Radiant Heating Anyone?

[Harv]

The first house I ever bought had a slab foundation with radiant heat. Can't tell you the specifics on the pump or heater, but for the 17 years I lived there, it worked flawlessly. Loved getting up on a cold morning and walking barefoot on the non-carpeted parts of the floot. /w3tcompact/icons/smile.gif

I did hear, however, that some houses in the area experienced some uneven settling after a particularly heavy rainfall one year, and some of those slabs cracked as a result. The cracks weren't so bad as to spoil the general integrity of the foundation, but enough to damage the radiant heating pipes. /w3tcompact/icons/frown.gif The carpets just started getting soggy for no apparent reason, and that was pretty much it. Had to turn off the system and come up with another way to heat the house.

Now, those houses were built some 50 years ago, so I'm guessing the technology has improved. I would be willing to try it again in a new build.

 

[DrDan]

Ok Todd - I had a nap and am a little less pissed at this software. I'll try again to answer your questions...

"Paste"

Do I need to stub out the zones in a convenient location and then run lines back to manifold or should I home run everything back to the manifold? <<I have three separate zones - a 30 X 40 room, a 15 X 30 room and a 25 X 30 room. I have all the manifolds located in one area where the heater and all is located. I see no reason why you couldn't mount the manifolds in separate areas and run PEX to them.>>
If I go with a 4" Slab, my guess is the PEX would be about 1 1/4" below the surface, which should be OK. Should I go with a 5" slab?<<Remember for the reinforcing screen to work they have to pull it up into the concrete a little. I went with a 4" slab and had no problems. Only thing is that the concrete man was reluctant to saw expansion joints fearing that a tube would be hit. I think I will be ok though because each room was a separate slab. For about $0.20 a square foot more you can go with 5" thick>>
Is a 50Gal Polaris enough for domestic hot water and radiant heating? <<That depends on your insulation and climate - in my installation peak load will be 23,000 btu and this baby will put out 85,000 I believe>>
Did you underlay the slab with rigid foam, 1/4" bubble wrap insulation or none at all? <<Here was my only "bone of contention" with Radiantec. I used R-Foil bubble-foil-bubble "Concrete Barrier" because it was less expensive and easier to install than extruded poly. Don Parmelli from Radiantec said not to use it because they didn't know anything about it - hadn't been out long enough. Ya right - It has been out for 9 years - about time they do a little research. Anyhow I talked with engineers at WE International that markets the "Concrete Barrier" and I placed more value in their data than Don's crap and went with it. I insulated the whole slab and went up 6" on the wall to insulate the edges of the slab. According to the R-Foil people - 70% of heat loss is at edges so we wanted that protected. I also did not want to use the ground as a heat sink and waste my $$$ storing heat so I insulated it all.>>
Did you insulate on the inside or the outside of the footings? <<I have a pole building so I just did the inside - but the important part is insulating the edge of the slab - if it connects to the footer ya better insulate the footer on the outside agains the ground>>
Did you make any connections under the slab prior to pouring or did you run continuous length PEX? <<No I did not want any connections under the concrete. The lime eats em up! In my 30 X 40 room I have (3) 300' Runs of PEX all leading back to the manifold In the 15 X 30 room I have 400' run of PEX to a single manifold, In the 25 X 30 room (2) 300' runds to a double manifold. You do not want a real long run because of the heat loss in the tube as the water travels through it. So you use lots of short runs all plumbed back to the manifold.>>

Hope this helps...

DrDan

 

[DrDan]

Nope you go in and find the moist spot and hammer out the concrete and fix the leak. They were probably using copper tubing and that rots after a few years. You can also use an IR detector to find a break if you ever get one.

Fingers crossed...

DrDan

 

[DrDan]

Something else I forgot to mention... Once this system is in place you can change heat sources pretty easily. I am building a woodshop in hopes of selling furniture to the NYC Market. Scraps (and mistakes) collect and bury you after awhile so I will have a nice woodburner in the shop. We are putting a coil in this heater and plumbing it into the Polaris Heater so when I'm burning wood the natural gas stays where it belongs (on the suppliers side of the meter) and when I run out of scrap the gas is there to keep it going. I am also into solar and have a gabled roof with one half facing South. You can put a heck of alot of solar collectors on that size roof! I just don't want to pay for them so if there are slow times in the shop I want to play with tubing, wood and glass and build my own. I have been toying with hyperbolic mylar shapes with a focus on the tubes for years. It's all pretty cool. Ya put fractional HP gear motors on the reflectors and have them track the sun. Other alternative is geothermal. I have always wanted a pond and have a friend here right now that wants to use a shovel to dig one about 30' deep mainly just for fuel cost. Can't beat that... Once you have the pond it's just a matter of putting tubing in the bottom of the pond and somehow you suck the heat out. I don't undersatnd geothermal yet - but it is an option I need to explore in the future.

I think it is about time we start getting serious about starving out these public utilities. Bunch of corporate arsehoos sucking the lifeblood out of our pockets. I'll do and spend whatever I have to to meet that end...

DrDan

 

[DrDan]

Glueguy LOL I get a kick outa you. It seems we have lots in common... Disconnect from the "grid" ASAP at any cost will be a savings no matter what if we live another 30 years or so. Just gives me a sense of pride to screw them at least outa my $$$.

DrDan

 

[jfakerj]

DrDan
Thanks. This makes me feel better about going through them being as radiantec is several thousand miles away. What makes the foil bubble stuff that you used better that theirs, and do you know where I can research the stuff you used compaired to theirs?

Jerry

 

[DrDan]

Talk to:
Erik Deckers
Director of Marketing
WE International, Inc
www.we-intl.com

He is the man who knows insulation...

DrDan

 

[jfakerj]

DrDan
Thanks, I'll do that.

Jerry

 

[DrDan]

Here's a copy of his email to me regarding the insulation. He is a real nice guy to talk with and real smart!

"Copy"

You said your manufacturer recommended that you put 4" of foam board
around the first 4 feet of the perimeter, and 2" of foam around the next
4' feet, but that you wanted to leave the center open so the ground
could become a thermal mass.

The reason they recommend 4" of foam around the first 4 feet is because
the heat will still penetrate 2" of foam (but not much). 2" of foam
board will reduce downward heat loss by approximately 88% (Concrete
Barrier reduces it by 77%). However, 4" of foam will NOT reduce the heat
loss by 176%. Personally, I don't see any reason to double up the foam
in this case.

Now here's where it gets a little tricky: **Downward** heat loss in a
radiant floor system like yours actually accounts for only 30% of the
total heat loss ("heat loss" is heat that does not go up into the
house). The remaining 70% of the heat is lost horizontally. It will
travel on top of the foam board and out through the sides of the
basement walls.

The way to prevent this heat loss with Concrete Barrier is simple. When
installing Concrete Barrier, just run it up the basement wall by 2". Any
horizontal heat loss will be stopped by the Concrete Barrier, and sent
straight up into the house.

Finally, I do not recommend leaving the center of the floor open so the
ground will serve as a thermal mass. The temperature of the ground under
the frostline is generally around 50 - 55 degrees. However, the
uninsulated part of your radiant heat system will continue to try to
heat it up. And because heat moves to cold, the heat will continue to
travel outward toward the cooler ground and the frostline. So while the
ground will become a thermal mass, it will never completely stop. You
will lose heat year after year this way. You can see examples of poorly
insulated basements and foundations on houses whose snow has melted
around the perimeter.

 

[Harv]

<font color=blue>find the moist spot and hammer out the concrete and fix the leak</font color=blue>

One guy in this particular tract brought in a contractor to do just that, and you're right -- it was (old) copper pipe. The more floor he busted up to get to the leak, the more leaks appeared. /w3tcompact/icons/tongue.gif I actually had some serious doubts about that contractor's qualifications. Sadly, after seeing what happened to that house, nobody else wanted to try it. Baseboard heaters started showing up. /w3tcompact/icons/frown.gif

I probably shouldn't have related that story in this thread, 'cuz my own experience was positive, and like I said, I would gladly try radiant again. /w3tcompact/icons/wink.gif