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Old 02-18-13, 09:18 PM   #1
mikek
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Default Opinions on installing radiant in basement

I'm in the process of finishing half of the basement in my house (~400sq ft) and would very much like to install radiant floor heating as I've never found basements that are heated with forced air to be very comfortable. Ideally, the heat would come from solar water panels, but that's a future project....likely another post as well

Anyway, the basement is currently got an uninsulated concrete slab and is constructed out of wood (2x6 on 12" centers). I plan to insulate the walls (trying to decide if I should have it done with spray foam or use fiberglass, again another post!)

I'm guessing that any attempt to put a radiant floor down without insulation over the floor will only result in the worms in the ground being a little warmer and my basement not getting much of the heat.

My questions would be, how much insulation do I need to make a difference? I've got a height constraint as the floor to ceiling distance is already a tight, so I can't add 2" of insulation + a subfloor and finished floor. I'm thinking of 1/2" insulation, 3/4" subfloor with PEX embedded and a 1/4" finished floor (likely an engineered floor, cork maybe?).

If this much insulation can make a difference, what kind of products are out there to facilitate an installation like this? While looking for answers in this forum, I ran across Olaf Piesche's blog and am very intrigied by his DIY installation method. Would something like that be suitable for my basement? I should note that there's never been a moisture issue. While I was moving my shower drain, I found that there is a vapor barrier under the slab, along with at least 6" of pea gravel (though that may only be around where there is plumbing?).

Thanks in advance for any information!
mike

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Old 02-19-13, 01:20 AM   #2
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Quote:
Originally Posted by mikek View Post
...Ideally, the heat would come from solar water panels, but that's a future project...
Solar radiant heating can be done, but solar heating actually comes uner the heading, 'Low Temperature Heating'. You can do it but to make it really successful, you will need to plan for it carefully. Many radiant installations use rules of thumb that were developed for high temperature heating, and suggest tube spacings and pumping rates expecting water heated to 140 F to 160 F, and when solar heated water is then used, it can be under-whelming.



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Anyway, the basement is currently got an uninsulated concrete slab and is constructed out of wood (2x6 on 12" centers). I plan to insulate the walls (trying to decide if I should have it done with spray foam or use fiberglass, again another post!)
There's a product called Roth Panel that is very high efficiency and it includes foam insulation in its manufacture, that is part of the product. This product is expensive, but for your situation, and since your basement isn't too big, it would be a very good match... even for solar.

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...(likely an engineered floor, cork maybe?)...
Engineered wood would (snap-lock) be pretty good, cork would be self-defeating, since it is a good insulator. Any floor containing vinyl (PVC) should be strictly avoided as it will out-gas, especially with radiant heat. Read up on the hazards of Vinyl (PVC). It'll make you shudder.

I was in a floor covering store the other day and the sales guy was pushing "High Quality Vinyl" flooring. I asked him if it contained PVC, and he turned white as a sheet and backed up a step and said, "This stuff is not green." Even the sales people know this stuff is a hazard... but they will sell it to you.

Insulate, insulate, insulate...

Good Luck,

-AC
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Old 02-19-13, 09:36 AM   #3
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What about doing the walls? Run the lines in the walls.
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Old 02-19-13, 01:00 PM   #4
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What about doing the walls? Run the lines in the walls.
As I recall, the feed temperature for radiant walls needs to be about 10 F higher than for a floor.

With an average January temperature of 49.3 F degrees... Go for it!

Don't for get to take lots of pictures for other EcoRenovatees...

-AC
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Old 02-19-13, 04:08 PM   #5
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Originally Posted by AC_Hacker View Post
Solar radiant heating can be done, but solar heating actually comes uner the heading, 'Low Temperature Heating'. You can do it but to make it really successful, you will need to plan for it carefully. Many radiant installations use rules of thumb that were developed for high temperature heating, and suggest tube spacings and pumping rates expecting water heated to 140 F to 160 F, and when solar heated water is then used, it can be under-whelming.
OK, good to know. Based on whether or not it was feasible, these were going to be my next questions.

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There's a product called Roth Panel that is very high efficiency and it includes foam insulation in its manufacture, that is part of the product. This product is expensive, but for your situation, and since your basement isn't too big, it would be a very good match... even for solar.
I assume the R value of these panels is a lot more per inch than I could get with sheet insulation?

Is there some formula I could run to figure out how much heat I'd be losing to the ground versus what I'd be putting into the room? I don't mind making bigger solar collectors, the heat is pretty much free compared to making it with LP.

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Engineered wood would (snap-lock) be pretty good, cork would be self-defeating, since it is a good insulator.
Is it that much more insulating than other wood type products? Just curious.

Thanks for the reply!
mike
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Old 02-19-13, 04:10 PM   #6
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What about doing the walls? Run the lines in the walls.
Interesting idea, trade floor area for ceiling height! Though I assume I'd still have to insulate the floor to keep it comfortable. My feet get cold through shoes while I've been working down there....
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Old 02-19-13, 04:13 PM   #7
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With an average January temperature of 49.3 F degrees... Go for it!
Not around my parts....High today was 5 and it's currently -18 with the wind chill!

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Old 02-19-13, 07:29 PM   #8
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Default Radiant floor with solar hot water input

Mikek
Radiant floor is the Holy Grail but like everything else it has to be approached with the proper technique. We heat our home with Radiant floor (solar & geothermal) so I can speak with some experience. But lets see what your goals are.

If you just want warm floors as simply as it gets. That would be some ridgid foam with subfloor ply and electric heat pad below hard surface flooring (no Carpet). This would be the easy least expensive. When you go down to the basement touch the timer within a few min. the floor is warm and your cozy for the duration your there.

If your planning on most efficient space heating to help with the whole home heating this may be a little different. The best aspect of the system is that large flat rock in the basement (the concrete floor). However this is an integral part of the heating system so it must be insulated and the plastic tubing be placed in the floor at a 4"- 6" spacing. Now it gets work extensive. It would involve smashing out the old concrete digging down minimum 2" more for ridgid foam and poring another concrete floor with the tubing in. You will also need a thermal break around the outer edge of the concrete 1 " foam should be enough.

For a heat source this can be LP gas water heater or a demand type will work. A small circulation pump will move water thru the tubing in the floor warming it to about 80-85 Deg F This heat will radiate to the living space above making it a little more comfortable. With these warm temps believe me a ceramic or porclin tile floor is the best.

Now you had mentioned you were interested in solar hot water. This heated concrete floor will make all the difference. When the sun is avalible the hot water from the panels can be directed to the floor. The floor will slowly warm during the day and release its heat through the evening. This will help keep your home warm and the basement comfortable for hours for free . The fact is the concrete acts like a big battery. I would suggest 3 pcs 4x8 flat plate panels min.

This project can DIY but if you have to hire out it could be prohibative cost wise. It would be a lot of physical work. But that warm floor is really nice

Randen
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Old 02-19-13, 08:27 PM   #9
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Default Location, location, location...

It looks like there are (at least) two people posting, and their requirements would be very differently met.

One lives in an area in Texas where the avg Janurary temperature is 49.3 F degrees,

...and the other lives in Rochester, MN, where the average January high temperature is 20 F and the average low temperature is 8 F.

You both will be flailing in the dark if you don't do a heat balance before you begin.

And if you're going solar, you'll need to do a solar analysis, too.

It's ironic, but to design a heating system for fossil fuel is easy, but the fuel is expensive. To design a system for low temperature heating is expensive (in terms of equipment and in terms of the time spent analyzing the heat load and how you can meet it with renewable... but the heating is very cheap.

But any way you slice it, if you want to go renewable, insulate, insulate, insulate!

Just ask someone who did it... ask randen.

-AC
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Old 02-19-13, 08:31 PM   #10
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Quote:
Originally Posted by randen View Post
If you just want warm floors as simply as it gets. That would be some ridgid foam with subfloor ply and electric heat pad below hard surface flooring (no Carpet). This would be the easy least expensive. When you go down to the basement touch the timer within a few min. the floor is warm and your cozy for the duration your there.
I had considered this for the bathroom, but it seemed like i'd mostly be heaing the ground with electric heat, which didn't seem very cost effective. How much insulation would you recommend in this case?

Quote:
Originally Posted by randen View Post
If your planning on most efficient space heating to help with the whole home heating this may be a little different. The best aspect of the system is that large flat rock in the basement (the concrete floor). However this is an integral part of the heating system so it must be insulated and the plastic tubing be placed in the floor at a 4"- 6" spacing. Now it gets work extensive. It would involve smashing out the old concrete digging down minimum 2" more for ridgid foam and poring another concrete floor with the tubing in. You will also need a thermal break around the outer edge of the concrete 1 " foam should be enough.
My wife had this same idea....the amount of work required for this would give me nightmares! quick back of the napkin calculation gives me 3.5 yards of concrete i'd have to bust apart and carry out with 5 gallon buckets. Then figure out a way to put it all back in in liquid form!

Quote:
Originally Posted by randen View Post
For a heat source this can be LP gas water heater or a demand type will work. A small circulation pump will move water thru the tubing in the floor warming it to about 80-85 Deg F This heat will radiate to the living space above making it a little more comfortable. With these warm temps believe me a ceramic or porclin tile floor is the best.
What kind of temperatures are required for the floor? I assume one doesn't want it too hot?

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Originally Posted by randen View Post
Now you had mentioned you were interested in solar hot water. This heated concrete floor will make all the difference. When the sun is avalible the hot water from the panels can be directed to the floor. The floor will slowly warm during the day and release its heat through the evening. This will help keep your home warm and the basement comfortable for hours for free . The fact is the concrete acts like a big battery. I would suggest 3 pcs 4x8 flat plate panels min.
Yes! The thought of using the slab as storage is enticing, since I wouldnt' have to give up any space to build a storage tank....

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Originally Posted by randen View Post
This project can DIY but if you have to hire out it could be prohibative cost wise. It would be a lot of physical work. But that warm floor is really nice
Yep, my plan is to do it all DIY, hopefully will finish before spring (which is the same goal I had last year

thanks for the input,
mike

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