Many homeowners and builders whose houses have basements are faced with the problem of whether basement insulation is necessary. At first consideration, it seems like a no-brainer; doesn’t insulation always increase the energy efficiency of a home? Of course, the answer is yes, but it should be considered whether the energy cost savings are worth the insulation investment and which is best to insulate, the space between the basement ceiling and the first floor or the basement walls.
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Two common basement insulation options are to be considered. One is to insulate the basement ceiling and the other is to insulate the basement walls.
Basement Ceiling Insulation
Based on simple math regarding thermodynamics, insulating a basement ceiling is not worth the cost. Many experts claim that even spending as little as $1,000 on basement ceiling insulation, it would take decades to recoup the costs in energy savings.
This conclusion is based on the fact that the purpose of insulation is to deter heat transfer. Since heat transference is a non-linear function, that is, it is greatest when the temperature difference between two areas is significant, insulation between the basement ceiling and the floor above is not cost effective. This is based on the theory that the average temperature of basement is 60 degrees and the temperature of the floor above it is between 70 and 72 degrees. This difference of 10 to 12 degrees means the transference of heat/cold between the two floors is extremely slow and insulation would have little or no effect on energy savings.
Basement Wall Insulation
Because basement walls are often made of exposed masonry inside and out, they are directly exposed to the cold ground with no impediments. If the ground outside is frozen, that means the basement walls are close to the freezing point.
Since many homeowners use the basement as a laundry room or at the very least as a storage area, closed-cell foam or Fiberglas insulation on the basement walls can make it a much more comfortable environment. Check with local building authorities to make sure the insulation chosen does not pose a fire hazard on exposed walls and does not require a drywall base.
General Insulation Considerations
Whether ceiling or wall insulation is chosen for the basement, other considerations should be addressed. These include air leaks and moisture control.
On top of the concrete/masonry foundation, the house’s wood framing begins. There is often a significant gap there that can significantly drain energy. If air can be felt flowing through this area on a windy day, insulation should be packed in the gaps to stop it.
This is not as easy to discover as air leaks as it can be almost invisible to the naked eye and can form on a variety of surfaces. It can seep in through virtually invisible cracks in concrete and masonry. If any beads of moisture are discovered, contact a basement waterproofing contractor for an assessment and advice on available preventive measures.