# Re: Tested thermal windows.

• posted on December 21, 2008, 5:38 pm

Get one of the IR thermometers that do spot readings. Point and read. They're cheap enough and will give you a surface reading, not an air temp reading. An air temp reading will most likely be misleading, and not be suitable for calculating values.
R
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• posted on December 22, 2008, 7:08 pm

I think you should also read your post. It was not clear what sort of sensor you were using, and the plasticine (not sic) will affect the reading (how much, I do not know).

Well, you could work it backwards. Figure out the theoretical total heat loss, allowing for body heat, latent heat from cooking, solar gain, shading coefficients, etc., and calculate based on a house with no windows, then find what the actual temperature is and figure out the heat loss from the windows and work that backwards to an R-value. Personally, I would read the manufacturer's literature and use that figure unless there is some major necessity to go through the calculation other than it's damn cold out and you have some free time on your hands. =:0

You don't have internet access, ebay and postal service? Exactly where are you plugging that cord in...? Scratch that, I don't want to know! :)~
I know I like being argumentative, or so every person on the planet tells me, but that doesn't mean that I am not steering you in the right direction.
The infrared thermometers can be had for \$25 including shipping, and will prove far more useful than mucking about with some calculations. You'll be able to locate heat loss than you don't even know you have, and that will save you money.
R
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• posted on December 22, 2008, 10:17 pm

Again, I don't know where you are going with this. It's a done deal, the R-value is a useful number for design purposes and nothing else. If you are building new, or planning on modifying what you have, then it would make sense to determine the R-value. But the R-value is a number that lies. It always does. It can be no other way. You'd be amazed at how many practicing practitioners ignore framing and do energy calculations based on the insulation's R-value alone.
R-value is an industry wide scam to give people a handle on something that they can't handle - the truth. Infrared imaging is the only way to find out where you have made mistakes and enable you to fix them. A tight building with so-so insulation will perform better than a drafty building with lots of insulation.
So what exactly are you trying to do with the R-value number? Is it idle curiosity or do you have plans to modify what you've built?
Have you used ResCheck? http://www.energycodes.gov/rescheck/ That's a good place to start (and in most cases finish) with energy conservation calculations.
This is another good site: http://homeenergy.org/archive/hem.dis.anl.gov/eehem/99/991110.html

Everything is always in thermal balance. If it's not, you're just not looking at the big picture. ;)
Caesar's Gratings!
R
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• posted on December 23, 2008, 2:59 am
"Ken S. Tucker"> wrote:

There a website that has R values for all the common materials but I don't remember what it is, DAGS.
Your materials usually say right on them their R value.
Typically 3.5" batt is R11 or R13 and 1.5" foam, closed or open cell, is unknown -depends on brand.
How did you fasten the vinyl siding to the foam insulation?
I recently saw vinyl lap siding that wasn't *hollow*, it had closed cell foam in the voids - looked kinda neet. Wonder how they do the laps, scrape the foam off the last 6"?
Anyway, I'm taking Rico's advice and doing a search on ebay for an IR thermometer, wanted one since I first saw them but though they were in the \$100 range.
Rode a muskrat 40 miles yesterday just to get a case of brews and a bag of buds.....