One of the throw-away notes you will sometimes see on construction drawings is, “seal gaps & cracks.”
This simple statement is meant to cover a range of air infiltration/leakage issues in the building fabric. It has been condensed to this simple statement because it is assumed that these air infiltration issues are dealt with as part of ‘good construction’ practice. For this reason, the sealing of gaps and cracks is not part of house energy ratings, (thermal performance assessments).
The assumption that the sealing of gaps and cracks is dealt with as a matter of course is a major problem. It is a problem because most of the time it is NOT dealt with and most building practitioners and energy assessors are unaware of the basic requirements.
Ceiling insulation installed with 5% gaps can cause a 50% reduction in thermal effectiveness. Ineffective sealing of windows, doors, roof lights exhaust fans etc. can also lead to excessive air leakage. This drastically reduces the efficacy of the building’s thermal envelope and causes a greater heating/cooling load than technically necessary, hence higher power bills.
As a part of our energy reports we include National Construction Code Part 3.12.3 – Building Sealing. This part of the code addresses all items of potential air leakage. By addressing air leakage and providing recommendations in report form there is less likelihood that this important component of energy efficiency is overlooked. Properly dealing with ‘gaps & cracks’ during construction will ensure that all insulation and energy efficient measures perform to their full potential.