All these wetheads and no feedback! I'm baffled........

PG

OK here's the deal. Putting an addition on the house. In the metro Detroit area. It will face NE. If my electrician says a slab is no problemo, and it's cheaper then a crawl, does it make sense to do the slab? Put the radiant in the slab and insulate under? Or put insulation over the slab then put the tubing in gypcrete? I posted this question earlier but got very little response. Was somewhat suprised. Thought I'd have all the experts weighing in on this topic. Or is this just not a big deal either way? By the way I'm a mechanical contractor. I do lot's of steam, hot water baseboard, and forced air. BUT.......I want the best in my house.

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PG

All you wetheads........I need your help!

OK here's the deal. Putting an addition on the house. In the metro Detroit area. It will face NE. If my electrician says a slab is no problemo, and it's cheaper then a crawl, does it make sense to do the slab? Put the radiant in the slab and insulate under? Or put insulation over the slab then put the tubing in gypcrete? I posted this question earlier but got very little response. Was somewhat suprised. Thought I'd have all the experts weighing in on this topic. Or is this just not a big deal either way? By the way I'm a mechanical contractor. I do lot's of steam, hot water baseboard, and forced air. BUT.....not much call for new infloor in our area. BUT...I want the best in my house. I'd really appreciate any feedback on this. Thanks!

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D.Carpentier

Well, ok.., here's my 0.02..

We did hydronic slab for the main level floor in our major reno.. and we love it.

Do you already have a boiler ? You might be able to get away with a reg water heater for a small (?) zone. This room isnt on the sunny side of the house, but you might want to look into some sort of prediction based boiler temp control (outdoor reset).. on a chilly night, the slab is on, then the warm sunny day starts and the house starts taking on heat. Problem is, the thermostats dont see the aniticipated heat soon enough, and keep on heating the slab until the thermostat set point is reached. This extra heat in your slab will keep on bleeding out into the room, and with the additional heat from the day/sun you will get a bump in the temp (depending on the mass of the slab etc etc).

Also, hydronic works best on floor finish like ceramic tile.. carpet isnt the best choice. We went with ceramic, porcelain, and laminate wood floors.

Also(2) (lol), keep in mind that hydronic doesnt circulate the air. I put an air handler in to supply the upper story of the house, and installed returns only in the lower floor ceilings. My theory on this was to try and draw some of the (stale) air out replacing it with other house air just by nature of pressure differential. Im still working on this one, as it seems i dont get the thermal travel of the air coming down the big staircase that i thought i would (upper floor warm air forcing down the stairwell by way of the pressure diff created by the returns in the lower floor).. but thats another story....

Anyhow, keep an open mind on it.

Cheers, Dave

Weezbo

Hello...

Maybe the best idea is to make the insulation a high priority first,then there are ideas as to what is the long term benifit of any given installation..to me if i have the dollars to do the job right away and the time ...i go for as much good work as i can do and get it done.when pouring a slab on grrade i make one pour.sure i am a mud shark and like just working my skills i wouldnt do two pours as i dont really see a great deal of benifit in the idea. having said that that is precisely what i am doing on my own home.25 years ago i thought of radiant in my slab and Knew i didnt have any funds for it so i planned. went with copper "finn tube"first.now i am going with a second pour with tubing and gypcrete over it. I rationalize this this way,now that i have a few dollars i can put the tubing in higher in the slab and get the benifit of a really nice low water temp radiant pannel and the insulated slab is extra thermal mass and is really strong and hasnt gone anywhere:) so i know it to be structurally sound.it is extra work and i gotta be a bit inventive in my application of materals however i know it is comming together and will work better as it were than a single pour where the tubing depth might not have been a certainty....i hope that helps

Ken_8

The reason we did not respond...

is because both designs are excellent - and equally so.

The designs in this case, are more structural than heating related.

From the heating perspective, the slab radiant would have much more thermal mass and be slow to respond either in slowing down or speeeding up "response time(s)." But gyp-crete et al, have always been somewhat less than perfect arrangements IMHO, compared to the integrity of tubing in 4+" of concrete.

End result? Gypcrete has faster response time and is comfort-wise slightly superior - while in slab is marginally more durable - and slower to respond.

NE corner? sun loading would be minimal. Yet another factor...

Need more coffee.

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Rudy

Ken is Right

> Maybe the best idea is to make the insulation a

> high priority first,then there are ideas as to

> what is the long term benifit of any given

> installation..to me if i have the dollars to do

> the job right away and the time ...i go for as

> much good work as i can do and get it done.when

> pouring a slab on grrade i make one pour.sure i

> am a mud shark and like just working my skills i

> wouldnt do two pours as i dont really see a great

> deal of benifit in the idea. having said that

> that is precisely what i am doing on my own

> home.25 years ago i thought of radiant in my slab

> and Knew i didnt have any funds for it so i

> planned. went with copper "finn tube"first.now i

> am going with a second pour with tubing and

> gypcrete over it. I rationalize this this

> way,now that i have a few dollars i can put the

> tubing in higher in the slab and get the benifit

> of a really nice low water temp radiant pannel

> and the insulated slab is extra thermal mass and

> is really strong and hasnt gone anywhere:) so i

> know it to be structurally sound.it is extra work

> and i gotta be a bit inventive in my application

> of materals however i know it is comming

> together and will work better as it were than a

> single pour where the tubing depth might not have

> been a certainty....i hope that helps

Rudy

Ken is Right

Slab or crawl is a structural issue. "Build it and it will heat." How big is the addition? For a small addition slab on grade radiant would work fine even with a converted DHWH. Make sure it's rated for closed loop. Insulation is the key for SOG. Especially edge. You really don't want to pay to melt the snow for two feet around the structure, do you?