When you conduct over 3000 Home Energy Audits per year you’re bound to run into some interesting opinions. Many people believe certain things about home energy consumption that are just not true. These “Energy Myths” have often been inherited from one generation to the next. “Grandma always said…” is the typical preface to many of these energy myths. But a whole lot has changed in the last 50-100 years that makes grandma’s recommendations obsolete. Sorry Grandma. So after hearing many different Energy Myths from many different energy customers, the staff of Conservation Consultants got together and compiled some of the most common ones into a list of… drum roll please…

The following forms of insulation are less commonly used than fiberglass and cellulose, but this doesn’t mean they’re less desirable. Most offer unique advantages over more traditional insulation, although they may have higher initial costs or other drawbacks as well. We urge you to consider them and make the decision that works best for your home, your finances and your environmental commitment.

Foamed insulation is a bit expensive initially, but lasts longer and insulates better than others. It is made of various materials in their liquid states, and can be sprayed, injected or poured into the building envelope. Because foamed insulation can be made of many different materials, its R-values vary widely, from around 3 to at least 8.

Fiberglass has long been one of the most common types of insulation. It comes in many different forms, but the basic concept is that glass is heated and spun to form tiny fibers that stick together haphazardly. The structure traps air well, making it a good insulator.

Cellulose loose-fill is best compared to fiberglass loose-fill because both offer the benefit of more effectively sealing the building envelope from heat transfer. Cellulose tends to offer a better R-value per inch (see chart below), and it is not a possible carcinogen. It also boasts some environmental credentials above those fiberglass can claim: it has a greater percentage of recycled content, its manufacture is about 8 times less energy-intensive and, when it is removed from a house frame, it can theoretically be composted. However, cellulose tends to be more expensive, and its installation can be more labor-intensive than that of fiberglass blankets. It’s especially important to ensure proper installation of sprayed-in cellulose because if it is left too wet, mold, mildew and even rot can form in the house frame.

An essential component of conserving energy is keeping conditioned air in your house and keeping unconditioned air out, meaning that in the winter hot air doesn’t escape and in the summer cool air doesn’t escape. Insulation plays a role in keeping your house warm too, but regular fiberglass insulation does not stop the flow of air. Typically insulation is effective at preventing heat transfer through materials (limiting your home’s ability to conduct heat), it cannot prevent air from actually sneaking in and out through holes and cracks. (The exception to this is sprayed-in Cellulose and some foam insulations that can both air seal and insulate)

One important alternative to fiberglass (link) insulation is cellulose. Cellulose is installed with machines that blow it into attics or spray it into wall cavities. Cellulose is made from shredded newspaper and is a good insulator because wood, from which the paper is derived, has a heat-resistant cellular structure. Typical R-values range from 3.5 to 3.7.Cellulose loose-fill offers the same benefits over fiberglass blankets as fiberglass loose-fill does: it is more effective at insulating an entire space because it can fill oddly shaped spaces and let less air through. In spaces like attics where the insulation rests on the floor, dry cellulose can be blown in, while in vertical spaces like wall cavities the shredded newspaper can be purchased that is dampened and sprayed into place to ensure even, effective application. This technique is used more often in new constructions.

R-value is a measure of a material’s thermal resistance – the degree to which a material allows or does not allow heat to be conducted through it. In our context it applies to the insulation used to keep houses warm in the winter and cool in the summer. It’s measured both by the thickness of a given insulation material and by the structure of that material, so 2 different types of insulation with the same thickness can have different R-values. Comparing the R-values of various types of insulation is one of the most important ways to determine what type of insulation to use, and how much.
If a home had no insulation at all, the thermal resistance would be measured by the amount of air within the wall cavity, the air would have an R-value of 1 per inch (extremely inefficient). Fiberglass, a common type of insulation, ranges from an R-value of 2 to 5 per inch, depending on the type. Although R-values are measured by thermal resistance per inch (like an R-value of 3 per inch), the reference to thickness is usually not used (so instead we just talk about an R-value of 3).
As we’ve said before R-values and insulation make up only one of the two parts of the “envelope.” The other equally important component of the envelope is Air Sealing.

Insulation is material that essentially serves as a barrier between your home and the heat or cold outside. Good insulation will conserve the heat within your home in winter, and will help keep heat from entering your home in the summer. A material’s ability to do this is measured by its R-value. There are many types of insulation, and many places in your home to put it.