# Best insulation for staple up radiant heat



## headrc (Jun 19, 2008)

After receiving feedback on the idea of a conditioned crawlspace for radiant heat ...(thx!)  ....I now wonder what is the best form of insulation put under staple up radiant heat (between floor joists ) ....any input would be appreciated.

Thx,  RH


----------



## Willman (Jun 20, 2008)

> I now wonder what is the best form of insulation put under staple up radiant heat (between floor joists ) ....any input would be appreciated.


IMHO The best bang for the buck is foil faced polyiso foam boards. Easy install great insulation value.


----------



## kshultz (Jun 20, 2008)

I'm not sure what is the "best" but my plumbing & heating guy used I think R-19 foil faced towards the radiant staple up tubes.  There is plenty of room in my basement, sounds tight in your.  Hope this helps.


----------



## WoodNotOil (Jun 21, 2008)

When I did my retrofit I was lucky enough to have fiberglass with a foil face already there and just flipped it over so the foil faced up.  I ran a little short and when I went to the store to get more they sold me Reflectix  2'x 25' Foil Insulation and it worked really well in the last three bays.  Each roll runs about $23-29 and it is very easy to install with staple gun.  It looks like aluminum bubble wrap.  Not sure how that compares in cost or R value to polyiso, but it may be easier to install in a crawl space.  Whatever you put up, make sure you leave an air space of about 6" between the staple up plates and the insulation.  That heated air space is one of the keys to making a floor work.


----------



## Bob Rohr (Jun 22, 2008)

R value is the key.  Those magic bubble foil products are not a direct replacement for 6" fiberglass batts, from my experience.

I also feel foil faced batts do little to add to the radiant reflective-ance.  First they are mainly red printing, and secondly a thin layer of dust eliminate any reflective value.

The biggest concern is the rim joist.  I'd use foam blocks and spray foam them in place to eliminate any infiltration, 4" or more thickness..  A small breeze against warn surfaces is both a condenstion issue and potential large heat loss area.  There is a huge delta t to be concerned with at the rim and band joist detail.  Warm joist space inside, outdoor temperatures an inch or so away.

I prefer staple up applications with aluminum transfer plates.  Keep the supply temperatures lower and a much better conductor than plain tube stapled to the floor.

 hr


----------



## headrc (Jun 24, 2008)

Any opinions for installing the Polyiso to the bottom of the joists ....giving an air space of about 8 inches between it and the pex tubing?  Thx,  RH


----------



## Toast (Jun 24, 2008)

I did this in my house.  I used Al flashing stapled up to the floor to transfer heat.  Then I used foil-bubble-bubble-foil stapled to the floor joist.  Fbbf is not the best bang for the buck. However, it is easy staple up, easy to cut, there is no dust, and it dosn't ich.  They say that it has an r-17 in that sort of application.

To say that a thin layer of dust will eliminate any reflective value -- This would be true if you are trying to reflect visible light.  However, we are trying to reflect infrared radiation, which will travel through a thin layer of dust.

jeffrey


----------



## headrc (Jun 24, 2008)

Jeffrey ...That is a solution I was really contemplating ....two questions ...has it worked well for you and what was the tickness of this insulator to give you a R-17?  Thx,  RH


----------

