radiant heating

Unknown

Of course it does. However I too have seen several old copper in slab systems running at boiler temperature, whose concrete is still viable, so I am not going to say that is a forgone conclusion that the slab will be wrecked. the pipe, however, did end up failing after a few decades, so I don't really care what the study says... I've seen enough failures to say why do it? we have a better choice now, PEX.

It's not how I design, but I can't say I have direct firsthand experience with wrecked concrete from high temps.

As for the cycling/control issue, sure, it's not going to be strictly ideal, but in this case it doesn't have to be.. I was thinking the slab would be blazing hot if run with the baseboard, but I dunno.. the baseboards will run in much shorter cycles, so maybe it'll even out with the mass of the slab. Again, I wouldn't design that way, but I'm not going to prophecy doom either.. it might work fine. I doubt it, but it's possible.

I would definitely say if anyone is going to try this, make the loop isolatable so if it really stinks, you can turn it off.

Personally, I'd put in a pump, tempering valve and a slab sensor and do floor warming the right way. Otherwise, I wouldn't bother... why do floor warming if you aren't going to make sure the floor is warm? "Occasional" floor warming doesn't sound very attractive to me, especially if the range is going to be stone cold in shoulder seasons to blazing hot at design.

But I don't know for sure that's how it's going to work. That's just the thinking that would make me never do this.

tim_30

radiant heating a very small room,question

Background:

My house was built in 1975 with a hydronic baseboard (180 deg) heating system. The roof and wall insulation are R-19 and R-11 respectively. I am building a very small entryway addition of 70 square feet that will have insulation of R-38 roof (ceiling), R-19 walls, and R-35 under the floor slab. The floor slab will be a 3-1/2 inch concrete slab with a slate tile finish surface. I want to install hydronic radiant heat in the slab and run it on the same zone as the living room that the new entryway will be open to.

Questions:

Is there any compelling reason why I shouldn’t run loops of 3/ 4 inch copper in the slab as an addition to the living room zone (operating at 180 deg) ? My Dad built his home 50 years ago with this type of heating in the floor slab with no problems to date.

How many linear feet of 3/ 4 do you think would be required for this scenario?

kevin coppinger_4

Back the truck...

up. Radiant slab and baseboard heat are 2 diferent animals...can't really be on the same zone. Temps are very diferent! 180F for baseboard 90-100F for a slab. 180 could very well crack the slab.
Get a heatloss done and ask someone to work with you. ..1/2 pex would be fine but you need to get the heatloss to figure out how much tube, what size pump, what temp, etc.
Your application for the radiant is ideal in a mud area...just don't throw tube in. Once the concrete is poured it will be hard to fix a design problem...kpc

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Ruthe Jubinville

Radiant heat

I have put radiant heat off a baseboard loop and had it work well. Send me a e-mail address and I will send you a diagram. I don't know how to add a diagram here. Jerry

tim_30

radiant heaat

Jerry,
I'm at timtriggs@comcast.net I'm looking forward to seeing your diagram

tim_30

radiant heat

Jerry Jubinville,
I'm at timtriggs@comcast.net I'm looking forward to seeing your diagram.
Thanks, Tim

Unknown

The vast majority of those systems have failed by now. Copper in slabs is not only a lot more work than PEX, it's just a bad combination. Your Dad is a lucky one.. for now, at least.

Constantin

Rob,

Doesn't it strike you as odd to heat a 3.5" thick slab with 3/4" thick copper pipe at 180°F hot water as Tim intends to?

I imagine that the concrete is going to experience extreme thermal cycling and isn't there a good chance that someones bare feet might get rather toasty as well?

Wouldn't there also be an issue with how to program a thermostat to anticipate the heat soaking effect of heating a cold slab with 180°F hot water?

Over at breaktime, Tim posted a link to a 1966 study by the portland cement group posted at Copper.org that claims no ill effects between concrete and copper. The collective experience on the Wall seems to indicate otherwise...

Just wondering.

hr

Here a link for some ideas

http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,62497,00.html

hot rod

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"