Cold Floor,Condensation,right forum?


Old 01-13-05, 02:50 PM
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Unhappy Cold Floor,Condensation,right forum?

Not sure where to ask this to get best response so here goes,

First I'll describe the structured area,Our bedroom has a 24" overhang outside the home,the overhang has no foundation under it,just open air and hangs off the foundation.The basement below the bedroom has a finished ceiling so there is no air movement to the floor above.

The problem,A few days ago we moved our dogs pillow that lays on that area and found it soaked on the bottom and frozen to the floor,quite a bit of mildew and slightly warped hardwood floors under it(no carpeting in this room).I realize that the pillow is insulating that portion of the floor and allowing it to be much colder and his bodyheat is warming it to cause the condensation.When we purchased the home the area of boards along the outside wall were darker but we thought nothing of it,now realize that perhaps carpeting may have been having the same effect and was torn up.

My question is,How can I fix the cold problem,I went outside and peeled off the bottom row of siding,filled the only cracks I could find at the sillplate with insulation and reinstalled the lap tightly to eliminate air draft.....the problem still persists .So what next?Pull the tiles at the basement wall ceiling and stuff with insulation,no heat,or put vents in the basement ceiling along the wall,some heat,,,maybe.Or is there a better was to warm the overhang floor.
Please give me some ideas,Thanks,Rick
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Old 01-13-05, 06:50 PM
Join Date: Jan 2005
Posts: 197
cold floor

Have you checked the backside of the bond-joist for insulation ?

It sounds like you would have to make a hole in your finished basement

ceiling in order to access this area. I don't think I would pack the entire

depth of the floor joist overhang cavity, but would cut pieces of fiberglass

batts to perfectly cover the individual sections of accessable bond-joist.

The foil face side of insul. should be towards the basement.

Good luck !
Old 01-14-05, 02:17 PM
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Not being a carpenter,What is the bond-joist and wouldn't the foil go up to the floor since that is where I want to retain the warmth?Please explain for me.

Old 01-14-05, 06:18 PM
Join Date: Jan 2005
Posts: 197
Bond Joist

The bond - joist is sometimes called a rim - joist. In any case, it is the
outermost piece of floor framing, the same lumber dimension as the floor
joists and in the case of an overhanging floor over a foundation wall, it
would run perpendicular to the floor joists.
The reason I said to put the foil side toward the basement is that the insul.would be applied to the interior of the bond joist, the cold air is on the other side (outdoors) and the foil should face the interior of the basement,
(the warm side)
If you open your basement ceiling and find no insulation at all inside the
framing of the overhang, it would probably be a good idea to just fill the
entire cavity with insul. and if you wanted to use a foil backer, put it towards
the bottom of the floorboard.
Good luck
Old 01-15-05, 06:52 AM
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Okay,now I understand,Looks like a good project for this weekend,Thanks
Old 01-16-05, 03:31 PM
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Use Plastic?

Pulled a row of ceiling tiles today.Found some insulation in the cavity,but it was fully wrapped with paper,seems to me that any cold draft would just find it's way around the insul as it was nowhere near a tight fit.Also found a crack about 1/4 to 1/2 inches wide with a draft coming through from under the overhang running horizontally to the block wall,I suppose that is part of the joint where the overhang meets the foundation.

I can't get to the seam outside the house right now(would need to remove 10 in of snow and dig out about a foot of dirt to get room under the house to work )So is there a permanant fix that I can do from inside,such as plastic stapled to the cavity cover(think bottom) then fill with insulation?(Concerned about condensation rotting wood)Can't get a caulking gun back into the cavity.Any other ideas to stop the draft or do I just fill with insulation and wait until spring to find cracks outside and caulk them then?
Old 01-18-05, 03:06 PM
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Anyone know the answer?
Old 01-18-05, 09:00 PM
Join Date: Jan 2005
Posts: 197
cold floor

Your last thought may be the best. Another idea might make sense too.

How long is this particular overhang? If it requires tearing out a lot of

basement ceiling drywall, you might wind up with less overall damage

to repair if you consulted a contractor who does a 2-part injectable

foam. They claim that moisture problems are eliminated with these pruducts

and it would also eliminate the settling problem associated with most

homeowner installed materials. If you pack fiberglass tightly, it actually

reduces the R value. If it's too loose, you get the same problem you have now.
Old 01-18-05, 11:02 PM
Join Date: Sep 2004
Location: Canada
Posts: 71
Rigid foam board and Polystyrene Insulating Foam

If you have room or access you might consider using rigid foam sheeting with sprayable polystyrene insulating foam made by Hilti to seal around all of the edges. I used this Hilti product in a barn like structure which had 1/4" gaps between all of the ceiling boards. It made a huge difference in slowing the heat transfer as it sealed all of the gaps and holes where heat used to transfer through.

Keep in mind that heat can also transfer through the studs and joists (also known as thermal bridges). It is also possible to apply thermal controls in these areas.

You may wish to spend some time researching the various insulating materials you have to choose from. Not one insualtion material is suitable for all situations. The three methods of heat transfer are radiation, convection and conduction. The standard and more popular insulations such as fiberglass only addresses conduction. When you take the other two forms of heat transfer the effectiveness can change dramatically.

"Air movement also greatly affects the R-value of fiberglass, as heated air moving through the fiberglass drastically reduces itís conductive value. ( see "Attic Insulation Problems In Cold Climates" March 1992, pp. 42-43 Nisson, J.D. Ned, JLC, in the R Value Fairy Tale )"

To better understand these concepts one needs to refer to the basics of "thermal dynamics and insulating" I am providing a link which should help understand how heat behaves and how insulations perform and fall short.


Last edited by wolfclan; 01-18-05 at 11:09 PM. Reason: Hyperlink

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