Use This Guide To:

1. Learn how to find and seal hidden attic and basement air leaks;
2. Determine if your attic insulation is adequate, and learn how to add more;
3. Make sure your improvements are done safely;
4. Reduce energy bills and help protect the environment

AIR LEAKAGE

If your house feels drafty or dry in the winter, it may have air leaks allowing cold, dry outdoor air into your living space. Sealing up leaks and drafts in your home is usually the most cost-effective improvement you can make.Most cracks and holes can be sealed with expanding polyurethane spray foam from a can. If you have a lot of sealing to do, consider buying a good quality foam gun that uses replaceable cans of foam. You also can use rigid foam board cut to fit into holes and then sealed.

Finding Leaks
The most accurate and comprehensive means of pinpointing leaks is a blower-door test conducted by a professional energy auditor. Efficiency Vermont can help you find a qualified technician in your area to perform this test. In new homes, the best time to inspect for and repair potential leaks is just before insulation is installed so that typical leak sources can be visually inspected and easily remedied. Air-sealing products must be installed according to the manufacturer's specification and per local fire code.

Tips on How to Find Leaks Yourself

• Check for attic-to-house leakage paths by lifting the attic insulation and looking for gaps and cracks in the attic floor and ceiling underneath.
• Check to see that these areas are sealed: Flues and plumbing vents, wire pathways, gaps around recessed lights and fans, and chimney penetrations through the roof.
• Discolored insulation-- on the warm side, at edges, or in the middle-- is an important clue since it means that dirt and dust are being filtered by the insulation through air movement, indicating a significant air leak nearby.
• Have the pipes in the house ever frozen? Pipes generally freeze because cold air blows across them. If there is heat tape on pipes or signs of repaired frozen pipes, it's a good indication that some work to reduce air leakage is in order.
• Icicles and ice dams are a sign of possible air leaks from the house to the attic.
• Dusty spider webs in basements and crawl spaces can indicate air leaks.
• Walk along the inside of exterior walls of the house on a windy day with a smoking incense stick to help pinpoint drafts. When the smoke moves horizontally, a leak is nearby.
• Be sure that the perimeter of the box sill (where the first floor sits on the foundation walls) and all of the penetrations through it are sealed.

SEALING BASEMENT AIR LEAKS

Stopping the Chimney Effect
Outside air drawn in through basement leaks is exacerbated by the chimney effect created by leaks in the attic. As hot air generated by the furnace rises up through the house (1) and into the attic through leaks (2), cold outside air gets drawn in through basement leaks to replace the displaced air (3). This makes a home feel drafty and contributes to higher energy bills. After sealing attic air leaks, complete the job by sealing basement leaks, to stop the chimney effect.

Locating Basement Air Leaks
A common area of air leakage in the basement is along the top of the basement wall where cement or block comes in contact with the wood frame. These leaks can easily be fixed in portions of the basement that are unfinished. Since the top of the wall is above ground, outside air can be drawn in through cracks and gaps where the house framing sits on top of the foundation. This perimeter framing is called the rim (or band) joist. In the basement, the above floor joists end at the rim joist creating multiple cavities along the length of the wall, and many opportunities for leakage

Seal All Gaps and Cracks around Rim Joists
Though you may not be able to see cracks in the rim joist cavities, it is best to seal up the top and bottom of the inside of the cavity. Also, rim joist air sealing is especially important at bump out areas such as bay windows that hang off the foundation. These areas provide greater opportunities for air leakage and heat loss. Caulk is best for sealing gaps or cracks that are 1/4 inch or less. Use spray foam to fill gaps from 1/4 inch to about 3 inches. We also recommend you seal penetrations that go through the basement ceiling to the floor above. Generally, these are holes for wires, water supply pipes, water drain pipes, the plumbing vent stack (for venting sewer gases), and the furnace flue (for venting furnace exhaust).

Materials Checklist for Basement Sealing

• Silicone or acrylic latex caulk and caulk gun
• Expanding spray foam

Caution: When sealing the furnace flue (which will be encased in a metal sleeve) use high-temperature caulk. Run a bead of high-temperature caulk around the pipe sleeve and around the metal frame.

What About Insulating the Rim Joist?
After air sealing the rim joist area it is relatively easy to insulate each cavity with rigid foam insulation or fiberglass batts. If using batts, just cut the insulation to fit and place against the rim joist without compression, gaps, or voids. If using rigid, foam into place. This could also be done in conjunction with finishing the basement, when you would insulate the basement walls floor-to-ceiling. Attic and basement air sealing will go
a long way to improve your comfort because your house will no longer act like an
open chimney.

SEALING ATTIC AIR LEAKS

Plug the Big Holes First
Don't worry about finding and sealing all the little holes in your attic; your biggest savings will come from plugging the large ones. Once in the attic, refer to your sketch to locate the areas where leakage is likely to be greatest: where walls (inner and outer) meet the attic floor, dropped soffits (dropped-ceiling areas), and behind or under attic kneewalls. Look for dirty insulation--this indicates that air is moving through it. Dropped soffits may be filled or covered with insulation and hard to see. Push back the insulation and scoop it out of the soffits. You will place this insulation back over the soffit once the stud cavities have been plugged and the soffits covered (If you have recessed "can" lights in your open soffits, please read about them on here before proceeding).

If You Have a Finished Attic, Seal Behind the Kneewalls
Finished rooms built into attics often have open cavities in the floor framing under the side-walls or kneewalls. Even though insulation may be piled against or stuffed into these spaces, they can still leak air. Again, look for signs of dirty insulation to indicate air is moving through. You need to plug these cavities in order to stop air from traveling under the floor of the finished space.

Caution: Some attics have vermiculite insulation, which may contain asbestos, a health hazard. Vermiculite is a lightweight, pea-size, flaky gray mineral. Don't disturb vermiculite insulation unless you've had it tested by an approved lab to be sure it doesn't contain asbestos. Contact your local health department for the name of an approved lab.

Furnace Flues Require Special Sealing Techniques
The opening around a furnace or water heater flue or chimney can be a major source of warm air moving in the attic. Because the pipe gets hot, building codes usually require 1 inch of clearance from metal flues (2 inches from masonry chimneys) to any combustible material, including insulation. Photos 5 and 6 show how to seal this gap with lightweight aluminum flashing and special high-temperature (heat-resistant) caulk. Before you push the insulation back into place, build a metal dam (photo 7) to keep it away from the pipe. Use the same technique for masonry chimneys.

Caution: Furnace flues (the pipe that removes your furnace exhaust) can be very hot.

Foam or Caulk Small Gaps in Your Attic
Even though most of the gaps spilling warm air into your attic are buried under insulation, you might be able to find evidence of these gaps. Look for areas where the insulation is darkened (see photo 8). This is the result of filtering dusty air from the house. In cold weather, you may also see frosty areas in the insulation caused by warm, moist air condensing and then freezing as it hits the cold attic air. In warmer weather, you'll find water staining in these same areas. Although the insulation is dirty, it is still okay to use. There's no need to remove and replace. After sealing the areas, just push the insulation back into place. If you have blown insulation, a small rake can be helpful to level it back into place.

Seal Small Gaps
Use expanding foam or caulk to seal the openings around plumbing vent pipes and electrical wires (see photos 9 and 10). Be sure to wear gloves and be careful not to get expanding foam on your clothes, as the foam is very sticky and nearly impossible to remove once it sets. When the foam or caulk is dry, cover the area again with insulation.

Complete the Job by Sealing the Attic Hatch or Door
Finish up by sealing the access hatch with self-sticking weather stripping (photos 11 and 12). If your hatch rests directly on the moldings, add 2-1/2 inch wide stops around the opening. The stops provide a wider surface for attaching the weather-strip and a space to mount hook-and-eye fasteners. Position the screw eyes so the weather-strip is slightly compressed when the hooks are latched. Cut a piece of fiberglass or rigid foam board insulation the same size as the attic hatch and nail or glue it to the back of the hatch. If you have pull-down attic stairs or an attic door, these should be sealed in a similar manner: weather-strip the edges and put a piece of rigid foam board insulation on the back of the door. Treat the attic door like a door to the outside. Pre-made insulated attic stair covers are also available from local home improvement centers or on the Web.

ADDING ATTIC INSULATION

Now that you've air-sealed your attic and basement, check your attic insulation levels
and add more if necessary. The attic is the easiest place to add insulation to improve your comfort and the energy efficiency of your home.

Do I Have Enough?
No matter what kind of insulation you currently have in your attic, one quick way to determine if you need more is to look across the span of your attic. If your insulation is just level with or below your floor joists (i.e., you can easily see your joists), you should add more. If you cannot see any of the floor joists because the insulation is well above them, you probably have enough and adding more may not be cost-effective. It is important that the insulation be evenly distributed with no low spots; sometimes there is enough insulation in the middle of the attic and very little along the eaves. To see how to add insulation out to the eaves, see Installing Rafter Vents. If your attic insulation covers your joists and is distributed evenly, you probably have enough.

How Much Should I Add?
Insulation levels are specified by R-Value. R-Value is a measure of insulation's ability to resist heat flow. The higher the R-Value, the better the thermal performance of the insulation. The recommended level for most attics is to insulate to R-38 or about
10 to 14 inches, depending on insulation type.

A Note about Natural Attic Ventilation
At first it may seem odd to add insulation for warmth and then purposely allow cold air to enter the attic through vents, but this combination is the key to a durable and energy-efficient home. Here's why: in the winter, allowing a natural flow of outdoor air to ventilate the attic helps keep it cold, which reduces the potential for ice damming (snow that melts off a roof from an attic that is too warm and then re-freezes at the gutters, causing an ice dam that can damage the roof). Proper insulation and air sealing also keeps attics cold in winter by blocking the entry of heat and moist air from below. In the summer, natural air flow in a well-vented attic moves super-heated air out of the attic, protecting roof shingles and removing moisture. The insulation will resist heat transfer into the house. The most common mistake homeowners make when installing insulation is to block the flow of air at the eaves. NEVER COVER ATTIC SOFFIT VENTS WITH INSULATION--use rafter vents and soffit vents to maintain airflow.

A Note about Attic Fans
Attic fans are intended to cool hot attics by drawing in cooler outside air from attic vents (soffit and gable) and pushing hot air to the outside. However, if your attic has blocked soffit vents and is not well-sealed from the rest of the house, attic fans will suck cool conditioned air up out of the house and into the attic. This will use more energy and make your air conditioner work harder, which will increase your summer utility bill. You don't want your unfinished attic cooled by your air conditioner. To prevent this, follow the air sealing and insulation strategies in this guide and make sure the attic is well-ventilated using passive vents and natural air flow.

Add the Right Kind of Insulation
When adding additional insulation, you do not have to use the same type of insulation that currently exists in your attic. You can add loose fill on top of fiberglass batts or blankets, and vice-versa. If you use fiberglass over loose fill, make sure the fiberglass batt has no paper or foil backing; it needs to be "unfaced." If you choose to add loose fill, it may be wise to hire a professional, as the application requires the use of a blowing machine, although some home improvement stores offer rentals of this machine.

Doing the Job
Laying fiberglass rolls is easiest for a DIY job. If you have any type of insulation between the rafters, install the second layer over and perpendicular to the first (again, the second layer of roll insulation should be unfaced with no vapor retarder). This will help cover the tops of the joists and reduce heat loss or gain through the frame. Also, when laying down additional insulation, work from the perimeter toward the attic opening. Never lay insulation over recessed light fixtures or soffit vents. Keep all insulation at least 3 inches away from "can" lights, unless they are rated IC (Insulated Ceiling). If you are using loose fill insulation, use sheet metal to create barriers around the openings. If using fiberglass, wire mesh can be used to create a barrier.

Installing Rafter Vents
To completely cover your attic floor with insulation out to the eaves you need to install rafter vents (also called insulation baffles). Complete coverage of the attic floor along with sealing air leaks will ensure you get the best performance from your insulation. Rafter vents ensure the soffit vents are clear and there is a channel for outside air to move into the attic at the soffits and out through the gable or ridge vent (see Attic Air
Flow graphic).

To install the rafter vents, staple them directly to the roof decking. Rafter vents come
in 4-foot lengths and 14-1/2 and 22-1/2 inch widths for different rafter spacings.

Rafter vents should be placed in your attic ceiling in between the rafters at the point where your attic ceiling meets your attic floor. Once they are in place, you can then
place the batts or blankets, or blow insulation, right out to the very edge of the attic
floor. Note: Blown insulation may require an additional block to prevent insulation from being blown into the soffit (see Page 4.5). A piece of rigid foam board placed on the outer edge of the top plate works very well for this.

ADDITIONAL SOURCES OF AIR LEAKS

If Your Heating and Cooling Ducts Are in Your Attic, Seal Them While in the Attic
Leaky and poorly-insulated ducts (especially in attics) severely compromise the performance of your heating and cooling equipment. Sealing and insulating your ducts
can increase the efficiency of your heating and cooling system by 20% and greatly increase air flow.

■ Check the duct connections for leaks by turning on your heating and cooling system fan and feeling for leaks--seal the joints with mastic or foil tape (household duct tape should not be used).

■ Pay special attention to all the duct penetrations going through the attic floor. Seal these with foam.

■ Ducts should also be insulated--if your ducts are uninsulated or poorly insulated (i.e., you see gaps or torn insulation), seal them first, then add insulation to keep the air in your ducts at your desired temperature as it moves through the system. Use duct insulation material rated at least R-6.

Materials Checklist for Attic Duct Sealing

• Duct sealant (mastic) or metal- backed (foil) tape
• Duct insulation material rated at least R-6
• Zip ties to hold duct insulation in place
• Gloves, safety glasses, mask, flashlight
  

NOTE: Duct sealant, also known as duct mastic, is a paste which is more durable than foil duct tape. It is available at home improvement centers. Traditional grey duct tape fails quickly and should not be used.

Caution: Check for Carbon Monoxide to keep your house safe. After making energy improvements that result in a tighter house, there can be an increased opportunity for CO to build up if your gas-burning appliances are not venting properly. Have your heating and cooling technician check your combustion appliances (gas- or oil-fired furnace, water heater, and dryer) for proper venting. For additional information on Indoor Air Quality (IAQ) issues related to homes such as combustion safety, indoor air contaminants, and proper ventilation, visit www.epa.gov/iaq/homes/hip-front.html.

Recessed "Can" Lights: Big Source of Air Leaks, But No Easy Solution
Recessed "can" lights (also called high-hats or recessed downlights) look great, but when they protrude into your attic space, they can make your home less energy-efficient. These recessed lights in a one-story house or in the ceiling of a second-story create open holes into your attic that allow unwanted heat flow between conditioned and unconditioned spaces. In the summer, hot attic air can make the rooms warmer, and in the winter can lights draw warm air up into your attic. Both the warm air leakage and the heat from the lights can cause problems. In cold climates, the heat melts snow on the roof and forms ice dams (water re-freezes at the roof edge). This is more likely to happen if the "can" light is close to the roof deck. Recessed "can" lights in bathrooms also cause problems when warm, moist air leaks into the attic and causes moisture damage.

Here are some suggestions for improving the recessed can lights in your attic:

Call a Professional to Properly Seal
Recessed lights can be sealed, but it is difficult and can create a hazard if not done properly with non-combustible materials. Since any old-style lights need adequate air space around them to vent the heat they create, it's best to consult with a professional before sealing them. Also, see "Caution" below. Alternatively, recessed lights can be replaced with ICAT (Insulated Ceiling Air-Tight) rated lights, which insulation can touch and are sealed to reduce air leaks.

When Replacing or Adding, Buy ENERGY STAR with ICAT
Look for ENERGY STAR qualified recessed fixtures that reduce energy use as much as 75%. However, it's important to check that any fixture selected meets your light output expectations since fixtures come with widely varying wattage bulbs and optics. Also, make sure fixtures have an ICAT rating to minimize heat loss.

Switch to More Efficient Bulbs
When keeping existing recessed lights, you can still reduce lighting energy use as much as 75% by installing ENERGY STAR qualified compact fluorescent light (CFL) bulbs. This includes CFL bulbs specifically designed for recessed lights with built-in reflectors matching the appearance of traditional incandescent reflector bulbs. As with new fixtures, it is important to make sure any CFL bulb selected meets your light output expectations. Also, check the packaging of the CFL to ensure that it may be used in an enclosed fixture. However, switching to CFL bulbs will not solve the air leakage problem.

Caution: Keep all insulation 3 inches from "can" lights, except those rated IC (insulation contact). You can use a piece of circular metal flashing or wire mesh around the light as a dam to keep the insulation away from the light.