The SIP
problem in Alaska has shown us another example with strong evidence that vapor
barriers on the interior side of a heated space (in cold climates) can be
critical. I take it painted gypsum
board (drywall) did not provide a sufficient vapor barrier in the houses
mentioned. This also suggests
SIP’s with their foam insulation core did not provide sufficient vapor barrier
due in part to the potential for insufficiently sealed seams and joints between
panels. Complete sealing and the
installation of a vapor barrier is recommended among other things.
Now how
many heating-degree-days does it take to have a cold climate; 3000, 4000,
7,000, 9000? Scott mentioned a
delta T of 40-50 degrees. In North
America, that probably equates roughly to anything north of Memphis TN. Our
delta T in St. Louis MO was about 60 a few nights ago.
Cheers,
Ralph
Bicknese
-----
Original
Message-----
From: Scott Waterman
[mailto:swaterma@AHFC.STATE.AK.US]
Sent: Wednesday, February 27, 2002
9:37 AM
To: BrunoM1@yucom.be;
ScottS@bumgardnerseattle.com; chris@koehn.com
Subject:
Greetings...
I have had problems
posting to the list, so I will reply to you who were interested.
I have seen some of
these houses, have a cd full of pictures, and have talked a lot to
some of the people involved. It seems that the problems are a result of several
factors, not the least of which involves following the manufacturer's specs.
Several of these homes with failed roofs were done by their respective
manufacturer in training local builders on how to use their product. Others
were homes owned and lived in by the builders or their manufacturer reps. So I
think it is not strictly an installation issue. Most of the manufacturers have
said that no vapor retarder is needed. BZZZZZT! In a cold climate with a 40-50
degree delta T and high humidity levels, the latex condom idea is only safe
practice.
BTW... many of these
homes have HRV's that are in good working order and are used.
If SIPS are to be used
in wet, cold, climates, manufacturers instructions must be exceeded. A vapor
retarder is required. All seems need to be sealed. Foams with longer cure
times must be used for spline sealing. The cost for replacing these roofs
is huge, $60 to 120K per house, and we have over 120 homes with these problems
noted. Insurers are backing off paying for claims, and the manufacturers are
running. Not a great situation, particularly for the homeowners and builders
who were promised this technology would work.
Just my $.02
Scott Waterman, Energy
programs coordinator, Alaska Housing Finance Corp.
