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under-floor heating in a BP shed

B

BallsDeepPythons

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Does anyone use flexwatt as a radiant/underfloor heating element? The reason I ask, my 10x12 ball python shed is fully insulated, floor, walls, and ceiling, but I have had three heaters going at times this winter. One radiator type, and two with thermostats to tell them when to come on. I guess this is a two part question, how much (if any) heat would 48 sq ft of 11" wide flexwatt put off? Second, is it safe to "sandwich" flexwatt between a sheet of plywood and a laminate flooring on the top of it?
 
As an HVAC pro, you're asking a lot deeper question than you realize.. Flexwatt probably doesn't put off the required btuhs to heat the room, AND it's not rated to be installed under/in a floor.

There is a heat cable you can install underneath tile that would do a much better job. However, you need to keep in mind that you have to insulate underneath the heat source to force the heat to go toward the direction you want (up), as heat doesn't naturally rise, it transfers. (Hot air rises, not heat).

Some questions:
What type of insulation does it have? 10'x12' x how tall? What's the outside temperature? Does it have a window or two? What is the u-value of the window? Is the door an exterior door? Do you use ventilation? Is there a crawl space, or air passage underneath the shed, or is it a slab on grade?

What I'm getting at, is that you need an accurate load calculation that takes into account the tightness/leakiness of the shed, the window(s), ventilation, r-value and type of insulation, etc. From that, one can determine the required BTUh's to maintain a set temperature.

Based on the size of 10x12, it seems like you have a leaky structure. Find and seal the leaks. Typically, if insulated with foam board (most recommended), that size should easily be heated with a 1000W heater. This is speaking from the experience of dealing with -35 deg. outside temps here...

One more thing... Once you can determine the proper amount of BTUh's required to heat the structure to 80 deg. (or whichever temp you're shooting for), you can determine how many watts of heat are needed. There are 3.412 BTUh per Watt of electric heat, so a 1000W heater will put out 3,412 BTUh. 1500W will put out 5,118 BTUh.

For your 11" flexwatt question, how many watts per foot is it? I'm thinking it's 10W/ft. Rounding the numbers, if you have 50' of 11" flexwatt, it should put off 500W. Will that heat the shed? Probably not. Again, I'd recommend that you find the heat leaks and stop them. (Fiberglass insulation is the worst possible insulation one could use to actually insulate with)
 
One other thing regarding the safety of using flexwatt the way you describe. Are you willing to burn down the shed and lose all your snake? I'd highly not recommend using it in that way.
 
It is just a portable type building, 6' sidewalls, one small window and a double walkthrough door. I have the worst insulation I guess lol, it is 2x4 construction so I used R13 (I think it is). It is not on a slab and has air passage underneath, but I did staple insulation in the floor as well. Sounds like I need to find my drafts and start sealing them up. The only reason I was thinking flexwatt is because home depot sells what looks to be exactly like flexwatt online as a floor heating element.

Thanks, for the tips.
 
for colder regions R-13 is kinda thin. I live in the SF bay area (70 degrees in Jan!) and used R-19 in my garage walls and ceiling. When we had a cold snap (25-35 at night) my garage got down to 50-55; keep in mind I have not finished sealing it and the floor is a cold cement slab.
In colder (winter) climates thicker insulation is better but useless if there are air leaks. you could try adding another layer of R-13 and seal up the shed really well, plus a 1500 watt oil filled radiator heater would probably help a lot. I use a 1500 watt DeLongi oil filled radiator type heater in my snake room (in the house with only 1 exterior wall) if it gets too cold and it works very well.

the fact that a shed is a stand alone structure with 4 of 4 walls being exterior walls does not help with heat loss either.
 
Being its an out building use two heaters with two seperate thermostats just in case one quits working. The other one will take over and you wont loose you pets.
 
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