the secret of thermal floor heating

A good reflective surface below the heat loop .. to keep the radiant heat focused upward and not down into the ground. 4x8 boards of this are available at Lowe's, Home Depot etc. Expensive but a must. Comes in 1/2" and up. Don't walk or damage it once it goes down .. pre-plan placement of rebar and skid surfaces for leveling the cement. In houses, allow one or two years open without carpet etc. before you install the finished floor .. tons of moisture will be coming off of it.

We cut shallow saw cuts in the cement to control cracks .. used an experienced cow barn cement worker to handle the ten inch foam, rebar and cement walls. He asked me to see my list of subs on my home and picked out three or four and gave me names to call instead .. saved me over $20,000 total on the job. We liked the cleanability of cement and just left it. In event of nuclear attack .. fall out of contaminates over hundreds of miles from the bomb site .. metal roofs and cement floors will keep you in a cleaner position. Shake roofs and carpet will kill a lot of people in WWIV.

All heat does not go up .. it is radiant .. waves .. half has to be reflected up .. insulation alone is a joke. Been there, don't that.

Good tips. We laid foil-bubble-bubble-foil which we taped with metal tape. We've used this on many projects:

1) Whey tanks - helps keep our 1,000 gallon tanks from freezing when temps drop sub-zero.

2) Roof of our cottage - reflects heat back down to us.

3) Our butcher shop refrigerated areas - reflects earth heat back down below floors, sun out, etc as we're working to keep the temperatures at 40°F down to -40°F in the various rooms. Coupled with thermal mass and heavy insulation it will make a long term difference. The biggest cost in our on-farm slaughterhouse is the energy.

Reflective barriers don't do all the work but coupled with air gaps, thermal mass, vapor barriers and void insulation like foam they are important tools in construction. Just be sure to put them in the right place.

Cheers

-Walter
Sugar Mountain Farm
Pastured Pigs, Sheep & Kids
in the mountains of Vermont
Read about our on-farm butcher shop project:
http://SugarMtnFarm.com/butchershop
http://SugarMtnFarm.com/csa

Walter .. please tell more about the reflective barrier on roof of cottage. What did you use and where. Thanks. Bob

It is the foil-bubble-bubble-foil (FBBF) which goes under various names like TekFoil, AstroFoil, etc. See:

http://www.farmtek.com/farm/supplies/cat1a;ft1_tekfoil_reflective_foil_insulation.html

I get ours from the local lumber yard but is is the same sort of stuff. Probably all manufactured at one place but under different names.

This is a reflective barrier. Some places hype it as insulation but really it should be coupled with real insulation like pink foam, etc. It also serves as a vapor barrier and it stops water from penetrating as well - slightly different than a vapor barrier.

Our roof is a 1.5" thick barrel vault of ferro cement. The FBBF covers our entire roof. On top of that we have a billboard tarp. The FBBF reflects the sun up during the summer which keeps our roof, and thus our cottage, cooler. In the winter it is serving the function to reflect the heat down back into our cottage. Above that the snow accumulates most of the time - think igloo. We have no other insulation on our roof and it only takes 3/4 cord of wood a winter to heat our cottage - no other heat than the passive solar gain and body heat from our family, refrigerator, computer, etc. That's very good. See photos here that link to articles:

http://images.google.com/images?q=site%3Asugarmtnfarm.com+cottage+arch+roof+foil

Eventually I plan to put more insulation, possibly foamed concrete, on the roof. I've done experiments with making insulating concrete in small batches but it isn't a project for this year. I want are roof that mice don't like. We have built several experimental ones using these techniques and I'm watching them age. In the end we'll put a hard cap of ferrocement on top of that and then soil to finish merging the house to the hill. But before we do that we have a tower we want to build in the back. Again, not a project for this year. Everything in its time.

See:

http://flashweb.com/blog/2007/09/dog-house-bottles-roof.html

and for much more:

http://images.google.com/images?q=site%3Asugarmtnfarm.com+house+arch+roof

Cheers

-Walter
Sugar Mountain Farm
Pastured Pigs, Sheep & Kids
in the mountains of Vermont
Read about our on-farm butcher shop project:
http://SugarMtnFarm.com/butchershop
http://SugarMtnFarm.com/csa

what about adding one layer of foil face polyiso instead of all blue/pink/white board . higher R value and foil face. not quite sure how to sperate a air space when you cover it with cement weight

I laid a 4000sf bamboo floor in a monastery, radiant water from electricity.

we used FBBF over the existing concrete floor, and then laid 2x4 on side for a floor support and race to run PEX through. then covered it with sand, then 2 layers of ply, then bamboo. floor temp is about 71 constant heat, as they sit on it averaging 6-8 hours a day.

4 years later, works like a dream, monks butts are warm.

on the pex we laid sand. The concern was that with cement we went over budget and with cob we went over time available. Ive done RHF in cob on 3 projects. I had hoped to do cob here, but time was of the essence and cob takes a long time to cure. The budget constraint on this project was compulsory. money did not exist beyond allocations, no second request was possible. cement was out.

so we brought in sand and used it to fill around the pex. cheaper than concrete, almost no clean up, and easy for a volunteer or monk with construction practice to get right.

2 weeks ahead of schedule and about $8k underbudget, we finished the floor.

the sand thermal properties were about 2% deviant from the concrete and the added benefit of- if there is a leak- the concrete doesnt have to be chipped up.

they did install new ceiling insulation.

theres no pics of the sand, but you can see the pex array, the FBBF and the floor stingers.  and the start of the floor finish.
http://www.flickr.com/photos/feralsophist/5219418897/in/set-72157625497639486/

other than the sand its pretty much what other here are discussing.

Interesting and good layout technique. Thanks for the photos of the monastery. We are eventually planning something like this for our cottage and first will be doing it in our butcher shop.

Nice work Deston'
the day school is also amazing !!!
lucky kids!