[GBlist] To superinsulate or not

[Jeff Chapman <jchapman@ctelco.net>]

I'm building a house for myself and my family in a moderately cold climate
-- the Front Range of Colorado.  The house will be passive solar to the
greatest degree possible and built of conventional materials.  The advice
I've gotten thus far is split about fifty-fifty on whether to go with more
than R-19 in the walls.  I intend to insulate the roof to a minimum of R-40
and where there are framed floors over a crawl space, I can get a lot of
insulation in these as well since I'm using 14" TJIs for joists.  There is
a sun space on the south side that will have a masonry floor for thermal
mass.

Some people are of the opinion that putting my efforts into reducing air
leakage is better than trying to get more insulation in the walls.  Others
definitely advocate higher R-value and eliminating the thermal bridging
caused by the framing.  I'd like to do 2x6s on two foot centers, and I'm
debating whether to add a layer of rigid foam on the inside or outside of
the stud walls.  It seems to add significant complications  either
way.  Another less appealing option is a double 2x4 stud wall in which case
I'd want to go 16" centers at least for the outside wall.  I've all but
eliminated the possibility of using SIPs unless I hear a more convincing
argument for them than I have thus far.

Has anyone got any thoughts on this subject?  Thanks for your help.


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