HVAC For Beginners

Home Insulation

A Guide to Improving Energy Efficiency

With this home insulation guide, we will look at the basics of insulating your home and how it can save you a lot of money.

Insulation is the process of separating an area that is warm from an area that is cold. This is accomplished by trapping air in tiny pockets. Air is a poor conductor of heat therefore these tiny pockets help to resist heat flow. This resistance to heat flow is known as R-VALUE. The R-VALUE of a product is set in the manufacturing process and is determined by the type of material as well as its thickness. There are factors which can cause this value to change after it is installed.

Settling is the process where the insulation material is compressed over time. This process means that less air is trapped in the pockets and therefore it is easier for the heat to flow. (The R-VALUE is lower.)

Another factor that can change the effectiveness of the insulation is moisture. Unlike air, moisture is an excellent conductor of heat. Therefore, any time that moisture is held in a material, more heat is transferred through that material. (The R-VALUE is lower.)

Types of insulating materials

There are four traditional types of materials used in home insulation.

Cellulose is basically recycled paper that is treated to resist pests and fire. It is typically blown loosely into attic spaces or combined with a glue/water mixture and blown into walls. The main advantage of this material is that it is the least expensive. A disadvantage is that it has a high rate of settling (typically 20%). Therefore, it can lose a significant part of it's R-VALUE over time. Another disadvantage is that, when it is blown wet into the walls, time is required before covering it with drywall so that it can dry out. If this is not done, mold and other indoor air quality issues can occur.

Fiberglass is the most common material used in home insulation. Although it is more expensive, it tends to settle less (typically only 1-3%) and therefore it retains it's R-VALUE better and longer than cellulose. Another advantage is that, the material does not retain moisture like cellulose. Therefore, if the material becomes wet, it will dry out and return to it's original R-VALUE. The product is available in blankets which are long rolls that can be cut to a desired length. Blankets are typically used in attics. When these blankets are precut into lengths that fit into wall spaces they are referred to as batts. This material is also available in bags for loose fill. This is typically blown into attics with a machine. (The machine is avaialable for rent at most home centers.) An advantage of this form is that it can fill in hard to reach areas.

Foam is another material commonly used for home insulation. This is available in rigid board form which can be used on the exterior of a home, basement walls, or walls in an unconditioned crawlspace. The spray foam (polyisocyanurate) is a combination of a resin, hardener, and air. It is typically mixed on site and blown into walls and attics. The main advantage is that the material expands when applied and is good at making an air barrier. The product also does not settle and is not affected by moisture. The main disadvantage is it is the most expensive.

The final material is known as a radiant barrier or reflective insulation. This is typically an aluminum foil that is incorporated with a foam board or a bubble wrap type material. Unlike the other materials, this product reflects infrared heat. This material is normally used in attics and on hvac ducts.

Non-traditional types of home insulation

The latest innovation is commonly referred to as "blue Jean" insulation because it is produced from recycled denim and cotton. The 90% post consumer recycled fibers are bonded together and formed into a batt for installation. The batts contain a fungal inhibitor to protect against moisture and mold. This is a very environmentally friendly product as there are no chemicals added and therefore no volatile offgassing. Another advantage is that it does not not irritate the skin and therefore is easier to install as no special protective equipment is required.

For situations where traditional forms of insulation are not practical, you can insulate your home by simply painting the walls and ceilings. This can save you money by insulating without the expense of remodeling as well as lowering your utility bills.

How much is needed?

The amount of insulation in a new home is usually regulated by local building codes. These codes typically give the minimum that is acceptable in an area.

In the absence of codes, the following recommendations are generally the most cost effective:

With the rising costs of energy, adding home insulation can be an investment that pays huge dividends.