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bob in edmonton
Registered Users
Posts:16
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| 08/09/2007 5:21 PM |
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Hello all-
I found this link when I was researchig SIP's,
http://www.sipweb.com/monitor/bc_main.asp
but the reason I am posting is to ask the question of how to put an air heated radiant floor on a floor other than slab on grade. One of the articles on the site references an ancient way of radiant heating. In a nutshell, on a grade, before you pour the concrete, you dig 3 triangular trenches running longtitudinally the length of the room, one in the middle, and one on each edge. After laying foam insulation in the trenches and the rest of the floor, Q deck is laid running perpendicular to the trenches. Concete is then poured for the floor. The middle trench is the supply. Air is blown from the supply trench through the voids in the undersurface of the Q deck to the ducts on either side. In the middle of each duct is a vent, similar, if not identical, to a regular forced air register, so the "exhaust" air is supplied to the room, obviating a second system for air handling in the usual hydronic system. It seems to work well, according to his website
http://www.chaleffandrogers.com/
Could you do this on a suspended floor such as over a basement?
There are some commercial companies that do this Air Floor and Legalett, if I remember correctly, but their websites only show it on a slab on grade.
Comments?
bob |
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woulfcc
Registered Users
Posts:185
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| 08/12/2007 3:48 PM |
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| Look again at legalett they do a suspended air radiant floor . |
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Changing how the world BUILDS!
One build at a time.
Woulf c.c. |
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MRM
Registered Users
Posts:1
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| 08/15/2007 8:35 PM |
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Bob. I am a builder in the Ottawa area and have installed Legalett air-heated slabs in suspended floors. Originally, the company only had a slab-on-grade design but now they are able to handle any type fo floor. I personally live in an ICF with Legalett floors and have absolutely no regrets. These two systems have made our winters somewhat more liveable. Edmonton would also qualify as a city that would appreciate these two systems.
Good luck.
Gerry |
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bob in edmonton
Registered Users
Posts:16
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| 08/15/2007 11:24 PM |
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Thanks Gerry!
I have an ICF house in the Rockies with a slab on grade with hydronic radiant and a fan coil for the upper level using hi-vel system. I am planning to build this one with an ICF foundation and SIP walls and roof (the SIP suppliers is tryiing to get me to do the foundation as well...)
What interested me in the "air floor" was that it fits in well with a passive solar house- it can pick up and store some of the radiant incoming from the windows and pass some on to the air as well as acting as a heat sink. Radiant hydronic can't relly do that.
The problem I have is visualizing how the floor will be supported, reinforced, and supplied with air. The Legalett site is not too clear on that. Any suggestions?
bob |
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NRT.Rob
Registered Users
Posts:360
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| 08/16/2007 11:15 AM |
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What is the benefit of "passing it on to the air"? If it sinks into the mass, it will reradiate out later. you can redistribute it with hydronics once it's in the mass as well, if you want to. Constant circulation hydronic radiant would achieve exactly the same thing, but instead of running a fan all the time, you get to run a much lower wattage pump all the time.
Do what you like and I"m not saying it doesn't work, I just don't see a any advantage to air based radiant systems. Part of the major benefit of hydronic radiant is not having to rely on air movement to move heat, which water is much better at than air is. |
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-=Northeast Radiant Technology=-
NRTradiant.com |
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bob in edmonton
Registered Users
Posts:16
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| 08/16/2007 12:13 PM |
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Hmmm....
I might have to go to a physics book...
The way I see it, in a hydronic system, the pipes are filled with hot air on demand, which heats the slab. If the slab is warm, say from the sun, and is not calling, there will be no circulation of fluid to take the heat out of the slab to somewhere else. The floor would be a passive radiator only to the room.
With constant air flow( or near constant) depending on the gradient between slab and air, heat will flow into the air from the slab and be taken out of the area via the airflow to other areas of the house.
I know fliud is a much better "container" for heat transfer, but with present systems, it seems to be one way.
I will still need some sort of air handling system for ventilation.
Correct?
bob |
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NRT.Rob
Registered Users
Posts:360
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| 08/16/2007 12:23 PM |
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That's not true if you use a constant water circulation system. Then the water is flowing all the time, you are only injecting heat into it on demand. If it is being heated in one area from another source, such as by passive solar, then the heat is moved to portions of the system with less heat.
Now in a large, multi zone system implementing constant circulation might be tricky. As it would be if you had equivalent zoning in an air system.
You will still need air handling for ventilation, yes. You could even use that to redistribute passive solar gain which might be less complicated than a constant circulation, multiple zone hydronic system. That doesn't make an IAQ sized air system appropriate for a full fledged heating system though.. the CFM requirements are higher in that case, as it is for cooling. So that means bigger fans, larger ducts, etc.
Granted, air is cheap. But it's not QUITE as much cheaper as it looks up front. If you add equivalent zoning as well as looking at power usage.... |
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-=Northeast Radiant Technology=-
NRTradiant.com |
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bob in edmonton
Registered Users
Posts:16
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| 08/16/2007 2:17 PM |
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I see what you mean. I guess a hybrid is the way to go with a hydronic floor and either a fan coil in a ventilation system or a separate furnace for the forced air.The forced air system would be easier to configure than the hydronic. It would have to be zoned to pick up warm air from the passive solar room and dump it into the system to be carried to the other areas. And it is available, tried and true technology!
BTW, for the hydronic floor, I was thinking of 3/4" Pex on 3/4" TG plywood glued and screwed on SilentFloor joists covered by 1 1/2 inches of concrete. Is this enough?
The undersude of the floor would be insulated with foam. Are reflectors of any use?
bob |
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NRT.Rob
Registered Users
Posts:360
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| 08/16/2007 2:20 PM |
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There is no reason to use pipe larger than 1/2", and with that install method you shouldn't anyway to keep enough concrete over the pipe. keep the tubing to 9" o.c. or tighter or you might notice heat striping.
reflectors would be of no use.
Best of luck! |
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-=Northeast Radiant Technology=-
NRTradiant.com |
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bob in edmonton
Registered Users
Posts:16
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| 08/16/2007 2:26 PM |
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Thanks Rob- I really appreciate the info.
Any criticism of the floor system? What would you recommend?
BTW< have you ever seen a house that used SIPs as a foundation?
bob |
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geodan
Registered Users
Posts:11
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| 08/16/2007 11:58 PM |
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What is the current wisdom on Gypcrete VS Concrete on one of these thin suspended slabs? I have joist / ply subfloor in and was going to use gypcrete for my mass... concrete would be much cheaper... so why isn't it used more often?
Thanks
George |
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