Air leakage is a major cause of energy loss, typically around 20% in older houses
Insulation is nothing without airtightness systems.
Consider a really thermally efficient wall - great, but, if we have holes through the junctions of the wall or worse still, a permeable wall structure, then the thermal effect we are hoping to gain from will be lost to fresh air.
If the building is constructed from a permeable structure such as a lightweight frame then the structure will need to be sealed to prevent air leakage. This can be achieved by using specially designed membranes fixed to the frame.
This will of course only seal the structure of the building, it does not address the problem of air leakage through gaps in the building which have not been designed for example gaps around the window frames. It is important to identify every penetration through the building fabric and to ensure that each penetration has been sealed, this is when being a pedant is an asset.
A common area which creates a problem is the underside of a cold roof, electrical penetrations even through sealed plasterboard can be a problem. Although edge sealed plasterboard is an accepted form of air tightness barrier we have all seen cracks form in plasterboard ceilings which would break the air tightness barrier.
There are two options for providing an air tight membrane in this situation, the first is to use a foil membrane stapled to the underside of the trusses / ceiling joists fix battens to form a service void onto which the plasterboard can be fixed. Alternatively any service wiring or ducting can be located above the foil membrane and brought through the membrane using the wire or ducting collars.
To help achieve this, a full range of products are available from Lowtherm Solutions by Clan to prevent air leakage from a building such as foil membranes which have different levels of SD value (Steam Diffusion) to take account of the varying diffusion requirements around a building. These products include pre-formed corners both internal and external and pre-formed seals to fit around floor joists and other penetrations through the fabric of the building. The DAFA Airstop system guarantees the serviceability of all DAFA products used within a building for a period of 25 years.