1st Floor Radiant, Stumbling Block

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trehugr

trehugr

Member
Dec 16, 2007
237
Greenwood, Maine
I keep finding myself going back to the question of installing radiant heat on the first floor. It's really a no brain-er for obvious reasons, lower temps for that loop/s, more efficient heat, less wood usage and not to mention a huge WAF factor. The benefits seem to thoroughly outweigh the negatives. The problem is, I have one huge negative to contend with and it's due to my lack of fore-thought.

Last year I finished our big screen room in the basement. Basically, it's half of the basement. I used 6" T&G;pine. Walls and ceilings. All of it blind nailed of course. I pondered for a long time it seems, weather to do the ceiling in pine or to put up some sort of drop ceiling. Well I did what I did and now it seems painful to tear down the ceiling to install the radiant and insulation.

I guess my questions are this. If it were you, would you tear it down to put in the radiant, or just keep the whole house baseboard heat ? Am I going to find it difficult to heat with the 180* water temps as opposed to 110* for radiant ? Is there a solution that I'm not seeing ?

I really don't want to regret anything I do with my new system. Too much money involved. Please, carpenters and heating techs, your 2 cents will be greatly appreciated.

Kevin
 
Part of my house has baseboard cast iron radiators. Never have bought or installed them myself but they appear to be similar size and shape of the fin-tube kind. I'm told they will work good down to 140* like any CI radiator. Just a thought.
 
trehugr said:
I keep finding myself going back to the question of installing radiant heat on the first floor. It's really a no brain-er for obvious reasons, lower temps for that loop/s, more efficient heat, less wood usage and not to mention a huge WAF factor. The benefits seem to thoroughly outweigh the negatives. The problem is, I have one huge negative to contend with and it's due to my lack of fore-thought.

Last year I finished our big screen room in the basement. Basically, it's half of the basement. I used 6" T&G;pine. Walls and ceilings. All of it blind nailed of course. I pondered for a long time it seems, weather to do the ceiling in pine or to put up some sort of drop ceiling. Well I did what I did and now it seems painful to tear down the ceiling to install the radiant and insulation.

I guess my questions are this. If it were you, would you tear it down to put in the radiant, or just keep the whole house baseboard heat ? Am I going to find it difficult to heat with the 180* water temps as opposed to 110* for radiant ? Is there a solution that I'm not seeing ?

I really don't want to regret anything I do with my new system. Too much money involved. Please, carpenters and heating techs, your 2 cents will be greatly appreciated.

Kevin
Click to expand...

If this is a home you will be living in for years to come, bite the bullet and do it the way you want. Can the ceiling be removed without destroying the wood?
 
Thats the problem, there's no way to remove the nails. Ill have to pull the boards from the nails. It has the potential of getting ugly.
 
Maybe if you remove the boards in the opposite order that they were installed, once you get the first board pried/torn out, you may be able to drive the nail heads through the tongue of the next board with the right size nail-set.
 
Are talking about putting in staple up? If so, I don't think you'll be able to heat with 110. I just retrofitted my entire house with warmboard. It was a big job and I'm glad we did it. Now i can heat my house with 90 degree on the coldest day. But I didn't live in the house during the remodel. I love the options it has given me, but my whole house is warmboard. I assume that you would sitll have some baseboard? So you'd have to run some high temps anyway. I think it my only option were baseboard v. staple up I would stick with the baseboard. It's just not worth the hassle.
 
nhjohn is correct. Depending on your heat loss requirements, your desired room temps on the coldest days, and any supplemental heat (or not) you have available on those days, AND the method of subfloor "Staple Up" installation you are considering, the actual temps you will need to run in your floor *may* be considerably higher than 110*. Unless your in a really tight, well insulated house, with the best subfloor installation you're likely to need more like 140* water, if your lucky. That would be an installation with the *thick* heat transfer plates that the PEX fits into -not the heavy gauge foil stapled below - and thus considerably more expensive to install.

This all hinges on the first thing that should be done - a heat loss estimate using an appropriate software. If you don't have this, you shooting with your eyes closed.

But basically, any subfloor install (that is not a warmboard, or thinset, or in slab installation, but attached to bottom of the existing subfloor) will require higher temps in the PEX on the coldest days in a typical house - Not 110*, more like 150*.

Hope that helps.
Nat
 
The maximum radiant supply temperature has nothing to do with the heat loss, assuming a "standard" installation (1/2" tube, 8" on center, transfer plates). It is a function of the desired surface temperature and the R-value of the floor.

Since you need to limit your floor surface temp to ~80 degrees, you can calculate (based upon the floor construction) what water temp will achieve that.

How thick is the subfloor and what sort of flooring is installed over it?

Joe
 
Joe,
you need to be clear about what you're saying.
The discussion was not about what the maximum supply temps would be.
I was only addressing his initial idea about the benefits of radiant - one being able to utilize 110* water - as reasons to tear down his previous ceiling work.
His supply temps have lots to do with his heat loss, and I wanted to make sure that he understood that he was going to need to run higher temps than 110* - and that needs to be part of his equation when deciding to go radiant, or not.

No?
 
As Hot Rod would say, "How about considering ceiling radiant ?" Easier install than tearing out your wood work. Drywall is cheaper than tearing out real wood carefully installed to look good.
 
Joe, the subfloor is 3/4 with a pergo type floor on top of that throughout the 1st floor except for the bedroom (carpet and pad)

Kevin
 
nmerrill said:
Joe,
you need to be clear about what you're saying.
The discussion was not about what the maximum supply temps would be.
I was only addressing his initial idea about the benefits of radiant - one being able to utilize 110* water - as reasons to tear down his previous ceiling work.
His supply temps have lots to do with his heat loss, and I wanted to make sure that he understood that he was going to need to run higher temps than 110* - and that needs to be part of his equation when deciding to go radiant, or not.

No?
Click to expand...

No. First, figure the maximum temp you will need to make the floor 80 degrees. If that temp is low, then you know radiant is a good option. If it's high, then look through all the options to see what can be done to make it lower.

In other words, if you know that it will work with 120-degree water, you can calculate the details at your leisure, content that you will potentially gain additional efficiency/practicality by lowering the water temp.

If you find that you need 160-degree water to get the floor to 80 degrees, then you immediately do the tedious work and figure out if the floor actually needs to be 80 degrees, or if you need to tighten up the tube spacing, or whatnot.

Joe
 
I don't mean to hijack this thread but I am a little confused. A friend of mine runs his radiant floor in concrete 24/7 at 90*. Place is always warm. I was thinking of doing the same in my house under the first floor because it is all open down cellar. I planned on running maybe 80* 24/7. Is there a problem with that? Why the higher temps of 120* or more?

Gary
 
GARYL said:
I don't mean to hijack this thread but I am a little confused. A friend of mine runs his radiant floor in concrete 24/7 at 90*. Place is always warm. I was thinking of doing the same in my house under the first floor because it is all open down cellar. I planned on running maybe 80* 24/7. Is there a problem with that? Why the higher temps of 120* or more?
Click to expand...

It depends on the construction of the floor. Each material has an R-value, just like insulation. In order to get the floor surface to the correct temp, you need the water to be a bit hotter, to account for the insulating properties of the floor. Floors can vary from R-0.6 to R-2.2 (plus more floor coverings like carpet or additional wood overlay).

If you have a floor that has a higher R-value, then you need to raise the water temp to "shove" the heat through.

Joe
 
[quote author="BrownianHeatingTech" date="1210265890
If you have a floor that has a higher R-value, then you need to raise the water temp to "shove" the heat through.

Joe[/quote]

Okay....now it makes sense. "Shove the heat through" is really what it does because the R value is really like a "R"esistance value. Never looked at it that way before. DUH!!!
Thanks Joe.

Gary
 
Not to change the subject, but I notice nhjohn stated that you used warmboard in a retro fit? Do they make custom sizes of warmboard to fit specific dimensions? How much does warm board cost and weight per square foot?? I remember that it SOUNDED expensive when I looked at it a number of years ago. Now I wished I would have used it rather than the gypcrete route.
 
I took out a pine tongue+groove wall a couple of years ago by cutting the nails with a reciprocating saw. Time consuming, but it saved the wood.

I retrofited my 1st floor with 1/2" pex and alum. plates and it works well. I have a sensor in the floor for temp and still have baseboards in the first floor for very cold days. My house is old and not well insulated. I love it and the comfort alone is worth the cost.

Keep in mind that if you are still running any baseboards the boiler will need to heat to 180* and the lower floor temp would most likely be accomplished with a mixing valve. Considering that I am not sure what sort of savings you would see. I heat with a gasifier and my wood only costs me in sweat, but at least when I come in from cutting I can warm my toes up on the floors!
 
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