28 air conditioning & ventilation
A breath of fresh air for new homes
Peter Haynes, product manager at EnviroVent, weighs up different options on ventilation for creating a healthy living environment in new homes.
indoor air pollution may have been a contribut- ing factor in the death of almost 100,000 individuals across Europe over the course of 2012. The report directly refers to the impact of indoor air quality on the health of people and how poor indoor air quality can lead to prema- ture death. Both organisations have called for greater understanding and for governments to look into the risks of poor indoor air quality resulting from contaminants, and how this is being exacerbated by increased levels of air tight- ness in homes. The report also highlighted that poor indoor air quality can also impact the health and intelligence of young children, thus impair- ing their future growth and development. With dust mites, mould and condensation also
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contributing to the mix, there are rising concerns around health problems, due to buildings being too well sealed. The question is, as homes become increasingly airtight, how can the indus- try create a healthy indoor environment for homeowners?
Air quality in new homes
Without a continuous flow of fresh air into and out of a dwelling to control the relative humidity, the indoor environment in a home can easily reach a high relative humidity of around 70-80 per cent, which results in condensation. The water droplets that form on colder surfaces can result in mould growth and, in some cases, damage to the building fabric itself. Not only does mould look unsightly, it can also be the root cause of some health issues. Damp con- ditions, for example, increase the risk of occupants developing, or exacerbating, existing respiratory conditions.
respond online at
www.hbdonline.co.uk A recent study by Professor Hazim Awbi at the
University of Reading, ‘The Future of Indoor air quality in UK homes and its impact on health’ has predicted a 80 per cent increase in asthma sufferers by 2050. Awhe reports is largely due to homes being upgraded to make them more ther- mally efficient. In the study Professor Awbi states: “Poor
indoor air quality is associated with a range of undesirable health effects, such as allergic and asthmatic symptoms, lung cancer, chronic obstructive pulmonary disease, airborne respira- tory infections and cardiovascular disease.”
recent report by the Royal College of Physicians and the Royal College of Paediatrics and Child Health stated that
Asthma affects five million people in the UK
every year. One of the ways asthma is triggered is through household dust mites and their airborne detritus, which flourish in damp, mouldy conditions. These dust mites thrive in homes that don’t have adequate ventilation, where relative humidity is high. When their detritus comes into contact with the skin or is inhaled, it can cause allergic reactions, resulting in asthma attacks, eczema, watering eyes, itching, sneezing and a runny nose.
“Without a continuous flow of fresh air into and out of a dwelling to control the relative humidity, the indoor environment in a home can easily reach a high relative humidity of around 70-80 per cent, which then leads to condensation”
It is essential therefore that effective ventila-
tion systems are incorporated within new homes and homeowners are informed about how they work and why they are essential for a healthy indoor environment.
Harmonising air tightness with effective ventilation
Understandably, concerns have been raised by the new build sector about how to harmonise the need for air tightness (Part L) with requirements for ventilation (Part F). To achieve Part F requirements, the most
favourable options are arguably either mechani- cal ventilation with heat recovery (MVHR) or positive input ventilation (PIV). PIV systems work by drawing in fresh, filtered,
clean air from outside and gently ventilating the home from a central position usually in the loft, above a landing in a house, or a central hallway in a flat or bungalow. They dilute moisture laden air, displacing it and replacing it to control humidity levels between 45 and 60 per cent. The requirement for new dwellings to
improve performance by an extra 7 per cent to meet the 2013 edition of Part L1A (energy effi- ciency for new building), further reinforced the prominence of PIV systems, which can give sav- ings on the Dwelling Emission Rate (DER). Where housebuilders are looking to build to
greater levels of air tightness (of 3ach@50Pa or below) MVHR is often specified to achieve a larger percentage reduction between the DER and TER (Target Emission Rate). A high per- forming MVHR system through SAP (Standard
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