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Insulation
is required in all external walls to prevent heat
loss in winter or heat gain in the summer.
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Insulations
ability to insulated is stated in R value. The higher
the R number the better the insulation.
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Insulation
placed in walls is covered by a warm side vapor
barrier to prevent moisture from settling in wall
cavities.
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If
moisture gets into the wall cavity mildew and rot
can result.
Insulation is placed between the wall studs in external
walls after the wiring, plumbing, HVAC and framing inspection.
After the insulation is placed a plastic vapor barrier
is placed over the insulation. Some types of insulation
have a barrier attached to the insulation. Fiberglass
insulation with a kraft paper backing is an example.
There are several different types of material that can
be used to insulate the walls. Fiberglass, cellulose
are common. Fiberglass batts are stapled into the cavity
and cellulose is blown into the cavity. Urethane foam
is also becoming more popular because of its high R
value, and its ability to stop air infiltration. Urethane
foam however is much more expensive than tradition fiberglass
batts.
Most exterior walls are constructed of 2x4 or 2x6 stud
walls. The thickness of the wall determines how much
insulation can be placed in the wall. Here are typical
R values for exterior walls:
Before insulation is installed,
it is important to fill all cracks gaps in the walls,
top and bottom plates, around pipes wires and ductwork
and any other penetrations in the exterior shell of
the structure. Urethane foam in a can be used for
this purpose. If outside air is allowed to infiltrate
the insulation cavity, the effectiveness of the insulation
is significantly reduced. Caulk is a good barrier
where the gaps are less than ¼".
| Insulation Type |
2x4 Framed Wall |
2x6 Framed Wall |
| Fiberglass batts |
11-13 |
19-21 |
| Cellulose fill |
14-16 |
21-23 |
| Urethane foam |
16-17 |
22-25 |
Fiberglass batts are the best option for the Do-it-yourselfer.
If you decide to pay extra for cellulose or urethane
the extra money spent will probably not pay for itself
in lower heating bills for many years.
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Type
and R-value of the insulation to be installed.
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Sealing crack and penetrations in walls around windows
and doors.
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Sealing
penetrations through top and bottom plates around
pipes wires and ductwork.
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Usually
an insulation inspection is required by the building
inspector.
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Check
that the insulation cover the entire cavity with
no bare spots.
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Check
around doors and windows for light leaks.
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Expanding
foam that is installed around windows and doors
can cause them to bind. Special low expansion foam
that is specially made for doors and windows should
be used.
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Many
Building jurisdictions require that a Building meet
the national energy efficiency requirements. The
national model is adapted for each state and city
in the country. The code is called the Model Energy
Code check or MECcheck. Check your local building
department to see if you are require to meet this
standard. You can download the MECcheck software
(free) from www.energycodes.org
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Consider
installing wall insulation yourself. The job is
not too difficult, and you could save some money.
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The
return on investment (ROI) for cellulose and urethane
insulation is 5-10 years.
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