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[little john]

read this subject here b4 didnt seem to get my answer so i joined, and im getting ready to pour the basement, was told to use the bubble stuff reflective foil side up directly on top of stone right to foundation wall then 6x6 wire mesh with pex tubing zip tied to it  then the concrete.  only 3 walls are 4-5ft below grade the rear wall is wood walkout basement. itll b on its own zone. only 1/3 of basement is getting finished with1" foamboard on block wall, but going to add 2 more loops to another area just to keep chill out, basement temp 45-55 degrees all winter with just dirt floor. whats your thoughts / recommendation.

[mlappin]

I wouldn’t use the bubble foil, eventually moisture will get to it and cause the foil to break down or come un bonded from the bubble part, go with styrofoam insulation board instead. I made the mistake of using the foil bubble foil for my sidewalk 15 years ago, even bought the stuff “especially” for use under concrete, still slowly but surely going to hell.

[coolidge]

2" foam board will do the trick

[atvalaska]

1st off kill the guy with the bubble wrap idea...u mite have to take him apart to keep him from coming back !!!.....then start here >http://www.cchrc.org/foundations    just remember compacted gravel (d1)  blur of pink ins ...6mill VB rebar/mesh …tubing in top 1/3 of slab and the more insulation under the slab the better ...trailer trash uses 2" minimum !.…do it RIGHT the 1st time...I don't care where u live the earth is cold &damp 24/7

[atvalaska]

Afternre reading your ? ...it seems as this space is a crawl space???

[little john]

 full basement just kept it out of the ground for windows all around, even going with foam board isnt it important to have a type of radiant reflective barrier to stop heat transfer downward.

[mlappin]

Not so much as heat wants to rise anyways, go with your vapor barrier under the foam and two inches of foam under the cement and I think you’ll be much happier in the long run.

Maybe something has changed over the years, but I used to work at a door factory that distributed the PlyFoil brand of radiant bubble insulation, they only gave an *estimated* R value on the stuff as if it was tested it would fail miserably compared to foam or fiberglass. They claimed the single bubble was an estimated R17 and the double bubble was an estimated R34. But this was also in applications that were always dry, like on walls and ceilings.

I’ve googled foil bubble insulation and came up with all kinds of articles about it, to be truly effective it needs to be held away from both surfaces, if in contact with one or both then the insulation value from conductivity is R-1 or R-1.1. The true insulating value comes from the fact that it is shiny so it reflects radiant heat, once in contact with the cement it’s no longer shiny.

I insulated our shop with the stuff as I got a few free pickup loads of it from work as it had some water damage, cut the bad sections out and used the rest, it’s better than nothing, but my time would have been better spend installing at least one inch foil faced foam board. I still may install foam board on the ceiling and add about four ceiling fans while up there.

[atvalaska]

full basement just kept it out of the ground for windows all around, even going with foam board isnt it important to have a type of radiant reflective barrier to stop heat transfer downward.

it needs 2" minimum to reflect... How do u hold up a 4" slab to get the 2" ?

[timbur]

2" foam is the only way to go !

 Bubble foil insulation is great for roof and walls , I have used it on just about every building I've built here , including under the vinyl siding on our house , the only true value bubble foil ins has , is the foil , the foil will reflect 97% of the heat  ( according to the sales rep I used to buy truckloads of it from when I was in the pole building industry ) the catch is that you have to have an air space for the heat to reflect .

When the foil is in contact , it will actually conduct , not reflect , all that the bubbles do at that point is create a thermal break .

Hot air rises , heat radiates 360 deg , your concrete slab will be in contact will the soil , ( 50 -53 deg ? ) , your goal is to stop the loss of heat to the soil .

R = resistance to heat loss , the higher the R value , the higher your resistance is to heat loss .

Sorry if my rant bored you , but next to wood stoves and Milwaukee tools , I love saving energy  ( and money saved by saving energy ).

Tim