insul-tarp

Do a search...

...this topic has been beaten to death on a number of occaisons. The upshot, IIRC, is that it has a R value of about 1 below ground, i.e. it's better than nothing, but barely so. ASHRAE has also published a comprehensive guide on sidewalk snowmelt options, so $60 and a bit of reading later, and you should be good to go.

aluminum film insulation

I find the reasoning behind the Low E shield to be faulty. "Foam board draining away heat"??!!. Although there is a difference between r-values of different foams, the range is from about 4 to 8 per inch with extruded polystyrene at 5 per inch. From what I've seen of polyethylene foam I expect it's near the lower end of that range due to the large cells in the foam. That puts it at about R-2.5 at most at 1/2" thick. Having the aluminum in the center will have virtually no effect on r value in this application. There's no radiant heat to reflect when it's in contact with anything except air. In this case it has foam glued to it. I think everyone should realize that it takes a certain thickness of foam to do the insulating under a slab. No easy outs.

Where does the water go?

I'm installing a 1600sf snow melting system. Where is ithe water supposaed to go when you seal underneath the cement with insultarp? I have a 60ft long driveway sandwiched between 2 houses. Rain and melted snow going through the pourous cement and expansion joints will need somewhere to go underground. I don't want that to be my foundation or my neighbor's foundation. R-1 to R-3 insulation doesn't seem worth a wet basement or damaged brand new cement. Any comments help on this issue would be appreciated.