Last month we spoke about hot-humid climates.
This month we will focus on the challenges of building
in a cold climate. It is important to control for
water, air and heat. Many areas need to be considered
in order to create a design that works for cold
climate areas:
1. Rain water infiltration is the largest source
of material deterioration in buildings. The exterior's
primary plane of water shedding (cladding, shingles,
metal roofing, etc) is not necessarily completely
watertight. A secondary drainage plane (usually
a housewrap or taped insulating sheathing) is installed
behind the main exterior water shedding surface.
This drainage plane in combination with flashing
details allow any water that may penetrate through
the exterior water shedding plane to drain back
out to the exterior.
2. Air leakage is the second most common mechanism
for depositing moisture in wall assemblies. In order
to control air leakage, a continuous plane of air
seal must be created. This air seal must be continuous
not only for each building assembly, but at the
connection between adjoining building assemblies.
3. The overhangs from the roof are designed to extend
a minimum of 12 inches from the exterior wall. This
amount of overhang will provide some protection
for the wall elements such as windows and doors
that are traditionally common sources of water leakage.
4. Use vented cathedral ceilings and attics that
are air-tight with the use of gypsum board and sealants.
5. Increase insulation with minimum R-21 in the
walls with wood studs at 24" o.c. plus R-5 sheathing
for the exterior. For the roof, use R-38 in the
attic and R-35 in the cathedral ceiling.
6. HVAC must be properly sized and high efficient.
Look for the highest SEER rating.
7. Install a bead of non-expanding urethane foam
between the window frame and the rough opening on
all four sides of the window. 8. Ducts should be
placed in conditioned spaces. Grilles should be
placed high on the wall to avoid being blocked by
furniture in bedrooms and low on the walls in hallways.
This will help create a even distribution.
9. Conditioned basement or crawlspaces should be
used to keep the living space more comfortable.
Read on find out about a design example that works
for a cold climate.
Article © Lisa A. Swan. Picture © buildingscience.com
