Hello Everyone! I am a long time Dan Holohan fan, from way back in the early 2000s’ when I got my hands on his Antique Steam Radiator ID and Steam system books. The Wall (website design) was a lot more basic, but just as informative back then.
I am moving into a 1972 construction house which was built with a two car garage on the ground floor, but the PO never installed a garage door! Boston suburb ...imagine the heat loss
I have a potential radiant floor loop design to consider in my garage (and have to do this before the garage door size is finalized). The house is presently heated with an oil fired forced air furnace. The garage floor area is about 340 ft. sq. There are no underfloor water issues; the house sits at the top of a hill.
I have a 30 tube thermal solar setup that I will be installing for the DHW. The radiant loop in the garage will be there to absorb the excess heat, when generated by the solar system. I’d like the garage slab loop to be potentially useful as a heat source zone (or at least some useful thermal mass) and may convert more of the house to radiant heat.
As I see it, I have one obvious and one less obvious way to add a hydronic loop (1) an additional thin slab pour with an embedded pex or (2) a plywood subfloor in the garage with pex under and some HD floor surfacing to accommodate the cars and an occasional floor jack.
Thin Slab - Design Considerations:
- Minimum additional thin slab thickness: I can raise the slab by up to 5,” but would prefer to minimize the elevation to save the headroom.
- Vapor barrier between the existing and new slabs?
- Thermal barrier between the existing and new slabs?
Subfloor - Design Considerations:
I know next to nothing about the plywood option, except that I think I’ve seen the routed plywood or composite panels with pex channels. If this is an option here then the design questions are:
- Suitable in the residential garage floor setting?
- Vapor barrier below?
- Thermal insulation between the slab and subfloor: yes or no?
- yes - to prevent heat loss into the slab below, but then no thermal mass
- no - no insulation, then thermal mass for storage might be possible
- Potential material stack:
- Vapor barrier
- Thermal insulation
- Pex panel
- ¾” Plywood Layer 1
- ¾” Plywood Layer 2
- Vinyl Tiling suitable for light garage use
- Seems to me that I can get away with about as little as 3” total additional thickness
- The plywood/PEX subfloor would start 20” inboard of the garage door with a short piece of concrete (new pour) extending from the subfloor and outside for an additional shoulder in front of the garage.
There is a lot I don’t know ...except that it’s a long way from theory to practice. What do you guys think of these ideas?