Energy Efficiency & Insulation


Effect of Dialing Down

Does turning the thermostat down really save energy?
Yes, the easiest way to cut heating bills or cooling bills is to adjust the thermostat. During the heating season, for every degree you dial down you reduce your energy use by 2.5 %. With a set back thermostat this doesn’t have to be a sacrifice. You can dial down at night and have the house warm when you wake up. Similarly you can dial down when you are gone during the day. Many folks have actually found that once they are used to it, they prefer living in a cooler house and don’t find it a hardship to have the temperature set at 65 degrees. It is not true that any savings you gain by turning the thermostat down are lost by the extra heat needed to reheat the house.

Energy Use of Refrigerators 

Will I really save energy by replacing my aging refrigerator?
Probably, Refrigerators are the single biggest user of electricity in most homes so switching to a new energy conserving model can produce dramatic savings.

The U.S. Environmental Protection Agency suggests that the average pre-1990 model use about 1,200 kilowatt hours per year. If you are paying the average price for electricity of 8 cents per kilowatt hour, an old refrigerator could be costing anywhere from $96 to $232 a year to run. The new models use much more effective insulation, more efficient compressors and better controls. A 20 to 22.5 cubic foot top freezer model can use as little as 457 kilowatt hours per year at an electricity cost of $36.

A field study performed by Wisconsin Division of Energy staff revealed other reasons to replace old refrigerators. Newer refrigerators are designed to run at top efficiency with a ‘duty cycle’ of 50 percent. The refrigerator compressor runs about half the time, and is off about half the time. Old refrigerators tend to run more than 50 percent of the time, and some never shut off. On average, older units run 70 percent of the time.

Older refrigerators are noisier than newer models. The compressor in old refrigerators runs more because moisture may have leaked into the fiberglass insulation. Wet fiberglass insulation doesn’t insulate. New refrigerators use rigid foam that can’t retain moisture. Buying a new refrigerator could save between $60 and $200 a year. More information about which models are most efficient in various sizes and styles is available at the links below.

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Fiber Glass Insulation

I have heard that I should avoid fiber glass insulation because it is health hazard. Is this true?
There have been allegations that fiber glass can cause cancer. The argument is that its fibers are close relatives of asbestos and can become imbedded in the lungs just as asbestos fibers can. However, Wisconsin Department of Health officials point out that fiberglass fibers are larger and they are soluble. These characteristics make it less likely that they will bypass the respiratory defense system and then become embedded in lung tissue.

A respected international group, the International Agency for Research on Cancer, recently reviewed the research related to cancer and fiberglass and concluded that fiberglass insulation could not be classified as a human carcinogen. For further information on this study, visit the web site of North American Insulation Manufacturers Association, the trade association of the fiberglass insulation industry. 

Nevertheless, fiberglass is an irritant to the respiratory system and to the skin. This is mainly a concern to workers who must handle the material. Anyone handling fiberglass should wear gloves, long sleeves and a dust mask to minimize contact with the insulation.

Installing Batt Insulation 

What are the guidelines for installing batt insulation in walls of a new home?
The most important thing to keep in mind is that the insulating value of these batts depends on them not being compressed. Batts should fit snugly into the stud cavity. If the batts are faced with paper or foil,unfold the flanges of the facing and staple them to the face of the stud. If you staple the flange to the side of the stud you will be compressing the insulation and leaving a void. When you encounter wires, do not stuff the insulation behind the wire. Instead cut the insulation, not the facing, so it fits around the wire.

Insulating Concrete Floors

What is the best way to deal with a concrete floor that becomes cold in the winter and damp in the summer?
One solution would be to add rigid foam insulation on top of the current floor and then to lay a new floor over the insulation. One or two inches of foam would probably be enough to solve your condensation problem and make your floor more comfortable in the winter.

Insulating Value of Straw

What is the insulating value of straw?
According to the Midwest Plan Service “Structures and Environment Handbook“, 20 inches of straw has an R-Value of 30 (see Table 631-1). Designers of straw bale houses claim R-Values of 45 for bale structures that are plastered on the inside and outside to better trap the air in the straw.

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Insulating an Older Home

Will insulating the walls of an older home cause moisture problems in the walls?
The answer is probably not. In most older homes the outside walls are loosely constructed so that moisture that enters the wall from the inside can easily escape. However, if the outside walls are tightly constructed so little air can escape the added insulation could make them colder and could lead to condensation against these walls and potential moisture damage.

Insulation and Humidity 

Will adding insulation increase humidity levels?
Added insulation will not usually increase humidity levels. However, weather stripping and other measures that reduce drafts will, because these measures will decrease air exchange and trap humidity.

Selecting Attic Insulation

Is spray insulation worth the extra costs?
Spray polyurethane offers a number of advantages for special situations. It has an r value of over 6 per inch. This means that when space is at a premium such as in an attic with 2 X 6 rafters you can easily get an r-value of over 30. A second advantage is that the foam does not require a space left between the roof deck and the insulation for ventilation. It is important to note that some shingle manufacturers require an air space under the roof deck to keep it and shingles cool. However, the effect of this air space on roof temperature has not been substantiated by recent research.

For more information about spray foam insulation, visit one of the following web sites. The Energy Efficiency and Renewable Energy Network provides a chart listing the Types of Insulation. You can also visit web site of the insulation contractors association (

What type of insulation is best for an attic?
Fiberglass or a related product rock wool and cellulose are the primary choices. Cellulose has a higher insulating value (r-value) per inch. It has an R-value per inch of between 3.2 and 3.8. while fiberglass has an R-value of 2.2 to 2.7 per inch; this means it takes more depth of fiberglass to provide the same insulation. Rock wool is closer to cellulose in insulating value.

Cellulose settles about 20% after installation as opposed to fiberglass which settles about 4%. Rock wool settles even less. Coverage information on the cellulose bag should reflect the settled r-values. To be sure you end up with the insulation value you expected specify insulation by the bag not the thickness to avoid problems with settling. Because fiberglass is much less dense, air can blow through the top few inches reducing the insulating value somewhat. However, the overall reduction is small.

Even though cellulose insulation is made of combustible paper, it is treated with chemicals to make it fire resistant and it must pass tests to confirm its fire resistance. Fiberglass and rock wool are both naturally non-flammable.

While cellulose fibers absorb water, water can be trapped between fibers in fiber glass. Both types of insulation lose insulating value when wet.

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Vapor Barriers 

How tight do vapor barriers have to be?

Vapor barriers are intended to keep water vapor from getting to the colder, dryer wall cavities from the relatively moist and warm interior of your home. In extreme cases, moisture entering wall cavities can cause decay of structural lumber and sheathing and can reduce the effectiveness of any insulation that is in the walls.

There is a rule of thumb that a vapor barrier should be at least 90 percent effective, which means it can tolerate a few small holes. However, air leaking into the walls is a major source of moisture in wall cavities and vapor barriers are often intended to serve as air barriers as well. Very small imperfections in an air barrier can allow large amounts of air to leak into walls. This means it’s important to carefully seal around electrical and plumbing fixtures and along the bottom of the wall where it meets the floor.


How much energy does a waterbed use?

Efforts to assess waterbed energy use suggest that usage ranges for 1,000 to 2,000 kilowatt hours (kwh) per year. Given electric rates of eight cents per kwh this means that a water bed could add between $6.70 and $13.30 per month to your electric bill.The amount of water that must be heated determines the energy use of water beds. Newer models are designed to use less water and therefore less energy. Mattress pads and regularly pulling the covers up on the bed can substantially reduce energy use.

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