As buildings have become better insulated, the amount of heat they lose has fallen dramatically – this is true even for dwellings that are constructed to the minimum standards of the Building Regulations.
What this means, in turn, is that the proportion of heat that’s lost through uncontrolled air leakage has become relatively higher. So for all self-builders who want to be energy efficient, airtightness merits close attention.
This reflects a key issue in construction: namely that many modern houses do not perform as well as they are designed to do. This is known as the performance gap, and poor airtightness is one of the major causes.
How & where buildings leak air
Most people think of air leakage in terms of the wind blowing into our houses. While this is partly true, in reality the situation is more complex.
Wind creates zones of positive and negative pressure around our homes, which both pushes air in and sucks air out. In addition, as we all know, heat rises and this can also generate positive and negative pressure zones within a building.
Air leakage occurs mainly at the junctions between different elements of the building and particularly between materials. Some components are naturally airtight, while others need to have an additional layer applied to achieve the desired performance.
Any open chimneys or ventilation bricks are of course free air passages to the exterior. Leakage also occurs through penetrations – a typical example would be from services, such as drainage pipes and cables – and even from light fittings if the airtight layer is on the inside of the structure.
What about ventilation?
We all need fresh air to breathe, of course, as well as to push unwanted toxins and odours out of the house. A completely airtight building would not be healthy and in fact would contravene the Building Regulations (Approved Document F), which sets out a minimum air change rate of 0.5ACH@50Pa.
The post Eco Homes: How to Make Your House Airtight appeared first on Build It.
Article reference Eco Homes: How to Make Your House Airtight
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