Basement Insulation Neccessary?

Old 02-07-03, 12:52 AM
Visiting Guest
Posts: n/a
Question Basement Insulation Neccessary?

When I finished my basement two years ago, I researched insulation and found that there was a lot of disagreement on whether it was neccessary. Some said insulate fully, some said insulate only the part above ground, and some said don't bother.

Since I hate working with insulation, I adopted the "don't bother" philosophy. I've got studs, then vapor barrier, then drywall. In the dead of winter the walls are warm to the touch. Did I do it wrong? (Of course, it's too late now, but I'm curious what people think.)

Maybe it's more important in northern climes (I'm in Virginia). One theory that convinced me was that if you had moisture, it could get into the insulation and cause problems, although a vapor barrier first could alleviate that problem. But the thing that sold me was the idea that, around here at least, the ground doesn't get all that cold, so what would you be insulating against?

Anyway, I'm sitting in my office in my warm, dry basement with no insulation wondering what others think about this!
Old 02-07-03, 03:49 AM
Join Date: Nov 2001
Location: Taylors, SC
Posts: 9,261
Upvotes: 0
Received 0 Upvotes on 0 Posts
insulation and moisture

This does not pertain exactly to insulation, but the the whole matter of all the information available about insulation, moisture, vapor barriers, and ventilation. I have a 1939 house built over a crawl space. The HVAC was added many years after the house was built. There are only six vents into the space under the house.

I have noticed that most new houses have a full size vent, about 8 x 16, every ten feet or so along the crawl space wall. I have read about what problems can result from moisture under a house. I have read about recommendations for ventilating under a house. I have read about mildew, rotting wood, and so on.

The ground under the house is quite damp most of the year. With all this about the moisture under the house and the potential problems, I became convinced that ventilation was inadequate here. I decided that I needed better ventilation. Then I read a pretty convincing argument that ventilation can cause problems by introducing moisture laden air into an area that was drier, creating its own problems. I was not totally convinced that the difference in moisture content could vary so much between the air under the house and the outside air, but I tried to hold the writer's argument in mind.

Then I mentally stepped back and took a look at what was right before my eyes. A house 60+ years old with no evidence of moisture problems; even the home inspector said that the ground was moist but that there were no problems or indications thereof.

For another opinion, I called an insulation contractor. He recommended that the floor under the house be insulated. I agreed. He also said that plastic sheeting 6 mil should be installed on the ground under the house to block the moisture.

It seems perplexing. The moisture has not been a problem for 60+ years. It may well be that the house was built more in harmony with the environment as it was then than houses in general are built now. It may be the luck of the draw that there are no problems. It may a time bomb ready to create all manner of problems from the moisture. But there seems to be no way to tell. My plan is to leave the moisture and ventilation the way they are and wait and see.

I suppose that we are all swept into the same current with general recommendations and standards that may not apply in every situation.

Of course, I may have felt differently about it if it were not going to cost $1000 to install the plastic. There is not enough room for me to get under the house and work on 50% of the crawl space. So I would have to pay someone to lay the plastic in at least that area.
Old 02-07-03, 08:38 AM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 17,505
Upvotes: 0
Received 1 Upvote on 1 Post
crawl way

Just my 2 cents. Hate to tell you how much insulation we have pulled out from in the joists over the years.So wet that it would run down your arms.What got us going the way we do it was a job I went to. They wanted AC put in their furnace. Looked around the home it was on a crawl way with a downflow furnace.
Asked how to get into the crawlway said they had a door to it on the out side of the home . Went there and opened it up . The door had heavy insulation on it. Went in and no duct work at all. Just a box hanging down from the furnace like a plenum with big holes in the side of it.The registers in the floor where just set in holes cut out of the floor. All of the walls had insulation on them and the joist space on the sill plate had insulation in them. The ground had a 6 mil poly on it. I ask how high was their heat bill and they said not bad and that there where 5 other homes just like theirs by them and their bills where about 1/3 higher and they had duct work on the furnace.Well you cant do that any more with code and all.But after that on a crawl way thats the way we would insulate them . We would use metal duct not FG duct board any more. We also cut in two hot air outlets and one return there in the crawl way . I find this way the whole crawl way works like a big heat sink for you. Oh we did do the AC job but put duct work on it
Old 02-07-03, 11:06 AM
Visiting Guest
Posts: n/a

Below a certain depth, the ground is a constant temperature year round. Something like 50 or 55 degrees.

So, if your office is 70 degrees, and the ground and foundation wall is 55 degrees, then there really isn't THAT much heat flow from 70 to 55.

Is there some heat flow? Absolutely.

Is there so much heat flow that it feels cold? Not in your case, as the heating system seems to be able to keep up with the load.

If the walls were insulated, would the heat flow be reduced? Yes.

The "Hot" set-up for insulating a basement is pretty much impossible to do unless you are building your basement now - basements are best insulated on the OUTSIDE.
Old 02-10-03, 04:03 AM
Join Date: Dec 1999
Location: United States
Posts: 2,484
Upvotes: 0
Received 0 Upvotes on 0 Posts
in a cold climate - insulate

In a cold climate, where winter highs are in the 20's and 30's, then insulating the basement is perhaps the best thing one can do to reduce the cost of heating the home (assuming the rest of the house is insulated and the windows are not drafty). This is not my opinion, rather from an energy audit I had done years ago.

I insulated my basement and the payback in energy savings was only two years.
Old 02-10-03, 08:20 AM
Banned. Rule And/Or Policy Violation
Join Date: Nov 2001
Location: USA
Posts: 1,820
Upvotes: 0
Received 0 Upvotes on 0 Posts
Appleye 1

There isn't a problem I see with your application. If you're comfortable and you don't see a problem with your heating and cooling bills, then doing anything else would not be recommended.

I do have some concerns about some of the replies to your post, especailly with moisture. This is because I see a lot of it in homes today, both old and new.

The biggest difference between an old home and new one is the materials used to make the home. The older homes used solid wood planking in the home and the new ones use plywood and similar products. Wood, solid or manufactured, absorbs moisture. The difference is that solid wood in most cases will dry out and still maintain its structual integrity and the manufactured wood will delaminate and will lose its structual integrity.

The other concerns I have with older homes and moisture are home improvement and developement. When older homes were first made, they were designed to have considerable amounts of air exchange. This air exchange provide a means to dry out the materials in the home through convection. People now improve their homes to save energy and increase comfort which actually reduces this air exchange. The result is these homes start experiencing moisture problems which they never experienced before. There is a very big debate on this known as the Sick Building Syndrome (SBS) between Architects, ASHREA and Energy Conservationists.

Look around you with all the developement. It is basically destroying the natural environment of wood destroying insects. Where do you think they are going to go? Let me put it this way, which do you think has a higher probability for wood destroying insects, a crawl space without a moisture problem or a crawl space with a moisture problem? Whenever I see an older home with a crawl space that has a moisture problem a picture immediately forms in my mind with a lady standing on a porch with a spoon clanging this metal triangle, yelling, "COME AND GET IT!" I do realize I'm showing my age with that statement and a few of you younger folks might not get it.

There are so many other concerns with moisture in homes today that I did not discuss, but I think I made my point.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: