​Common sources of air leakage, Part 2

Attics, continued:  Quite often, the greatest source of air leakage and energy loss in homes is the attic.  These are some additional ways that conditioned air can leak from the home into the attic:
 
5.  Chases for plumbing, electric, HVAC, etc.  

• These must be completely sealed. 

• Conduits must be sealed between the conduit and the framing as well as blocking air flow through the conduit
• When a chase is intended for future use, a temporary closure can be used. 
• Chases will require an air closure after all items are routed through the chase.
• Air flow inside the chase can often be stopped from the lower level or the attic.

6.  Attic hatches and pull-down stairs.

• Attic hatches and stairs should have a tightly-fitting, insulated cover.  A couple of 2" layers of solid foam attached to a board work well for an attic hatch.  Weather stripping creates a tight seal.

7.  HVAC and ventilation fan ductwork.

• All connections should be taped or sealed with mastic.  Zip ties alone are not sufficient to stop air leakage.
• Ventilation ductwork should have an effective damper.  Most built-in dampers are quite leaky.  Effective in-line dampers can be used to limit backdrafting.

8.  Attic walls (knee walls) between conditioned and unconditioned space.  Air flow must be prevented both through and underneath the wall.

• Blocking must installed between trusses or floor joists, extending to the ceiling drywall below.  Sealant must be complete around ductwork, pipes and other penetrations to this under floor space.

9.  Bonus rooms.  Truss packages which lack bottom plates leave a gap between the drywall and the floor sheathing.

• Blocking must be installed to prevent this gap.

 
Doors & Windows:  While potentially leaky, doors and windows are surprisingly easy to deal with in a new home.
1.  Gaps between framing and doors & windows.

• For a complete air barrier, sealant should continue across shims.  A combination of foam and caulk may be helpful.

Note the gaps around the shims which are not air sealed. Foam does not appear to continue above the frame, although it may be caulked.

​2.  Installation must be level and square.  Any doors or windows which do not open and shut properly can often be instances of poor installation.  Not only are these difficult to operate, they do not seal as well as the manufacturer intended.
3.  Gaps under doors.

• Caulk is often skipped or poorly executed under exterior doors.

4.  Doors to interior unconditioned space.  These may include doors to the garage, attic storage, mechanical rooms, basements.

• Doors must provide a complete seal.  It is all too common to find interior doors with large gaps being used at the entrance to an unconditioned basement.
• Door frames must be foamed and sealed to the framing, similar to an exterior door.

 
Thanks for reading.  We'll have more suggestions in Part 3.