Radiant Floor Heat Basics, California

[Norcalz71]

Living in Northern California near SF, temperatures are not usually a huge concern. That said, cold slabs are not fun to work on.

My parents are building a new shop space, a 1200SF L-shaped building w/ a 30x23 front and 23x22 "back" section. We are still unsure if we want to do in-floor heat BUT, construction starts soon and we are tossing around putting the infrastructure in place regardless.

The thought was 2 zones, one on the front 30x23 and one on the back 22x23 as they may be walled separate at some point. Any thoughts on SF cost for putting in the insulation/PEX/etc now and just plumbing the lines up to a manifold that we may (hopefully) setup in the future? Would a small tankless unit be enough to handle a building of this size?

The coldest it gets in winter here regularly is mid 40s on average. It will dip below freezing at night a couple of times each winter. The rest of the year 65-85 is pretty normal, the floor heat was more a thought for laying on the ground working on cars/bikes.

This has ended up being one of those last minute items we are throwing back and forth, but don't have any background on the subject really.

 

[finn]

Not worth it if the daytime temperatures are typically in the forties.

Spend your money on an inexpensive hanging heater and a lift. You can get both for the cost of a radiant system that you will only use a couple of times per year.

You wil be warm and won’t have to lie on the floor so the concrete temperature won’t matter.

 

[Dick in Wisconsin]

Not worth it if the daytime temperatures are typically in the forties. Spend your money on an inexpensive hanging heater and a lift. You can get both for the cost of a radiant system that you will only use a couple of times per year. You wil be warm and won’t have to lie on the floor so the concrete temperature won’t matter.

Mr. Finn offers what is probably good advice.

I have Radiant Floor Heat in the 1000sf race shop. Really like it; but keep in mind that the temps in SE Wisconsin are lower in the winter than what the OP indicates. I used a NG boiler. In the OPs situation, he might get by with a residential water heater, which is often frowned on by GJF posters.

Do you have another garage or shop that you could shoot the floor temps in? That might help you decide.

Doing a good job of insulating under the floor and around the perimeter of the slab will likely help keep the floor warmer. In addition to insulation under and around the slab, make sure you put a thick vapor barrier under the slab/insulation to keep moisture from migrating through the slab.

 

[mygarageone]

With what you have and where your at , I think if you insulate the floor and side wall , that will be your best bet . Then put in a small hot dawg unit , it will heat that place up in a heart beat .

 

[PoorOwner]

given a new shop build your priority is to get it high enough for lifts so you don't have to lay on the ground.

 

[Norcalz71]

10' walls, hopefully cathedral ceilings in front and also maybe in the back. Lift would be ideal although for the uses we have planned it might limit our space a bit, the building would be bigger but this was the limit by zoning. We do have another 20*30 building with the machinery, that heats up relatively quick with our 220v (forget power) space heater but doesn't help on the cold floor.

Definitely a luxury if anything, one of my trucks does not fit in our main garage so I've done plenty in the driveway and it's doable for sure.

With regards to insulation one detail I am not sure on is the interface between the slab and stem wall. The garage is on a very slight slope (call it 16-18" of fall from the doors to the back wall which is 46'). This will require so.e baby stem walls at the back that taper down to zero at the front, so the plans call for those walls on a footing, then fill, and then vapor barrier rebar and concrete slab.

What does the vertical insulation at the stem walls look like relative to the slab? Obviously the horizontal/flat insulation would just lay below the footprint of the slab, but where does the vertical insulation terminate? Does it start above the vapor barrier and (can't imagine) peak through at the slab surface at the walls? Or does the very perimeter of the slab on get say 4" of cover (,6" slab) so that the vertical can stand up 2" past the horizontal insulation at the wall interface.

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