Roofing
| Final grade | Soffit
and fascia | Electrical
and gas laterals | >>House
wrap | Masonry | Stucco
| Siding | Exterior
concrete | Exterior
paint | Foundation
parging
Modern house wrap has been popular in residential
construction since the mid-1980's. Before house wrap
was developed, building felt was used extensively
to protect the structure. The job of house wrap is
to keep moisture from soaking into the structure but
to allow water vapor to exit. They also serve a second
purpose of keeping wind from infiltrating the wall
cavities. Even a well-built home will have gaps where
air and water can infiltrate. Preventing air infiltration
is one of the keys to effective insulation.
Since it is virtually impossible to keep water and
air from penetrating almost any exterior surface,
some type of barrier is required.
House wraps are installed over the exterior sheathing.
Generally it is installed soon after the sheathing
to protect the home during construction. In order
for house wrap or felt paper to be effective, seams
must be overlapped and sealed according to the manufacturers
instructions. The overlap must be installed so that
water will run on top of the lower piece and not behind
(similar to roof shingles).
Insulation is shown to be effective when it's dry
and the air is still. When it's wet or when air is
allowed to circulate through the insulation, it loses
much of it's effectiveness. Tests have show that insulation
can lose more than 50% of it's effectiveness under
adverse conditions.
According to a nationwide DOE study energy savings
of between 16%-29% were realized using house wrap.
It typically costs between $300-$400 to wrap a 2000
square foot home. According to the study, the house
wrap paid for itself after an average of 14 months.
Heating costs varied depending on house size, fuel
type and heating system.
A modern 2000 sq. ft. house has over ½ mile
of construction joints. Each of these joints has the
potential for air penetration. According to the study
house wraps were effective in reducing energy cost
in all climates.
The Code requires a moisture barrier behind porous
materials such as brick, stucco and stone. However,
there is generally no requirement for a barrier behind
siding attached to structural rated sheathing. Traditionally,
15 lb. building felt has been used behind porous masonry.
Many experts believe that building felt is still the
best moisture and water barrier to use under any exterior
surface. However, it has some disadvantages: It is
much more labor intensive to install; it's more difficult
to seal the edges and seams; and it doesn't hold up
well to sun and wind if left exposed during the construction
process.
Another benefit of house wrap is the protection that
it offers during the construction of the home. Most
house wraps are UV protected so exposure during the
construction won't harm them. House wrap that resist
water infiltration will protect the structure during
construction.
Leaks around windows and doors are common even in
new construction. Most sidings are not waterproof,
and water will penetrate them in extreme weather conditions.
If your windows and doors are not sealed, they will
eventually leak. Tar based adhesive paper wrapped
around the window opening will keep the window or
door from leaking. Make sure that the window installer
(framer) follows this method:
