[Greenbuilding] Insulating shallow crawl spaces

Alan Abrams alan at abramsdesignbuild.com
Fri Apr 13 09:42:01 CDT 2012


<I have a deep energy retrofit project on an old framed house where there
was no excavation for the crawls space.  The result is that the front,
downhill side of the house has adequate room for installing insulation.
However, much of the house has less (18”-24”).  The floor condition is good
enough that we are not considering removing the floor.  The room height is
insufficient to consider adding insulation to the top of the floor.  How do
I insulate the floor. >

we have insulated many floors over 18" (code minimum) crawlspaces from
underneath.  so why not go with foil faced polyiso panels on the inside of
the crawlspace walls; a 15 mil vapor barrier on the subgrade, lapped up the
walls and sealed to the mudsills; foam or caulk bandboards and intersecting
joists; fill joist cavities with full depth mineral fiber batts, install
foil faced polyiso panels on the underside of the joists; tape those joints
and tape to the VB.

note-a strick interpretation of the code says to install a thermal barrier
over the foam...though this is almost univerally ignored, even by
inspectors.  all that might depend on the accessibility of the crawl, and
whether there is mechanical equipment present.  consult the relevent legacy
reports and your local official...

-a


*Alan Abrams**
Abrams Design Build LLC*
*A sustainable approach to beautiful space*

6411 Orchard Avenue Suite 102
Takoma Park, MD 20912
office  301-270-NET- ZERO (301-270-6380)
fax      301-270-1466
cell     202-437-8583
alan at abramsdesignbuild.com
www.abramsdesignbuild.com
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