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sandy2982 04-08-2008 03:27 AM

Advice - PEX tubing !
I am researching a boiler/water heater combo that heats water
for shower sink etc and also heats and pumps water through a radiant
floor heating system. I would like to avoid baseboard units in the
basement (existing slab-unfinished basement). Has anyone heard of laying down treated sleepers on the slab,
running the PEX tubing in the bays and installing plywood over that? Is
there a way to heat the basement with this radiant system of tubing and
fins without the exposed fixtures?
I found the supplies on and they have a really good deal. I just wanted to make sure that this was the best solution to my problem. Any advice is greatly appreciated!

Piedmont 04-09-2008 01:54 PM

I agree with you, that baseboards stink.

Here's some things you have to watch out for. First, you have to watch out screwing around with ceiling & floor heights in basements. Building codes as I recall want family rooms and bedrooms having 7' 6" ceilings but you are allowed to have 1/3rd of those rooms have 7' ceilings. Hallways & bathrooms can have 7'. So, doing what you say if you raise the floor high enough and your ceilings go below 7'6" when all said and done you won't be able to get the permit to convert it to habitable/living/finished space until you get the ceiling back to 7'6" at least.

Radiant floors need insulation under them, and usually that insulation is foil faced (as radiant energy is a form of light you want to reflect it UP but that foil also helps disperse the heat away from the PEX). Otherwise, you'll be spending energy trying to heat the planet earth and you won't win!

So, back to what I said about height you'd need to cover the floor with foam insulation first (Extruded Polystyrene), then foil, then your sleepers & pex, then plywood, then flooring. What's your ceiling height again!?

Lastly, you can get boards that go directly on the floor that take radiant floor tubing that lower your height but make sure they're basement/slab compatible. An example thermalboard, to install it over a basement floor you have to lay down a vapor barrier, then 5/8" treated plywood, then the thermalboard, then your flooring on top of that adding about 1 1/4" without flooring. But thermalboard with 3/8" PEX tubing will limit the length of tubing you're allowed and they recommend insulating under first with R5 insulation which will make its profile 2 1/4" (without flooring).

You can go with baseboard heating which causes you to have to keep your boiler temps higher in winter so they work properly (they don't work well sending anything under 140F through them) and baseboards are always in your way... if you have the ceiling height and plan on spending lots of time in the basement and at this residence I'd spend for the extra $ to do radiant floor in the basement even with its associated costs as walking around on a cold basement floor stinks, and I hate baseboards too! But, if you don't have the ceiling height not much you can do at this point besides get the baseboard and cover the floor with carpeting approved for basements to try to reduce the cold feeling.

jogr 04-09-2008 03:36 PM

Ceiling height requirements vary by area. Check with your local building department for your local codes. This will also change the height of your first basement step which will likely make it awkward and probably out of code.

sandy2982 04-16-2008 05:26 AM

Hi Piedmont & jogr,

Thanks for that timely advice. I m working on it.. I m checking on the local codes. Once I get the right one I will start work. Hoping to give you guys a pic of whats the outcome !! :)

Termite 04-16-2008 01:51 PM

Two other ideas:

There is a product out there that consists of metal plates with channels that the tubing lays into...Then the plates are fixed to the underside of the floor sheathing between the joists. The heat from the water is directed upward into the floor.

The other option is to lay out the PEX on the floor and pour a layer of lightweight concrete over it. It is generally self-leveling, and makes a great base for carpet or tile. It doesn't have to be very thick at all either.

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