Unwanted air leakage from heated or cooled living area has the highest return of comfort and savings, testing is recommended.
Air Sealing has the biggest savings for your energy investment. The primary target for air sealing is at the top of the building.
Be careful if you think your old or new house is fully insulated.
Air sealing unwanted air leakage from the heated or cooled living area has the highest return of comfort and savings so it should be tested. Fancy curved arches or drop soffits in the kitchen or bath often are not sealed. Also, the Department of Energy’s recommendation for attic insulation is R-50 or almost 15” of insulation. Finally, is the access hatch to the attic sealed, insulated, and boxed in?
Drop soffit before air sealing
After air sealing drop soffits and insulation
Insulation Materials are not Equal, nor is the Installation!
Oak Ridge National Laboratories has tested the performance of various types of insulation in many different applications. One source of such information is available at championinsulation.com. Fiberglass batt insulation only performs at its rated R-value when it is sealed in a six-sided box. Walls usually have outlets and switches and some other minor penetrations. The problem is that fiberglass batts have almost no resistance to air movement across the edges and length-wise.
Box sill insulation
Laid horizontally open to the attic space above, fiberglass batts lose some effectiveness because air can “loop” through the fibers reducing the effective R-value of the insulation. I do note that fiberglass batt insulation in attics performs better than blown fiberglass. In my area, some new houses have 6” or R-19 un-faced fiberglass batts in the cavities contacting the interior surface followed by 6” to 12” of blown fiberglass. An Infra-red scan sees the fiberglass in the cavities but still sees the ceiling joist lumber because the blown fiberglass is not really performing.
Many builders now use blown cellulose insulation because the blown fiberglass is not sealed and therefore has air looping through the insulation from the attic space. Some studies have claimed up to a 50% reduction in effectiveness when temperatures drop below freezing. I prefer using cellulose that is recycled newspapers with borate fire retardants. Cellulose is twice as effective as blown fiberglass for sealing air leakage, six times better sound attenuation than fiberglass, and very adaptable for a variety of uses. My recommendation from past experiences is to blow over the blown fiberglass with 4” to 6” of blown cellulose to seal in the fiberglass and help it perform better.
Frequently Asked Questions . . .
My house is always cold. Do I need a larger furnace?
There are lots of possible solutions, but a larger new furnace is probably the least desirable. A new furnace by itself may just heat the neighborhood more efficiently. More directly, insulation added after air sealing unwanted leakage should improve the comfort of your home. Over time, such energy and insulation improvements can even pay for themselves from savings. In the distant future when a new heating system is needed and you are ready for that major investment, the furnace can probably be a smaller size and a high-efficiency, sealed combustion unit might save additional money.
My house is drafty. Do I need new windows?
We all get calls from window salesman at night, along with billboard ads, and television pitches, but there are a lot more cost-effective air sealing and insulation work to be done before investing in expensive new windows. Proper sidewall insulation often cuts off the air leakage that you thought was coming in the windows. After all, most houses are 85% walls and 15% windows. There are a lot of good reasons to have new windows (ease of cleaning, thermopane glass, and sashes that move because the old windows were painted shut), but energy savings is usually the least effective, with paybacks stretching out to almost 75 years.
Will insulation keep my house cooler in summer?
The basic answer is yes. The detailed explanation is that air sealing and insulation improvements can just about save as much money on your air conditioning bill as it did on your heating costs in winter. Usually, your house will be more comfortable without any mechanical air conditioning running. A new description called a “night wash” suggests airing the home out at night by opening windows and then closing up the house in the morning will keep the house six to seven degrees cooler than the outside by the end of a hot day. Now this is nothing new to our elders or most any mature farmer, but is valuable. Ceiling fans on low speed and regular fans on low speed do wonders because such air circulation “tricks” your skin into feeling cooler. When the weather gets really hot for those 7-10 “beastly” days of summer, we all have the choice to run the air conditioning as a “necessity.”
In my professional experience, I believe that central air conditioning is over sold in Wisconsin. I live in a neighborhood where many people run the central air from May until October. When I walk the dogs at night, I hear the A/C compressors running, even though the outside temperature may be a comfortable 65º at 9:00 PM. In Wisconsin, much of the A/C cooling load is actually for dehumidification not cooling. In the past, my light-commercial dehumidifier in the basement, put out air that was nine degrees hotter than the ambient air and the dry room temperature got as high as 87º. Still, this is where the dogs would hang out whenever they got the chance.