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How much and what kind of insulation is needed for a new construction (add on) basement floor under cement slab with radiant ( hydronic) heat planned ?

We are bumping out the back of our house and thinking we would like to finish the new basement area at some time I n the future.

So think it would make sense to put in radiant heat when the cement is being poured.

I've have several conflicting opinions on what kind of insulation

And what is the minimum r value for this area ( northern New Jersey )

Different people have quoted

Dow tuff r rigid foam that is over $40 per 4x8 sheet x 2"

Others suggest just going with 2" of the pink Foamular 250.

Which is only $16 per sheet.

I've also seen bubble type insulation rolls that are even cheaper ($99 for 400 sq feet) and claim to be good options.

Were on a tight budget but don't want to make a bad decision that may turn into a problem layer , just to save a few bucks.


  • kcopp
    kcopp Member Posts: 4,443
    2" styrofoam is....

    The only real option. The bubble stuff is TOTAL garbage. The blue-board is tried and true. You have 1 chance to do it right. here is a link w/ more info.

  • SWEI
    SWEI Member Posts: 7,356
    The difference in cost

    between 2", 3" and 4" is worth exploring.  Run a heat loss calc on them, look at the BTU difference, figure the cost of fuel using http://www.eia.gov/neic/experts/heatcalc.xls and see what makes sense.
  • Steamfitter66
    Steamfitter66 Member Posts: 117
    xps or eps

    The bubble wrap is a waste of money. Any brand of Foam board is fine. Tuff-R is not for below grade applications. 16 a sheet is a good price. you can use the 150 in most applications.

    Check pricing on EPS as it is usually more cost effective and long term performance is about the same.
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