Plan Your Attack

Knowing that air leaks in your home can waste up to 30% of your yearly energy bill makes some of us want to arm ourselves with tubes of sealant and spray foam and run around like a mad doctor stamping out air leakage disease with a shot here, and a shot there.  It's great that you feel inspired, and there is indeed some low hanging fruit in the air sealing world (see below).  But before you set off to fill every nook and cranny with goop, you'll want to slay some larger energy dragons first. Where do they live? Most likely in your attic and basement. In simple terms, cold air infiltrates your basement (and perhaps your walls), then rises through your home (creating drafts) and exits through your attic. This is known as the chimney effect. In order to minimize this effect and enjoy the greatest initial energy savings, we recommend that you seal your attic and cellar first, then take care of holes and cracks in your interior and exterior walls and around windows and doors.

In this article, we take a look at attics, basements, low hanging fruit, and those areas best tackled by professionals.

Attic Culprits

Kneewalls
If you have a finished attic, you may have kneewalls (the side walls under the eaves). In many cases, the insulation and/or air barriers behind the walls and under the floor are inadequate to minimize air flow.

There are three steps to effectively sealing attics with kneewalls:

1. Sealing air leaks between the heated and unheated space. This includes installing rigid foam insulation blocks between the joists and sealing them in with spray foam or caulk.

2. Installing or adding more insulation above the flat ceiling, on the floor of the outer attic space and the sloped ceiling of the finished space.

3. Installing or adding more insulation batts behind the kneewalls (with the vapor barrier toward the heated side of the wall).

Attic Access
If you have an attic door, attach fire-coded rigid insulation to the back, then weatherstrip around the sides and top and add a door sweep.

If you have an attic access panel, insulate the back with a minimum R-20 rigid insulation, then add weather stripping around the perimeter. Make sure the latches provide a tight fit.

If you have pull-down stairs, create an insulated overhead cover that will fit above the stairs and can be hinged or slid to the side when you go into the attic. Install weatherstripping around the perimeter of the door.

Recessed Lights
Recessed lights can be a source of significant air leaks. The most energy efficient (and also the most expensive) option is to replace them with ceiling mounted lights or airtight fixtures. If you want to continue using your old fixtures and minimize air leakage through them, experts recommend installing a box built from wallboard and sealed with caulk around each fixture to stop the air leakage. If you go this route, be sure each box is constructed to prevent insulation from contacting the fixture and creating a potential fire hazard (3" minimum clearance is recommended). To get an idea of the scope of impact of this issue, check out our interconnected house video. [http://www.energycircle.com/blog/2009/02/25/video-the-interconnectedness-of-energy-in-our-homes/]

Soffits, Bulkheads and Dropped Ceilings
Cover any large open holes into the attic space with plywood that is caulked into place to minimize air infiltration, then lay insulation over the plywood.

Chimneys
If you have a metal chimney, check the condition of the metal collar where it meets the roof and repair if necessary.

If you have a brick chimney, check for gaps between the chimney and the wood framing around it. Fill any gaps with 24-gauge aluminum flashing, then seal with furnace cement or caulk rated to 400°F.

Plumbing Vent Stacks
Seal any gaps around the pipe with an expanding foam sealant.

Basement Culprits

Now that you've helped minimize the chimney effect by sealing the attic, it's time to complete the job by moving to the cellar.

Rim Joist
The rim joist is the board nailed to the ends of your floor joists in the cellar (the perimeter framing). Outside air can be drawn in through the cracks that exist above and below the rim joist and the sill plate it sits on. To seal these cracks, run a bead of caulk for cracks that are 1/4" or less or use spray foam to fill gaps for 1/4" to 3". Start by filling the gap between the sill plate and foundation. Then seal along the top and bottom of the rim joist on each end of the house (the rim joists that run parallel to the floor joists). Finally, seal the top and bottom of each cavity along the rim joists on the sides of the house (perpendicular to the floor joists).

Before you put your caulk and foam away, seal around any utility penetrations that pass to the outside (including dryer vents or other ductwork, dog fence and other wiring, and electrical, phone, gas, cable or water utility related pipes).

Now that you've successfully slayed the largest energy dragons, you can move on to sealing windows and walls, armed with caulk and foams to squeeze even more dollars out of your energy savings.

Low Hanging Fruit

Some air sealing work is so easy and effective that it's akin to apples falling into your hand.  Here is a short list of things that you can do on a dull Saturday that will have a great impact on the energy efficiency of your home.

Weatherstrip and insulate attic doors, access panels or pull-down stairs

Seal (using an appropriate expanding foam) around plumbing vent stacks

Caulk or foam along sill plate, rim joist and rim joist cavities

Best Handled by Professionals

Some air sealing tasks are best left to professional contractors. (These are the hard to reach apples - worth getting, but not worth breaking an arm to grab).

Hire a professional to:

Replace, augment or install insulation in hard to reach places (such as behind kneewalls or above attic ceiling). A pro will be able to tell you about alternatives and the cost of each.

Repair and seal the chimney exterior.

Insulate behind soffits, bulkheads and dropped ceilings.

• Install boxes over recessed lighting fixtures.
• Install rigid foam under attic floor boards and seal it in with foam or caulk.