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We've divided the topic into the following areas to "blanket" the issue: R-Value Heat (energy) tends
to flow toward cooler areas, and insulation is rated by how well it resists heat
flow. The higher the R-value (resistance), the better the insulating power. But
don't let the resistance to "heat" flow fool you into thinking that insulation's
not a factor in warm climates. It just works in reverse there, keeping the warm
air from flowing into interior spaces you're paying to keep cool. That's why the
R-Value's an important criterion in any climate.
The density of an insulating material determines its R-value. Just because it's
thick doesn't mean insulation has a high R-value. In fact, manufacturers are now
packing more R-value into many fiber glass products by increasing the density
but keeping the thickness the same. So you can now get R-15 insulation into a
2x4 wall where R-13 used to be the max and R-21 into a 2x6 wall where R-19 was
the old maximum. Nearly everything has some resistance to energy flow like windows, shades and curtains. But they're pretty low with R-values around 1 to 3 so windows are usually a big source of energy loss compared to solid walls.
It comes in rolls or batts of varied thicknesses that match the the most common
framing sizes (3-1/2", 5-1/2" and 6-1/4") with R-values ranging from R-11 to R-38
or it can be blown in. When installing fiber glass insulation use a good dust respirator, protective eyewear, work gloves and a loose-fitting long-sleeved shirt. Several insulation manufacturers now offer fiberglass batts that are enclosed in a plastic wrap, which helps reduce the number of fibers that are released inot the air during installation. You can rent the blower equipment and apply cellulose yourself, but it's most often installed by professionals who can do it much more quickly and at prices not that much higher than the price of the rental. The R-value of an application is determined by the height or thickness of the blown material with 12" giving you about an R-38. Polystyrene is usually sold in 4x8 panel form, and it's most commonly used on exterior and foundation walls. It's also used to insulate roofs where there's no attic space available (like on vaulted ceilings or timber roofs). There
it's sandwiched between two layers of sheathing above the roof framing. Its thickness
ranges from 1/2" to 2" with an R- value of "5" per inch. It's a newer product so it's not that well known and it's only available through professional contractors, but it has properties which may lead to wider use.
Colder climates require insulation values from R-38 to R-49 in the attic. That's
12" to 15 1/2" of fiberglass or cellulose insulation. It's not as critical in
warmer climates, but in the summer heat builds up in the attic and radiates down
into the living spaces. So codes usually require a good layer of insulation there,
too, (R-19 in South Florida, for example) to keep cooling costs down.
If you're going to add fiber glass to existing insulation, use unfaced rolls.
That is, don't use a vapor barrier with existing insulation. It would trap moisture
and dampen the lower layer. To ensure a good seal, install the rolls perpendicular
to existing insulation rows. Locate air leaks in the ceiling and seal with caulk by using a smoking incense stick to locate drafts. Insulate around pipes and flues. But leave a 3" space between metal flues, chimneys and recessed lighting fixtures unless fixture is marked "I.C." (Insulated Ceiling). Don't insulate all the way along the ceiling joists to the soffit. This prevents outside air from ventilating the attic. In colder climates, ice dams become a problem if snow melts over a warm
attic area, runs down the roof, dams up behind unmelted snow over the cold soffits,
backs up under the shingles, freezes and expands causing water damage and leaks
in the roof.
To prevent ice dams, extra insulation is needed where warm air from the
interior of the house escapes to the attic. Proper attic ventilation is
also needed to keep the roof surface cold so snow won't melt at the top and refreeze
at the bottom. Insulating Walls Exterior walls require an R-19 rating according to most local codes. There's a couple of ways to accomplish that:
People
who live in older homes with little or no insulation in the walls can often save
a lot of money by retrofitting insulation--often reducing their heating bills
by up to a third, depending on where they live. The most common method is to blow cellulose into the home's exterior walls, through holes drilled into each stud cavity. That's usually done outside, and the downside is the holes are visible on some types of siding after the job is done.
A
frequent area to leak cold air is where the house meets the foundation. Foundation/basement
leaks account for 20% of heat loss in an uninsulated or poorly insulated home.
The important area to insulate isn't the basement walls, but the area where the
house meets the foundation. This is also the place a lot of moisture gets into
the house.
The sill plate should be caulked if gaps are present. During new construction,
an insulating gasket is installed under the sill plate. But the big heat loss
culprit is the rim joist. Leaks at the top around the floor joists and leaks at the sill plate are common in older houses. It's pretty easy to remedy. Cut a batt of fiber glass insulation and fit it into the cavity. If you have an older house and insulated here, you should be able to feel the difference the insulation makes.
Insulating Crawlspace Walls and Joists Crawlspaces should be insulated, too. A poly vapor barrier is installed
on the unfinished (sometimes dirt) floor after you've finished insulating, to
prevent tearing the barrier.
Insulation in the joists above the crawlspace can be held in place with short
pieces of wire. Remember, the kraft paper side faces toward the warmest room.
To insulate the walls, a lath strip can be nailed to the sill plate to hold insulation.
Cut to length with about 2' of overlap at the floor.
But even when a vapor barrier is present, problems can still develop if the installers don't foam cracks and gaps in the framing and sheathing before insulating and if they don't seal every seam and break in the vapor barrier after insulating. Even the smallest gaps like the holes in an electrical box have to be sealed or moisture can penetrate. | |||
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More How-To Information: Our Weatherization and Insulation video is available in the Hometime Store. GO! | |||
Fiber glass is the most popular material for do-it-yourselfers
because of its versatility, low cost and easy installation. It's used in attics,
walls and floors for both heat retention and sound control. 
Cellulose is literally shredded paper sold by the bag and blown
loose into attics and walls. 
The attic is the biggest area for energy loss. During heating season,
warm air rises and radiates up into the colder attic space. 
So, is it worth the cost? A 2x6 stud is about $1 more than a 2x4, but
spaced on 24" center. Contact your local or state public service or utilities
department to help calculate the savings difference. For example, in one Hometime
instance, the 2x6 with R-21 would save about 3% on the monthly fuel bill. 
Vapor barriers are recommended in most parts of the country to keep
moisture from penetrating and condensing in the insulation. Excessive moisture
can also rot the framing, siding or drywall.