Radiant heat under weird floor

[Deleted User]

unless there's a very good reason/s to go to radiant floors, i wouldn't bother

MrsEener

Radiant heat under weird floor

We just bought an 80 year old house in Chicago that has wide wooden planks over the joists, then 3/4" X 2" strips of wood running perpendicular to the planks every 16" or so and then tounge and groove hardwood floors nailed to the strips. So there is a 3/4" cushion of air between the plank "subfloor" and the hardwood floor. I was really hoping to install under floor (between joists) radiant heating, and then I saw how the floor was constructed and I was wondering how that cushion of air would affect the system.

Brad White_203

Unless

your heat loss has been reduced significantly by insulation and air sealing, that floor has a good amount of insulation value within it's construction to lessen the output. You may get enough heat for mild days, just not "Chicago Mild" days.

Start with a good heat loss and make sure the home is improved first. But even so, my experience says that your floor assembly, if you are trying to drive the heat up through it, will require much hotter water temperatures and get less net heat output for it. Might take the edge off and need supplemental heat elsewhere is my guess.

claysdad0818

Underfloor

That air gap will basically kill the heat transfer. You need good conduction to transfer the BTU's to the floor surface. Lose the nailers and install the floor directly on top of the subfloor and you should be good to go. Another option would be to install pipe in between the sleepers (no more than 12" o.c.). You would have a slightly lower fluid temperature since you're not transferring heat through two layers of wood, only one.

Ted_5

still will work

you need to do a heat calc, but it still should work for most rooms. Do you have any rooms with 3 outside walls and glass or doors? In rooms like that you may need to add some radiators. In the rest of the house it would work as long as you put 2 pipes per/joist bay with good transfer plates and good insulation, it will still warm up that air space and the floor surface. For insulation under the floor use bubble foiler with a 2" air space then a 6" bat or R-19 under that.

Ted

[Deleted User]

is the 3/4\" 'space'

accessable from underneath? no? lotta work but, pull up your t&g and put the tubing in that space

MrsEener

Thanks so much for the replies. Really appreciate it.

Steamhead (in transit)

What kind of heat

does the house have now?

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

MrsEener

boiler/radiators