Common sources of air leakage, Part 1

​Many builders we work with are looking for ways to improve the infiltration scores on the homes they build.  In 2022, Pennsylvania building codes have begun to require an infiltration score of 3.0 ACH50 or less.  Some homes under construction have been permitted under the previous standard of 5.0 ACH50, but we will soon see all homes needing to meet the more stringent requirement.  In this series we will focus on types of air leakage common to most new homes.
 
Attics:  Quite often, the greatest source of air leakage and energy loss in homes is the attic.  The following are places that conditioned air can leak from the home into the attic. 
 
1.  Poor quality seal packages.  

• Ensure that all rough HVAC, electric and plumbing is 100% complete before the insulation seal package is done.  It is common for contractors to add "forgotten" items after the insulating work is done.
• Consider keeping attic sealing work in house.  In other words, have your lead carpenter do the work.  Insulation contractors typically do not have the attention to detail, nor the motivation to do this well.  At a minimum, builders could require an inspection of the air seal package before insulation is blown into the ceiling.

 
2.  Joints between the top plates and drywall on both interior and exterior walls.

• All joints should be sealed. 

Close inspection will reveal that the foam is incomplete at the ends.

3.  Penetrations through the top plates for electrical wires, pipes, etc.

• Wire penetrations are often inadequately sealed.  Sealant must completely surround the wire.

Foam does not appear to completely surround the wire at the left.

​4.  Penetrations through the drywall:  Electrical boxes, recessed can lights, smoke detectors, fire sprinklers, HVAC registers, ventilation fans, etc.

• An electrical box will leak between the box and the drywall as well as through the wiring holes.  These can be effectively sealed by foaming completely over the box.
• Recessed lighting fixtures should be ICAT labeled and gasketed.
• HVAC register boots must be sealed to the drywall.  This is a code requirement as well as helping to pass infiltration and duct tests. 

​We hope you found this information helpful.   Additional sources of leakage to the home will be discussed in future posts.