Air Sealing and Weatherization
Air Sealing and Weatherization, for Comfort, Energy Efficiency, and Energy Savings.
Contributed by the Sierra Club
Your Hole Ridden Home
Leaving cracks and crevices for air to leak in and out of your home can make life feel drafty and uncomfortable. It can allow moisture-laden air to sneak inside, increasing the likelihood of condensation, mold, and rot. It can swell your energy demand, adding 20% to your bill for heating and cooling. To avoid this fate, prepare your house for winter and other sorts of inclement weather. In other words, weatherize!
Some people worry that a tighter house means poor indoor air quality. While it’s true a healthy home needs fresh air, it’s important to be able to control when and where that outdoor air enters and indoor air leaves.
Many older homes are extremely leaky, and even newer homes often aren’t airtight. You may be aware of drafty spots around doors and windows, but air is likely escaping in other places, too. Here’s where the air leaks out in most of our homes: Source: www.consumerenergycenter.org
If you’re a handy do-it-yourselfer, you can probably do the more obvious air sealing and weatherization work yourself, but it may take a pro to get at some of the less accessible spots.
When shopping, look for Low- or no-pollution materials. Choose water-based caulks, and choose sealants that have little or no solvents or volatile organic compounds (VOCs).
•Find the leaks. Just how leaky is your house? Here’s how you can find out:
◦The paper test. Shut a window or door on a piece of paper. If you can pull the paper out intact, you’ve got a leak that’s wasting energy.
◦The flashlight test. At night, turn off the home’s interior and exterior lights, and shine a flashlight in areas where you suspect leaks in exterior walls, windows, and doors. Have a partner stand outside and make a note of where rays of light shine through.
◦The incense test. On a cold and windy day, turn off the furnace and depressurize the house by turning on any exhaust fans like the kitchen and bathroom fans. Then walk around the house with a lit incense stick, passing it close to areas where there are likely to be leaks. When smoke gets sucked away or blown into the room, you’ve found a leak.
•Prioritize. Seal the largest leaks first. That probably includes 1) sealing and insulating heating and air conditioning ducts that run through garages, crawl spaces, attics, and basements, 2) installing weather stripping around doors and windows, 3) using caulk or spray foam to fill cracks and gaps around windows, pipes, and vents that pass through walls, and other penetrations.More specifically, plug leaks around plumbing and electrical conduit penetrations, joints where different parts of the building meet such as the floors and walls, at dropped ceiling areas and kitchen soffits (the lowered ceilings above wall cabinets), and in outside walls. If you see dirty spots in the attic insulation, it means that air is being pulled through it. Move the insulation aside, find and seal the leaks, and replace the insulation.
•Do the ducts. Heating and cooling ducts are notorious for leaking around their joints and seams–either because they were sloppily installed in the first place or because they got jarred or moved during remodeling or other work on the house. Ducts typically waste more than 10% of a home’s heating and cooling energy. That’s a lot of your money–and a lot of greenhouse gases–going up into thin air. If the ducts only run through areas of the home that are insulated, heated, and cooled, like a finished attic or basement, it’s not a big deal if they leak. But when ducts run through uninsulated spaces, it’s a big problem for two reasons. Energy is wasted through air leaks in the ducts. And your home health can be compromised if the ducts run through spaces where they can pick up air from car exhaust, stored paints, and other contaminants. So it’s important to make them airtight. Inspect them carefully and seal all joints and seams. Use duct mastic, a sticky putty sold in tubs in home improvement stores. Don’t use duct tape for sealing ducts–it’s notorious for losing its stickiness after only five years or so.Once the ducts are all well sealed, insulate them with duct insulation. Make sure it wraps all the way around the ducts; don’t leave any gaps. Tape the seams with a high quality tape such as aluminum foil tape, or for an even more secure attachment, use metal fasteners designed to hold duct insulation in place.
•Handle the hot spots. You may also need to plug gaps in the attic around chimneys and water-heater or furnace flues. But these conduits require special treatment because they get hot. Most building codes require that combustible materials be kept 1 to 2 inches away from them. Cut aluminum flashing to fit around them and block any gaps in the attic floor. Use a special heat-resistant caulk to seal the flashing in place. Check with your local building department for details.
•Add weather stripping. Install felt, foam, rubber, or metal weather stripping to reduce air flow around the moving joints of doors and windows. You can also use weather stripping to form a tight seal around attic access hatches or doors. Metal (copper, stainless steel, aluminum or bronze) weather stripping holds up much longer than felt or foam. Vinyl performs well as a weather stripping material, but environmental and health hazards have been linked to vinyl’s manufacturing and disposal so avoid using it.
•Zap door gaps. If there’s an air gap underneath exterior doors, install a door sweep or threshold. Most home improvement stores carry a number of threshold products; choose one that won’t drag on your carpet or floor when you open the door.
•Fix the switches. Electrical outlets and switch plates on exterior walls account for only about 2% of air leakage, but there’s a cheap and easy fix. Pick up some foam gaskets designed to fit behind an outlet or switch plate at any hardware store. They take just a minute or two to install.
•Large holes and crevices can be tightly stuffed with cotton or fiberglass insulation, but it needs to be packed densely to prevent air flow through the fibers. One handy trick to create a better air barrier is to first pack the insulation into a plastic garbage bag, and then stuff it into the cavities.
•Use caulk to fill smaller cracks and joints up to about one-fourth inch wide. Some types of caulk are paintable, some are designed for indoor use only, and some remain flexible so that they retain their seal when in contact with materials that expand or contract. Water-based caulks are healthier to work with; unlike solvent-based caulks, they don’t give off noxious fumes, and can be cleaned up with water. Follow the instructions on the caulk’s packaging: good surface preparation and proper use of the caulk are keys to an effective, long-lasting installation.
•For cracks wider than one-fourth inch, use a spray foam sealant. Expanding polyurethane foam sealant expands a lot as soon as it’s applied, so it does a great job of filling in larger cracks and irregularly shaped crevices. Water-based foam sealant only expands by about 25% and is good for smaller cracks and spots where too much expansion might be a problem.
•In basements, a common spot for leaks is where the concrete or cement block wall meets the wood frame (this area is call the rim or band joist). If your basement walls are unfinished, you’ll have access to these areas and can seal cracks with caulk or spray foam.
Benefits to you
You’ll feel more comfortable because your home won’t be as drafty.
Sealing the air leaks in your home can cut your cooling and heating bills by 20% or more, which will save you hundreds of dollars per year. If you do it yourself, the cost of basic caulking, weatherstripping, and air sealing is very low so you will be making money almost immediately! Even if you hire a pro, you will likely get your investment back in less than a year.
Air sealing can extend your home’s life and reduce its maintenance costs by keeping mold and rot in check. It conserves precious fossil-fuel reserves and reduces emissions of greenhouse gases.
•Ignoring dampness and rot. If you discover damp or wet insulation in the attic, or rotting attic rafters or floor joists, it’s time to call in the pros. You may have roof leaks or structural deterioration that needs immediate repair.
•Leaving the damper open. If you have a fireplace with a damper, make sure it’s completely closed when the fireplace is not in use. An open damper wastes as much energy as an open window.
•Can lights. Conventional recessed “can” lights are like big holes in your ceiling. They need air space around them or they’ll overheat, making it tough to seal and insulate around them. It’s best to replace these light fixtures with the newer ICAT (insulated ceiling airtight) recessed fixtures-they’re sealed to reduce air leaks and designed so that insulation can go right over them. If replacement’s not in the cards, hire a professional insulation contractor to properly seal around the cans with noncombustible materials.
•If you are reasonably handy with home repairs, you can tackle many energy-efficiency and indoor-air-quality improvements yourself. This website is filled with tips for tuning up your home and we have “how to” videos below. You can also get more detailed directions on how to seal air leaks from Energy Star’s free publication “A Do-It-Yourself Guide to Sealing and Insulating with Energy Star.”
•Many local utility companies offer free or low-cost energy-efficiency evaluations. They usually also have publications with tips on how to do your own energy audit and home performance improvements. Check your local electricity provider’s website to see what is available.
•Alternatively, you can hire an energy auditor or home performance contractor, who will pinpoint leaks and recommend the most cost-effective fixes. Some of these specialists will do the repair work themselves, while others will refer you to contractors who specialize in weatherization. Be sure to check the results before you pay the bill. If a company has installed weatherstripping, for example, examine each door and window to make sure none were missed. Open and close the windows and doors a few times to make sure the weatherstripping isn’t loose and doesn’t impede their operation.