[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

GBlist: Polyisoc



Hello,

I am a homeowner currently involved in a fairly extensive retrofit of a
home. I don't know that my question is directly related to green
building practice, but it certainly bears on the health of the structure
and the occupants within.

My house was built in 1965. The house was built without an interior
vapor barrier. The walls are insulated with fiberglass, however the
batts are only 2.5" thick, and they are a low-density fiberglas. Based
on the infomation I've been able to locate, I estimate that the total
insulative value of my walls (including wallboard, sheathing, and
siding) is around R-8 to R-9. Even in our moderate (western Washington
State) climate, this is inadequate insulation. 

My current plan for retrofitting additional insulation consists of
adding 5/8" of high density foil-backed foam (approx. R-4.5) to the
exterior sheathing under the siding. I'd like to add a thicker layer of
foam but that would require extensive changes to the exterior trim,
doors, and windows. The seams between sheets of foam will be taped, and
all the penetrations sealed with expanding foam. The new insulation will
extend from the top plate to the foundation. The interior walls will
receive 2 prime coats of vapor-resistant  paint followed by a top coat
of latex. 

As you might expect, my primary concern is that water will condense
within the wall cavity and either rot the framing or encourage insect
infestation. I've gone to a lot of trouble to try to eliminate sources
of moisture within the house, but even so I recognize that some moisture
is going to find it's way into the walls. I haven't been able to locate
any authoritive information regarding the long-term effects of the type
of retrofit I have planned. Does anyone have experience with this kind
of insulation retrofit, or are you aware of studies that assess this
approach? I will appreciate any information that you can provide.
Thanks.

Regards,
	Glenn Minch
	Redmond, WA  USA
______________________________________________________________________
This greenbuilding dialogue is sponsored by CREST <www.crest.org>
Environmental Building News <www.ebuild.com> and Oikos <www.oikos.com>
For  instructions send  e-mail to  greenbuilding-request@crest.org.
______________________________________________________________________