Radiant Flooring Retrofit vs Crawlspace Heating for Warm Floors?

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Old 09-03-18, 07:46 AM
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Radiant Flooring Retrofit vs Crawlspace Heating for Warm Floors?

Hi All,

We are in the middle of doing construction drawings/blue prints to remodel our downstairs (including totally renovating kitchen, moving a bathroom, knocking down some walls, and - importantly - replacing most if not all flooring). The total flooring area of downstairs is maybe like 1700 square feet, and we are located in the New York City suburbs.

We have a crawlspace underneath our entire downstairs, and its a slab floor, not dirt. Awhile ago, we had it foam-sprayed insulated from floor to just above where the cement walls meet the wood framing (joists?). So, the crawlspace is a conditioned space, about 4 feet tall.

We were thinking of dropping a loop from our boiler (high efficiency) into the crawlspace to warm the floors above, i.e., the downstairs floor (which does not have insulation under them).

However, the architect mentioned something called WarmBoard, which uses warm water through pex, and which can be installed right above the subflooring. Its radiant floor heating.

I have a couple questions about all this:

1. Does anyone have thoughts on what would be more efficient and cheaper to run: (i) dropping a heating loop into the crawlspace, or (ii) installing WarmBoard (or similar).

2. What would be cheaper to install? I think the builder had said he is taking down sheet rock in most places, so I assume the current hot water base boards would be removed and probably replaced (? they are like 60 years old now) - if I'm right, the calculations would obviously include the cost also of replacing the baseboard heaters. (Or are they just generally re-used, even at that age?)

3. If we are keeping the hardwood floors currently in one of the rooms (just refinishing), is there a way to get radiant heating under there?

4. If radiant flooring is the way to go, does anyone have any recommendations? I've heard of both WarmBoard and EcoWarm (and both companies include comparisons to each other on their respective websites). One of these, or another company?

5. With radiant heating, what happens if there is a problem somewhere? Does the whole floor need to be ripped up to find and locate where the problem is?

6. Anyone have thoughts on my idea of dropping a heating loop into the crawlspace? Would that actually work?

Any advice would be greatly appreciated! Thanks!
 
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Old 09-06-18, 01:01 PM
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Hi All,

Just wondering if anyone had any thoughts/advice on my radiant flooring vs. baseboard loop in crawlspace question.

Thanks in advance!
 
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Old 09-06-18, 06:02 PM
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Your crawlspace is totally insulated? Why are your first-floor floors so cold? Maybe an area rug would be a lot simpler?
 
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Old 09-07-18, 08:54 AM
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Yep, crawlspace is totally insulated, with foam spray going from the floor up until just over where wood framing meets the concrete walls.

I didn't mean to imply that the floors were cold - they're not. In the dead of winter, they may be slightly cool to the touch. But - I like the feel of warm floors, and I've also read how it may be more efficient than baseboard heat based on a variety of factors (e.g., depending on the radiant flooring brand, may use lower temp water than baseboard heat; several other reasons I've read, etc.).

So - I guess my question is better phrased as: what would be the best way to warm up the floors to a warm temperature, from a slightly-cool-to-the-touch temperature, choosing between heating-loop-in-crawlspace vs. radiant heat?

Thanks again!
 
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Old 09-07-18, 10:12 AM
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Check out the information for radiant floor heating at SupplyHouse.com.

Heating the crawlspace will not provide the warm feeling you are hoping for in the floors above. They will just feel as warm as the space they are in. Radiant floor heating will definitely provide the warmth.

Here are three methods I have used that have worked satisfactorily for me.

PEX tubing in Quik Trak panels on top of the subfloor and directly under the flooring. In one case the flooring is engineered wood. In the other the flooring is 1/4 inch cement board with 1/4 inch tile. Both are in bathrooms and provide a nice warm floor however in both cases it is not the primary heat in the room. Hot water baseboards provide space heating.

PEX tubing in Joist Trak panels attached to the bottom of sub flooring between joists. The flooring above is 3/4 inch wood subfloor and 3/4 inch white oak T&G flooring in a 105 year old house. This is in a kitchen/dining area that is also heated by hot water cast iron and fin-tube radiators. The radiators were undersized for the space, so the floor heating provides supplemental space heating as well as warming the floor.

Bare fin tube radiation (no covers) installed in enclosed joist space under a greenhouse floor. Below is 3/4 inch plywood on joists with 4 inches closed cell spray foam insulation exposed to outside temperatures, then a cavity formed by a second set of joists on top of that. The cavities are insulated on the bottom (top of the plywood) with 1/2 inch foam board insulation and 1/2 inch plywood. Fin-tube radiation is suspended in the cavity below 3/4 inch plywood with 1/4 inch thick commercial carpet squares or rubber tiles as the finished floor. The joist cavities are open at one end to allow heated air to rise up into the greenhouse for space heating but because the air flow is limited the floor is also warmed.

That third option is similar to your crawl space but a much smaller volume.

I think to avoid having to heat a large volume of air in the crawl space you should consider the direct under floor installation. The joist installation would be very difficult to achieve in a 4 foot high crawl space but I suppose is possible.
 
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Old 09-07-18, 11:28 AM
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Ok, thanks for the advice.

If we do go with radiant floor heating (which it looks like we probably will based on your advice), do you know which brand is considered the best/best value? I've seen WarmBoard and EcoWarm, and now the Quik Trak you mentioned. I'm sure there are many, many others, and they all seem to work basically the same.

Also, unless using the Joist Trak panels you mentioned, I would need to remove the current hardwood flooring first, yes? Can I do a combo of QuikTrak and JoistTrak that would be controlled at the same time? (Or are they all controlled room-by-room, etc.?)

We will have a professional (plumber? HVAC? carpenter? flooring person?) do the install, but I like knowing as much info as I can before I talk to the professional.

Thanks again!
 
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Old 09-07-18, 02:27 PM
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For me, price is the deciding factor. PEX for heating is not the same as PEX for plumbing. Make sure it has an oxygen barrier.

If you have existing flooring, you should use the Joist Trak method mounted from below rather than remove and replace flooring with new. Both methods of mounting can be used in a single run of tubing.

I think the limit for a PEX run is 200 feet. If your areas require more than that in total they should be made separate runs from a manifold. They could be controlled as one zone or separately. Check the info on SupplyHouse.com website for information about area coverage, tubing spacing and sizes, manifolds, controls, etc.

High efficiency boilers are very compatible with floor radiant because they can run at the lower temperatures that radiant needs (approx. 90 to 120 degrees) to prevent the floors getting uncomfortably hot. Conventional systems that run at higher temps (160 to 180 degrees) usually include bypass controls on the manifold to provide the lower temperature water.

My installations have all been DIY so you might actually have to have a carpenter or flooring guy install the Traks and a plumber/HVAC guy to install the PEX, manifold, and controls or maybe an HVAC guy does it all. I don't know..

I run my conventional boiler at 150 degrees for the house space heating and the floor heating is for comfort rather than for primary heating, I just run that water through the floor loops in parallel with the radiators whenever those zones are running.
 
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