Seal Up Air Bypasses Before Adding Attic Insulation (Or You’ll Be Wasting Money).
Attics are one of the easiest and most cost-effective places to add insulation. But you’ll increase the effectiveness of insulation substantially if you first seal up air bypasses around chimneys, plumbing vents, wires, interior walls and exhaust fans—places where warm, moist interior air escapes into the attic.
Heat has a natural inclination to both rise and migrate to colder areas. Combine these two tendencies and you can see why air bypasses can reduce the effectiveness of attic insulation by 30 to 70 percent. You can track down bypasses by lifting existing attic insulation and checking for dark patches of moisture or dust. Or head to the attic on a cold day and feel for pockets of warm air or use a stick of incense to check for drafts.
Before installing (or adding) attic insulation, take these steps:
Use caulk and expanding foam sealant to close air gaps around pipes, ducts and electrical wires where they enter the attic.
Cut and fit strips of 24-gauge sheet metal between the masonry chimney and the surrounding wood framing. Use high-temperature caulk to seal the flashing where it meets the chimney.
Install weatherstripping around the perimeter of the attic access opening, then use screw hooks to pull the hatch tight against the weatherstripping. Glue rigid extruded foam insulation to the top of the hatch.
Careful Installation Increases the Insulation’s R-Value by Over 20 Percent.
Leaving 5 percent of a wall uninsulated will reduce the entire wall’s R-value (resistance to heat flow) by 20 percent. It doesn’t take much more time to install fiberglass insulation properly.
The most important steps you can take:
High-Density Insulation Can Pay Off.
Insulation is rated according to its R-value, or resistance to heat loss: the higher the R-value, the higher the insulating value. Standard fiberglass insulation has an R-value of about 3.5 per inch of thickness; this provides an insulating value of R-11 for 2x4 walls and R-19 for 2x6 walls. But if you’re serious about energy savings, you can buy better-performing products. High-density types of fiber-glass insulation, with more fibers and air spaces per square inch, offer R-values of up to 4.25 per inch. Some provide R-15 for 2x4 walls and R-21 for 2x6 walls. There’s also high-density insulation for ceilings and attics. You’ll wind up paying more and in many cases you’ll need to special-order it, but high-density insulation delivers up to 35 percent more insulating value per inch.
You can also pack 5-1/2 in. thick insulation into a 3-1/2 in. thick wall to increase its R-value, but the compressed R-19 batt will only yield an R-value of about
When You Insulate Attics and Crawlspaces, You’ve Got to Vent Them Too.
Since insulation changes the way attics and crawl-spaces “breathe,” it’s critical that you maintain or install proper ventilation. At first, it seems odd to add insulation for warmth and then purposely create ventilation “holes” for cold air to enter. But if you don’t do this, you’re setting yourself up for moisture problems.
When you add insulation to attic rafters and attic floors, it’s important to maintain at least a 1-in. continuous air space between insulation and roof sheathing, from eaves to ridge. This air space flushes out moisture. It also helps maintain a “cold roof,” which prevents ice dams from forming in the winter and excessive heat from damaging shingles and increasing cooling costs in the summer. The biggest mistake homeowners make with installation is to install it so it blocks the flow of air at the eaves. The best way to avoid this problem is to install inexpensive air chutes to keep the space open.
Newly insulated crawlspaces also need proper ventilation. The standard procedure is to insulate the ceilings of unheated crawlspaces and the walls of heated crawlspaces. To reduce moisture migration if there’s no slab, a 6-mil polyethylene vapor barrier should be laid on the ground in both cases. At least 1 sq. ft. of ventilation should be installed for each 1,500 sq. ft. of floor area.
Visit www.ukhhomeinsulation.co.uk to get professionally installed, guaranteed loft insulation. You may be eligible for a grant and with that, it may cost less than DIY insulation.