Better Home Insulation
Can Save You 25%

Home insulation is not simply the purview of professionals. Armed with the basic principles of heat flow, you can vastly reduce your heating and cooling bills. Proper home insulation also reduces sound transmissions, making your house a quieter place in which to live.

Other great ways to save are included in our strategies to save money which include energy conservation tips to implement around the home.

Heat Flow

According to the zeroth and second laws of thermodynamics (there is actually a zeroth law!), heat flows to a place or object that is less hot until the two systems' temperatures are identical. How does this happen?

Heat may move by convection (air current), conduction (through a liquid or solid material) and radiation (through electromagnetic waves such as sunlight).

Home insulation materials that limit heat movement by convection are foam insulation, fiberglass insulation such as wall and attic insulation, and vermiculite insulation. These work by limiting air flow and because these materials are not in themselves good heat conductors.

Foam insulation is used to control heat conduction from materials such as metal or masonry. An example is vapor-barrier-lined foam lining placed on a slab basement floor beneath carpeting.

Radiant barriers control radiant energy using a foil sheet attached to a backing such as paper, cardboard, plastic or wood. It is used typically between roof rafters, floor joists or wall studs. Improve your home's insulation by installing it across inside roof rafters or on top of attic insulation to control summer heat gain or winter heat loss.

R-Value

An insulation’s R-value identifies its resistance to heat flow. The higher the R-value, the better the home insulation provided. Since the type, thickness and density of home insulation go into determining its R-value and its effectiveness, consider that:

Insulation Types

1. Blanket Insulation: Offered in rolls or batts, these are constructed of fiberglass or mineral wool (rock or slag wool) and may be paper/vapor barrier backed. In hot or humid areas, this vapor barrier may not be needed. Check your local building code. This is the “greenest“ home insulation, as it is made from renewable resources.
   
   
2. Blown-in Insulation: Typically cellulose, fiberglass or rock wool. It usually is blown in professionally but may also be poured from bags for attic insulation. For walls, pouring this loose insulation from your attic down into stud spaces is not as effective, as it will not penetrate below window framing and will likely be of varied thickness when there is plumbing or wires in these spaces. Professional installation uses pressure to ensure even distribution in walls.Many home improvement stores and rental centers now offer insulation blowers for the do-it-yourself project. A 3/4 hp blower will insulate a 1,000 sq. ft. attic to R19 in about one hour.
   
   
3. Foam Insulation: You can buy spray foam insulation in aerosol cans for small jobs such as ceiling-to-attic or foundation cracks. Professionals use pressure equipment to spray entire wall areas where it may be difficult to achieve coverage with fiberglass or mineral wool, such as on sloped or cathedral ceilings. Closed cell foam insulation is less vapor permeable and has a higher relative R-value than open celled varieties. Rigid foam insulation comes in panels and is excellent where space is limited, as it has R-values about twice that of other insulators per thickness.
   
   
4. Radiant Barriers: All materials give off thermal radiation by virtue of their temperature. Attached between a roof deck and roof shingles, to the top or underside of roof joists, or on top of attic insulation, these insulators reflect thermal radiation that would otherwise enter your attic space or ceiling’s insulation. They also have a low thermal absorption, so they stay cool. The simplest application is to lay it on top of existing attic insulation with the reflective side up.

Where to Insulate

Safety comes first. Always wear eye protection. When installing attic insulation, be sure that where you step or kneel is able to support your weight. If adding home insulation to areas containing electrical wiring, turn off the power before insulating.

For fiberglass insulation, cover all skin and wear a mask over your mouth, as fiberglass particles will cause a contact itchiness or throat irritation. However, both the World Health Organization and the International Agency for Research on Cancer have determined that environmental pollution from fiberglass insulation is not a safety concern, and that it does not need to be listed as a carcinogenic agent.

The U.S. Department of Energy’s Oak Ridge National Laboratory Building Envelope Research team has issued a helpful diagram outlining where to add insulation.

How Much Do You Need?

This is a three step process requiring a screwdriver and a ruler. First, measure the insulation depths you now have. For attic insulation, this should be straightforward. For wall insulation, unscrew an electrical socket plate or light switch plate at various locations to measure. For floor insulation, do the same with a ceiling light fixture or by removing a suspended ceiling panel.

If you can’t see the R-value printed on any of the insulation you now have, use this chart to calculate it.

Now that you know the type and depth of home insulation you have, find out how much you need using the DOE Climate Zone insulation calculator.

Let’s say you now have 4 inches of rock wool attic insulation. Using the chart above, it’s R-value is 4 x 2.8 = 11.2. If you live in Zone 5, you should have R=41 in attic insulation. Therefor, you need to add R=30 in additional insulation. You should add it directly over the existing insulation. If feasible, place it perpendicular to the existing attic insulation to further limit heat flow.

Sealing Cracks

Just adding home insulation is not enough. It is important to limit the flow of warm, moist air into or out of your house. In summer an air leak will carry warm, humid air inside. In winter, a leak will carry moist warmer air from your bathroom into your attic, where the moisture may condense and contribute to rot. Seal these leaks before you insulate, when you can best see and feel them.

Affording It

Since warm air rises and cool air sinks, insulating your attic and your basement or foundation slab give you the best return on your investment. For your walls, windows are by far the greatest area of heat gain or loss. Instead of investing thousands to upgrade to double or triple glazed windows, look into lined curtains or insulated blinds. Consider using outdoor shading and wind blocking to improve the performance of your home’s insulation.

Even in these fiscally tight times, there are state and federal incentives and rebates to promote renewable energy and energy efficiency. As a general rule, you can expect to recover the cost of insulating your home in 5-6 years, assuming fuel costs stay the same. As fuel costs rise, this recovery period will be shorter.

When planning your budget, remember to include the increase in home value you will enjoy with a more efficient home.

For more information, visit this excellent home insulation site.

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