your HVAC system
HVAC system components
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HVAC systems vary widely in terms of the individual components that make them up and how they are set up within a building. Most systems contain some common basic components: • Boilers 1 produce hot water (or sometimes steam) for distribute to the working space. This is done either by heating coils 2 which heat air as part of the ventilation system, or through hot water pipes to radiators 3 • Cooling equipment 4 chills water for pumping to cooling coils 5 . Treated air is then blown over the chilled water coils into the space to be cooled 6 through the ventilation system. As part of the refrigeration cycle in the chiller, heat must also be rejected from the system via a cooling tower or condenser 7 • Pumps are used throughout the system to circulate the chilled and hot water to the required areas throughout the building • Stale air is extracted, usually using a fan, via separate ducts and expelled outside 8
• Controls are used to make components work together efficiently. They turn equipment on or off and adjust chillers and boilers, air and water flow rates, temperatures and pressures. A controller incorporating one or more temperature sensors 9 inside the workspace sends a signal to the heating or cooling coils to activate • If there is a demand for heating or cooling then the controls may also send a signal to the chiller and boiler to operate as required. There are often other control panels on the chiller or boiler too, allowing users to have greater control.
Heat expelled 7
Boiler 1
Chiller 4
Panel
HVAC controller
Hot water
Sensor HVAC control panel 9
Inlet vent
Heating coils 2
Cooling coils 5
Incoming air (fan)
HVAC system types
There are many different approaches to using HVAC systems and buildings will typically use combinations and variations of a few standard approaches. HVAC systems are generally described according to how they use air, water or both to distribute heating and cooling energy to the space. To find out more about different types of system and their savings opportunities, ask your site engineer, maintenance technician or call the Carbon Trust. There should also be a building log book providing details about the HVAC system. This can be supplied by the building’s facilities manager.
Working area
6 Extract vent Exhaust air 8 Air extract (fan)
Fresh air in
Radiator 3
Stale air out
The more you understand your system, the better prepared you will be to make savings
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Identify your business needs
Why do air conditions need to be controlled?
Temperature, humidity and air quality are controlled for a number of reasons: • To provide comfort for building occupants • To enable a process to be undertaken
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What conditions should be maintained?
Start by determining what temperature and air quality standards the HVAC system should provide. HVAC for processes For processes and stored materials, it is important to concentrate on what is really required: • Does the process or material deteriorate outside a particular temperature range? • Is it moisture or air quality condition that makes the difference or is it a combination of both these factors? For instance, it may be that deterioration of a stored product is caused by mould growth or corrosion which is actually caused by excess moisture on its surface. This requires control of the product temperature and of moisture in the air so that condensation does not form. HVAC for staff comfort When providing comfort for building occupants, it is important to understand how comfort is achieved and the many ways that people perceive it. The combination of air temperature, surrounding surface temperatures, humidity, clothing, body fat, nerve sensitivity and metabolic rate is different for every person – so comfort is difficult to achieve with one fixed set of conditions. Rather than set the conditions at specific levels, it is more beneficial to set bands which allow greater flexibility.
Did you know?
• Heating costs can increase by 30% or more if the boiler is poorly operated or maintained • Heating typically accounts for about half of the energy used in offices • Heating costs rise by about 8% for each 1ºC of overheating.
• To avoid deterioration of stored products and materials. Temperature, humidity and air quality may vary greatly and fluctuate at different rates. It is therefore important to always identify core business requirements and use this to inform any proposed improvements to an HVAC system. Most businesses will have a variety of reasons for controlling the condition and quality of the air in their buildings and these should be prioritised. For instance, in a refrigerated cold store, it is probably more important to preserve the food than to maintain the comfort of workers. This is not to say that workers should be ignored – they should be provided with suitable clothing to keep them comfortable while working.
Low-cost measures for immediate savings
• Learn how to set thermostats, how to control your HVAC system to provide the conditions actually needed and to only operate as and when necessary • Find out about the building log book which should explain the services in simple terms • Ask the landlord or managing agent where the controls are and how to use them • If any controls are labelled ‘do not touch’, explore why. There may be a valid reason but it may just be for the convenience of the maintenance person • Investigate whether ‘optimum start’ and ‘optimum off’ timers which can adjust the start and finish times for different weather conditions could be appropriate for your system.
If staff members occasionally work late and alter controls, don’t forget to reset them or install a timer to automatically restore normal settings
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Reduce the need
The types of HVAC systems and how they are used have a big impact on the amount of energy consumed and the levels of comfort provided for staff and/or customers. Even in a building that has full air conditioning and cooling, it may not be necessary for them to be switched on all of the time. Using natural ‘free energy’ to heat, cool and ventilate a building can help save substantial sums of money and give building occupants greater control over their environment.
Opportunities for energy saving
Passive heating, ventilation and cooling
This is the control of heat from the sun along with ventilation in order to benefit a building and avoid discomfort. To maximise energy savings, it pays to organise a system so that nature provides the majority of fresh air and temperature requirements. Expensive ‘artificial’ and mechanical systems can then operate to fine tune the desired temperature and environmental conditions. As simple as it sounds, natural ventilation relies on air flow through openings of a room or building, preferably from opposite sides. It also applies to rising hot air being replaced with cooler air sucked in through windows or vents from a lower level. Making the most of natural ventilation is a simple and cost-effective way of achieving big savings.
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When cooling is required inside a building, and if it is cooler outside than in, simply open doors, vents and windows. This will increase airflow, reduce heat and perhaps provide all the ventilation that is needed. Be aware, however, that opening windows in air conditioned buildings may increase the energy used by the system. Some businesses use what is known as a ‘mixed mode’ system, which uses a combination of both natural and mechanical systems. The building uses natural ventilation, heating and cooling where possible, with mechanical systems being used only when needed. There are various advantages to such a system: • The building becomes more adaptable to a wide range of requirements • The occupants have more control over their environment • Businesses can cut down on energy spend and carbon emissions.
Myth
Turning air conditioning thermostats down as low as they can go cools the building more quickly.
Reality The temperature drops at the same rate but then overshoots, making it uncomfortable for the staff and using more energy than necessary. If controls are not coordinated, the temperature could even go low enough for the heating system to be switched on. Both systems then operate at the same time. Remedy Set thermostats correctly and educate staff to dispel this myth. As a last resort, protect thermostats to prevent tampering where possible.
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Reduce overheating
Before installing cooling equipment, always identify where the excess heat is coming from – sunlight, equipment, lighting and refrigeration are often the main sources. Consider shading windows on the outside or replacing window panes with special heat reflective glass to prevent heat build-up. Alternatively, internal blinds can be angled to redirect useful light onto the ceiling while cutting out much of the sun’s heat. Energy using equipment, lighting and refrigeration are also major heat emitters in a building. As a general rule of thumb, the more energy efficient equipment is, the less heat it produces. So installing low-energy lighting and keeping equipment operating at peak efficiency reduces cooling costs. Consider zoning to match building
Daylight blinds
Daylight blinds enable natural light to enter the space by re-directing it onto the ceiling, thereby alleviating any discomfort felt by the occupants from direct daylight. Many daylight blinds also have perforated blades to retain the employee’s view out of the window. For more information please refer to the Carbon Trust’s How to Implement Solar Shading (CTL065) guide.
Night cooling
Night cooling is an established technique where cool night air is passed through the building to remove heat that has accumulated during the day. When the building fabric is cooled, it will absorb more heat the following day, meaning lower internal temperatures. The movement of cool night air may be natural or fan-assisted. This free cooling of the building reduces energy consumption otherwise used by mechanical cooling and ventilation, leading to cost savings.
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The benefits of daylight blinds
Reduces brightness at the window Ensures light distribution deep into the interior
occupancy and reduce costs
Many buildings have problematic areas with different time and temperature requirements where only one overall heating or cooling control system exists. A solution is to ‘zone’ the building, installing separate time and temperature controls for individual areas. Zoned areas can provide better conditions as occupants in each area will have greater control over their immediate environment. It will also be more cost efficient, as HVAC can then be turned down or off in unused zones. For more information please refer to the Carbon Trust’s How to implement heating zone controls (CTL148) guide.
Protects from heat and glare Provides a view outside for staff
Direct sunlight Diffuse overhead light Maintains the natural daylight spectrum
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Good housekeeping and staff comfort
Understanding the needs of building occupants and informing them how to operate systems effectively can pay dividends.
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Opportunities for energy saving
A common sense approach to comfort and temperatures
There are many factors which effect how warm people feel, including: • Air temperature • Solar radiation • Air speed • Humidity • Activities performed • Clothing All these factors should be taken into consideration when attempting to create a comfortable environment for people to work in. Ensure workspaces are shielded from draughts and direct sunlight. These are no-cost solutions that save money and help maintain comfort.
Adjust your system
At times it makes sense to use the outside temperature to adjust the conditions inside your building. However, when the heating, ventilation or air conditioning systems are on, it is possible to save up to one third on heating or cooling costs by reducing the amount of outside air that enters a building. It is always better to adjust the system rather than open a door or window and let heated or cooled air out. For example, when the heating is on too high, staff open windows to make the space more comfortable. Try adjusting the thermostats instead.
Did you know?
Comfort cooling by traditional air conditioning systems is very expensive. In the right circumstances low energy alternatives such as evaporative cooling systems can cut energy consumption by up to three quarters. For more information on how to cut your air conditioning costs please refer to our dedicated Air Conditioning Advice pages
Turn off and power down
Try limiting the time that equipment is switched on and use ‘power-down’ facilities on copiers, faxes, printers and computers during the day where possible, as these heat the workspace. Dim or switch off lighting if there is sufficient daylight and use as little as possible at night.
Train staff on how to operate air conditioning units and heating controls
Staff should receive guidance on recommended operating temperatures and how to set heating or cooling units correctly. Louvres (movable slats to guide the cool or heated air) are a feature on most air conditioning units and staff should be able to operate these to maintain a comfortable temperature. Display instructions on individual units and ensure that remote controls have accessible and obvious storage spaces.
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Ensure controls are in place and HVAC systems operate at times and levels to reflect demand
HVAC loads will vary at different times and in different parts of a building throughout the day. Well-set time controls should ensure that systems only operate when and where required, in order to match core business hours. It is also worth regularly checking settings. Many systems are set incorrectly because someone has made a short-term adjustment and then forgotten about it. For more information, please see the Carbon Trust Technology Guide on Heating Controls (CTG065).
The Carbon Trust has promotional materials which help encourage people to be energy efficient
Further information
For further information on raising awareness in your business see the Carbon Trust’s pack, Creating an Awareness Campaign (CTG056).
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Involve staff – run an awareness campaign
Engaging employees is crucial in eliminating energy waste. Motivate staff – encourage them to review their own working practices and suggest ways to make their tasks more energy efficient. Before staff can begin to save energy, they must be made aware of areas of potential waste in their own workplaces and the important part they play in controlling the temperatures they work in.
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Understanding and using controls
An efficient HVAC system provides just the right temperature and environmental conditions while using the minimum amount of energy. Once the ideal comfort conditions for a building have been identified, good controls can help maintain these conditions.
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Opportunities for energy saving
There are two main types of control:
• Time controls ensure systems only operate when and where the building is occupied • Temperature controls ensure systems provide the correct required temperatures.
Maintain appropriate local temperatures based on outside conditions
If it is cold outside, building occupants will typically be wearing warmer clothing, so ensure temperatures are set accordingly. The reverse applies in summer if cooling is in operation. People will dress for warmer weather so do not freeze them with expensive overcooling.
Don’t overheat buildings
The optimum operating temperature range for a building will depend on the type of activities being performed. Recommended heating temperatures for particular buildings, activities, and processes are provided in the following table.
Set time controls to match occupancy
Check controls are appropriately set and displaying the correct time and date. Adjust if necessary to ensure heating and cooling only operate when and where required. Optimum start and stop controls can be used to minimise the out of hours operation of heating and cooling plant.
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Sector Offices/service companies
Building/room type Computer rooms Banks, building societies, post offices Offices
Temperature (ºC) 19-21 19-21 21-23 22-24 20-22 19-21 19-21 11-14 16-19 19-21 22-24 19-24 22-24 19-22 17-19 19-21 19-21 19-21 19-21 16-19 19-21 19-21 19-21 19-24 20-25 15 28-30*
Hospitality
Restaurants/dining rooms Bars Hotels
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Schools/further and higher education Industrial/factories
Educational buildings Heavy work Light work Sedentary work
Hospitals and healthcare
Bedheads/wards Circulation spaces/wards Consulting/treatment rooms Nurses’ stations Operating theatres
Public buildings
General building areas Law courts Libraries Exhibition halls Laundries Churches Museums and art galleries Prisons
Retail Sports and leisure
Retail buildings Changing rooms Sports halls Pool halls
Source: Adapted from Environmental Design CIBSE Guide A, 2006 *Depending on pool water temperature
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Don’t let heating and cooling operate at the same time
Set controls to give a wide gap between the temperatures at which heating and cooling systems turn on. Set a gap of around 4 – 5 ºC between the heating and cooling thermostat set points to create a comfortable ‘dead band’. This will help to keep occupants happy and increase cost savings. Unless this is implemented, both systems may operate simultaneously and waste energy and money. For more information please refer to the Carbon Trust Technology Guide on Heating Controls (CTG065). Do not rely on your maintenance technician: fine tune your controls to suit your business. The Carbon Trust’s Technology Guide on heating controls details further solutions for HVAC systems. These include: • Set temperature controls to the correct temperature and then leave alone • Fit thermostats in the right place (away from draughts and heat sources – including direct sunlight) and set correctly • Consider fitting Thermostatic Radiator Valves (TRV) to radiators to provide more localised control
• Consider upgrading or refurbishing controls if current controls are not providing comfortable conditions • Consider installing modern seven day time switches which can be programmed for different daily schedules • Consider interlocked control of the HVAC system to prevent fans, heating and cooling operating when not required • Match ventilation flow rates to demand and control operating times using temperature, humidity and CO2 sensors • Consider weather compensation and optimum start controls to adjust heating and cooling in line with the changeable UK climate Call our advice line on 0800 085 2005, or consult a qualified heating technician to discuss options available.
Further information
Investing in heating controls can save thousands of pounds and many will pay back their investment in just a couple of years. Energy efficiency financing is also available from the Carbon Trust to cover the costs of purchasing and installing them – call 0800 085 2005 or visit www.energyefficiencyfinancing.co.uk for more information.
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Diagram of ‘dead band’ control indicating recommended temperatures
0ºC
5ºC
10ºC
15ºC
20ºC
25ºC
30ºC
35ºC
40ºC
Heating is on until temperature reaches 19ºC
Cooling is on when temperature exceeds 24ºC
Heating and Cooling both off between 19ºC and 24ºC — a ‘dead band’ of 5 degrees
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Maintaining existing systems
Maintenance matters. The right approach, implemented properly, will keep your HVAC systems running efficiently, minimise the risk of breakdown and make the most of your energy savings.
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Maintenance and energy management go hand in hand – both have the common objectives of: • Ensuring a building and its services continue to function reliably, efficiently and effectively. • Ensuring the health, safety and comfort of occupants. • Protecting and enhancing the value of investment in a building and its equipment. Checking that HVAC systems are working as intended will help to prevent them from using energy ineffectively and also lower the risk of breakdown and spiralling costs. In this way, regular maintenance of equipment and controls makes good business sense.
Opportunities for energy saving
Regular maintenance for optimum performance
HVAC components must be kept free of dirt and other obstructions in order for them to operate efficiently. The overall system should be serviced annually either by a maintenance technician or a professional contractor. Routine maintenance should be regularly undertaken to identify potential problems at an early stage.
Did you know?
Energy consumption can increase by up to 30% if regular maintenance is not undertaken. Don’t be afraid to ask if you think your system isn’t operating correctly. If staff complain about problem areas in your building, act on it immediately. Always contact your maintenance technician with any concerns.
Maintain boilers
Have boilers serviced regularly by a reputable firm. Gas-fired boilers should be serviced once a year; oil boilers twice a year. A regularly serviced boiler can save as much as 10% on annual heating costs.
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Check condensers
Condensers are usually located on the outside of buildings and reject heat that has been removed from inside the building by the cooling system. Ensure condensing and evaporating devices are clean and well maintained. Check condensers are not obstructed, for example by equipment or vegetation.
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Clean fans, filters and air ducts to improve efficiency by up to 60%
There is no point in having an efficiently running system if the conditioned air gets stopped by a solid wall before reaching the work space. Blockages in HVAC systems are common and increase running costs, so make sure that the filters are regularly checked. Consider fitting pressure gauges to indicate when replacement of filters is required.
Stay safe
Heat exchangers and cooling tower water treatment processes should be spotless. This saves energy and prevents health problems such as Legionella.
Check air conditioning and comfort cooling plant
Ensure cooling plant is regularly maintained to avoid operating at reduced levels of efficiency. Replace insulation on refrigerant pipework as poor condition will affect the temperature of the refrigerant flowing through the system and thus consume more energy in maintaining the required temperature. Pay specific attention to pipework located outside a building. Check for refrigerant charge and leakage. If your refrigeration plant contains more than 3 kg of refrigerant then the F-Gas regulations state that you must have a schedule of regular inspection for gas leaks.
Insulate to accumulate
Boilers, hot water tanks, pipes and valves should be insulated to prevent heat escaping. Payback can usually be expected within a few months of installation with continued savings in subsequent years. For more information please refer to the Carbon Trust’s How to implement thermal insulation to HVAC services (CTL145) guide.
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Looking at hardware opportunities
When refurbishing or putting in a new HVAC system, it pays to specify the most efficient system possible. Remember that day-to-day running costs may soon outweigh the capital costs of installation and so the more efficient the system, the less expensive it will be to run.
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Always:
• Select the most appropriate HVAC system for your requirements. • Prioritise energy efficiency in the design and installation stages. • Implement and maintain good system controls. • Set up and maintain the HVAC system effectively (this may be through a maintenance contractor).
Is close control of humidity needed?
Yes
Energy Efficiency Financing
Investing in energy efficient equipment makes sound business and environmental sense, especially with the easy, affordable and flexible Energy Efficiency Financing scheme brought to you by Carbon Trust Implementation and Siemens Financial Services. To find out more visit www.energyefficiencyfinancing.co.uk
Investigate whether comfort cooling is needed (without humidification) Investigate whether full air conditioning (comfort cooling plus humidification) is needed
No
Does the building have to be sealed against noise or pollution?
Yes
No
Are there high internal heat gains?
Yes
No
Will it be acceptable for the occupied space to exceed 28ºC for a few hours on a few days each year?
No
Remember:
The solutions outlined here don’t just apply to refurbishment and new build – they should be discussed when renting a building or moving premises. Some managers insist on a rent review to discuss these issues with the landlord. After all, you bear the costs of your landlord’s inefficient equipment so it’s up to you to choose carefully. Always seek expert guidance before investing in a new or upgraded system.
Yes
Try passive cooling
Options
• Natural ventilation • Mechanical ventilation • Mixed mode (a combination of the above) • Night cooling
Energy efficient mechanical options
• • • • Chilled ceilings or beams Displacement ventilation Fan-coil units Mixed mode (any combination of the above and natural ventilation)
Cost, complexity and maintenance all increase when mechanical cooling is installed
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Upgrading or installing component parts of an HVAC system
Once inefficient components have been identified and need to be replaced, avoid simply exchanging like with like. Ensure that the replacement is of the highest possible efficiency. • Replace conventional boilers with condensing boilers where possible • Motors are used extensively throughout many HVAC systems so it pays to replace standard motors with new high efficiency ones. It may also be worth investing in Variable Speed Drives for motors to reduce speeds and save energy • Many HVAC systems also have a variety of pumps and fans – consider direct drive pumps and fans which are more efficient than those that are belt driven • Consider the opportunity for Heat Recovery and recirculation to recover a portion of the heat generated in your building or process and re-use it to warm fresh air as it enters the building. See our Heat recovery guide at www.carbontrust.co.uk/heatrecovery • Consider a Building Energy Management System (BMS or BEMS). A BEMS based on a network of controllers offers closer control and monitoring of building services performance, including heating ventilation and air conditioning. This is shown on a computer screen in real time and allows the performance of plant to be monitored and settings to be changed quickly and easily. BEMS can reduce total energy costs by 10% or more so they are well worth considering.
As part of the Enhanced Capital Allowances (ECA) scheme, an Energy Technology List has been produced. The list details all energy-saving technologies and products that qualify for the ECA scheme and should be used as a guide when purchasing new HVAC system components. See the box on the right for more information.
Case study
What other organisations are doing?
A spectacle lens coating business discovered that the room where the lenses were coated had a much higher energy usage compared with the rest of the site. With the help of a Carbon Trust loan they installed a gas water heating system, new air conditioning and insulation and are set to save almost £5,000 a year as a result.
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Upgrading or installing an entire system
The choice of a passive or a mechanical cooling approach can be determined by a series of relatively straightforward questions about a building and its internal environment. The flow chart on the previous page presents a summary of these questions and indicates whether comfort cooling or full air conditioning is required. When replacing HVAC systems, some managers choose like-for-like equipment, believing this will minimise disruption to the business. Planning upgrades carefully and keeping the system maintained at its peak will mean that emergency decisions and inefficient purchases can be avoided. For more information please refer to the Carbon Trust’s How to implement Building Energy Management Systems (CTL149) guide.
Tax incentives
Enhanced Capital Allowances (ECAs) are a straightforward way for a business to improve its cash flow through accelerated tax relief. The ECA scheme for energy-saving technologies encourages businesses to invest in energysaving plant or machinery specified on the Energy Technology List (ETL) which is managed by the Carbon Trust on behalf of Government. The ECA scheme provides businesses with 100% first year tax relief on their qualifying capital expenditure. The ETL specifies the energy-saving technologies that are included in the ECA scheme. The scheme allows businesses to write off the whole cost of the equipment against taxable profits in the year of purchase. For further information please visit www.carbontrust.co.uk/eca or call the Carbon Trust on 0800 085 2005.
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Next steps
There are many easy low and no-cost options to help save money and improve the operation of your HVAC systems and your building.
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Step 1. Understand your energy use
Look at your HVAC system components and check the condition and operation of all pieces of equipment. Monitor the consumption of the building over, say, one week to obtain a base figure against which energy efficiency improvements can be measured.
Step 3. Prioritise your actions
Draw up an action plan detailing a schedule of improvements that need to be made and when, along with who will be responsible for them.
Step 5. Make the changes and measure the savings
Implement your energy saving actions and measure against original consumption figures. This will assist future management decisions regarding your energy priorities.
Step 4. Seek specialist help
It may be possible to implement some energy saving measures in-house but others may require specialist assistance. Discuss the more complex or expensive options with a qualified technician. Call the Carbon Trust Advice Line on 0800 085 2005 for further advice.
Step 2. Identify your opportunities
Compile an energy checklist. Walk round your building and complete the checklist at different times of day (including after hours) to identify where energy savings can be made. An example checklist is on page 19.
Step 6. Continue to manage your business for energy efficiency
Enforce policies, systems and procedures to ensure that your business operates efficiently and that savings are maintained in the future.
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Appendices
Action checklist
HVAC 19
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Action checklist
Start saving energy today. The principles of reducing energy costs are essentially the same for all HVAC systems:
Action
Reduce the need. Turn off unnecessary equipment during the day and especially out of hours to reduce heat build-up in the space. Set higher switch-on temperatures for cooling and lower temperatures for heating. Set a gap or ‘dead band’ between heating and air conditioning control temperatures of about 5ºC. This improves occupants’ comfort, cuts operating costs and reduces wear and tear on both systems. Turn HVAC systems off out of hours, unless the building is ‘night-cooling’. Consider installing automatic controls to ensure equipment stays off. Look into areas that appear too hot or cold and consider localised thermostatic controls. Look out for draughts especially around poorly-fitting windows and doors. Install draught proofing to reduce heat losses and increase staff comfort. Check insulation levels and increase wherever practical to reduce the need for heating. Walk around your site at different times of the day and during different seasons to see how and when heaters and coolers are working. Check time and temperature settings. Take advantage of free-cooling. Where external temperatures are colder than the required internal temperature, you can ventilate the building with fresh air. ‘Night cooling’ is useful for cooling the building efficiently in summer.
Start saving energy today. The principles of reducing energy costs are essentially the same for all HVAC systems.
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Go online to get more
The Carbon Trust provides a range of tools, services and information to help you implement energy and carbon saving measures, no matter what your level of experience.
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Call us on 0800 085 2005 – Our experts offer independent, authoritative advice. Lines open 8.30am-5.30pm, Monday to Friday. Website – Visit us at www.carbontrust.co.uk for our full range
of advice and services.
Energy
Saving Plan – The Carbon Trust Advice Line can work with you to highlight areas for review within your organisation and can then provide you with a structured Energy Saving Plan. Call today on 0800 085 2005 and ask one of our advisors how an Energy Saving Plan could help your organisation cut carbon emissions and save money. Carbon, Cut Costs – This tool gives you an introduction to energy
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Footprint Calculator – Our online calculator will help you calculate
saving and helps you create a personalised action plan for your site, estimating the cost and carbon savings you could make in your workplace.
your organisation’s carbon emissions.
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than you might think to bring about real change.
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www.carbontrust.co.uk/casestudies Energy Efficiency Financing – Investing in energy efficient equipment
makes sound business and environmental sense, especially with the easy, affordable and flexible Energy Efficiency Financing scheme brought to you by Carbon Trust Implementation and Siemens Financial Services.
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The Carbon Trust is a not-for-profit company with the mission to accelerate the move to a low carbon economy. We provide specialist support to business and the public sector to help cut carbon emissions, save energy and commercialise low carbon technologies. By stimulating low carbon action we contribute to key UK goals of lower carbon emissions, the development of low carbon businesses, increased energy security and associated jobs. We help to cut carbon emissions now by: • providing specialist advice and finance to help organisations cut carbon • setting standards for carbon reduction. We reduce potential future carbon emissions by: • opening markets for low carbon technologies • leading industry collaborations to commercialise technologies • investing in early-stage low carbon companies.
CTV046
www.carbontrust.co.uk 0800 085 2005
The Carbon Trust receives funding from Government including the Department of Energy and Climate Change, the Department for Transport, the Scottish Government, the Welsh Assembly Government and Invest Northern Ireland. Whilst reasonable steps have been taken to ensure that the information contained within this publication is correct, the authors, the Carbon Trust, its agents, contractors and sub-contractors give no warranty and make no representation as to its accuracy and accept no liability for any errors or omissions. Any trademarks, service marks or logos used in this publication, and copyright in it, are the property of the Carbon Trust. Nothing in this publication shall be construed as granting any licence or right to use or reproduce any of the trademarks, service marks, logos, copyright or any proprietary information in any way without the Carbon Trust’s prior written permission. The Carbon Trust enforces infringements of its intellectual property rights to the full extent permitted by law. The Carbon Trust is a company limited by guarantee and registered in England and Wales under Company number 4190230 with its Registered Office at: 6th Floor, 5 New Street Square, London EC4A 3BF. Published in the UK: October 2011. CTV046 © The Carbon Trust 2011. All rights reserved.
Heating, ventilation and air conditioning
Saving energy without compromising comfort
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Heating, ventilation and air conditioning
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Preface
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Reducing energy use makes perfect business sense; it saves money, enhances corporate reputation and helps everyone in the fight against climate change. The Carbon Trust provides easiest effective advice to help businesses take action to reduce carbon emissions, and the easiest way to do this is to use energy more efficiently. This overview of heating, ventilation and air conditioning introduces the main energy saving opportunities for businesses and demonstrates how simple actions save energy, cut costs and increase profit margins.
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Introduction
Heating, ventilation and air conditioning (HVAC) systems control the temperature, humidity and quality of air in buildings to a set of chosen conditions. To achieve this, the systems need to transfer heat and moisture into and out of the air as well as control the level of air pollutants, either by directly removing them or by diluting them to acceptable levels.
Heating systems increase the temperature in a space to compensate for heat losses between the internal space and outside. Ventilation systems supply air to the space and extract polluted air from it. Cooling is needed to bring the temperature down in spaces where heat gains have arisen from people, equipment or the sun and are causing discomfort. Heating, ventilation and air conditioning systems vary widely in terms of size and the functions they perform. Some systems are large and central to the building services – these were probably designed when the building was originally commissioned and use ventilation to deliver heating and cooling. Other systems may provide heating through boilers and radiators, with some limited ventilation to provide fresh air or cooling to certain parts of the building such as meeting rooms. In some cases, individual comfort cooling units have been added to a building to overcome a specific overheating problem that had not been thought of at the time of the original design.
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So if heating, ventilation and air conditioning can be separate systems, why consider them holistically? The answer lies in the interaction of these services with each other and with the building. By considering HVAC systems as individual elements rather than as an interacting system, it would be easy to overlook a major area of energy wastage – that one component might impact on another. For example, it would be wasteful to increase heating inside a building while the cooling system is fighting to reduce temperatures. It is therefore useful to look at how the elements of an HVAC system interact with each other and fine tune each part to save energy and money.
Did you know?
The true definition of an ‘air conditioning system’ is one which has the ability to control temperature, humidity and air quality within precise limits, yet the term is often applied to systems which simply cool the space. These cool air systems are more correctly referred to as ‘comfort cooling’.
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Energy consumption
Heating, ventilation and air conditioning can account for the majority of money spent by an organisation on energy. Even small adjustments to these systems can significantly improve the working environment and at the same time, save money.
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How much energy do HVAC systems use?
There are five important factors that determine the energy use of an HVAC system: • The design, layout and operation of the building – this affects how the external environment impacts on internal temperatures and humidity; • The required indoor temperature and air quality – more extreme temperatures, greater precision and more refined air quality consume more energy; • The heat generated internally by lighting, equipment and people – all of these have an impact on how warm your building is; • The design and efficiency of the HVAC plant – provides heat, cooling and moisture control exactly where it is needed in the building; • The operating times of the HVAC equipment and ability of the controls – these limit operation to exactly when it is needed.
Making savings
• Reducing the need – The design and specification of buildings and HVAC systems have a big impact on energy use and hence, energy spend. Sometimes natural ventilation provides the best solution to HVAC needs – see page 7 to find out more. • Changing staff behaviour – The way occupants use a building and its HVAC systems plays a big role in how a building performs. See page 9 for tips on how staff can learn to control their environment efficiently. • Understanding and using controls – Most HVAC systems are fitted with controls. Learning how to set and regulate these can provide substantial savings and enhance comfort conditions for building occupants. See page 11 for more information. • Maintaining existing systems – Regular maintenance is vital for maximising energy savings and avoiding costly breakdowns, as explained on page 14.
Heating 46%
• Hardware opportunities – If you are considering upgrading or refurbishing your HVAC systems, there are some good opportunities for energy saving. Page 16 shows how new, efficient equipment can often pay back its costs very quickly. Total carbon emissions from energy use in public and commercial buildings 2008
Other Catering 6% 6%
Computing 8% Cooling and ventilation 7% Hot water 6%
Lighting 21%
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Technology overview
Identify your HVAC system
HVAC system components
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HVAC systems vary widely in terms of the individual components that make them up and how they are set up within a building. Most systems contain some common basic components: • Boilers 1 produce hot water (or sometimes steam) for distribute to the working space. This is done either by heating coils 2 which heat air as part of the ventilation system, or through hot water pipes to radiators 3 • Cooling equipment 4 chills water for pumping to cooling coils 5 . Treated air is then blown over the chilled water coils into the space to be cooled 6 through the ventilation system. As part of the refrigeration cycle in the chiller, heat must also be rejected from the system via a cooling tower or condenser 7 • Pumps are used throughout the system to circulate the chilled and hot water to the required areas throughout the building • Stale air is extracted, usually using a fan, via separate ducts and expelled outside 8
• Controls are used to make components work together efficiently. They turn equipment on or off and adjust chillers and boilers, air and water flow rates, temperatures and pressures. A controller incorporating one or more temperature sensors 9 inside the workspace sends a signal to the heating or cooling coils to activate • If there is a demand for heating or cooling then the controls may also send a signal to the chiller and boiler to operate as required. There are often other control panels on the chiller or boiler too, allowing users to have greater control.
Heat expelled 7
Boiler 1
Chiller 4
Panel
HVAC controller
Hot water
Sensor HVAC control panel 9
Inlet vent
Heating coils 2
Cooling coils 5
Incoming air (fan)
HVAC system types
There are many different approaches to using HVAC systems and buildings will typically use combinations and variations of a few standard approaches. HVAC systems are generally described according to how they use air, water or both to distribute heating and cooling energy to the space. To find out more about different types of system and their savings opportunities, ask your site engineer, maintenance technician or call the Carbon Trust. There should also be a building log book providing details about the HVAC system. This can be supplied by the building’s facilities manager.
Working area
6 Extract vent Exhaust air 8 Air extract (fan)
Fresh air in
Radiator 3
Stale air out
The more you understand your system, the better prepared you will be to make savings
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Identify your business needs
Why do air conditions need to be controlled?
Temperature, humidity and air quality are controlled for a number of reasons: • To provide comfort for building occupants • To enable a process to be undertaken
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What conditions should be maintained?
Start by determining what temperature and air quality standards the HVAC system should provide. HVAC for processes For processes and stored materials, it is important to concentrate on what is really required: • Does the process or material deteriorate outside a particular temperature range? • Is it moisture or air quality condition that makes the difference or is it a combination of both these factors? For instance, it may be that deterioration of a stored product is caused by mould growth or corrosion which is actually caused by excess moisture on its surface. This requires control of the product temperature and of moisture in the air so that condensation does not form. HVAC for staff comfort When providing comfort for building occupants, it is important to understand how comfort is achieved and the many ways that people perceive it. The combination of air temperature, surrounding surface temperatures, humidity, clothing, body fat, nerve sensitivity and metabolic rate is different for every person – so comfort is difficult to achieve with one fixed set of conditions. Rather than set the conditions at specific levels, it is more beneficial to set bands which allow greater flexibility.
Did you know?
• Heating costs can increase by 30% or more if the boiler is poorly operated or maintained • Heating typically accounts for about half of the energy used in offices • Heating costs rise by about 8% for each 1ºC of overheating.
• To avoid deterioration of stored products and materials. Temperature, humidity and air quality may vary greatly and fluctuate at different rates. It is therefore important to always identify core business requirements and use this to inform any proposed improvements to an HVAC system. Most businesses will have a variety of reasons for controlling the condition and quality of the air in their buildings and these should be prioritised. For instance, in a refrigerated cold store, it is probably more important to preserve the food than to maintain the comfort of workers. This is not to say that workers should be ignored – they should be provided with suitable clothing to keep them comfortable while working.
Low-cost measures for immediate savings
• Learn how to set thermostats, how to control your HVAC system to provide the conditions actually needed and to only operate as and when necessary • Find out about the building log book which should explain the services in simple terms • Ask the landlord or managing agent where the controls are and how to use them • If any controls are labelled ‘do not touch’, explore why. There may be a valid reason but it may just be for the convenience of the maintenance person • Investigate whether ‘optimum start’ and ‘optimum off’ timers which can adjust the start and finish times for different weather conditions could be appropriate for your system.
If staff members occasionally work late and alter controls, don’t forget to reset them or install a timer to automatically restore normal settings
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Reduce the need
The types of HVAC systems and how they are used have a big impact on the amount of energy consumed and the levels of comfort provided for staff and/or customers. Even in a building that has full air conditioning and cooling, it may not be necessary for them to be switched on all of the time. Using natural ‘free energy’ to heat, cool and ventilate a building can help save substantial sums of money and give building occupants greater control over their environment.
Opportunities for energy saving
Passive heating, ventilation and cooling
This is the control of heat from the sun along with ventilation in order to benefit a building and avoid discomfort. To maximise energy savings, it pays to organise a system so that nature provides the majority of fresh air and temperature requirements. Expensive ‘artificial’ and mechanical systems can then operate to fine tune the desired temperature and environmental conditions. As simple as it sounds, natural ventilation relies on air flow through openings of a room or building, preferably from opposite sides. It also applies to rising hot air being replaced with cooler air sucked in through windows or vents from a lower level. Making the most of natural ventilation is a simple and cost-effective way of achieving big savings.
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When cooling is required inside a building, and if it is cooler outside than in, simply open doors, vents and windows. This will increase airflow, reduce heat and perhaps provide all the ventilation that is needed. Be aware, however, that opening windows in air conditioned buildings may increase the energy used by the system. Some businesses use what is known as a ‘mixed mode’ system, which uses a combination of both natural and mechanical systems. The building uses natural ventilation, heating and cooling where possible, with mechanical systems being used only when needed. There are various advantages to such a system: • The building becomes more adaptable to a wide range of requirements • The occupants have more control over their environment • Businesses can cut down on energy spend and carbon emissions.
Myth
Turning air conditioning thermostats down as low as they can go cools the building more quickly.
Reality The temperature drops at the same rate but then overshoots, making it uncomfortable for the staff and using more energy than necessary. If controls are not coordinated, the temperature could even go low enough for the heating system to be switched on. Both systems then operate at the same time. Remedy Set thermostats correctly and educate staff to dispel this myth. As a last resort, protect thermostats to prevent tampering where possible.
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Reduce overheating
Before installing cooling equipment, always identify where the excess heat is coming from – sunlight, equipment, lighting and refrigeration are often the main sources. Consider shading windows on the outside or replacing window panes with special heat reflective glass to prevent heat build-up. Alternatively, internal blinds can be angled to redirect useful light onto the ceiling while cutting out much of the sun’s heat. Energy using equipment, lighting and refrigeration are also major heat emitters in a building. As a general rule of thumb, the more energy efficient equipment is, the less heat it produces. So installing low-energy lighting and keeping equipment operating at peak efficiency reduces cooling costs. Consider zoning to match building
Daylight blinds
Daylight blinds enable natural light to enter the space by re-directing it onto the ceiling, thereby alleviating any discomfort felt by the occupants from direct daylight. Many daylight blinds also have perforated blades to retain the employee’s view out of the window. For more information please refer to the Carbon Trust’s How to Implement Solar Shading (CTL065) guide.
Night cooling
Night cooling is an established technique where cool night air is passed through the building to remove heat that has accumulated during the day. When the building fabric is cooled, it will absorb more heat the following day, meaning lower internal temperatures. The movement of cool night air may be natural or fan-assisted. This free cooling of the building reduces energy consumption otherwise used by mechanical cooling and ventilation, leading to cost savings.
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The benefits of daylight blinds
Reduces brightness at the window Ensures light distribution deep into the interior
occupancy and reduce costs
Many buildings have problematic areas with different time and temperature requirements where only one overall heating or cooling control system exists. A solution is to ‘zone’ the building, installing separate time and temperature controls for individual areas. Zoned areas can provide better conditions as occupants in each area will have greater control over their immediate environment. It will also be more cost efficient, as HVAC can then be turned down or off in unused zones. For more information please refer to the Carbon Trust’s How to implement heating zone controls (CTL148) guide.
Protects from heat and glare Provides a view outside for staff
Direct sunlight Diffuse overhead light Maintains the natural daylight spectrum
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Good housekeeping and staff comfort
Understanding the needs of building occupants and informing them how to operate systems effectively can pay dividends.
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Opportunities for energy saving
A common sense approach to comfort and temperatures
There are many factors which effect how warm people feel, including: • Air temperature • Solar radiation • Air speed • Humidity • Activities performed • Clothing All these factors should be taken into consideration when attempting to create a comfortable environment for people to work in. Ensure workspaces are shielded from draughts and direct sunlight. These are no-cost solutions that save money and help maintain comfort.
Adjust your system
At times it makes sense to use the outside temperature to adjust the conditions inside your building. However, when the heating, ventilation or air conditioning systems are on, it is possible to save up to one third on heating or cooling costs by reducing the amount of outside air that enters a building. It is always better to adjust the system rather than open a door or window and let heated or cooled air out. For example, when the heating is on too high, staff open windows to make the space more comfortable. Try adjusting the thermostats instead.
Did you know?
Comfort cooling by traditional air conditioning systems is very expensive. In the right circumstances low energy alternatives such as evaporative cooling systems can cut energy consumption by up to three quarters. For more information on how to cut your air conditioning costs please refer to our dedicated Air Conditioning Advice pages
Turn off and power down
Try limiting the time that equipment is switched on and use ‘power-down’ facilities on copiers, faxes, printers and computers during the day where possible, as these heat the workspace. Dim or switch off lighting if there is sufficient daylight and use as little as possible at night.
Train staff on how to operate air conditioning units and heating controls
Staff should receive guidance on recommended operating temperatures and how to set heating or cooling units correctly. Louvres (movable slats to guide the cool or heated air) are a feature on most air conditioning units and staff should be able to operate these to maintain a comfortable temperature. Display instructions on individual units and ensure that remote controls have accessible and obvious storage spaces.
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Ensure controls are in place and HVAC systems operate at times and levels to reflect demand
HVAC loads will vary at different times and in different parts of a building throughout the day. Well-set time controls should ensure that systems only operate when and where required, in order to match core business hours. It is also worth regularly checking settings. Many systems are set incorrectly because someone has made a short-term adjustment and then forgotten about it. For more information, please see the Carbon Trust Technology Guide on Heating Controls (CTG065).
The Carbon Trust has promotional materials which help encourage people to be energy efficient
Further information
For further information on raising awareness in your business see the Carbon Trust’s pack, Creating an Awareness Campaign (CTG056).
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Involve staff – run an awareness campaign
Engaging employees is crucial in eliminating energy waste. Motivate staff – encourage them to review their own working practices and suggest ways to make their tasks more energy efficient. Before staff can begin to save energy, they must be made aware of areas of potential waste in their own workplaces and the important part they play in controlling the temperatures they work in.
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Understanding and using controls
An efficient HVAC system provides just the right temperature and environmental conditions while using the minimum amount of energy. Once the ideal comfort conditions for a building have been identified, good controls can help maintain these conditions.
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Opportunities for energy saving
There are two main types of control:
• Time controls ensure systems only operate when and where the building is occupied • Temperature controls ensure systems provide the correct required temperatures.
Maintain appropriate local temperatures based on outside conditions
If it is cold outside, building occupants will typically be wearing warmer clothing, so ensure temperatures are set accordingly. The reverse applies in summer if cooling is in operation. People will dress for warmer weather so do not freeze them with expensive overcooling.
Don’t overheat buildings
The optimum operating temperature range for a building will depend on the type of activities being performed. Recommended heating temperatures for particular buildings, activities, and processes are provided in the following table.
Set time controls to match occupancy
Check controls are appropriately set and displaying the correct time and date. Adjust if necessary to ensure heating and cooling only operate when and where required. Optimum start and stop controls can be used to minimise the out of hours operation of heating and cooling plant.
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Sector Offices/service companies
Building/room type Computer rooms Banks, building societies, post offices Offices
Temperature (ºC) 19-21 19-21 21-23 22-24 20-22 19-21 19-21 11-14 16-19 19-21 22-24 19-24 22-24 19-22 17-19 19-21 19-21 19-21 19-21 16-19 19-21 19-21 19-21 19-24 20-25 15 28-30*
Hospitality
Restaurants/dining rooms Bars Hotels
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Schools/further and higher education Industrial/factories
Educational buildings Heavy work Light work Sedentary work
Hospitals and healthcare
Bedheads/wards Circulation spaces/wards Consulting/treatment rooms Nurses’ stations Operating theatres
Public buildings
General building areas Law courts Libraries Exhibition halls Laundries Churches Museums and art galleries Prisons
Retail Sports and leisure
Retail buildings Changing rooms Sports halls Pool halls
Source: Adapted from Environmental Design CIBSE Guide A, 2006 *Depending on pool water temperature
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Don’t let heating and cooling operate at the same time
Set controls to give a wide gap between the temperatures at which heating and cooling systems turn on. Set a gap of around 4 – 5 ºC between the heating and cooling thermostat set points to create a comfortable ‘dead band’. This will help to keep occupants happy and increase cost savings. Unless this is implemented, both systems may operate simultaneously and waste energy and money. For more information please refer to the Carbon Trust Technology Guide on Heating Controls (CTG065). Do not rely on your maintenance technician: fine tune your controls to suit your business. The Carbon Trust’s Technology Guide on heating controls details further solutions for HVAC systems. These include: • Set temperature controls to the correct temperature and then leave alone • Fit thermostats in the right place (away from draughts and heat sources – including direct sunlight) and set correctly • Consider fitting Thermostatic Radiator Valves (TRV) to radiators to provide more localised control
• Consider upgrading or refurbishing controls if current controls are not providing comfortable conditions • Consider installing modern seven day time switches which can be programmed for different daily schedules • Consider interlocked control of the HVAC system to prevent fans, heating and cooling operating when not required • Match ventilation flow rates to demand and control operating times using temperature, humidity and CO2 sensors • Consider weather compensation and optimum start controls to adjust heating and cooling in line with the changeable UK climate Call our advice line on 0800 085 2005, or consult a qualified heating technician to discuss options available.
Further information
Investing in heating controls can save thousands of pounds and many will pay back their investment in just a couple of years. Energy efficiency financing is also available from the Carbon Trust to cover the costs of purchasing and installing them – call 0800 085 2005 or visit www.energyefficiencyfinancing.co.uk for more information.
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Diagram of ‘dead band’ control indicating recommended temperatures
0ºC
5ºC
10ºC
15ºC
20ºC
25ºC
30ºC
35ºC
40ºC
Heating is on until temperature reaches 19ºC
Cooling is on when temperature exceeds 24ºC
Heating and Cooling both off between 19ºC and 24ºC — a ‘dead band’ of 5 degrees
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Maintaining existing systems
Maintenance matters. The right approach, implemented properly, will keep your HVAC systems running efficiently, minimise the risk of breakdown and make the most of your energy savings.
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Maintenance and energy management go hand in hand – both have the common objectives of: • Ensuring a building and its services continue to function reliably, efficiently and effectively. • Ensuring the health, safety and comfort of occupants. • Protecting and enhancing the value of investment in a building and its equipment. Checking that HVAC systems are working as intended will help to prevent them from using energy ineffectively and also lower the risk of breakdown and spiralling costs. In this way, regular maintenance of equipment and controls makes good business sense.
Opportunities for energy saving
Regular maintenance for optimum performance
HVAC components must be kept free of dirt and other obstructions in order for them to operate efficiently. The overall system should be serviced annually either by a maintenance technician or a professional contractor. Routine maintenance should be regularly undertaken to identify potential problems at an early stage.
Did you know?
Energy consumption can increase by up to 30% if regular maintenance is not undertaken. Don’t be afraid to ask if you think your system isn’t operating correctly. If staff complain about problem areas in your building, act on it immediately. Always contact your maintenance technician with any concerns.
Maintain boilers
Have boilers serviced regularly by a reputable firm. Gas-fired boilers should be serviced once a year; oil boilers twice a year. A regularly serviced boiler can save as much as 10% on annual heating costs.
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Check condensers
Condensers are usually located on the outside of buildings and reject heat that has been removed from inside the building by the cooling system. Ensure condensing and evaporating devices are clean and well maintained. Check condensers are not obstructed, for example by equipment or vegetation.
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Clean fans, filters and air ducts to improve efficiency by up to 60%
There is no point in having an efficiently running system if the conditioned air gets stopped by a solid wall before reaching the work space. Blockages in HVAC systems are common and increase running costs, so make sure that the filters are regularly checked. Consider fitting pressure gauges to indicate when replacement of filters is required.
Stay safe
Heat exchangers and cooling tower water treatment processes should be spotless. This saves energy and prevents health problems such as Legionella.
Check air conditioning and comfort cooling plant
Ensure cooling plant is regularly maintained to avoid operating at reduced levels of efficiency. Replace insulation on refrigerant pipework as poor condition will affect the temperature of the refrigerant flowing through the system and thus consume more energy in maintaining the required temperature. Pay specific attention to pipework located outside a building. Check for refrigerant charge and leakage. If your refrigeration plant contains more than 3 kg of refrigerant then the F-Gas regulations state that you must have a schedule of regular inspection for gas leaks.
Insulate to accumulate
Boilers, hot water tanks, pipes and valves should be insulated to prevent heat escaping. Payback can usually be expected within a few months of installation with continued savings in subsequent years. For more information please refer to the Carbon Trust’s How to implement thermal insulation to HVAC services (CTL145) guide.
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Looking at hardware opportunities
When refurbishing or putting in a new HVAC system, it pays to specify the most efficient system possible. Remember that day-to-day running costs may soon outweigh the capital costs of installation and so the more efficient the system, the less expensive it will be to run.
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Always:
• Select the most appropriate HVAC system for your requirements. • Prioritise energy efficiency in the design and installation stages. • Implement and maintain good system controls. • Set up and maintain the HVAC system effectively (this may be through a maintenance contractor).
Is close control of humidity needed?
Yes
Energy Efficiency Financing
Investing in energy efficient equipment makes sound business and environmental sense, especially with the easy, affordable and flexible Energy Efficiency Financing scheme brought to you by Carbon Trust Implementation and Siemens Financial Services. To find out more visit www.energyefficiencyfinancing.co.uk
Investigate whether comfort cooling is needed (without humidification) Investigate whether full air conditioning (comfort cooling plus humidification) is needed
No
Does the building have to be sealed against noise or pollution?
Yes
No
Are there high internal heat gains?
Yes
No
Will it be acceptable for the occupied space to exceed 28ºC for a few hours on a few days each year?
No
Remember:
The solutions outlined here don’t just apply to refurbishment and new build – they should be discussed when renting a building or moving premises. Some managers insist on a rent review to discuss these issues with the landlord. After all, you bear the costs of your landlord’s inefficient equipment so it’s up to you to choose carefully. Always seek expert guidance before investing in a new or upgraded system.
Yes
Try passive cooling
Options
• Natural ventilation • Mechanical ventilation • Mixed mode (a combination of the above) • Night cooling
Energy efficient mechanical options
• • • • Chilled ceilings or beams Displacement ventilation Fan-coil units Mixed mode (any combination of the above and natural ventilation)
Cost, complexity and maintenance all increase when mechanical cooling is installed
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Upgrading or installing component parts of an HVAC system
Once inefficient components have been identified and need to be replaced, avoid simply exchanging like with like. Ensure that the replacement is of the highest possible efficiency. • Replace conventional boilers with condensing boilers where possible • Motors are used extensively throughout many HVAC systems so it pays to replace standard motors with new high efficiency ones. It may also be worth investing in Variable Speed Drives for motors to reduce speeds and save energy • Many HVAC systems also have a variety of pumps and fans – consider direct drive pumps and fans which are more efficient than those that are belt driven • Consider the opportunity for Heat Recovery and recirculation to recover a portion of the heat generated in your building or process and re-use it to warm fresh air as it enters the building. See our Heat recovery guide at www.carbontrust.co.uk/heatrecovery • Consider a Building Energy Management System (BMS or BEMS). A BEMS based on a network of controllers offers closer control and monitoring of building services performance, including heating ventilation and air conditioning. This is shown on a computer screen in real time and allows the performance of plant to be monitored and settings to be changed quickly and easily. BEMS can reduce total energy costs by 10% or more so they are well worth considering.
As part of the Enhanced Capital Allowances (ECA) scheme, an Energy Technology List has been produced. The list details all energy-saving technologies and products that qualify for the ECA scheme and should be used as a guide when purchasing new HVAC system components. See the box on the right for more information.
Case study
What other organisations are doing?
A spectacle lens coating business discovered that the room where the lenses were coated had a much higher energy usage compared with the rest of the site. With the help of a Carbon Trust loan they installed a gas water heating system, new air conditioning and insulation and are set to save almost £5,000 a year as a result.
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Upgrading or installing an entire system
The choice of a passive or a mechanical cooling approach can be determined by a series of relatively straightforward questions about a building and its internal environment. The flow chart on the previous page presents a summary of these questions and indicates whether comfort cooling or full air conditioning is required. When replacing HVAC systems, some managers choose like-for-like equipment, believing this will minimise disruption to the business. Planning upgrades carefully and keeping the system maintained at its peak will mean that emergency decisions and inefficient purchases can be avoided. For more information please refer to the Carbon Trust’s How to implement Building Energy Management Systems (CTL149) guide.
Tax incentives
Enhanced Capital Allowances (ECAs) are a straightforward way for a business to improve its cash flow through accelerated tax relief. The ECA scheme for energy-saving technologies encourages businesses to invest in energysaving plant or machinery specified on the Energy Technology List (ETL) which is managed by the Carbon Trust on behalf of Government. The ECA scheme provides businesses with 100% first year tax relief on their qualifying capital expenditure. The ETL specifies the energy-saving technologies that are included in the ECA scheme. The scheme allows businesses to write off the whole cost of the equipment against taxable profits in the year of purchase. For further information please visit www.carbontrust.co.uk/eca or call the Carbon Trust on 0800 085 2005.
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Next steps
There are many easy low and no-cost options to help save money and improve the operation of your HVAC systems and your building.
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Step 1. Understand your energy use
Look at your HVAC system components and check the condition and operation of all pieces of equipment. Monitor the consumption of the building over, say, one week to obtain a base figure against which energy efficiency improvements can be measured.
Step 3. Prioritise your actions
Draw up an action plan detailing a schedule of improvements that need to be made and when, along with who will be responsible for them.
Step 5. Make the changes and measure the savings
Implement your energy saving actions and measure against original consumption figures. This will assist future management decisions regarding your energy priorities.
Step 4. Seek specialist help
It may be possible to implement some energy saving measures in-house but others may require specialist assistance. Discuss the more complex or expensive options with a qualified technician. Call the Carbon Trust Advice Line on 0800 085 2005 for further advice.
Step 2. Identify your opportunities
Compile an energy checklist. Walk round your building and complete the checklist at different times of day (including after hours) to identify where energy savings can be made. An example checklist is on page 19.
Step 6. Continue to manage your business for energy efficiency
Enforce policies, systems and procedures to ensure that your business operates efficiently and that savings are maintained in the future.
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Heating, ventilation and air conditioning
19
Appendices
Action checklist
HVAC 19
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Action checklist
Start saving energy today. The principles of reducing energy costs are essentially the same for all HVAC systems:
Action
Reduce the need. Turn off unnecessary equipment during the day and especially out of hours to reduce heat build-up in the space. Set higher switch-on temperatures for cooling and lower temperatures for heating. Set a gap or ‘dead band’ between heating and air conditioning control temperatures of about 5ºC. This improves occupants’ comfort, cuts operating costs and reduces wear and tear on both systems. Turn HVAC systems off out of hours, unless the building is ‘night-cooling’. Consider installing automatic controls to ensure equipment stays off. Look into areas that appear too hot or cold and consider localised thermostatic controls. Look out for draughts especially around poorly-fitting windows and doors. Install draught proofing to reduce heat losses and increase staff comfort. Check insulation levels and increase wherever practical to reduce the need for heating. Walk around your site at different times of the day and during different seasons to see how and when heaters and coolers are working. Check time and temperature settings. Take advantage of free-cooling. Where external temperatures are colder than the required internal temperature, you can ventilate the building with fresh air. ‘Night cooling’ is useful for cooling the building efficiently in summer.
Start saving energy today. The principles of reducing energy costs are essentially the same for all HVAC systems.
Download
HELP
Heating, ventilation and air conditioning
20
Go online to get more
The Carbon Trust provides a range of tools, services and information to help you implement energy and carbon saving measures, no matter what your level of experience.
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Call us on 0800 085 2005 – Our experts offer independent, authoritative advice. Lines open 8.30am-5.30pm, Monday to Friday. Website – Visit us at www.carbontrust.co.uk for our full range
of advice and services.
Energy
Saving Plan – The Carbon Trust Advice Line can work with you to highlight areas for review within your organisation and can then provide you with a structured Energy Saving Plan. Call today on 0800 085 2005 and ask one of our advisors how an Energy Saving Plan could help your organisation cut carbon emissions and save money. Carbon, Cut Costs – This tool gives you an introduction to energy
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Carbon
Cut
Footprint Calculator – Our online calculator will help you calculate
saving and helps you create a personalised action plan for your site, estimating the cost and carbon savings you could make in your workplace.
your organisation’s carbon emissions.
www.carbontrust.co.uk/onlinetraining Case Studies – Our case studies show that it’s often easier and less expensive
than you might think to bring about real change.
www.carbontrust.co.uk/carboncalculator
Publications – We have a library of publications detailing energy saving techniques for a range of sectors and technologies.
www.carbontrust.co.uk/casestudies Energy Efficiency Financing – Investing in energy efficient equipment
makes sound business and environmental sense, especially with the easy, affordable and flexible Energy Efficiency Financing scheme brought to you by Carbon Trust Implementation and Siemens Financial Services.
www.carbontrust.co.uk/publications
Events and Workshops – We offer a variety of events and workshops ranging from a high level introduction to our services through to detailed technical energy efficiency training.
www.carbontrust.co.uk/events
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The Carbon Trust is a not-for-profit company with the mission to accelerate the move to a low carbon economy. We provide specialist support to business and the public sector to help cut carbon emissions, save energy and commercialise low carbon technologies. By stimulating low carbon action we contribute to key UK goals of lower carbon emissions, the development of low carbon businesses, increased energy security and associated jobs. We help to cut carbon emissions now by: • providing specialist advice and finance to help organisations cut carbon • setting standards for carbon reduction. We reduce potential future carbon emissions by: • opening markets for low carbon technologies • leading industry collaborations to commercialise technologies • investing in early-stage low carbon companies.
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The Carbon Trust receives funding from Government including the Department of Energy and Climate Change, the Department for Transport, the Scottish Government, the Welsh Assembly Government and Invest Northern Ireland. Whilst reasonable steps have been taken to ensure that the information contained within this publication is correct, the authors, the Carbon Trust, its agents, contractors and sub-contractors give no warranty and make no representation as to its accuracy and accept no liability for any errors or omissions. Any trademarks, service marks or logos used in this publication, and copyright in it, are the property of the Carbon Trust. Nothing in this publication shall be construed as granting any licence or right to use or reproduce any of the trademarks, service marks, logos, copyright or any proprietary information in any way without the Carbon Trust’s prior written permission. The Carbon Trust enforces infringements of its intellectual property rights to the full extent permitted by law. The Carbon Trust is a company limited by guarantee and registered in England and Wales under Company number 4190230 with its Registered Office at: 6th Floor, 5 New Street Square, London EC4A 3BF. Published in the UK: October 2011. CTV046 © The Carbon Trust 2011. All rights reserved.
