B1004U
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| 04/23/2009 3:24 PM |
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I have a question regarding icenene spray-in insulation and Radiant heat. I am planning on putting radiant heat in my house this summer, staple up in the joists. For the majority of my house, i will use insulation bats, but i have an addition that is quite drafty underneath, and I thought it would be good to use spray in insulation in that area.
In order to use staple-up correctly, it is my understanding that I need to have about an inch of air space below the tubing and distributers. Below that goes the reflective barrier and insulation. My question: has anyone done this to create a solid enough "barrier" so that when you spray in the insulation it doesn't collapse the airspace?
If so, how'd you do it???
Thanks,
B1004U
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NRT.Rob
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| 04/23/2009 3:28 PM |
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| if you use conductive plates to the subfloor, airspace and radiant barrier are very optional. |
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-=Northeast Radiant Technology=-
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B1004U
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| 04/23/2009 3:35 PM |
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I trust that you are saying that:
(A) it is not significantly more efficient to leave a space for the heat to spread out. Conductive plates get the job done just fine, and (b) that is is fine just to spray in icenene insulation right over the cunductive plate?
Why then have i been told that the 1" space is so important?
thanks
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NRT.Rob
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| 04/23/2009 3:40 PM |
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the space is very important if you are doing a suspended tube application without plates. With plates, the space is a very minor difference. The radiant barrier is helpful (and everything you can do to help a plateless system is often wise), but with an appropriate downward R-value and plates, I don't regard its addition as anything near critical.. in fact, if the cost would reduce the rest of the insulation, I would skip it entirely and focus on regular insulation.
With spray foam, the big issue is making sure foam doesn't get between the plate and the subfloor. a cardboard shield is quite adequate. |
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-=Northeast Radiant Technology=-
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B1004U
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| 04/23/2009 3:48 PM |
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This is great info! And fast!
So from what i understand, you are saying I could staple up the tubes, add the plates, then simply put a layer of cardboard in to protect the spray in from getting between the sub floor and tubing.
Thoughts- I could use the cardboard to (a)create a space, or(b) attach a reflective barrier. But it sounds like you would neither of these steps would be critical. The plates do the job for me. Is that right?
The only thing i didn't understand is "appropriate downward r-value." I assume you are saying the plates SERVE as the appropriate downward R-value. is there something more that creates the appropriate downward R-value?
Thanks again! |
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NRT.Rob
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| 04/23/2009 3:49 PM |
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| Insulation creates R-value. All radiant floors need insulation underneath. so it's about plates, and insulation. |
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-=Northeast Radiant Technology=-
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B1004U
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| 04/23/2009 3:52 PM |
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| Thanks! |
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Dana1
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| 04/24/2009 9:56 AM |
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Icynene is relatively opaque to radiated heat (unlike fiberglass, which is translucent), so if that's the insulating material of choice- what Rob said.
Air gaps create the potential of thermal-bypass air currents flowing laterally along the joist bays- it's always better to use heat spreaders and snug the insulation (even fiberglass) right up against the tubing & plates to limit lateral air flow, PARTICULARLY when the space below is known-drafty as in your case. (You might consider having the insulation crew insulating and air-sealing the entire band-joist & foundation sill while they're there- it's usually THE single largest infiltration gap in homes-it leaks more than all the doors & windows combined in most cases.)
You can get another effective R4-R6 out of an air-gap + radiant barrier, but for cost of labor & material to do it RIGHT it's usually cheaper to go with higher R-value higher-density fiberglass for similar benefit. With low-density fiberglass it may be worth (I wish somebody would actually measure this in a radiant application) rolling out permeable radiant barrier stapling it BELOW the fiberglass (on the cold side of the FG), which is much less labor intensive, and if experiments in FL in FG-insulated attics, has 1/2-2/3 the benefit of putting the radiant barrier on the warm side of the FG. (All of which is completely irrelevant to a foam-insulated radiant system like yours... :-) ) |
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NRT.Rob
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| 04/24/2009 10:04 AM |
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| you would never want the vapor barrier (reflective barrier) on the cold side of your insulation. If you were between two heated spaces, the bottom of joist radiant barrier might do something. but if you were over a cold basement, that would be a very bad idea. |
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-=Northeast Radiant Technology=-
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Dana1
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| 04/24/2009 1:00 PM |
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The perforated aluminized-polyester radiant barrier that comes in 4' & 8' wide rolls doesn't behave anything like a vapor barrier (or much of an air-barrier, for that matter.) The perforations, while individually small, comprise something like a percent or three of the entire surface:
http://www.radiantguard.com/images/products/detail/Ultra.jpg
http://images.neutralexistence.com/Ra-flect_radiant_barriers.jpg
Using anything BUT this type of RB on the underside of insulated joists (or in an insulated wall) can be in invitation for mold.
I agree, UN-perforated aluminized polyester, or worse, aluminized mylar/aluminized polyethylene bubble pack radiant barriers are bound to create mold issues if applied to the underside of joists over unconditioned space. (In most US climates it would be an outright DISASTER over a crawlspace.)
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B1004U
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| 04/24/2009 3:40 PM |
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OK- Just as a final "clarifying" statement...
For the portion of the house where i will be using spray-in icenene, it sounds like i should put the pex tubing, then the conduction plates, then cardboard to protect the tubes, then spray in. Is that right?
My questions:
1) Should i not even bother purchasing the reflective barrier?
2) Should i "snug" the cardboard up under the plates to make sure there is as little dead air space as possible?
3) I can't help but think i could kill many birds with one stone if there was such as thing as 18" strips of cardboard that had a reflective side, so i could put them in in an "arc" position (a 16" joist bay) using their own flexibility as tension to hold them in. This would create a reflective barrier, protect the tube from the spray, and possibly even alleviate the need to add conduction plates, or at least improve the downward r value by using them in conjunction with plates... AM I CRAZY? Do these exist?
Now, for the rest of the house, where it is a basement and not as drafty, where i will be using FG insulation, it sounds like the way to go is pex tubing, conduction plates, reflective barrier, then good R value FG.
Questions:
1) Do i leave the airspace and then the barrier and then good insulation, or
2) Do i take Dana's recommendation. Once again foregoing the reflective barrier, and putting good FG insulation right up to the conduction plates?
3) Dana, when you say "higher density higher R-value" insulation, what R-value specifically do you have in mind?
Thanks for the insight! |
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Blueridge company
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| 04/26/2009 11:58 AM |
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A key question, where are you located? with the systems described in a less cold climate like where I am in the Pacific NW, plates are not always used. If in a cold clime like Michigan or Maine plates are a good idea.
As to a handy product we sell that may work well in place of cardboard is NT Barrier foil. http://www.blueridgecompany.com/radiant/hydronic/179/tvm-ultra-no-tear-nt-radiant-barrier
This is like the blue tarp used to cover your wood pile only it is foil on both sides and perforated.
Here is the trick, it is sold in a 4 foot x 125 foot role, much like a presto log. You can cut the role with your skill saw resulting in a manageable 16" x 125' reflective perforated easy to use unit.
It is a sleeper of an item that has great applications.
Dan
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Dan
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radiantbarrier
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| 04/26/2009 6:11 PM |
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| Have to ask ??? why go to all the bother when we sell a product already that is 16 inches in width? our product comes 16 wide by 125 see www.greeninsulationproducts.com and look for microfoil |
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B1004U
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| 04/27/2009 8:07 AM |
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So- I called the local Standard plumbing Hydronics division, and they actually said they sell the product i described above: a 16" stiff material that is reflective on one side that can be placed in the joist bay in an arc position that holds itself in with a natural bow. The call it... drumroll please.... Reflective panels! They do a few things does a few things (according to the manufactureres). (A) provide a radiant barrier, (B) maintain an air space, and (C) do the same job as the conduction plates and are just hell of a lot easier to put in...
Anybody have any experience with these? I guess my question is... It sounds ideal for my Icenene application, but should i use it in conjunction with the conduction plates or instead of the conduction plates? Secondly, when i am doing a more typical staple up with FG insulation, should i just forgo any reflective barrier as Rob mentioned above? Or maybe use these instead of conduction plates with good insulation as Dana mentioned? Dana, Rob, any thoughts?
Thanks! |
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BadgerBoilerMN
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| 04/27/2009 8:23 AM |
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Sorry, known of it is true. Extruded aluminum panels, foam or high density fiberglass is are the best values. The rest is snake oil. These thing cost more for a reason; they work. You will heat more space at lower water temperatures saving real dollars regardless of climate. Radiant barrier are of little value in sub-floor applications.
You start with an accurate heat load analysis for each room. |
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MA
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Blueridge company
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| 04/27/2009 8:29 AM |
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Micro foil is interesting but insulation is not what is needed in this application, it is air space and reflection, the spray foam is the insulation. The NT Barrier is about .19 cents per foot SQ. a low cost alternative to card board or foil faced card board.
Dan
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Dan
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BadgerBoilerMN
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| 04/27/2009 8:41 AM |
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I think we are getting our applications mixed up here. You have to pick one. An air space (1") is only beneficial in suspended tube systems whereby most of the heat is transferred first by convection. Foil is a very small factor in such a system (small enough to be ignored).
By contrast, a system using emission plates does not benefit from an air space as most of the energy is conducted directly to and through the floor.
Of course we don't know the heat load (unless I'm missing something) so we can't speculate on the proper design.
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MA
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radiantbarrier
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| 04/27/2009 8:44 AM |
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| MicroFoil is a REFLECTIVE FOAM INSULATION you can put it anywhere in the joist box you want. giving you distance from the pex. it has self seaming tape on both sides so you stick the tape to the joist side and also staple it so a nice tight seal and NO cutting with a skill saw as it comes in 16" wide rolls!!! |
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BadgerBoilerMN
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| 04/27/2009 8:52 AM |
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And as for all intents and purpose no value other than the critical need to make the space air-tight.
Aren't you the guys that advocate the (completely debunked) use of foil "under" a slab?
Do we have to refer to Mr. Bean again? |
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MA
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NRT.Rob
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| 04/27/2009 9:05 AM |
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let's not pigpile radiantbarrier again.. to his credit he does not advocate for slab foils, he sells "The Barrier" which, while sued for FTC violations like the rest of the tarp products out there, is actually a foam insulation product and has value under a slab.
However microfoil is just a radiant barrier, while it has some foam in its construction it is not "foam insulation". Real R-value is still necessary in the joist bay, IMHO. If someone wants to spend extra to put in a radiant barrier, and get some benefit for some amount of time from it, that's up to them... as long as it doesn't reduce the real r-value installed, I'm good.
Morgan, the purpose of cardboard is just to keep spray foam from getting under the plates. Many people skip that step of course, but it's a concern at some level at least. foam can get into pretty small spaces and expand.. |
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-=Northeast Radiant Technology=-
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