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A
recent study instigated by the American Environmental Protection
Agency has identified indoor air quality as one of the top
five urgent environmental risks to public health. The problem
of indoor air pollution is largely avoidable through the implementation
of sufficient ventilation, yet many of us choose to ignore
the seriousness of the issue, and fall short of the requirements
of Part F1 of the building regulations, taking heed only when
visible structural problems such as moisture and damp arise.
However, given the increasing onus on human health, as manifested
in Minister for Health Micheal Martin’s imminent ban
on smoking in pubs, there is mounting pressure on the construction
industry to deliver buildings with a sound interior air quality
that does not pose a threat to the health of occupants. The
implications of poor ventilation are potentially life threatening
and can result in fatal asthma or lung cancer.
Health
Implications
It is hardly surprising that, as a people who spend up to
90% of our time indoors Irish people are almost constantly
exposed to some form of indoor pollutant. Naturally occurring
pollutants such as dust mites, fungus and mould thrive in
Ireland, and rapidly occur when there is dampness in a structure
and a relative humidity of or in excess of 70%. Something
as essential as breathing, and everyday functions such as
cooking, bathing, dishwashing, washing and drying clothes,
and heating buildings, can create up to 5 Kg of moisture per
day independently adding to an already humid indoor environment.
Health problems such as eye and throat allergies, asthma,
headaches, tiredness, coughing, wheezing, and even mental
confusion can result from cases of high humidity, and are
also triggered by unventilated residue, emanating from pets,
dusty window coverings, bed linen, cigarette smoke, pollen,
mouldy plant soil, and firewood (which can generate problematic
mould spores when damp). Furthermore, chemical sources of
indoor pollution, as can be found in many building materials,
paints, varnishes, electronic equipment, photocopiers and
printers, cleaning fluids, and polishes commonly cause headaches,
breathing problems and allergies, and can even prove fatal
at extreme levels.
Radon gas is perhaps one of the most dangerous indoor pollutants,
as it is colourless and odourless, making it impossible to
detect without the intervention of experts. Radon occurs naturally,
and is emitted through ground cracks beneath a building. If
left undetected it is possible that the radon will reach levels
well in excess of the legally permitted levels (400 BQ.M3
for the work place, 200 BQ.M3 for the general public), in
which case the likelihood of contracting lung cancer will
be dramatically increased. Radon can occur anywhere, and as
such all buildings should take appropriate precautions. Ventilation
fixed to expel the gas at ground level, in conjunction with
effective floor sealing can effectively combat the problem.
From a health perspective the main objective of ventilation,
is to keep the level of pollutants in buildings at an acceptably
low level. Through employing the correct ventilation techniques
it is possible to drastically reduce building related illnesses
and provide a healthy interior environment.
While the health of occupants should be an essential requirement
of a building, this should be allied with evaluating the structural
elements and ensuring the stability of the structure. The
impact of poor ventilation on a structure is likely to cause
considerable damage over time, leading to problems such as
excessive moisture, damp stains, smoke stains on structural
surfaces, build up of dirt, condensation and deterioration
of décor. Though the results of some of these problems
may initially seem only superficially detrimental, the long
term effects can cause serious problems. It is costly to repair
damage caused directly as a result of poor ventilation and
it can be dangerous to leave the problem untreated. Structures
under the pressures of poor ventilation are prone to weakening
and can prove unsafe as surfaces eventually rot and dilapidate.
Indeed, the increasing stress on high insulation standards
in virtually all types of building places a growing emphasis
on proper ventilation. The benefits of seeking advice from
experts cannot be understated, given the various criteria
buildings are obliged to fulfil. In this regard, the most
efficient and effective ventilation system, to suit the needs
of a particular building, should be installed. It is also
important to keep timber floors well ventilated, as this will
prevent dampness and reduce energy consumption caused by irregular
airflow. Loft ventilation and ventilation for appliances are
also essential. Loft ventilation serves to diminish moisture
build up in the ceiling, whilst the ventilation of appliances
such as gas cookers and paraffin heaters prevents the release
of dangerous gases into a structure’s habitable environment.
The
Regulations
The current building regulations for ventilation, Part F1,
stresses that the main functions of a ventilation system on
a general level should:
‘provide an adequate supply of fresh air for using an
area or building; achieve occasional rapid ventilation for
dilution of pollutants and of moisture likely to produce condensation
in habitable rooms, kitchens and rooms containing sanitary
appliances; and extract moisture from areas such as kitchens
and bathrooms, where it is produced in significant quantities’.
The
Systems
When selecting a ventilation system best suited to an individual
structure there are many options to consider. Natural ventilation
includes systems such as trickle ventilation, passive stack
ventilation (PSV), fan assisted and wind tower ventilators.
The simplest form of natural ventilation is to open a window.
However this is generally only suitably effective when combined
with a ventilation system. Mechanical ventilation systems
typically installed in poorly ventilated Irish buildings include
mechanical extract systems, mechanical supply systems, and
mechanical ventilation systems with heat recovery (MVHR).
Additional dehumidifying systems are also often installed
to prevent the build up of moisture in a structure and control
humidity levels.
Natural ventilation is dependent upon temperature levels and
wind pressure in order to operate efficiently, as air is required
to circulate through the ventilated structure. The most basic
form of natural ventilation; opening windows, helps to banish
odours from rooms such as kitchens and bathrooms, and can
provide comfort during warm summer days, through a constant
flow of fresh air. The most effective way of keeping timber
frame buildings cool in summer is to leave windows closed
during the day and open at night.
Trickle ventilation is most commonly used to prevent condensation
and reduce humidity. The system is simply a series of small
openings set into a window frame in order to provide permanent
air flow and wind pressure regulation. Trickle ventilation
systems are best installed in all habitable rooms of a building
and can also be fitted to wet rooms as an alternative to another
form of ventilation such as PSV.
Passive Stack Ventilation (PSV) is an effective system used
to extract moisture and control humidity in kitchens and bathrooms,
through the reliance on a sufficient air supply from another
source. PSV is particularly attractive from an environmentally
conscious point of view as it is simple and energy efficient
when correctly installed.
Fan assisted PSV differs from PSV only in that a low powered
fan of approximately 40W is added to enable the general system
to run on a site where its performance would otherwise be
restricted.
Wind tower ventilators, another natural ventilation system,
function in a similar way to the general PSV system. They
differ in that they tend to be of a larger size, and possess
an altered internal mechanism. Wind tower ventilators do not
rely specifically on an alternative source of air supply and
are typically installed in small open structures such as public
halls.
Mechanical Extract Systems are the most basic of the mechanical
ventilation systems and provide practical ventilation whenever
needed. These systems are best suited to wet areas that lack
opening windows, such as kitchens, bathrooms and WCs.
They extract odours and moisture and are popular due to being
reasonably energy efficient and having a long lifespan in
comparison with traditional fans.
In contrast to typical extract systems, mechanical supply
systems work to deliver ventilation through the release of
air taken from an uninhabited area of a structure. These systems
are often used in existing buildings that suffer from condensation
and are low in power usage, which ultimately makes these systems
effective and energy efficient.
Finally, mechanical ventilation systems with heat recovery
(MVHR) differ from the other mechanical systems in that they
are able to reclaim heat that would otherwise be lost through
the ventilation. MVHRs ‘extract’ heat from wet
rooms and ‘supply’ it to dry rooms. They control
humidity, and can be installed as a system for an entire building
or instead as individual room units. MVHRs are extremely effective,
especially during winter months, and can run continuously
for periods exceeding six months.
It is valuable that the consumer talks to an expert prior
to the installation of a system, in order to make the most
of the system and conserve energy. Good ventilation is a fundamental
requirement for a building to be fit for occupation, and can
play a vital role in securing the health of occupants, the
structure, and ultimately the value of a building.
Further
Reading: the Green Building Handbook, Volumes 1 & 2, edited
by Tom Woolley, Sam Kimmins et al, published by Spon Press.
Available at www.sponpress.com
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