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    SLAB INSULATION (3 Posts)

  • smklin smklin @ 4:27 PM
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    SLAB INSULATION

    Can i use foil insulation does it acutally work its half the cost compared to 2'' foam board. Thoughts please thanks
  • kcopp kcopp @ 6:19 PM
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    No...

    It is a waste of money. It does NOT work. 2" blue board is the best way to go. If you are trying to save money do 2" around the outside for 4 feet then fill in w/ 1"... 2" is the best way to go.... spend the money once and never have to worry about it again.
    This post was edited by an admin on March 15, 2013 9:54 PM.
  • icesailor icesailor @ 7:54 AM
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    Two "R's"

    I have always understood that there are two "R's" to insulation. Reflective and Resistance. Any foil faced insulation has Reflective value. Anything that that resists the flow of heat or cold energy through it is Resistive. You can have both. You can roast a pig in your yard on a sunny day with mirrors by reflecting the energy from the sun on the pig but you can't cook it with a 4'X4' piece of 1" poly insulation. The front surface will be hot but the backside will be Outside Air Temperature. Use the same piece of insulation with a foil face and you can cook the pig.
    I recently saw someone replace all the metal duct work with 1" insulation glued inside when fabricated for a HVAC system in the cellar of a customer. The house was 5 years old. The new contractor said that the new metal duct covered with Bubble wrap has a higher "R" value than the old duct because the bubble wrap said it was "R-10" on the label on the roll. Like the TV ad that says that they can't tell a lie on the Internet, they wouldn't lie on the label. Maybe the "Reflective" R value was R-10 but not the Resistive valve. Concrete slabs have their largest heat loss around the edges listed as "Edge Loss" with the greatest being the first 24".
    Bubble Wrap insulation is on a roll and less than 1/2" thick when rolled out. It depends on the resistive air in the bubbles for the resistance. Consider using 2" thick foam sheets for the edges and 1" thick ones for the insides. Or thicker.
    If there is a question of "R" Value, get the manufacturer to give you a letter on company stationary that their R=11 Bubble Wrap is equal to the "Resistive" valve of R-11 fiberglass insulation. They won't do it. But I've seen DIY'ers cover their entire outside wall system with bubble wrap and Sheetrock over it. Claiming that their wall structure is equal to the fiberglass batts.
    It isn't. Don't be cheap. Use the sheets.
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