[Greenbuilding] Residing a home in Minnesota

[Laren]

Hello Bob;

  Be careful of sugestions you read.  Since you have a
continuous vapor barrier on the interior side of your walls,
DO NOT PUT A VAPOR BARRIER ON THE EXTERIOR
SIDE.     In other words, do not wrap the house in a non-
permeable foam (as seems to have been suggested in an
earlier post).      That would trap moisture inside the walls,
and could turn them into mold farms. It could destroy your
house, and also make you very sick. The only kind of foam
that could be used, would a breathable foam, such as EPS
(Expanded PolyStyrene) which is the assembled beads,
like in the white blocks used in packaging.    DO NOT USE
A CLOSED CELL EXTERIOR FOAM SHEATHING WITH
YOUR INTERIOR VAPOR BARRIER.    Since your walls
(because of the vapor barrier) will not allow moisture to
dry to the interior, it must be allowed to dry to the exterior.

  In your very cold climate, having an interior vapor barrier is
not a terrible thing, and further north it may be recommended.
Your heating season is long enough that isolating interior gen-
-erated moisture from the walls can be an effective strategy
However, there must be a VAPOR BARRIER ON ONLY ONE
SIDE OF A WALL. So, since you already have  a vapor barrier
on the interior side, and you only need to resurface the exterior
side, you need to take care to not create/install one on the
exterior side.

  Use a vapor permeable air barrier (house wrap) under your
siding, to seal your walls from air leaks, while allowing moisture/
/vapor (but not water) to still pass through.    With an air space
(most likely provided by the siding mounting system) this can
also function to allow any wind driven water//rain, to drip to the
bottom, behind the siding, then outside. Take care to seal all
the edges of your house wrap. Tape it around openings, like
doors and windows. It is possible to air seal the walls fairly
well, this way, but you should also check for air leakage, on
the interior side, next Winter. Fiberglass insulation will allow
air to easily pass. Check electrical outlets, and install foam
insulators. Check the base of the walls, and if you find cold
air coming in, remove the moldings and caulk. If you have
a basement, spray foam is a good way to seal and insulate
band joists, since you will not have a non-permeable foam
on the exterior.  If you heat the basement, don't leave it
uninsulated.

     With a house of tha era, the sheathing is bound to be
4x8 sheets, so blowing cellulose into the walls would not
make a lot of difference.    But, you will want to check the
attic, and if you install it yourself (free blower from a big
box store) you could go with 16-20" of cellulose     Just
make sure to baffle the soffit vents, so they do not get
blocked.   Check your windows and doors for leakage.
It may be worthwhile to remove the casings and fill
around them with a window/door type foam. After 35
years, weather stripping may also be worn and leaky.

  Also check the efficiencies of your furnace and water
heater.  It may be cost effective to replace them, especially
since they are probably already getting old. Check your bath
and kitchen vents. They may be promoting a lot of air leakage.
It is extremely unlikely that you will ever seal that rambling
1980s house to anywhere near needing to promote ventilation,
so focus on sealing virtually every leak you can find.

-Laren Corie-
Design and consultation for energy efficient homes, since 1975
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