Experience with electric radiant slab floor heating or radiant ceilings?
Hello,
Does anyone have any experience with electric radiant slab floor heating or radiant ceilings?
I’m finishing my basement and don’t want to put any flooring over the slab, just stain and seal. I’m at the very top of Climate Zone 4 (northern VA) and attempting to make the 310 sq. ft. space into a master bedroom. I was hoping one of these solutions would allow me to warm my floor in the mornings during the colder months.
Researching electric radiant on GBA I found the Q&A Spotlight, “Mounting Baseboard Heaters Unconventionally.” The article mentions radiant ceilings and how the delivery of radiant heat raises surface temperatures first. I hoped the radiant ceiling would be a viable option for my needs.
Thanks for any info or advice,
Nicole
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More details about the structure and planned insulation in case it’s applicable:
> built in 1940, cinder block walls (CMU), no exterior or interior insulation
> gas heat, the space is conditioned; damp but not wet, cold in summer and cool in winter.
I’ve installed an interior french drain, put down a gravel layer, and I’m looking to purchase EPS that will go below the poly vapor barrier. Unfortunately, my ceiling height is already below 8 ft with only that gravel layer down so I’m hoping to get away with only 1 in. EPS.
The decision to stain and seal the slab helps with my ceiling height, saves some money, and it’s an esthetic I like; but, the floor temperature won’t be livable for me. The bathroom upstairs has an electric heat mat below the tile that makes winter bearable.
My plan for wall insulation includes:
> apply 2 coats AQUAFIN-1K to CMU
> 2.5 in. of recycled ISO to CMU w/ foam-compatible adhesive (need to make sure this is ok)
> 1 in. ISO to bring up R-value or 1.5 in. THERMAX ISO if I decide not to frame and drywall
P.S. Thank you to the GBA community for the Q&A’s, blogs, and articles that have been invaluable for my research and education. Also, to Martin Holladay, Malcolm Taylor, Dana Dorsett, and Trevor Chadwick for responding to my Q&A buying EPS insulation: https://www.greenbuildingadvisor.com/question/brands-of-eps-insulation-for-a-concrete-foundation.
Dana’s reclaimed recommendations helped me find the ISO I mention above.
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Replies
Nicole,
You can install electric radiant ceiling panels if you want. They work.
The main disadvantage of any electric resistance heating method is the high cost of the fuel. Electricity is expensive.
If you are going to heat with electricity, you might find it simpler and cheaper to simply install a few electric resistance baseboard heaters.
Even better: install a ductless minisplit heat pump, and cut your fuel bill to one-third of what it would be with electric resistance heat.
Thank you Martin.
The ductless minisplit seems overkill -- unless I didn't fully understand the articles I read. The space is conditioned and I am adding insulation. I was just worried the concrete slab without flooring on top would undermine the temperature of the whole basement and make it uncomfortable for a person like me who always has cold hands and feet.
Nicole
I used electric radiant heating as backup heating in a passive solar home. Advantages include:
1. Very comfortable heating. Its akin to being in sunlight, with soft radiant heat that heats you and objects rather than heating the room air. Resistance heating (e.g., electric baseboard or wall units) tend to heat air, which then dissipates around the room and heats up objects. People feel more comfortable with warm objects in a cool room than with hot air and cool objects.
2. Some claim that you are more comfortable with a lower thermostat setting with radiant heat than with heating via air. It might make you more comfortable at a couple degrees cooler, not a big deal, but might lower your utility bills a little.
3. Generally, radiant panels are installed on the ceiling or high on the wall to radiate around the room, therefore don't constrain furniture placement as much as resistance heating units. They are rather thin so low ceiling height wouldn't be much of a problem.
Personally I don't like baseboard heaters because you can't put furniture in front of them without affecting their operation. Most people tend to have a lot of furniture along walls. Wall units aren't as constraining since they take up less space linearly along the wall, but some of them use fans to help dissipate heat, which adds some noise that some people find undesirable. Radiant units don't need fans.
I'd recommend using surface mount radiant units, or cove units to be located higher on the wall. They typically cost a few hundred dollars each. The type I used was installed behind the ceiling drywall. So it took a long time to heat up the drywall before heating the room. That worked fine for bedrooms, since it worked overnight, and with a solar home, didn't require immediate heating at bedtime. But wouldn't be useful for heating a room quickly.
Minisplits are 2-3 times more efficient than radiant or resistance heating. So if your heating load is higher, they are a good choice if their cost can be offset by lower heating bills over their 20ish year lifespan.
Another alternative is to use a cheap plug-in electric space heater. They cost well under $100 and heat the room quickly.
Thank you Robert this is helpful. It seems like the surface mount radiant units would be a good fit for me.
Nicole
Robert,
I used Cove heaters on one project and wasn't convinced that much of the heat they give off was radiant as opposed to convective - closer to a ceiling-mounted baseboard, than the radiant heat you have in your place. Given their price I don't think I'd specify them again.
Electric flat panel radiators are more comfortable than cove heaters or baseboard, and if sized correctly can be more comfortable than radiant ceilings too. Cove heaters have the advantage that they can't be blocked by furniture, but are only marginally more comfortable than cheap baseboard convectors.
At the low heating loads of an insulated basement bedroom it probably doesn't much matter. If air conditioning is also goal, a half-ton PTHP would handle both, and use less than half the kwh for heating that a resistance-heating solution does, (with all the charm & elegance of a Holiday Inn Express :-) ). The newer versions with the scroll compressors are a lot quieter than the old-school versions, but not nearly as quiet as a mini-split.
With the inch of EPS under the subfloor, a patch of low-voltage mesh type radiant under the finish floor located where you expect your feet to land in the morning (operated on a simple timer, not a room thermostat) might be your best wintertime comfort-enhancer.
Getting to the optimal heating solution usually starts with the heat load calculations. Do you have any idea what the actual design load is here? (I'd hazard it's about 2000 BTU/hr or less after insulating the walls, but that's just a WAG.)