Underslab insulation testing

hr

for comparing various insulations. I took an 18" square of 1" Dow board, InsulTarp, and Refletix product to a near by ice rink.

I placed sensors between the top of the insulation and some concrete blocks I poured.

The blocks were prewarmed to 68° F in my shop. The ice was 17°F, air temperature at 1 foot above 40°.

Interesting results. I may adjust my test set up and do an overnight test.

The sensors, were epoxied to some copper but still pressed into the soft bubble products. Think I may recess them into the concrete.

I also tried some seat of pants tests :)

Wish I had a data logger, be interesting to watch a minute by minute test over a 24 hour period. Gets cold standing around for hours :)

I may retry Tue for an overnight period, as the ice comes down on Wed.

Any thoughts or ideas for me. I may try some bubble pieces with all the bubbles popped, just for grins :)

hot rod

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Mike Kraft_2

The \"Thinker\"

on a whoopie coushin:)! What results?Try a cut of "Low E" also.You certainly have some pull and seem to get around a bit.

cheese

Ken_8

HR, as long as you

have ambient air directly impacting the sensor(s), won't the results be compromised by that event - as well as the heat loss of the sensor to the ice below (through) the insulator?

Or, was the intention? To have the warmer ambient air be the "constant" and the actual heat loss from the sensor into the ice "sink" be the calculated value?

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hr

Good questions

I really didn't know what to expect when I arrived. Didn't realize the ice was that cold! The air temperature in the room is controlled to 60°,seating level, the manager told me. Of course closer to the ice it gets cooler.

Even if my blocks got to 40° I still have a delta T between the 17° ice surface to measure the heat transfer.

Maybe I need to sensor the top of the blocks, also?

Ideally I would have a heat source driving the blocks? Not sure how much equipment they will allow me to haul in

hot rod

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Mike T., Swampeast MO

Ice temp at 17° should be about 20° lower than ground under a "normal" slab???

Air temp at 45° (at least that's what it looks like on the big thermometer but angle isn't dead-on) should be about 20° lower than "normal" air as well???

Concrete chunks at 68° should be about 20° below absolute maximum panel temp???

---------------------------

An idea for introducing heat to concrete chunks...

The chemical "heating pads" made for back pain???

Maybe two pads per "slab" at opposite corners on top of insulation. Don't I hear that tubes usually wind up at/near the bottom of slabs anyway???

Mike T., Swampeast MO

After 48 hours...

Pour 32° water on all the concrete chunks to see if any freeze...

Larry Weingarten

enclosures

Hello: How about building some 2" foam boxes to cover the concrete. That way the major heat transfer will be out the bottom and ever if you don't get absolute R values, you will get numbers to compare one insulation to the next percentage-wise. Are you taking bets on the winner?

Uni R

Some ideas...

Maybe take three styrofoam coolers. Either invert them for use or cut a 1' square hole in the bottom. Put 75°F water in three bags that will fill each cooler. Effectively the bottom of the bag will be sitting on the insulation's surface. When you are ready, put them in the cooler with a sensor between the bag and the cooler's wall (mid-hieght) and same spot for each one. Then see how fast they drop. Might be a lot faster and a lot more accurate.

Weezbo

Did nt we all do a dry ice experiment or two?

seems like you are having fun at least:) the innovative gotta do this sorta stuff or you wont be belived...experiments need Knowns and controls and you gonna hate this outsider intervention observers.... along time ago i read a book "Tell them what they want to hear"a book on logic if you had some cheap electric clocks from the thrift store,had a fixed temp n.c. (low temp) sensor, conducted your experiment...when ever the temp warmed up and opened the clock would stop...? you sleeping at home not watching the clock:)

jerry scharf

my $.02

Hotrod,

All this may b overkill, but I couldn't resist setting up the lab test framework.

For data collection, I just love the Maxim (Dallas Semiconductor) 1-wire system. With a laptop, a 1-wire USB interface, free software and a run of sensors, it's almost mindless to do the data collection. Given the simple thermistor sensors with good accuracy cost less than $5 each, you can use a bunch without breaking the bank. Hooking them up is a matter of wiring them to three wires bus style, signal, ground and DC power. They say that you don't need DC power, but IMO the sensors are much easier to deal with when they have it.

I would set up with three themistors per run, one at the ice, one at the bottom of the slab and one at the top. I'm thinking that the poorer insulators may raise the ice temperature below them, and thus give an artificially high appearent R value.

Handy calibration technique for the TO3 thermisters: Get a surgical rubber glove, stuff a few sensors with pigtails in each finger and dunk them all in a water bath. The temperatures will rapidly approach stability, and you have the offsets for each thermistor from the group. Because each thermistor has it's own unique 64 bit ID, once you have it, you won't get confused with which offset is for which thermistor.

I think they are by far the best thing out there for adding computer driven sensors to these kind of systems.

I like the idea of the inverted cheap styrofoam coolers with a fixed amount of water at a given temperature. If you could pour the slabs to fit the bottom of the coolers, that would be perfect. I think the idea of isolating the ambient air from the slab will make analyzing the insulation action of the much simpler. In thinking about it, a 4th thermistor halfway up the outside cooler will allow you to compute the thermal loss throgh the cooler to the air as well.

What were the results of the seat of the pants tests?

jerry