RE: [GBlist] RE: SIP roofs rot in wet climates

["Mark Bondurant" <rarearth@earthlink.net>]

If a continuous warm-side vapor barrier is mandatory on a SIPS roof, the
builder loses the huge advantage of being able to apply the ceiling and
soffitt (with finishes if desired) before installing the panels.

Would an acceptable alternative be to install the SIPS panels without a
vapor barrier and then install something like 1 inch extruded polystyrene
foam board on top of the panels between perlins running @ 24 inch centers?
(This would be a configuration for a metal roof.) The foam board would
eliminate the exterior OSB as a condensing surface. The purlins would be
used for the metal roof attachment.

What do you think?

Mark Bondurant

>Ralph Bicknese wrote:
> 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.
> 
> 



--- Mark Bondurant
--- rarearth@earthlink.net
--- EarthLink: It's your Internet.



______________________________________________________________________
This greenbuilding dialogue is sponsored by REPP/CREST, creator of
Solstice http://www.crest.org, and BuildingGreen, Inc., publisher of
Environmental Building News and GreenSpec http://www.BuildingGreen.com
______________________________________________________________________