Saving thousands of dollars over time is no exaggeration about the effects of adequate insulation in homes and buildings. Insulation creates a buffer against the transfer of heat. Heat is one of the most powerful forces in the universe and it’s always moving from hot to cold.
In the summer, heat wants to move into cooler spaces, like your home. In the winter, the process reverses and it escapes into the outdoors where it’s cooler. It takes a great deal of energy to stop heat from moving to cooler temperatures, but insulation thwarts it.
How it Works
The air bubbles trapped inside insulation slow the movement of heat in or out. Its ability to do so is measured by how long it can resist temperature change, known as R-value. The R- stands for resistance and the numbers after it indicate how many hours it will slow temperature change. R-13, for example, resists temperature change for 13 hours. R-30 prevents heat gain or loss for 30 hours.
Kinds of Insulation
The most common type of insulation used in homes and buildings is fiberglass in the form of rolled batts. Builders use it inside attics, walls and basement ceilings. It’s inexpensive, durable and easy to install. The next most common kind of insulation is loose cellulose, made from recycled paper and treated with borates that are chemicals to retard moisture absorption, insect invasions and fire. Loose insulation is used in walls and ceilings and installed with blowers.
Both fiberglass and cellulose have the same R-value per inch of depth. According to the U.S. Department of Energy (DOE), one inch of either has an R-value of 3 to 3.8. Foam insulation R-values exceed that of fiberglass or cellulose. Foams’ R-values range from 3.6 to 8, which is why they’re used in tight spaces in walls, ceilings and attics.
How Much Do You Need
The DOE recommends that homes in the U.S. in cold climates have up to 20 inches in the attic and those in warmer climates at least 10 inches. The amount you need depends on the kind you choose.
Foam provides the best resistance to thermal or heat transfer but it’s also the most costly. Rigid foam boards are easy to install but sprayed-on foams almost always require a professional who has the equipment to apply it. Closed cell foam products offer the highest R-values and are used on roof decks turning attic spaces into livable areas or in tight corners.
Most homes use 2 x 4 framing and use R-13 batts. There’s nothing to gain by putting thicker batts inside them or overstuffing them with loose insulation. It’s the air spaces in insulation that make it effective and when it’s packed in tightly, it loses air and its R-value falls.
While adding insulation isn’t a complicated or expensive project, there is a learning curve associated with installing it. Before contractors install it, they recommend sealing all the air leaks in the walls and attic first. It is possible to add insulation over the existing material in the attic as long as it isn’t damaged from moisture or mold.
Batts should be placed perpendicular to existing insulation to prevent thermal bridging and air leaks. Although home centers rent blowers to install loose insulation, the job is messy and requires some skills to blow into wall cavities.
Applying sprayed foam requires a high skill level, special equipment and protective breathing apparatus and clothing. Rigid foam sheets are fairly easy to install, but care has to be taken to cut them for a tight fit and prevent moisture buildup between the structure and the insulation.
Increasing insulation in areas where it’s lacking will lower heating costs. It also provides greater comfort year-round, since temperature swings will be minimal. It’s the most durable and affordable way to achieve greater energy efficiency.