One of the primary concerns when building new homes today is energy efficiency. This can be achieved by using many different techniques, including making them more airtight. This can bring some benefits but it can also cause problems with air quality. Airtight homes still need to be able to breathe, which means installing adequate ventilation.
There’s no doubting that families, and society as a whole, can benefit from more energy-efficient homes. Greener houses can be carbon neutral or produce lower carbon footprints, which is better for the environment. Recent government data revealed that housing accounts for almost 30% of the UK’s total energy use, meaning that any reduction can have a major impact on a nationwide scale.
Energy Performance Certificate data showed that 84.4% of new-builds have the top A or B energy-efficiency rating, compared to 2.2% of existing properties. As a result of this increased energy efficiency, the owners of new-builds were spending an average of £443.30 a year on their energy bills. This was well under half of the £1,072 that the average owner of an older home was spending.
Energy efficiency can be improved by upgrading air-tightness, as well as using better insulation, double glazing filled with argon gas (which lets the sun in but reduces heat loss), and modern building materials.
Stewart Baseley, executive chairman of the Home Builders Federation (HBF) said, “Today’s new homes are significantly more energy efficient than their predecessors, delivering huge benefits both for their owners and the environment. Owners are saving hundreds of pounds a year in energy bills due to the modern design of their homes and the materials used to construct them.”
No regular home is completely airtight, but modern building design and construction reduces the rate of air exchange between the indoor and outdoor environments. This can help cut draughts and the heat loss that can occur as warm air seeps out and colder air comes in. It can also mean that pollutants in your home have nowhere to go and can build up to unpleasant, or even dangerous, levels.
Glasgow School of Art’s Mackintosh Environmental Architecture Research Unit (Mearu) studied 200 modern homes that had been designed to be airtight. It found “widespread evidence of poor ventilation, with bedrooms being a particular problem”.
Professor Tim Sharpe, head of Mearu, said, “Poor indoor air quality is hard for people to detect. There are clear links between poor ventilation and ill health, so people need to be aware of the build-up of CO2 and other pollutants in their homes, and their potential impact on health.
“Modern homes are increasingly airtight and can also contain a great number of pollutants and chemicals, many of which can have serious health effects.” He added that people with chronic obstructive pulmonary disease and asthma were at particular risk from poor indoor air quality.
By definition, a relatively airtight home has very little in the way of natural ventilation. This is ventilation that relies on natural movements of air, usually through fixed vents, adjustable ‘trickle vents’ or air bricks. Even in an airtight house, you can improve natural ventilation by opening a door or window but this is not an ideal solution. Air transfer can remain slow on a still day, it can be problematic if it is cold or wet outside, and it’s not advisable to leave your doors or windows open when you leave the house.
Mechanical ventilation is a better solution for airtight homes. This ranges from extractor fans fitted in specific rooms, such as kitchens and bathrooms, to whole house ventilation. Balanced ventilation systems gently extract old, stale air out of the house while drawing in fresh, filtered air from outside.
The best solution for ventilating an airtight, energy-efficient home is a Mechanical Ventilation with Heat Recovery (MVHR). This passes the outgoing stream of air through a heat exchange unit. This extracts a large proportion of heat from the air and transfers it into the incoming air. It can help to improve your energy efficiency, which is the point of more airtight home designs in the first place.
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