[Greenbuilding] air gap in walls

[Stephen Collette]

Hello everyone,

I did an inspection on a house this week that had odour issues. This  
was a new west addition (300 ft2) to the existing farmhouse. It is a  
sunroom with heaps of windows and half a dozen skylights. A sort of  
octagon sunroom. Heated with radiant floor, electric baseboard and  
tied into the homes existing forced air. The house has it's own air  
con as well, and the addition has a self standing wall mounted unit.   
The homeowner complained of a sour smell. The homeowner DID request  
all of those things be installed, as he called himself a britches and  
belt kind of guy.

The builder installed window seats around most of the octagon. He  
spray foamed the walls and cathedral ceilings (3/12 pitch inside and  
out) with Icynene. 4 inches of it.  For the larger window seats, he  
left the rest with just air.

Construction from the outside in-
Mabec wood siding
typar
chipboard
Icynene and 2X6
air gap
poly
drywall

The window seats are about 18 inches. It seems odd to have this air  
gap.  I would have figured filling it with something or put the poly  
closer to the insulation. I'm concerned about moisture issues with  
this build up. I would appreciate any thoughts on this one.

I'm in Lakefield, ON just northeast of Toronto, and considered cold  
climate, despite the global warming thing going on here.

Thanks

Stephen

Stephen Collette B.B.E.C
Principal

Your Healthy House
Indoor Environmental Inspections & Building Consulting
www.yourhealthyhouse.ca
stephen at yourhealthyhouse.ca
705.652.5159