Insulating a basement in old house

Old 10-30-06, 07:02 PM
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Insulating a basement in old house

I live in an old 3-decker, the new windows helped with drafts and the blown insulation in the north and west wall helped too but my floors are freezing in the winter and the cold sucks the heat right out of my feet in winter, plus my heating bills have jumped almost 35% in about the last 2 years. The furnace itself isn't that old but when it hits 10 degrees or less the house is chilly. The 2nd and 3rd floor apartments are always toasty in winter though with a similar furnace.

The cellar only has the water heaters and furnaces for the 3 apartments/floors. The cellar has what looks like ~3" insulation batting in the ceiling to help insultate a hole here and there in my floor- but it's just cold. 2 3/4 of the cellar walls are 80% or more below ground, the cellar floor itself is dirt, the walls are cement - now over brick I am guessing, 25'x50' total area. There are new basement windows that allow for air flow in summer when they are open so moisture isn't too much of a factor. It is usually very dry except in August or April/May seasons that are rainy and humid- but still mostly dry I have never seen wet floors down there.

A lot of advise seems to be don't insulate the basement ceiling -insulate the walls instead. The landlord is willing to spend about $1000 dollars but I prefer her money be spent well to help warm my toes and really help reduce my heating bill. Are walls really the way to go and forget the ceiling insulation? What is the difference in cost? I don't want her to have a moldy basement- but she was talking about an 8" batting to get an R-19 level.

She's an elderly lady so I don't want her to spend money futilely if there is a better solution to fix this cold.

Looking for people that know their stuff
Old 11-04-06, 02:27 PM
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Check along where wood sills joint masonry walls in basement. Fill all gaps with caulk or spray foam insulation, depending on size. This is a crucial area where there can be cold air flow. Inspect duct work to make sure it is insulated and not allowing heat to escape.

Heat transfer from floor below and ceiling does occur. Installing vapor retarder before insulation or fiberglass batts with vapor retarder facing heated space above can be done. When ceiling is insulated it will tend to make the basement colder, and ducts and pipes should be insulated. For more info go to

Cold temperatures of outside soil will transfer into basement via masonry. Insulating walls may help. Rigid foam insulation must be covered with drywall or some other material approved by the building codes in your area.

Carpet has some insulative value and provides warmth to the floors. That may be an option. 2nd & 3rd floor apartments are warmer because heat tends to rise. Ceiling fans can be adjusted to improve heat circulation and direct it from the ceiling and make for uniformity in room temperature.

Dirt floors in basement should likely be covered with 8 mil minimum polyproplylene vapor retarder. This will help to keep warm, moist from rising into basement and up through floor above. Dehumidifier can be used to control humidity. Opening basement windows during warm, humid months allows additional humidity into the basement and can compound humidity problems.
Old 11-04-06, 05:36 PM
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Heat transfer occurs in a variety of ways. Insulation prohibits heat Loss/Gain, which is quite useful in your situation. However, we must look at the other sources of heat loss. Judging by your description, the major source of your discomfort is probably the dirt floor. The solution is what twelvepole noted, applying a moisture barrier (plastic sheeting) over the dirt floor.

While that may be the solution, this is the reason. It has to do with the "Gas Law". Basically all this states is for a liquid to change state into a vapor, the liquid must be absorbing heat. For a vapor to change state into a liquid, the vapor must be losing heat. For example, the more your soda can sweats in the summer, the warmer the soda gets. The more steam you see coming from your coffee cup during the winter, the cooler the coffee gets.

To apply this to your situation is fairly obvious, however is often overlooked. The moisture in the ground outside is absorbed by the dirt in the basement through Equilibrium. The moisture in the dirt floor evaporates into the basement. However, for a liquid to change state into a vapor, that liquid must be absorbing heat. I'll give you 3 wild guesses where it is getting the heat from, the first two don't count. A moisture barrier applied over the dirt floor prohibits evaporation, thereby making your floor warmer.

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