heating, ventilation & air conditioning

NEEN FACT SHEET
Energy Efficiency:
heating, ventilation &
air conditioning (hvac)
HVAC is typically responsible for around 40% of the energy consumption
in a building. Frequently, this is the largest energy consuming type of
equipment on a site and can therefore provide significant scope for saving
energy and money. This fact sheet covers common types of HVAC and will
guide you in the right direction to identify energy efficient HVAC initiatives.
What is HVAC?
HVAC is an acronym for heating, ventilation and air
conditioning. It refers to all the different systems, machines and
technologies that are used to regulate the temperature and air
quality in an indoor environment.
Energy Consumption of HVAC
systems
In many buildings HVAC is the largest energy consumer.
Figure 1. Energy breakdown for a typical office space
Why HVAC matters
Efficient HVAC systems do more than just make an area
comfortable; they can help to reduce running costs, improve the
working environment, increase productivity and safety, improve
aesthetics and reduce greenhouse gas emissions.
Increasing the efficiency of your HVAC system is an effective
way to cut energy consumption, generate financial savings and
reduce your organisation’s environmental footprint - whether
you are in an office, church, school or even a sporting facilities.
Identifying your HVAC system
Typically, the energy consumption within these HVAC systems
are split as follows:
The majority of smaller organisations will have HVAC in the
form of split or window based systems, or plug in heaters of
various styles.
Figure 2. HVAC energy breakdown (%)
For organisations that are located within commercial
buildings, HVAC is often provided as part of a centralised
system within the ‘base building’. In these scenarios, energy
used by the HVAC system is often not contained within the
energy bill and is instead charged back to the building owner
and recovered in the form of leasing costs.
Organisations in this scenario will typically have more
limited control on the HVAC system. It may be necessary to
collaborate with the building owner/manager to influence the
implementation of any efficiency projects
National Energy Efficiency Network
Fan energy consumption is greatest, followed by energy
involved in cooling (through a refrigeration compressor), heating,
pumping and finally the energy required to reject heat in cooling
towers (or condensers). Therefore, a reduction in the use of fans
generally offers the greatest potential for saving energy.
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April 2015
Energy Savings through hvac
There are two key areas where savings can be made:
• Quick wins – areas that can be addressed at no or low cost
almost straight away
trategic – those areas which are more complex, or require
S
more capital investment
•
Quick wins
•
•
•
•
Turn HVAC units off – Turn off systems when they are
not required. Frequently systems are left running over
weekends or overnight when no-one is there to feel the
benefit. Utilise timer functions to ensure these systems
are switched off
Optimise temperature/humidity settings in each area
– Set heat to the lowest temperature possible and
cooling to the highest temperature possible. Use
deadbands to ensure heating and cooling never operate
at the same time. A deadband is a temperature range at
which neither heating nor cooling is turned on – this
should be around the ideal room temperature. The CIBSE
Guide gives recommendations on ideal temperature set
points for various building areas/activities.
Minimise heat gain (in summer) – There are a number
of heat producers in a typical building. These range
from heat emitted from computers, screens and
photocopiers to lights and even people. Switch off
or use sleep mode for all unrequired equipment and
cooling, so these systems will not need to work as hard
to achieve set points.
Minimise ventilation rates – Each air change
(ventilation rate) requires fresh air to be either heated or
cooled as appropriate. This consumes energy. Adjusting
ventilation rates to suit occupancy and activity type
reduces this requirement.
Strategic opportunities
The following are some of the most common types of energy
saving projects worth considering. They are listed in order of
complexity and size of HVAC system:
Maintenance – Regular
maintenance of existing (or new)
systems is a critically important
part of keeping HVAC systems as
efficient as possible.
Efficiency can decrease by as
much as 40% if the appropriate
maintenance is not carried out. Some examples of important
maintenance are: keeping filters, fans and air ducts clear of dirt
and other obstructions; tuning burners on boilers; checking
refrigerant charge on cooling systems; keeping condensers
or cooling towers clear of contaminant build-up; checking the
condition of insulation on chilled/heated pipework and ensuring
National Energy Efficiency Network
that moving parts have the correct amount of lubrication, eg
actuators/linkages on damper controls or bearings on fan
motors. It pays to have qualified HVAC contractors service this
equipment on at least an annual basis.
Insulation/draught-proofing/shading – Minimising heat gain in
summer and heat loss in winter makes perfect sense. Improved
insulation can reduce energy requirements for
heating/cooling by as much as 25%. In colder
climates, draught proofing can reduce heating
requirements by as much as 40%. Shading can
be as simple as planting a tree or bush outside
a window, which can help to reduce solar heat
gain in summer by as much as 70%.
Variable Speed Drives (VSDs) – The fans and pumps in an
HVAC system generally do not need to run flat out all of the
time. During these times, a throttle is normally used to limit
the flow of fluid while the fixed speed motor runs at full speed.
Devices called VSDs can slow these motors down to achieve
the same effect, but saving energy in the process.
Economy cycle – Installation of additional external temperature
and humidity sensors, as well as motorised dampers and
extra fans, can help to reduce air
conditioning costs. An economy cycle
on air conditioning systems uses outside
air to cool down the inside of a building
whenever the external temperature is
cooler than it is inside.
Upgrade cooling systems – If your cooling system is
approaching 10 years old or more, it is likely to be inefficient.
Advancement in cooling technology means that there are many
systems on the market today that are many times more efficient.
If you have an older system, it is worthwhile considering an
upgrade based on energy savings (as
well as a need to replace certain types of
refrigerant gas, e.g. if you have a system
that uses R22 gas, this must be replaced
by 2015).
Upgrade heating systems – Many older building heating
systems consist of gas-fired water heaters (or boilers).
Older systems generally have an 80% or less efficiency
rating (meaning that 20% of the energy
put into the heater is wasted). Modern
boilers can achieve efficiency ratings of
greater than 90%, meaning that 10%
efficiency savings can be achieved.
Cogeneration/Trigeneration –
Cogeneration or trigeneration units are devices that generate
electricity (usually from natural gas, but they can use different
fuels such as biomass e.g. wood or animal waste). In the
process of generating electricity, waste heat is produced. This
can be recovered and used either as hot water (or steam) for
heating systems, or can be converted (via a process called
absorption) to chilled water and used in cooling systems. These
units are currently very expensive but can lead to huge energy,
cost and carbon savings.
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April 2015
Energy recovery ventilation systems – Ventilation systems
are bad for efficiency as they take air that has been heated or
chilled by the building systems and vent it outside, bringing in
hot (in summer) or cold (in winter) air which then needs to be
cooled or heated all over again. Energy recovery systems are
available which use heat exchange technology to recover some
of the thermal energy from outgoing air and transfer this to the
incoming air.
Ground-Source Heat Pumps – These devices use the thermal
energy of the earth as a source for heating or as a heat sink for
cooling. Below a certain depth, the temperature of the earth
does not vary from season to season. This can be utilised by
pump systems to either preheat, water or air for internal use.
In summer, the indoor heat can be transferred via pipes and
transferred or dumped into the ground, with cool air being
carried back via water to the building. This saves energy and
money.
Heating, Ventilation and Cooling (HVAC) in small buildings
– Heating and cooling in smaller buildings can cover a lot of
equipment, but in the NFP sector, these are most likely to
be individual units (heating and/or air conditioning) or locally
controlled systems. If you have a number of individual heaters
and coolers/air conditioners, it may be worthwhile replacing
these with split reverse cycle air conditioning units. Due to the
properties of the refrigerant gas, these can provide much more
energy efficient heating and cooling.
Evaporative cooling – If the site has relatively low humidity
levels, then an evaporative cooling unit can be just as
effective as a refrigerated air conditioner, but with much lower
running costs. Evaporative cooling does not use the vapour
compression of a refrigerant or absorption refrigeration
cycles. Instead, it relies on the evaporation properties of water
(something called “enthalpy of vapourisation”), which means
that to achieve the same result, much less energy is consumed
in the process. Some advantages of these systems are that
they are less expensive to install, run and maintain - and there
is no potentially harmful refrigerant used (only water). Some
disadvantages of these systems are that they humidify the
air (so can affect comfort), and their performance is limited by
local humidity conditions (so they are not as effective in humid
regions).
Heat pumps – Heat pumps can also be an extremely efficient
way to generate heat. They work like a reverse refrigerator,
meaning that, due to the properties of the ‘refrigerant’ gas, you
can get many times more ‘units of heat’ out from these than the
‘units of electricity’ you put into them. On average you get 3-5
times the heat energy out, compared to the electrical energy
you put in. This makes them very efficient indeed, so if you have
an older electrical element or resistance heater, then a heat
pump would be a worthwhile investment.
National Energy Efficiency Network
HVAC Upgrade - Case study
15 Barry Drive, Canberra
The three-storey office building at 15 Barry Drive in Turner is
fairly typical of the low-rise office buildings found in Canberra.
However, the 1980’s building had 20 year old systems which
needed upgrading.
A comprehensive investigation process ensued. This
addressed the environmental performance of several building
aspects, including the HVAC system. The investigation
revealed the extent of the building’s aging HVAC technology
and its obvious inefficiencies.
A building services upgrade was slated for 2008. This
included: replacement of (BMS) controls for the building
monitoring system for the HVAC system and exhaust,
modification of chilled-water valves, outside-air-intake
modifications, return-air duct alterations and the installation of
two variable speed drives for levels one and two.
Also scheduled were air and water balancing, and the
installation of new ceiling tiles to improve both insulation and
the performance of the building fabric that separates the office
space from the plant area.
Following completion of the works, improvements in both
energy efficiency and comfort were immediately noticeable.
Useful links
CIBSE Guide A, Section 1.3
Thermal comfort recommendations
http://www.arca53.dsl.pipex.com/index_files/thermco2.
htm
Case Study - 15 Barry Drive, Turner, Canberra Information
on HVAC, controls and building fabric upgrades
https://www.airah.org.au/imis15_prod/Content_Files/
UsefulDocuments/CS_Barry_Drive.pdf
Energy Efficiency Exchange
Heating, Ventilation and Air Conditioning
http://eex.gov.au/technologies/heating-ventilation-and-airconditioning/opportunities/
Australian Government, Department of Industry
Heating, Ventilation and Air Conditioning
http://industry.gov.au/Energy/EnergyEfficiency/NonresidentialBuildings/HVAC/FactSheets/Pages/default.aspx
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April 2015
for further information
NEEN – National Energy Efficiency Network
NEEN is a national initiative
to promote open learning
and collaboration amongst
faith-based and not-for-profit
community organisations, with
the aim of increasing energy
efficiency and establishing a
positive energy future for
the sector.
What makes the NEEN
initiative so powerful?
NEEN provides small to medium
sized community organisations
with the resources to reduce
energy consumption and the
opportunity to connect and
collaborate on a range of
initiatives that foster a resilient,
sustainable future for the not-forprofit sector and the communities
they serve.
An Open Invitation
No matter where you are on
your journey to achieve your
sustainability goals, you’re
welcome to join the NEEN
community. Make the connection
and discover a better energy
future for your organisation.
Acknowledgements
This project was funded by the Australian Government – Dept of Industry – Energy
Efficiency Information Grant Program. The Level 1 Energy audits and opportunities
assessments were carried out by Energetics on behalf of the NEEN program.
Disclaimer
The information contained in this document is of a general nature only and does
not constitute personal financial product advice. In preparing the advice no account
was taken of the objectives, financial situation or needs of any particular person.
Therefore, before making any decision, readers should seek professional advice
from a professional adviser to help you consider the appropriateness of the advice
with regard to your particular objectives, financial situation and needs.
Government Disclaimer
This Activity received funding from the Department of Industry as part of the
Energy Efficiency Information Grants Program. The views expressed herein are not
necessarily the views of the Commonwealth of Australia, and the Commonwealth
does not accept responsibility for any information or advice contained herein.
Discover, Inspire, Engage, Transform
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National Energy Efficiency Network
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April 2015