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The performance of Irish buildings has been blighted for too
long by failure to deal with our damp climate, combined with
massive, avoidable heat loss. Heat recovery ventilation, a
technology that has become a standard building application
in Scandinavian countries, is rapidly gaining recognition
in Ireland as a solution to both problems.
The
onus on reducing energy usage in buildings is continuing to
grow in Ireland, and is set to impact heavily on the whole
country over the next few years, through a variety of legislature
changes. This includes the introduction in 2004 of a carbon
tax, which is set to penalise CO2 intensive fuel usage. On
top of that there is the EU Directive on the Energy Performance
of Buildings, which, as was reported in the last edition of
Construct Ireland, will introduce energy certification for
buildings as a key factor in sales or rental, sets minimum
energy performance standards for new build and major refurbishment,
and demands the consideration of energy saving measures for
many categories of buildings. When you add to this list the
increased thermal performance demands on buildings posed by
the changes last January to part L of the Building Regulations,
the fact that judgement day regarding the Kyoto protocol is
edging ever nearer, and the fact that nearly half of Ireland’s
CO2 emissions derive from energy use in buildings, alarm bells
start ringing. Clearly, Irish buildings are under immense
pressure to improve in terms of energy performance, and it
falls to architects, engineers, developers, self builders,
home owners, employers and government to consider ways to
improve energy efficiency, reduce emissions and in so doing
lower the running costs of buildings.
According
to Kirk Shanks, a research engineer with the Energy Research
Group, who is actively researching developments in ventilation,
“between a third and half of an Irish building’s
heat loss typically occurs through cold air exchange”.
However, ventilation plays a key role in the health of occupants
and the structure of a building, and there are consequently
minimum requirements set out in part F1 of the Building Regulations.
An apparent dilemma exists here, as buildings are required
to both retain heat, and circulate air. How can modern buildings
fulfil their energy requirements and provide adequate air
circulation at the same time when each function seems to undermine
the other?
Heat
Recovery Ventilation is a technology that, whilst having been
in existence for some time, is now rapidly gaining recognition
in Ireland as an extremely efficient, health-beneficial, cost
effective solution to saving energy. Scandinavian in origin,
the Heat Recovery Ventilation System (HRV), follows the unique
approach to environmentally harmonised living the Scandinavians
are renowned for. The basic function of a Heat Recovery Ventilation
System is to provide a continuous supply of clean, fresh air
throughout the building while at the same time dispensing
heat for cold periods. Technically, a HRV operates as follows:
Firstly,
a single set of ducts accumulates moist, stale air from the
wet areas of the building such as the kitchen, laundry and
bathrooms. This stale contaminated air travels through the
HRV unit and is released outdoors; another ducting system
then takes in fresh clean air from outside. As the two air-streams
bypass within the centre of a non-energy consuming heat transfer
exchanger, heat is displaced (without the air-streams intersecting)
from the emitted stale air to warm the fresh incoming air.
As the two air-streams remain separate, no contamination occurs.
Finally, the HRV unit succeeds in retaining up to 95% of the
energy from the exhausted warm, stale air. This allows clean,
filtered air to be distributed throughout the building –
where and when needed. The majority of Heat Recovery Ventilation
systems are also supplied with automatic humidity sensors
that are able to augment the rate of ventilation when required,
such as when a shower or bath is in use.
As
well as entire building systems, Heat Recovery Ventilation
systems also come as room units. Such units provide similar
rates of air exchange to conventional fans, making them an
attractive alternative as a result of their ability to provide
extract and supply. The systems are most suitably installed
in areas of high humidity, such as kitchens or bathrooms.
In
contrast to conventional ventilation systems, a HRV is well
advanced to offer year round comfort in the building, as while
also drawing fresh air in it serves the dual purpose of keeping
the living areas at a warm, constant temperature. More than
35% of heat loss in today’s homes can be attributed
to ventilation, as where high-quality conventional systems
are well equipped to handle the procedure of air exchange
they tend to create an uncomfortably cold living environment
in the process. This ultimately means that energy that might
have been wasted in re-heating a naturally ventilated building
can be saved with a HRV.
An
advanced Heat Recovery Ventilation System may be in constant
operation for as long as six months of the year (or more)
and run at a lower annual cost than a natural ventilation
system. It will also be capable of converting all the air
in an average sized building over a three-hour period. Present
Building Research Establishment (BRE) standards in the UK
advocate an ideal ventilation rate of between 0.5 and 1.5
air changes per hour. Countries such as Sweden, with extensive
expertise in the area of controlled ventilation lean towards
a level at the lower end of the range - The Swedish standard
stipulates 0.5 air changes per hour, as do the Canadian and
German (DIN) standards.
From
a structural perspective, a lack of quality ventilation can
be extremely destructive. The most obvious sign of poor ventilation
is condensation, which is most commonly visible on cold surfaces
such as windows. However, condensation can also occur in other
vital constituents of a building, such as masonry or timber.
Here moisture is easily absorbed, and with continued accumulation
problems such as rot, mould, and deterioration of decoration
are likely to result. A HRV will combat this problem by completely
drying out the actual framing, insulation and interior cladding
of the structure. The system will also dry out damp furniture,
curtains and carpets.
As
a result of a HRV’s ability to keep a building dry and
air filtrated, the inhabitants can also be kept healthy. A
Heat Recovery Ventilation system will alleviate the symptoms
of asthma, cold, hay-fever and other allergy sufferers by
removing airborne pollution and irritants such as chemical
gases that leech from building materials used in construction,
paint odours, dust, dust-mites, and pet hair. A HRV will also
extract smoke and cooking odours.
Recent
surveys by the DETR (Department of the Environment, Transport
and the Regions) and The Building Research Establishment in
Britain have discovered that 1 in 10 homes have CO (carbon
monoxide) levels above World Health Organisation guidelines.
Carbon monoxide is a highly toxic gas, which if left undetected
can lead to death or serious illness. As has recently been
document in the press, carbon monoxide poses a great risk
in Ireland, and the gas, which leaks from faulty central heating
systems, boilers, and other gas fuelled appliances is a danger
that must be addressed. Due to a HRV’s ability to remove
gases from buildings, the potential for CO poisoning to the
occupants will be greatly reduced upon installation.
Installing
a Heat Recovery Ventilation System will also lead to improved
security and noise reduction, as well as aesthetic enhancement.
There will no longer be a need to relentlessly open windows,
nor will there be a requirement for distasteful grills and
fans on the internal and external walls.
The
installation of a HRV is easy and involves minimum maintenance.
Upon selecting a system it is advised that the volume of the
building be estimated, as this will establish the amount of
air to be ventilated and consequently the size of system that
is needed; the type of property must then be considered. A
typical two storey Irish home may need to be visited by a
specialist, whereas a single storey structure will be simple
to ascertain. In the case of new build, specialists can be
consulted by architects to decide the best option.
Today,
as market interest increases and technology advances, the
quality of HRV’s is constantly improving. Where old
systems operated at an approximate 65% efficiency, new systems
are able to function with an efficiency of up to 95%, therefore
retaining almost all heat generated inside the building and
maintaining a very comfortable indoor environment.
Installing
a Heat Recovery Ventilation system will not only save money
on electricity bills and improve the health and comfort of
a building’s occupants, it will also play a vital role
in protecting valuable energy resources for generations to
come. |
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