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Questions About Home Sealing

What is a home envelope?
The exterior of your home is also called the “envelope” or shell. (See the orange line showing the envelope in the diagram at left.) The insulation, outer walls, ceiling, doors, windows, and floors all work together to control airflow in and out of the structure, repel moisture, and prevent heat from being lost or gained inside your home. A high-performance envelope helps maintain a consistent temperature even under extremely hot or cold conditions. The goal of Home Sealing is to improve the home envelope to make homes more comfortable and energy efficient.

What is air sealing and why is it important?

Air sealing is simply closing holes, cracks, and gaps where air can pass into or out of your home. On hot and cold days, you pay money to run an air conditioner or a furnace to maintain your home at a comfortable temperature. A house that leaks air costs more to heat or cool because your system must work longer to “condition” the air. In addition, if you happen to sit next to one of those leaks, you are uncomfortable because the room feels hotter or colder. Sealing those air leaks will help you maintain your home at a comfortable temperature all year long and help lower energy bills.

The biggest holes are most often found in the attic and the basement. Caulk, spray foam, and weather stripping are the most common materials used for air sealing.

Why is insulation important?
Insulation is designed to resist heat flow – that is, if it is hot outside, insulation greatly reduces the amount of heat you can feel inside a house. Or, if it is cold outside, insulation helps keep the heat inside the house. Without insulation, the walls of your house would be very hot to the touch during the summer and your air conditioner must work harder to keep you cool. In the winter, a lack of insulation makes walls very cold to the touch and the furnace must work harder to keep you warm.

However, insulation works best when air is not moving through or around it. Therefore, it is very important that air leaks be sealed to ensure that you get the full performance out of any insulation that is installed.

To get the biggest savings, the easiest place to add insulation is in the attic. When adding insulation to your house it is important to first evaluate how much and what type of insulation you currently have in you attic. The Recommended Levels of Insulation table can help you determine what is most cost-effective for your home.

The most common types of insulation are fiberglass (batt and blown), cellulose, rigid foam, rock wool, and spray foam.

Can I over-seal my house? (Make it too tight?)
While it is possible to seal a house too tightly, it is unlikely to happen in most older homes because they are much more leaky than they should be. A certain amount of fresh air is needed for good indoor air quality and there are specifications that set the minimum amount of fresh air needed for a house. If you are concerned about how tight your home is, you can hire an energy specialist who can perform an air leakage test with a “blower door.” If a home is too tight, fresh air ventilation can be added.

Is Home Sealing something I can do myself?
Yes! There are air sealing and insulation activities you can do yourself and it is worth doing. A handy homeowner can seal up holes, weather strip doors, caulk pipes and wires, and often insulate attic floors, basements, and crawl space walls. It’s important to remember, however, that air-sealing is just as important as insulation.

You can also hire an energy specialist who uses special tools, like a blower door, to find hidden leaks and are experienced at sealing and adding insulation. The blower door can also test how tight your home is after sealing. A Home Energy Rater or other energy consultant can perform a blower-door test and develop a plan for the most cost-effective measures to improve your home. Also, blown-in and sprayed insulation are usually best left to professional installers who have all the equipment. If you hire a contractor, shop around and get several written bids. Remember that a quality installation is more important than low cost. At the end of a job, contractors that install insulation are required by the Federal Trade Commission to provide you with a signed receipt that shows the R-value of the insulation they added.

What is reflective insulation (a radiant barrier)?
Reflective insulation (also called a radiant barrier) is a metallic foil material (usually aluminum) designed to block radiant heat transfer across open spaces. According to the Dept. of Energy’s (DOE) Radiant Barrier Fact Sheet, reflective insulation can be effective at reducing cooling bills and, possibly, reducing heating bills in homes. DOE also states that the performance and long-term cost-effectiveness of the product depends on number of factors, including: where the product is installed, how the product is installed, and the amount of existing insulation currently in the home. DOE and the Florida Solar Energy Center (FSEC) have excellent and detailed web sites that explain how the product works, general guidance on the best way to install the product, which climates the product is most cost effective, and energy savings one could reasonably expect. Please read through these sites for more information on this product category:
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