Primary Secondary - Heat Loss, Flow Rates & Water Temps

 
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Adamiscold
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Post by Adamiscold » Tue. Aug. 19, 2008 10:33 am

Option 2: demo floor, remove 2" of grade and do it "the right way" (2"insulation, plus gravel, + 4" concrete)
So you would go 6+ inches below where the floor is now and just build up to the same height you have now? My biggest concern would be and I'm not expert here but the pinning below the concrete walls, which I suppose wouldn't be a problem since you would come right back to the original floor height.

 
BIG BEAM
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Post by BIG BEAM » Tue. Aug. 19, 2008 9:46 pm

There is also a new product call insul tarp.I use it under slabs now and it seams to work good.It's a thin insulation with a vapor barrier and reflective material all in one.About 1/2" thick.I think what makes it work so well is the reflective material not the R value.After all ground temps are what 55F and the slab is about78 or 80.
DON

 
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beatle78
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Post by beatle78 » Wed. Aug. 20, 2008 8:52 am

insul tarp? hmmm... I like the looks of this stuff!

http://www.insulationsolutions.com/products/insultarp/


 
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Adamiscold
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Post by Adamiscold » Wed. Aug. 20, 2008 8:58 am

The only problem with a tarp or even insulation board with a reflective material on it is it needs an air gap in order for the reflective material to work. You look at the Dow 1/2 inch reflective foam board insulation it has an r-value of 3.3 but with an air gap of 3/4 inches the r-value goes to 6.1.

 
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beatle78
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Post by beatle78 » Wed. Aug. 20, 2008 12:41 pm

They show the foil side and being down against the ground and then insulation and the white layer is the top.

does the insulation between the reflective side and the top side count as an air gap?

 
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Adamiscold
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Post by Adamiscold » Wed. Aug. 20, 2008 3:18 pm

No there's no air gap with that. If things like Insul-Trap and those rolls of reflective insulation were as good as they claimed to be wouldn't the brand name insulation people be selling a similar product? It has an R-rating of 7.5 and it's 3/4 inches thick. Closed cell spray foam I think I've seen it go as high as having an r-value of 6.5 an inch. If you had "extra money" then one could say that they wanted to use it as a vapor barrier and still place foam board on top of it, but use it by it's self? I wouldn't recommend it. 2 inch foam board I believe can be as high as an R-20 rating.


 
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Post by BIG BEAM » Fri. Aug. 22, 2008 9:07 pm

I don't think the R value is that important when you're dealing with a temp diff of 20F.I think it is VERY important if it's 0F outside and 72F in the house.The new thinking with reflective coatings is that the air gap need only be a molecule thick for it to work well.I have no links to support that just in talking to two enginers I know in Canada.
DON
BTW a few weeks ago I was installing some pex in a cellar that had insul tarp installed and when I was working there with the sun beating down on me I noticed that I couldn't get away from the heat.Usually you can feel the cool dampness even through insul but with the insul tarp you could feel the heat from the sun even on your face when bent over.I was roasting.I know this is a seat of your panls type of thing but it was very differant from anything I have experienced before installing pex.

 
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Post by Adamiscold » Sat. Aug. 23, 2008 8:32 am

I don't think the R value is that important when you're dealing with a temp diff of 20F.I think it is VERY important if it's 0F outside and 72F in the house.The new thinking with reflective coatings is that the air gap need only be a molecule thick for it to work well.I have no links to support that just in talking to two enginers I know in Canada.
DON
Well 20 degrees may not sound like much but it's 20 degrees worth of heat that you are paying to heat the ground underneath your house and over time that money will add up. Remember we are talking about insulation underneath concrete and the colder the temperature is beneath it the quicker it's going to cool off and cool off your room and fire up your heat source. The better it's insulated the longer it will hold it's temperature, so the less your heat source will have to run saving you money.

If you look at the big companies like Dow they have two R-values listed on there 1/2 inch reflective insulated foam boards one with an air gap(maximum r-value) and one without(minimum r-value). The air gap has a higher rated R-value 6.1 with a vertical 3/4 inch air gap compared to 3.3 R-value without one. 3/4 of an inch offers the maximum R-value that you can achieve with this board having a bigger or smaller air gap decreases the R-value.
BTW a few weeks ago I was installing some pex in a cellar that had insul tarp installed and when I was working there with the sun beating down on me I noticed that I couldn't get away from the heat.Usually you can feel the cool dampness even through insul but with the insul tarp you could feel the heat from the sun even on your face when bent over.I was roasting.I know this is a seat of your panls type of thing but it was very differant from anything I have experienced before installing pex.
Having anything shiny that is reflecting the sun light is going to make you warm. I can lay down a sheet of Dow insulation board and the sun bouncing off the reflective material is hot, it's like standing in the sun with no breeze to cool you off. It's the air that's in between you and the reflective material that's allowing for the heat to be redirected if there was sheet rock right up against it blocking the sun light from reflecting then you wouldn't have been able to feel it. If you search around and see how they install reflective material in ceilings or on walls you see they usually add firring strips before adding the sheet rock because it gives an air gap to be heated up and that heated air is what is absorbed in the sheet rock and goes back into the house. Look at radiant flooring with reflective material installed underneath it, there is an air gap. There is no air gap on a tarp that has how ever many hundreds of pounds of cement laying on top of it.

 
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Post by coalkirk » Sat. Aug. 23, 2008 8:48 am

There are a number of threads dealing with concerns about heat loss. Keep in mind that if your boiler is inside, any standby heat loss is in the heated envelope of your home. If your concern is to minimize it for summer use, that's another matter. Personally, I like my boiler room nice and toasty. :blowup: (not that toasty)

 
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Post by beatle78 » Sat. Aug. 23, 2008 9:19 am

BIG BEAM wrote:I don't think the R value is that important when you're dealing with a temp diff of 20F.I think it is VERY important if it's 0F outside and 72F in the house.The new thinking with reflective coatings is that the air gap need only be a molecule thick for it to work well.I have no links to support that just in talking to two enginers I know in Canada.
DON
BTW a few weeks ago I was installing some pex in a cellar that had insul tarp installed and when I was working there with the sun beating down on me I noticed that I couldn't get away from the heat.Usually you can feel the cool dampness even through insul but with the insul tarp you could feel the heat from the sun even on your face when bent over.I was roasting.I know this is a seat of your panls type of thing but it was very differant from anything I have experienced before installing pex.
BIG BEAM,

Do you do a lot of radiant slab installations? If so, do you have any field observations of comparisons, between insul-tarp and regular pink foam board installations?

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