When it comes to keeping heating and cooling costs in check, insulation is the first line of defense. In the winter, heated air moves from living spaces to attics, garages, and the great outdoors. Heating systems fire up to replace all that lost heat. In the summer, air conditioners kick on as heat moves from the outside in. Insulation in the attic, exterior walls, and floors can help resist this heat flow, making homes more comfortable and slashing energy bills and pollution. Homes built today are usually well insulated, but many older homes–even those built as little as ten years ago–can benefit from added insulation.
- Start at the top. More heat moves up and out through the roof than through walls or the floor, so tackle the attic first. Fortunately, attics are accessible in most homes. Adding insulation to existing walls, on the other hand, is often difficult and expensive, but you might want to consider it in cold climates, or when you are remodeling.
- Blanket your tank. Cut hot water energy use by wrapping the water heater with an insulating blanket. They’re inexpensive and readily available at home improvement stores.
- Pamper your pipes. Insulate hot water pipes and heating and air conditioning ducts wherever they run through spaces that aren’t heated or cooled.
- Get paid to insulate! Check www.dsire.org for state, local, utility, and federal rebates and other incentives for energy efficiency.
When shopping, look for
- Healthy materials. Choose insulation with no added formaldehyde.
- Performance. An insulation’s “R-value” tells you its resistance to heat flow. So knowing an insulation’s R-value per inch of thickness allows you to compare the performance of different insulation materials. Check out the supplemental chart for more detail on the more common types of insulation: cellulose, cotton, fiberglass, foam board and spray-in-place foam. When shopping around, you may also come across other kinds of insulation, like sheep’s wool or mineral wool made from rocks.
- Cost.Product and installation costs vary greatly depending on the design of your home, the amount and type of insulation, and local market factors. Here are some general guidelines:
- Fiberglass blankets or “batts” are often the standard insulation offered. The cost of formaldehyde-free fiberglass batts and conventional fiberglass bats is roughly equal so be sure to ask for the formaldehyde-free product.
- Loose-fill insulation typically costs less to install than insulation sold in batts. When correctly installed, loose-fill blocks heat flow better because it does a better job of filling nooks and crannies.
- Cellulose also may cost less than fiberglass, but installation may be more, in part because there may be fewer contractors in your area who install cellulose.
- Cotton batts cost 50% more than fiberglass batts, but installation costs are about the same.
- Sustainability. Choose insulation with high recycled content.
- What’s the right amount of insulation? It depends on the climate, your home’s design and whether it’s the roof, walls, or floor that needs insulating. The Energy Department provides rough estimates for minimum installation levels in six climate zones, but to get a more precise figure for your location, check with your local building department. Remember that building codes are minimum requirements. Given the climate crisis and rising energy costs, the smart choice often means exceeding code.
- Radiant barriers aren’t a type of insulation, but when installed in the attic they can reduce cooling costs by 2% to 10%, depending on the climate and the amount of insulation in the attic. Radiant barriers are made of aluminum foil glued to a rigid backing like plywood or oriented strand board (OSB), or to a flexible paper or plastic backing. The radiant barrier is usually attached to the underside of the roof sheathing or the rafters. To work properly, the shiny surface faces down toward the attic. That may sound counterintuitive, but here’s what’s going on: When the sun heats up the roof surface, the roof radiates heat into the attic. Aluminum foil is good at blocking that heat, and you want the shiny side where it won’t get dusty, facing down. If the attic is accessible, installing a radiant barrier is a relatively straightforward retrofit project. Radiant barriers keep the attic cooler in the summer by reflecting heat back through the roof. When the attic stays cooler, the whole house is more comfortable. A radiant barrier is most effective in regions with hot summers. In the winter, a radiant barrier helps a bit with keeping heat from escaping through the roof, but its main purpose is blocking summertime heat gain.
…to your wallet
Adding insulation–especially in the attic–is an excellent investment that can pay for itself within a few years if you have high heating or cooling bills. It will also give you a quieter and more comfortable home. If you plug air leaks and insulate you can expect to lower your heating and cooling costs by 20%, potentially saving you hundreds of dollars per year.
…to the Earth
It’s a win-win. As you lower your utility bills by adding insulation, you reduce your emissions of CO2 and other pollutants from fossil fuels. If you also choose insulation made from recycled materials, you’ll make an even bigger contribution because recycled products require less energy to manufacture and they keep reusable resources out of landfills and incinerators.
- Air leaks. Most insulation can’t stop air leaks through cracks in walls and gaps around windows, pipes, and other penetrations. Before insulating, take the time to seal them.
- Drips. If insulation becomes wet, it’ll lose much of its effectiveness. Before adding insulation, take care of plumbing leaks and other spots where water might get in.
- Shoddy installation. Too often, insulation isn’t properly installed, even when a professional contractor does the work. Sometimes blankets of insulation (also called “batts”) are compressed or bunched up. Sometimes loose-fill doesn’t reach all the corners, and gaps are left around pipes and other obstacles. Poor-quality materials can lower the effectiveness by as much as 30%–and that means money and energy down the drain, not to mention uncomfortable spots in your home. Take the time (or make sure your contractor takes the time) to get it right. Make sure the insulation is in contact with the surface it’s meant to insulate and completely fills wall cavities without being bunched up or compressed. Pay particular attention to tops and bottoms of walls, attic corners, and hard-to-reach places like exterior walls around tubs and showers.
- Dust problems. Fiberglass can be a skin, eye, nose, and throat irritant. When working with fiberglass insulation, avoid direct skin contact and always wear a quality dust mask or respirator to prevent inhalation of the glass fibers. Controversy abounds about the potential health impacts if glass fibers get lodged in one’s lungs. While some health organizations and regulatory agencies consider fiberglass a possible human carcinogen, others do not.
- Formaldehyde. Conventional fiberglass batts use formaldehyde adhesive to hold the fibers together. Formaldehyde is a carcinogen that can slowly evaporate from the insulation and enter your living spaces. Fiberglass batts with no added formaldehyde are now available at a cost comparable to that of conventional batts. Loose-fill fiberglass and the other insulation materials listed in the supplemental chart are not made with formaldehyde.
- 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.
- If the insulation in your home is spotty or nonexistent, you may be able to solve the problem yourself in certain areas, such as an accessible attic. For DIYers, the U.S. Department of Energy has good information that will help you evaluate current levels of insulation and figure out how much more to add. You can pick up formaldehyde-free fiberglass batt insulation at most home improvement stores. If you want to buy cotton batts or loose-fill cellulose (or rent cellulose blower equipment), call around to check local availability. If you plan to install loose-fill cellulose yourself, check with the manufacturer for safety and installation instructions, and check your local building and fire codes. Look at our supplemental table to learn more about each type of insulation.
- You may want to consider hiring a home performance contractor. The pros can be especially helpful evaluating walls, crawl spaces, and other hard-to-reach areas. Here are some tips for the hiring process, and beyond:
- It’s standard practice to get several written quotes. Make sure the quotes include the installed R-value, so you can fairly compare them.
- Ask about air sealing services and costs.
- Ask about green options.
- Ask how quality will be ensured, especially for areas that are out of sight, like inside walls (some contractors check quality by using an infrared camera that shows where materials are missing). Shoddily installed materials can reduce the product’s effectiveness by as much as 30%, which means you won’t get the comfort or energy savings that you’ve paid for.
- When the work is complete, check the results before you pay the final bill. If you hired a company to thicken the attic insulation, for example, go up into the attic to see if the workers did a quality job.
- Read our article “How to hire a contractor” before making any hiring decisions.