How to Insulate Your Crawl Space
There’s
a right way and a wrong way for insulating your crawl space, depending on where
you live. Do you know the difference? We do — read on!
Take a look under your
house. Damp, dangling insulation is a sure sign of outdated or shoddy
installation. If your house was built before energy-conserving building codes
were standardized in 1990, you may find no insulation at all. The U.S. Dept. of
Energy currently recommends insulation with an R-value of at least R-9 in
floors.
To keep things cozy underfoot, you’ll need to select the right insulation approach for your local climate. Winter temperature is the continental divide:
To keep things cozy underfoot, you’ll need to select the right insulation approach for your local climate. Winter temperature is the continental divide:
·
In moderate or dry
climates without the threat of sustained subfreezing temperatures, insulation
between floor joists makes sense.
·
Where winter
temperatures are extreme, opt for insulating the walls and sealing off the
crawl space entirely.
Floor
insulation for moderate climes
If your winter temps seldom linger below freezing, you’re in luck. Six-inch-thick, R-19 fiberglass batts installed between floor joists -- along with careful moisture control and mold prevention -- gets the job done. Best of all, at roughly $1 per square foot, it’s easy on the pocketbook.
Here’s what it takes to do it right.
If your winter temps seldom linger below freezing, you’re in luck. Six-inch-thick, R-19 fiberglass batts installed between floor joists -- along with careful moisture control and mold prevention -- gets the job done. Best of all, at roughly $1 per square foot, it’s easy on the pocketbook.
Here’s what it takes to do it right.
·
Support: Fiberglass batts should be unfaced and
installed so they make contact with the underside of the subfloor. Wood lath
placed every 18 inches or a crisscross webbing of wire provide the best batt
support. Avoid stay rods (aka tension rods). They compress the fiberglass,
lessening its insulation value, and can pop loose.
·
Ventilate: An insulation contractor can calculate
the ventilation your crawl space needs and will cut in new vents as required.
·
Seal
the subfloor: Holes
for electrical wiring and plumbing should be sealed with
spray foam insulation.
·
Insulate plumbing
pipes and HVAC ducts
to prevent heat loss and freezing.
Closed-cell
spray foam combines thermal and moisture protection, but at $5 per square foot,
it's too pricey for most budgets. However, it might be your only alternative
for filling the webbing between truss-type joists.
Avoid open-cell spray insulation -- it soaks up moisture like a sponge.
Enclosing your crawl space: The cold climate choice
In a cold climate, the most efficient technique is to insulate the walls of your crawl space and close it off from the elements by sealing all air leaks. That way, plumbing pipes and HVAC ducts are protected from freezing temps, helping to conserve energy.
The best method is to insulate crawlspace walls with rigid insulation. At about $5 per square foot for professional installation, including materials, it comes at a cost but offers a permanent solution. You can do the job yourself for about half the cost, but it’s a challenging, time-consuming DIY project.
A thorough job also includes:
Avoid open-cell spray insulation -- it soaks up moisture like a sponge.
Enclosing your crawl space: The cold climate choice
In a cold climate, the most efficient technique is to insulate the walls of your crawl space and close it off from the elements by sealing all air leaks. That way, plumbing pipes and HVAC ducts are protected from freezing temps, helping to conserve energy.
The best method is to insulate crawlspace walls with rigid insulation. At about $5 per square foot for professional installation, including materials, it comes at a cost but offers a permanent solution. You can do the job yourself for about half the cost, but it’s a challenging, time-consuming DIY project.
A thorough job also includes:
·
Nixing
the vents: Simply closing
the vents in your foundation won’t do the job. Vents must be removed
and the holes sealed.
·
Insulating
the rim joist: Use closed-cell
spray foam to insulate the rim (aka band or perimeter) joists — the joist that
rests on top of your foundation walls.
·
Insulating
the foundation: Glue rigid foam
insulation board to the inside of foundation walls, using waterproof
construction adhesive, and seal all seams with waterproof tape. A 4-by-8-foot
sheet of 2-inch-thick expanded polystyrene insulation (R-value 7.7) is $26. A
double layer is recommended.
·
Add
a vapor barrier: Whether the
floor of your crawl space is bare earth, gravel, or concrete, it is going to
exude moisture. A 6-mil polyethylene plastic vapor barrier covering the ground
keeps the wet at bay.
·
Get
rid of moisture: Moist household
air is bound to cause condensation in the crawl space. In addition, any
slight plumbing leak can build up over time. A dehumidifier
or sump pump eliminates the moisture that mold loves.
Make moisture control
a priority, warns Chuck Henrichsen, owner of Clean Crawls, a Seattle insulation
firm. “If you don’t, your crawl space becomes a Petri dish.”
With crawl space sealed off from cold and moisture, your crawl space can be linked to your household HVAC system via vents. That way, warm air is circulating under your floors, warming them up and helping to keep you toasty. There's no need to cool off your crawl space in summer, however; close vents when your air conditioning is running.
With crawl space sealed off from cold and moisture, your crawl space can be linked to your household HVAC system via vents. That way, warm air is circulating under your floors, warming them up and helping to keep you toasty. There's no need to cool off your crawl space in summer, however; close vents when your air conditioning is running.
“Visit HouseLogic.com for more articles like this.
Reprinted from HouseLogic.com with permission of the NATIONAL ASSOCIATION
OF REALTORS®."
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