Air Leakage Into Attics

Heated air rises in the winter and moves from the home up into the attic.  It leaks through gaps in the vapour barrier, electrical fixtures and wiring holes along with any attic hatches that are not well sealed.  Look up into your attic in February to see if any frost is present on the underside of the roof sheathing.  If so you have air leakage.  

Often it is only the north or east sides that have the frost present.  The only way to get frost covering most of the sheathing is by air leakage.  This frost eventually melts and is absorbed into the wood sheathing allowing moulds to form until the wood dries.  The cycle repeats the next season allowing the moulds to slowly develop.  The same air leakage is the prime cause of ice dams as well.

There are often only moulds and discolored wood present on the north and east facing parts of the roof sheathing.  This is due to the rapid drying of the south and west sides from the heat of sunlight.

Adding better ventilation from the soffits to the attic and out roof vents will help, however the air leakage needs to be stopped to save energy and stop the frosting completely.  

Paul Battle / The House Doc specializes in the treatment for moulds in attics and in air sealing to stop any more returning. 

613-297-2996  paul@thehousedoc.ca 

© The House Doc 2011