View Full Version : Radiant Heating Design Help

06-03-2011, 02:58 AM
I am planning a retrofit to my heating system, which today consists of two wall-mounted
has heaters, installed probably 60+ years ago when the house was build.

The house is on slab on grade. Temperatures are mild, almost never bellow freezing.
We never heat the house at night, and during the day lowest temps are in the high 30's.
First floor has 2,200 sq.ft. and I'd like to have 4 spare circuits for possible attic expansion.

After a few months of web reading I came up with a floor sandwich:

and a layout:

I still need help with the design.

I would appreciate any critique or advice. I would not mind paying for competent advice, but so far I was not able to cut through the thick, it's just too much info out there.

06-03-2011, 06:20 AM
Your sandwich system adds 3"+ to the floor. Are you ok with lowering your ceiling height that much? You show hot water heat, Where are you planning to get the hot water?
This is a job for a reliable heating contractor. He will figure out how many total btu are needed for your house, and design the zones. I am guessing your house does not have the insulation factors shown in that diagram.

06-03-2011, 08:45 AM
I am raising the ceiling with 12", less 3" due to the floor raising. Final ceiling height will be about 105".
I can get domestic hot water from a traditional, tank-based water heater, or from the same boiler used to heat the house.
I have not decided yet, I am open to a suggestion.

I have two water heaters in house now, each holds about 35 gal. Secondary was installed for convenience, when I added a bathroom.
They've been working 24 hours/day for about 20 years without a glitch and they cost a few hundred dollars. Hard to beat.

I am planning to insulate all the walls and the roof with R19. Slab is not insulated, maybe I can add 2" of XPS on the sides.

If someone knows the "reliable heating contractor" who can design this system, I'd like to know. I am planning to do the installation
myself with the help of a few friends.

Tom Sawyer
06-03-2011, 02:29 PM
I can design it for you. I get $ 246.00 an hour for engineering design systems and I would guess that the bill would be around 5 grand or so.

06-06-2011, 04:24 AM
When designing a residential radiant floor heating systems the designer (preferably Radiant Panel Association certified) will always start with a heat load analysis. A certified designer will have all the weather data for your area and can determine the type of radiant panel that best serves your heat load and your person preferences.

A potential designer should have CAD drawings and pictures of his work and will require a drawing, which should include the house with all its rooms and windows and all insulation values, if known. From this information the radiant designer can determine if the radiant panel you have chosen will work efficiently and keep you comfortable.

As you suggest, a combi water/space heating system appears to be in order. I just finished a radiant floor design in Oakland, CA using a sub-floor radiant system, condensing sealed combustion water heater and sub-assembly, including heat exchanger, pumps and control system with the all important outdoor reset.

Here in Minneapolis we often use this system for basement heating which is not on grade and retrofit slab-on-grade with sandwich radiant floors and European panel radiators.

The sandwich system you have referenced here is sub-standard for your area, increasing floor height unnecessarily without appreciable improvements in performance. "Reliable heating contractor" is good but trained and experienced radiant heating professional is even better.


Tom Sawyer
06-06-2011, 01:45 PM
damn, there goes that commission :)

08-06-2011, 02:16 PM
It is always a good idea to talk to at least 3 different contractors before going forward. When you are ready to make a decision, get three bids from contractors that have a license, so that you are protected. This is a project for someone who has the knowledge on heating systems. www.crazymountainheaters.com

08-14-2011, 11:22 AM
It all looks good to me, but you could use a 1.5 x 1.5 sleeper and gain some insulation. Be sure your insulation is treated for ants.