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Over the past few years, insulating
a home has become quite a science and many homeowners
are choosing to insulate with foam. This has become
a specialty at R-Tech and we have discovered a few
techniques that can improve the R-value of a home.
A foam insulated house can be even tighter by paying attention to details.
For instance, the home can be framed a little differently.
Other common leakage spots are cathedral ceilings with doubled up 2x12s
or I joists that are not sealed at the time of installation.
Windows are another area where air leaks can occur.
We encourage a 1/2" tolerance
around all of the windows. That way our foam guns are able to reach all
the way to the exterior wall. A lot of the time it is less than 1/4".
At this point, we can only seal it, but cold air continues to travel
all the way to the inside of the jam. This makes for a condensation
point, especially on vinyl windows.
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Wrapping the home in
Tyvek is also a concern. In some cases, the Tyvek
is wrapped all the way around window and door cripples.
We recommend that the top and sides go on the outside
of the nailing strip. The bottom should wrap in one
inch.
The purpose of this is to allow the first bead of foam to attach to the Tyvek.
The second run of foam attaches to the sill plate and to the window jam. I would also like to talk about using one inch of
foam board instead of oxboard on exterior walls. Twenty
five percent of exterior walls are stud framing. This
one inch of foam board gives a nice thermal break over
the studs. It also provides a drainage plain for water
on high driving storm days. This eliminates the need
for Tyvek. The two-pound foam gives the house the structural
strength it needs. The one inch of foam board is also
semipermeable, so any moisture through dew point that
gets in, can
get out. 
The
one question that most people raise is about the
structural integrity of the home. One inch
foam with a two-pound foam board is plenty to
give
the home strength. The best feature is the insulation factor. An
extra R-5 is added over all studs and headers.
A final detail involves the framing of windows and doors. Using 2x4s
and 2x6s in conjunction allows us to foam up and over any seams and
increase
the R-value on any seams.
These are some of the ideas that I used on
my own house. It is 3,300 square feet and as of December 31, I had
spent only $166 on heating this
year. I believe our house will last for years and years without the
worry of mold or rot.
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