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Staple up radiant heating tracks

Glenn Sossin_2
Glenn Sossin_2 Member Posts: 592
Al, I agree no foil is required, but don't you think it would be an advantage to have it? This kind of application is where I would want to put it, unless of course he's trying to create a radiant ceiling below.

I'm sure you would agree, any downward heat energy flow would be primarily radiant - I believe its commonly held to be 93%. The foil surface, having an emissivity of .03, theoretically reflects 97% of that energy back upward.

While I agree, its not required, don't you think it would be advantageous to have??


  • Stupidhead
    Stupidhead Member Posts: 1
    staple up radiant heating tracks

    I'm putting in radiant under floor heating above an unheated 4 ft. crawl space in Minnesota. Heating contractor says to go with Wirsbos Pex clips at $200.00 or Their aluminum 4 in. wide tracks at $1500.00. Does it really pay in the long run to go with the aluminum tracks? How much insulation and what type is best under these type of installations? All boiler, manifolds,& tankless water heater, will be in this insulated crawl space(Dirt floor). Can we go with half clips and half aluminum tracks to save some cash? My insulation idea is 2 in. foil faced foam and the rest of the joist area filled with 9 in. fiberglass. Clips, tracks, tubing, & insulation will be installed by myself(30 years construction trades). Thanks, Stupidhead.
  • Al Letellier_9
    Al Letellier_9 Member Posts: 929
    what to use

    The answer lies in what you need for BTU's/sq. Ft of output in the flooring. Your contractor should be able to tell you the difference. The plates will allow lower temps to be used and the insulation needs no air gap. You can put it directly against the tubing. Use a minimun R19 and no reflective quality is required. I would use the plate simply for the increased efficiency. More up front cost, but better return on your investment.

  • R16 blocks 93.5% of downward heat flow as well, and it doesn't lose effectiveness if it gets dusty.

    I disagree that the radiant downward flow is the only thing worthy of consideration. Depending on your water temperatures, your joist cavity air temperature is also greatly elevated. It may not be a particularly good convection path (unless, of course, you're doing suspended tube with an airspace, which is set up specifically to start a convective loop) but it will heat up the joist cavity and that will drive additional downward loss beyond direct radiance.

    reflection does work in this application, but it's not the end of the story and I personally wouldn't trust it long term. If you do, it certainly doesn't hurt anything unless you are REPLACING real R-value with reflective insulation. But I personally advise my clients to put their money into more R-value than in reflectivity..

    If you're just using using foil facing, I think the reflectivity is not quite as good as you mention, but I don't think it's much more expensive either, so why not?
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    The HVAC Guys wrong ??

    They use a foil faced insulation in an open attic space to cover air conditioning ducts. Purpose being to reflect the radiant energy absorbed into the attic space from the roof. Are you saying that is worthless also?? Thats more likely to see dust than the inside top 1-2 inches of a joist bay.

    The R16 blocks nothing. It slows down the heat transfer while the foil actually does block a significant portion of the downward radiant energy. The R stands for resistance.

    I was not saying to use just the foil, I agree this would not be a prudent choice. The point was, in my opinion, it would help increase the effectiveness of his installation.

    My home was built with TGI beams. I took foil faced kraft paper and stapled it to the underside of the top flange, foil face up, creating a dead air space. I can't tell you it had any measureable effect, but it has an impact.

    You really don't like foil do you.
  • ALH_4
    ALH_4 Member Posts: 1,790

    The foil theoretically may do something, but I tend to think it's more about marketing than insulating quality.

    My question is whether cardboard sheet stapled to the joists beneath the plates would be nearly as effective or possibly more effective than polished aluminum sheet installed in the same way. Blocking the airflow to the space below is the most important factor in my opinion.
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592

    There is a product like that, its called paramax. Its a foil faced cardboard that partially curls upward in theory to create a parabolic reflector.

    The foil is an added plus - not the end all be all as alot of the bubble mfg would promote.

  • Glenn, the "blocks" arguement is a fallacy. Heat goes to cold, period, end of story. If it's reflected, it will still go to cold at some point, you don't get to hold on to the heat forever. At least in our residential situations where we are trying to keep a box warm or cold, the difference is esoteric at best.

    All you can do is slow down how fast heat goes to cold in our situations. R16 slows down the rate of heat trasmittance by 93.5%. Reflecting a similar amount will result in a similar heat load over time. You *might* get a small performance benefit from reflection, but it's small if it's present at all.

    And yes, the dust factor on reflective insulation SPECIFICALLY in attic spaces was well established and tested by ORNL. the site's a little slow right now, but here's the link ;http://www.ornl.gov/sci/roofs+wall/radiant/rb_02.html I see no reason to think that HVAC guys know some little known fact about foil barriers that the rest of us are not privy to. As the foil slab insulations show, just because something is marketed for a particular application doesn't mean it's particularly good at what it's supposed to do.

    I'm not trying to call you out Glenn, I'm just trying to have a fuller discussion. You have to understand.. I run into systems ALL THE TIME where people thought that because something is a "radiant barrier" that it has magic properties that make it good insulation for a radiant system. And they also marvel at how warm and toasty their basement is, not connecting that to heat loss from the radiant overhead! In part, they think this due to the marketing speak of that segment of the industry. And then well meaning people such as yourself repeat those marketing points that have no bearing on anything important here in reality... ALL insulation is just slowing down heat loss in residential homes... well, it makes me react.

    I do have to note that the amount of dust in a joist application is highly debateable. I just personally choose not to risk it. R value doesn't care if it gets dusty. Neither of us are physicists though, and I'm not trying to say my word is gospel on this matter... just how I feel about it based on what I've read and seen... and this is a discussion board ;)

    So no, I don't really like foil. In part because the foil industry has years of deceptive marketing practices under its belt and I spend a good portion of my time (like now) dealing with their deceptions. It does have a place. Two places, actually: in walls, and facing downward in ceilings. That's it, IMHO. For heat reflectance to attics, you're far better off going for a white roof. For joists, seal them up tight and use real R-value. Add foil if you really want to. and for attic ducts.. well, get the ducts into conditioned space. If you can't, insulate the heck of out them. Anything else is a band aid.

    But I'm sure you have some very well thought out arguements, and I look forward to hearing them.. in all seriousness!!

  • I am obviously overracting a little for some reason though. Sorry you're standing in my line of fire right now glenn. I'll go back to work now and be quiet ;)
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    Tough exchanges

    Rob - its ok, I like the exchanges. I don't think we are here for target practice. I think this is a place to learn and exchange ideas. Although, I must admit, you have to be careful in the choice of words you use.

    I have been burned by foil. I started using it over 10 years ago. Initially I beleived the hype - no reason not to. I was given a copy of an DOE report from late 80's stating that in a hot box test, a sheet of foil had same performance characteriscs as 6" of fiberglass batt. How could the DOE be wrong ??

    To the best of my knowledge, I was the first wholesaler on LI selling a foil bubble product called TekFoil. We sold it for installation in two mud jobs, one had to be pulled up because of the floor flexing cracking the grout. Live and learn. The manufacturer said it was ok to do. I didn't question them.

    The only application I will sell it for now, is a basement wall, the poly side against the block to act as a vapor barrier, the foil side facing into the stud bay with pex either looped in the bay or traveling across the front. This seems to work very well. See attachment

    I believe RIMA was formed to try and quantify all these claims and try to develop a standard for measuring the effectiveness and proper applications of these foil products. It amazes me, these companies are still out there pushing this stuff and contractors still buy it.
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    3 components

    I understand your comments, but perhaps your mis-interpreting my direction. To the best of my knowledge, the heat energy we are trying to control is made up of conduction, convection, and radiation. The foil is only effective in blocking the radiant component of heat energy. It is a great conductor. I was not trying to imply it could address all three.

    Batt insulation primary affects the conduction component, the foil affects the radiant component. My point is, together - they make a more effective installation than just the batt alone.
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    Foil Chips

    Here's an intersting application for foil. Found this application about 10 years ago when I was preparing to teach a class to contractors on radiant heat. Used in SW US.

  • ALH_4
    ALH_4 Member Posts: 1,790

    Hopefully they blow in at least 24" of those "chips". ;-)
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    More than 1 of these companies.

    If you watch the video, the claim is to install 7-8 layers of these chips. The multiple layers keep the bottom layer clean so it can reflect the radiant component of heat energy.

  • but then, isn't it just reflecting back up to a shiny downward facing layer? I guess I'm not seeing it. Go Go white roof ;)

  • This is a fine comment. But that "reflects 97%" statement, on its own, is one that I constantly have to address Glenn, because it is basically meaningless in a residential heating application. The way "slowing down" heat loss is dismissed as worthless in the ads (and, if you are not a trained heating person, in your earlier comment) is very, very misleading to the general homeowner.
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    reflect heat to its source

    Again,to be clear I'm not endorsing this - their logic is it keeps the heat in during the cold months and keeps heat out during the summer. The iddea is, reflect the heat back to its source. Who knows. As my Grandmother used to say " go figure"

    Instead of a white roof how about solar panels. Hope to be selling a total package from Roth by end of year.

  • I understand what they say.. I'm questioning the mechanics of how it works. seems once you get under the dusty layer (presumably, by re-radiation from the top layer) you get a refractory chamber reflecting up and down...

    anyway yeah, bag the whole thing. solar! we just had two reps from a solar company in here for 3 hours today.. learned a heck of a lot too. fun stuff!
This discussion has been closed.