Need help with an experiment!

[custom1]

Here's the deal. I want to settle the insulation under slab debate once and for all.(in my mind at least). I started the experiment today. Sort of Myth Busters style. I will post all the details, results and some photos after I'm done. Basically I set up a test bed, filled with sand, and place a container in it, first by itself, then surrounded by insulation(1 5/8" thick door cutout material).

Next I want to try the bubble/foil stuff, but I don't have any and don't want to buy a whole roll just to test. So if anybody has a scrap left over, about 2' x 2' would be plenty, send me a PM and I will respond with an address you can mail it to. I will gladly refund the postage. I may try polystyrene foam also, I have to buy some anyway.


John

 

[Pure Oil]

Well this should be good. I presume you will be running a multiple test of all combinations at the same time to get the exact same temp's. I for one am curious. Now, another thing to keep in mind is the "hotwater tubes" that you place in the slab area before it is poured. I've heard you get a nice warm concrete floor. Anyway, I'll be watching for your results in the future.

 

[banzaitoyota]

I have some FBF here

 

[custom1]

I think it actually should be bubble/foil/bubble. In practice the foil will get eaten away by some chemical in the concrete over time. But I will try the FBF for the test if we can't come up with the other.

John

 

[custom1]

Re: Need help with an experiment! Results

Ok. Here is what I did. I filled a 27"l x 31"w x 9"d plastic tub with damp sand.

And then dug out a hole for a 8"l x 12"w x 4"d plastic container to hold water, to simulate the concrete slab.

I placed the sensor from a wired indoor/outdoor thermometer under the center of the water container.

I then ran three tests over two days. The ambient air temp both days was in the mid 40's. The water temp at the beginning of each test was 125 degrees. The water was covered on each test by a piece of the door cut-out foam, to simulate the r-value of the building. The sensor was 1 3/4" below the water container for each test. I placed a thermometer in the water and ran each test until the water dropped to 100 degrees.

The first test was with no insulation at all for a baseline. During this test the water dropped to 100 degrees in only 1 hour, and the sand raised 13 degrees from a starting temp of 42.7 degrees to 55.7 in the same time.

The second test was with 1 5/8" door cut-out foam surrounding the water on the bottom and all four sides. This time it took 3 1/2 hours for the water to drop to 100. And the sand only raised 2 degrees from 41.1 to 43.2 in the same time.

The third test was with some Bubble/foil/bubble insulation surrounding the water on the bottom and all four sides. This time the water dropped to 100 in 3 hours. And the sand raised 5 degrees from 42.8 to 47.6 in the same 3 hours.

I did not get any polystyrene to try yet.

So my conclusion so far is the door cut-outs are really good, and I will be using 2 layers of these under my radiant slab. (Hey they're free!) The Bubble foil stuff worked better than I thought it would, but not near as good as the foam cut-outs.

I'm not sure if I covered everything(its late), so questions and comments are welcome.

John