basement insulation

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  #1  
Old 02-15-03, 12:18 PM
whitey2
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basement insulation

I have to correct a problem with a recently purchased vacation home located in a cold climate. The foundation is concrete block with no exterior insulation. The previous homeowner installed the interior walls by using free standing(not attached to the block) untreated 2x4's tight to block and installed R-13 batts between the studs. The batts are paper backed with the vapos barriar on the warm side of the suds and is in contact with the block wall. It is finished with 1/2" drywall. Seeing as the home is not used all the time, the basement does not have constant air movement. There is green mold on the drywall and the insulation feels damp. I removed a 3 foot square area of the wall to reveal a wet block wall. After being exposed for a week, the wall dryed up. Do I tear down and dispose of the wall and start over? Is anything salvagable? There doesnt appear to be a drainage problem.
If I must start over, this is what I was told to do.
Use 1" rigid foam board(the cheaper white stuff) tight to the wall, install 2x4 wall with treated floor plate, regular 2x4 stud wall, insulate with R-13 non faced batts, no vapor barriar, 1/2" drywall. Does this sound correct?
 
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  #2  
Old 02-16-03, 10:49 PM
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When you removed a portion of the wall and it revealed moisture on the block and it dried up afterwards, should tell you something. Poor air movement in the basement would have produced condensation on the wall and everywhere else for that matter, except on the block.

What you are experiencing is common because basement wall installation like yours is common. Wood, masonry and insulation all have different rates of absorption and expulsion towards moisture. Fiberglass has a very slow rate of absorption and a very fast rate of expulsion towards moisture. Masonry on the other hand has a very fast rate of absorption and a slow rate of expulsion towards moisture. When to two different material touch each other, the probability of condensation is high.

What exactly does this mean? In most cases the masonry takes humidity out of the basement. This is because the ground surrounding the masonry can usually absorb the moisture in the block. When the ground is wet because of rain or poor drainage, instead of the masonry being dried out by the ground, it now absorbs the moisture in the ground. Yes, that is correct, masonry can either remove humidity in the basement or add to it depending on the moisture content in the ground that surrounds it. This by the way is normal.

The way to avoid the moisture problem you are experiencing is to not allow direct contact of the wall with the masonry, especially the insulation. This is done usually by installing the wall with an one inch dead air space between the wall and the masonry. You must also make sure the ground slopes away from the foundation wall around the house and the leaders extend 8 feet away from the house.
 
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Old 02-17-03, 04:34 AM
whitey2
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I was afraid this was going to be the answer. So in other words, i need to tear down the wall and start over, after making sure the exterior drainage is not the problem. Is this a correct statement?
 
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Old 02-17-03, 09:14 AM
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That is correct.
 
  #5  
Old 02-18-03, 01:41 PM
rbisys
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Greetings,

If you put in foam you could still get mold.

Remove existing. Install a radiant barrier(RB) system. I would put one layer between the studs and one over the studs like a VB. The RB will not condensate and there will be no mold problems. Install a 1/2" plastic "J" channel along the bottom of the drywall. Use thin typr RB material.

The foam is about 20% eff., the RB 97%.

Thank you for considering my opinion.
 
  #6  
Old 02-20-03, 08:50 AM
Brewbeer
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Concrete is porus like a sponge. In climates with cold winters and hot summer, concrete needs to "breathe". Any vapor barrier in this application will prevent this from occurring. Not sure if a radiant barrier system is a vapor barrier or not.

Heat transfer occurs in three ways: Convection (heat flow through a fluid, i.e., air currents moving heat);
Conduction (heat flow through a solid material, i.e., put you hand on the concrete wall and it will feet cold); and
Radiation (heat flow through electromagnetic radiation, i.e., the warmth of the sun on your skin)
A good insulating system will insulate against all three.

To reduce heat transfer by convection, seal gaps in the building envelope, and stop air from circulating inside wall cavities. This is effectively done with any insulation that fills the entire void space.

To reduce heat transfer by conduction, install insulation that has a high r-value. Foam (against the concrete wall) and fiberglass/cellulose (inside the framing stud bays) works well.

Because radiant heat transfer is primarily a hot surface phenomenom, considering the physics of radiant heat transfer, and the relatively cool temps of a basement system, I don't see (and haven't seen any studies) how a radiant barrier would be effective in a basement insulation system. The physics of electromagnetic radiation don't support the use of an RB system in this application.
 
  #7  
Old 02-21-03, 03:08 PM
rbisys
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GReetings,

Sorry Brewebeer,. I don't where you came up with all that, but, that kind of interpetation is why buyers don't understand how heat transfer works in a building. Most of this misinformation is pushed by the FG industry. To them radiant energy is a myth.

Consider. Why do you want to put a high conduction/emissivity material in the cavities. If you have an airspace, you have a situation calling for a low emissivity material. To put FG in a cavity just increases the heat flow. Consider, FG is about 95%+ airspaces, radiant energy travels at the speed of light. An engineering manual shows that glass is about 95% emissive. That's why heat energy goes right thru glass. All this and I haven't even mentioned the increase in heat trans fer and storage due to moisture. Framing only accounts for about 15% of the conductive surfaces. Oh yes, RB do not condensate or store moisture. Excellent VB too.

You mention convection but your solution is for infiltration. FG is not good against infiltration. RB are solid metal. The rate of convection is very small, less than 10%.

You say radiant heat is a hot surface phenomenom, Hot by what definition. If you have a 70 deg interior surface temp and the out side wall is -20 deg. is 70 degs hot? Delta T 90 deg. When the attic FG upper surface temp gets to 160 Degs and the interior temp is 80 degs, is that hot? Delta T 80 degs.

I'm sorry, I don't what physcic you're quoting, but, I've used RB in basements, including my own, and crawl; spaces for years and have gotten very good results, and no mold. The problem is, you haven't used RBs. So, if you e-mail me your address I'll send you an info packet, with drawings, so you can install yourself and find out 1st hand.

Oh yes, one of the demos I have in the winter is to have someone put their hand about 1" from a RB sheet in a cold room and feel the body heat refecting. And please, don't tell NASA that RBs don't work in a cold temp enviroment. They'll be crushed. To think, all these years.................

Thank you for considering my opinion.
 
  #8  
Old 02-21-03, 04:28 PM
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insulation

Try this www. and just see what the US government thinks about that RB over FG .With FG you get a pay back.


http://www.ornl.gov/roofs+walls/radiant/RB_02html ED
 
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