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Q: Dear Energy Wiz,
Should there be a space between the concrete wall and the frame wall I am installing in my basement? Also, what kind of insulation should I use in between the wall framing? Should I also use a poly vapor barrier behind/between the frame wall and the concrete wall? Thank you for your time.
-- Mr. Williams
The Energy Wiz!
The Energy Wiz!

A: Dear Mr. Williams,
The biggest problem associated with insulating basement walls is the possibility of getting moisture behind the insulation. The moisture can come from inside the house in the form of condensation on a cold basement wall, and moisture from outside the home that does not drain away from the house and seeps through the basement wall. The important thing to realize here is that concrete and gypsum board are not vapor barriers, most molds feed on cellulose products, such as wood, and molds like dark places. Since you can't control the light behind a wall (it will be dark), you need to control the moisture or what the mold feeds on.

Now almost any insulation can be used, even blown in cellulose provided it has been treated to prevent mold growth. We have seen a number of basement wall installations use a product called polyisocyanurate, which is an insulation board, with an R-value of about R-7 per inch of thickness (ie...R-14/2inch, R-21/3inch, etc.). This was recommended as a best practice solution at a recent workshop, foil faced polyiso board applied directly against the basement wall, followed by a 2x2 or 2x4 framing over the polyiso. Another best practice is the use of steel or alluminum framing members instead of wood over the polyiso. The foil facing on these boards provides a vapor barrier and drainage plain for any moisture that might condense on the basement wall or come through the basement wall from the outside. It is also recommended that the gyp board be left 1/2" off the floor to keep it out of any moisture that might drain down the wall.

In the following list of web sites, there is some good information at on insulating basements, but please be reminded that a lot of this work has been done in the southern part of the country where the emphasis is on high humidity in a warmer climate. I believe that in our area, any problems with moisture in a basement or crawlspace will likely come from condensation on a cold basement wall.

Please also make sure that your home has good drainage away from the basement walls on the outside of the home.

Visit these web sites for information on moisture and mold:





  • I hope this information has been helpful. Please don't hesitate to write or call our office with any further questions you might have.

    The Energy Wiz

    The Energy Wiz recently received several questions about biomass from a 6th grade student. Here are the Wiz’s responses:

    Q: Dear Energy Wiz, What kind of waste does biomass produce, if it does?

    A: First of all there are many types of biomass fuels, and different ways to produce energy from it. Probably the most common form of biomass energy is ethanol. Gasoline with ethanol can be found at most service stations. Ethanol can be burned in some special cars by itself, instead of gasoline, but most often it is mixed with gasoline, and that can be burned in any car. Ethanol is a type of alcohol and burns very clean when compared to gasoline. Ethanol can be made from a number of different biomass products. Corn is the major source of today’s ethanol, but ethanol can also be made from sugar cane, a number of different grasses, and various stovers (Stover is what is left in the field after a farmer takes the grain from the field).

    Biomass energy can also be produced from burning waste products such as stover, wood or wood waste. This type of biomass energy is produced in a couple of different ways. One way to produce energy from stover or wood waste is to burn it straight from the field, forest, or from saw mill wood waste just by making a fire from it. When wastes are burned in this way, other waste byproducts such as carbon monoxide (CO), carbon dioxide (CO2), and nitrous oxide (NOx) are produced. Just burning biomass by making a fire is not a very clean or efficient was to utilize this energy resource.

    Another way to get the energy from stovers, wood, and wood waste, is to burn it slowly in an air tight room. As you probably know, a fire needs air to burn. If you put biomass in an air tight room, and only give it a little bit of air, it burns very slowly, like the coals in a grill, and gives off a gas that will also burn if you give it more air. That process is called gasification, and is a cleaner way of burning biomass. The gas that is given off using this gasification process can actually be burned in an engine like the one in your parents’ car, but to do that, the car would need to have some special things added to it which would cost a lot of money. What usually happens is that the gas that this burning process gives off is burned in a special engine right where the gas is made. That special engine then turns a shaft on a machine called a generator, and that generator makes electricity. Here, too, there are emissions, or pollution, but the emissions are more like those of a car.

    Another type of biomass energy comes from the excrement from farm animals (the stuff that's left when farm animals go to the bathroom). Some farms use a machine called a digester to make energy from this animal waste. There are also some cities that make energy from human waste in this manner. What happens, is that the waste is gathered, usually by washing the pens that the animals live in. Then the waste goes into a type of drain or sewer, kind of like the sewers in town, and finally to the digester. Once the waste is in the digester, bacteria and enzymes work on the waste and give off a gas called methane. Again, this is not a liquid gas, but more of a gas like the air we breathe, except that it will burn. This gas also is usually burned in an engine that turns a generator which, in turn, makes electricity. The emissions, or pollution, from burning this gas are usually pretty clean. We still get some pollution, but less than what comes from a car that burns gasoline.

    One other biomass energy source is biodiesel. Most trucks on the highway burn a liquid called diesel fuel. A farm product called soybeans can be made into a liquid that is just like diesel fuel, and can be burned in those same trucks. You can also make biodiesel from animal fat, such as the waste grease that a restaurant used to cook french fries. The pollution from engines that burn biodiesel is almost the same as the pollution that comes from burning regular diesel fuel, with some positive differences. The advantages are less sulfur dioxide (SOx) is produced and biodiesel helps lubricate the engine, which makes it last longer.

    What risks are there with biomass energy?
    The risks are very similar to the risks that we see in other things we do every day. With ethanol, the risk might be that a food product is converted to an energy product. But not all of the corn turns into energy. Much of what is left of the corn is still made into food products. The same is true of using soybeans to make biodiesel. Of course, using waste grease from a restaurant to make biodiesel is a good thing since the waste grease would otherwise go into a landfill or sewer. Using animal waste to make gas for burning is also a good thing. Animal waste usually has a bad odor, but when it is put in a digester to make "biogas," it takes the odor away, and what is left is a kind of dirt that is good to put on gardens or farmland and helps plants grow.

    Your Friend,
    The Energy Wiz Editor's Note:
    The staff at the Energy Office respond to many inquiries on a variety of topics from Nebraskans. From time to time, the Quarterly will share some questions — and the answers — with readers. Home Energy Loans Energy Statistics State of Nebraska Home Disclaimer Webmaster