> What are you building this new radiant floor on?
The floor is being built on an existing 1st story floor that is in a 120 year old house.
> Concrete basement?
The house does have an existing concrete basement, but I will not be heating the basement.
> Wood platform over crawl space or lower floor?
Part of the house that I'll likely work with later is of this configuration.
> square footage area?
The project I am focusing on now is a small room, aprox 12' x 12'. If this works as I intend, I will continue with the rest of the house.
> Location?
Portland, Oregon.
Heating Degree Days = 5496
My location's design temp is 17 degrees F.
> More clues...
The space under the floor is unheated.
The room has only one outside wall, which is insulated with 6" XPS between the studs, completely sealed at each layer (3 layers).
One outside window 30" x 60" double glass.
Floor is insulated to R-28.
Ceiling is insulated to R-18.
Walls insulated to R 15.
My heat source is a very small (1/3 Ton) GSHP that I have built and tested.
I am quite confidant that I can easily heat this room using a conventional built up (AKA: sandwich) floor, but I am trying to achieve the lowest water feed temp that is reasonably possible.
So I am trying to build a system (ground loop, heatpump, radiant floor) that would be described as Very Low Temperature Heating.
I would like the water feed temps to be below 90 degrees, the lower, the better.
The floor will be (from top down)...
linoleum
hardibacker
extruded aluminum spreader plates
PEX
rigid insulation board that can withstand floor loading.
So my question is, what kind of rigid insulation board is available that can withstand floor loading?
Best,
-AC_Hacker