Infrared Panels for Supplemental Heating
Hello From Toronto,
I am the owner of a 100 year old brick house that has a central air heat powered by a high efficiency gas furnace. The two floor house is split into two separate units, unfortunately the duck work is not very efficient. There is only one air intake on the first floor, located close to the thermostat. The second floor is closed off from the first floor, the second floor air has no direct path to the air intake.
The result is that we have to bump up the thermostat to get enough heat to the second floor.
I am hesitant to go too far down the road of looking into new duct work for a gas furnace, eventually I want have a heating system that is fossil fuel free.
I am curious about using infrared heating panels to deliver supplemental heating to the second floor. They emit far infrared energy to heat objects (including people) directly, no convection heating. Does anyone have experience with this technology? https://infraredheat.ca/
Thanks,
Jonny
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Replies
Hi Jonny,
I have read some positive discussion around Redwell panels being used for either primary or supplemental heating. I can’t speak first-hand about it but I thought I’d share the resource.
Consider installing a mini-split upstairs.
Hey Jon, good idea. I have also been looking into a min-split, estimate from an installer came out to about 4k for one room, 8k for two and 11k for a system that would cover the whole second floor.
Some of the higher end infrared panels I was looking at top out in the $800 range.
I'm having troubles figuring out the operating costs for the two different systems, i know part of this is because it depends on insulation and the outdoor temperature. Here is a break down of the for infrared operation cost. https://infraredheat.ca/far-infrared-operating-costs/ .
Does anyone have experience operating a mini-split in Toronto climate?
Aduck,
Short form, radiant is not efficient, it is silent, it might suit you, mini-splits offer AC. The ones you are looking at are expensive and have some properties you need to consider. Also, why not make the stair well more open to the second floor so your cold upstairs air has an easier path to the return duct below. A large perforated panel in the bottom section of any doors at the top of the stairs would help.
The TL/DR version:
I use radiant cove heaters in a very insulated home in CZ6b. For every Kwh of electricity I put through them I produce approx. 3412 BTUs of heat. I am quite sure that you will have exactly the same energy output in Toronto with whatever panel or cove heater you use. There is nothing special about the efficiency of radiant per se. Each Kwh will produce ~3412 BTU of heat, so calculating your costs of operation will be dependent on local electric costs and how well insulated your house is. And how warm you wish to be.
A mini-split with current low temp capacity will handily outperform any radiant heater. Even at the -15C range, some units will perform about twice as efficiently. If you spend a significant amount of days with lower temperatures your functional energy usage may fall to parity due to pan heaters and resistance heat boosters dinging the COP of the pump. Still, most of the year you will experience a significant efficiency advantage with minis. Bonus advantage - you get AC too.
So why do I have cove heaters and not a mini-split? For the same reason you may chose to.
At the time I needed to commit to a heating choice for our home, mini-splits were exotic and the quote I got was absurdly large. Also, too large in output, but mostly nuts for cost. My electricians suggested cove heaters, which they had been putting in high altitude homes as adjunct heat sources for some time. Simple, low cost, no maintenance and the key selling feature to my spouse, silent. (well maybe a few clinks and pops when kicking in)
IF you are just polishing the heat in a few rooms for comfort during the coldest times and have the panel capacity for the wiring, you MIGHT find the cost balance in your favor. You can feed them hydro electric power for quite some time on the cost difference. I used the cove heaters recommended by the electricians. They are doing fine 5 years out and now come in more colors. The link is - https://www.radiantsystemsinc.com/heater-features/pricing
Each foot of length provides approx 500 BTUs with the shortest being nominally 3'. The average cost per foot is about $30, which I think you will find attractive compared to the flat panels you provided a link to. Some do not find them to be "attractive" aesthetically, but then some are repelled by wall cassettes (my spouse). I can tell you that, like wallpaper, they disappear from one's conscious mind pretty quickly.
I can also tell you that there are two things to be aware of when considering panels. Both sides get warm and spots under furniture don't since the heat is very directional. I grew up with ceiling panels in one part of the house and while the top of my head was very warm, the floor was not and sitting with ones feet under a table or desk showed just how poor the insulation was. If you have done extensive upgrading of the insulation in your 100 yr old home this problem may be lessened.
Any radiant panel or cove will get warm "all over" not just the face. This is helpful if draping a towel over the panel, a variant similar to the freestanding glass ones shown on Redwell. It is not so helpful if the backside is just warming your attic or outside wall. Spacing the wall panel off the wall will promote convection behind it and I assume the wall panels are set that way. The cove heaters do create warm air as shown on the website I provided.
It is misleading to say that no air is heated by infrared. It is just very poorly heated. Most of the air temperature change you derive from infrared will be due to conduction heating of the air from the rooms walls and contents. This may be a fatal flaw in attempting to use infrared heat in your particular conditions. If you already have chilly walls or poor attic insulation, then you will quite likely find the minis a better choice for perceived comfort.
Overhead panels will do nothing to warm the walls. The rate of heat transfer from objects underneath the panels will be so low relative to losses through the walls or windows that you WILL perceive the room as cold. I know that my mostly hairless head registers the air temperature as cold. If I put a thermocouple on objects, all is true to the thermostat. The air temperature of furnace air is well above 100F nearest the furnace and likely still above 85F for your starved upstairs . The air temperature of forced air systems does indeed give a cozier feel. The air temperatures of mini-split heads are similar in nature. Making the room warm by bathing it in very warm air is very different than warming objects, which then have to warm the air.
All the brochure materials I saw at the sites shown above all make the same dubious claims about efficiency. We may be "designed" to absorb warmth from the sun, but then I guess many materials are. The chlorophyll in leaves is actually reflective of far infrared, but that's a different discussion.
One major thing to consider is your electric panel capacity and just how you plan to get the wiring or the line sets up through walls to the second floor. There are under rug heaters offered which might be a possible option. If you have some way to run cords safely and don't have cats that sharpen their claws on everything, you might find this option viable.
Thanks for your reply Roger. I checked out the cove system you used, it seems to claim a lot of the same kind of infrared magic as the ducoterra product. One difference I am curious between the two products is the cove system seems to be designed for some convection heating whereas the ducoterra products mention putting the panels on the ceiling rather then the wall to reduce the amount of heat loss from moving air (I assume they are talking about convection heating).
This is from the FAQ section of the infrared website:
"Q. Is there a difference in energy consumption between ceiling and wall placement?
Yes, the difference occurs because the surface of panels placed on the wall cool down more rapidly than that of ceiling-mounted panels. This is due to airflow past the panels; electricity is required to overcome these losses, hence, the panel will consume a little more energy.
Place the panel on the ceiling wherever possible for optimal heat distribution and lower energy consumption. In a radiant ceiling system, 80% of the energy is converted to Infrared, 60% for radiant wall-mounted systems and 50% for radiant in-floor systems. The dynamic efficiency of hot air systems (gas furnace and ducts) in comparison, is only around 35%."
I've taken note of your comments about the limits of line of sight heating, because of this I am leaning towards any of use of this technology as a secondary heat source to help in cold spots that aren't well service by an air unit (for example in a tiny bedroom with the door closed at night)
It gets very expensive to heat with resistance heaters on Toronto. As Roger has pointed out, there is no "magic" to infrared heating inside the house, all resistance heaters have exactly the same efficiency.
For low cost heating, especially in place that is separated, you can't beat a mini split. In our climate a correctly sized hyper heat unit will easily average a COP of 3, that means it will be 1/3 the operating cost of the panel heaters. This generally means a ROI of a couple of years even with the silly cost of getting these installed here.
The best compromise is to install a wall mount unit in the upstairs hallway to do the bulk of the heating. You can then add small electric baseboards in each one of the rooms for a bit of extra heat around the perimeter. With doors open, the wall mount will do most of the heating and the baseboards will run only sporadically during those cold snaps.
This would also fix the bane of older houses which is sweltering 2nd floor during the summer.
It would also allow you to separate the two places into sperate zones so each area has its own thermostat. With a well sized setup, you should be able to close the ducts to the 2nd floor completely.
Do not install a multi split with a wall mount in each room no matter what the hvac tech says. These are impossible to size correctly as the wall mounts are usually at least 3x the load of each room. These cause a lot of efficiency and comfort issues. If you want to heat the entire upstairs with a heat pump and skip the baseboards, go for a slim ducted unit.
Thanks everyone, this is all so helpful and very much appreciated. At this point I am looking at putting in a vent between the two apartments to increase return air flow or just biting the bullet and creating two separate zones. I'm leaning towards the two separate zone approach, this would allow for AC upgrade and avoid the headache of trying to navigate an increase in sound going between the two apartments.
For the two zoned approach is seems that a mini -split is the best option. The first contractor i talked to advised for 3 heads, it has been suggest here that one head is enough. I've attached a floor plan, let me know if you have any thoughts on unit sizing, head placement and quantity.
Lastly some people are mentioning a slim duct system? Sorry for being a little slow on the uptake, is this a particular brand of minisplit or is this something different then the mini-split?
Slim duct systems are available from multiple manufacturers. Same concept as traditional mini-splits, but you run ducts and distribute air from the floor/ceiling, as opposed to having an unit mounted on an exterior wall.
Here's one example: https://www.mitsubishicomfort.com/products/indoor-units/horizontal-ducted
https://youtu.be/JlKOT_rLc2I
John,
I'm not clear if it's two apartments, or just two sort of separate units within one house. But if it's the former, there are building code implications to having ducts serving multiple units and penetrating party walls you should explore before making any decisions.
I have no doubt that you could improve the comfort burning more fuel.
My wild guess is your comfort issues have much more to do with lots of warm air leaking out of the upstairs rooms and escaping into the attic and or inadequate insulation.
Try to find someone test your house with a blower door before and after they air seal and insulate your house before you throw more fuel at the problem.
Walta
I completely agree, I am so excited to redo the roof insulation (and look into cool roof since I have a flat roof). My main motivation for doing this now is that the duct work in the house is a disaster, no return air on the second floor and there are fist sized gaps in the ducts in the basement as it turns around various beams. I don't want to be on natural gas for climate reasons so I don't want to spend time or money improving super old ducts that might be gone completely in a couple of years.
Insulating and leak improvements will come but in the short term I hope to at least improve the efficiency of how I burn climate friendly fuel.
The footprint looks pretty compact. Is this a semi or a row-house? Do you know what the insulation is in the walls and attic? How old are the windows? Is the living room open to the hallway?
Looking at the layout, I think the simplest is to install baseboard heaters in the bedroom, kitchen and bathroom and install a wall mount hyper heat unit either in the living room or the hallway. If you have an accessible attic, it is pretty simple to run wires for the baseboards up there and fish them down the walls. Most likely you'll need between 500W to 1000W units in each room, so not a lot of extra demand capacity.
As long as the doors are open, the mini split would do the bulk of the heating for the house, the baseboards would rarely if ever kick in. At night time with the bedroom door closed, that baseboard would run a bit more but even that is not a huge energy cost.
A slim ducted unit would be nicer but it is a much more intrusive install as you have to find a spot for the unit and run ducts to each of the rooms. Most likely you will never recover the install cost in energy savings VS wallmount+baseboards.
This would let you disconnect the ducts to the 2nd floor, as a bonus, if you have separate hydro meters, the 2nd floor unit would now be responsible for all their energy costs.
Great questions. There is no doors between the living room, hallway and the kitchen. There is a large window in the west facing living room that is double glazed, but older. The house is semi-detached, the shared wall is to the south (kitchen/bathroom). The exterior walls is uninsulated brick. I don't know about the insulation in the flat roof, we just got the house a year ago 1.5 years ago. It seems like there is multiple layers of roof so when the current one ends its life cycle in about 4-5 years I am going to look into bumping insulation.
I am leaning towards doing a single mini-split heating head for the whole floor, with the understanding that I might need additional backup radiant heat in the bedroom for nights with door closed. How important is head placement?
The contractor was recommending a slim duct unit with 15,000 BTU's and 1.5 ton cooling, does this seem oversized?
Your place is about 19x25. Assuming 8' ceilings and 15% glazing that is around 430sqft of double brick walls (~R4) and 70sqft of clear double pane (R2). Lets hope there is at least R11 batts in the attic.
In Toronto's design temp of 2F and 70F room temp, you loose:
-7300BTU through walls
-2400BTU through windows
-3000BTU through ceiling
Add in some additional loss for air leaks and take away some for heat from appliances and people, you are probably around 12000BTU. Each kW of supplemental heat adds 3400BTU of additional heat, so a 150000BTU unit is oversized.
Something like a 9k Fujitsu would easily cover your load even without supplemental heat. These can deliver a bit over 15000BTU at 5F, so that is plenty of extra capacity:
https://ashp.neep.org/#!/product/30810
Just make sure the unit comes with a pan heater, they have a number of different models that don't come with one.
Generally it is easiest to place the head on an outside wall. I would put it on the exterior living room wall near the bathroom blowing towards the hallway and kitchen. One thing to watch is that you don't want to place it anywhere where it will directly blow air at people sitting.
Note that my house's appliances and people contribution is measured to be < 3000 BTU/hr. Even lower at night.
Say a 100 year old house is 15 ACH@50 and it's very windy with design day temperatures. Adding it all up, I get more like 18K BTU/hr even with two 1kW heaters.
> so a 150000BTU unit is oversized.
We agree on this part :-).
It's currently cold enough that measuring furnace burner on-time is going to provide much better sizing data than the above assumptions. But it still needs a reasonable wind adjustment. Or do a proper Manual J.
Jonny Deshman,
Apologies if I somehow crossed up making a post to Aduck with yours. Regarding your return comment #7, I went to both Comfort Cove and Ducoterra's sites to try and review the FAQ answer you were quoting. I didn't find the specific one, but WOW, I underestimated the magical thinking around infrared heating. I found many of the assertions truly remarkable.
I will leave it at stating my disbelief that basic physics can be defied merely by positing various percentages. As I noted, my real life experience with resistance heating is that a heated mass will emanate heat in all directions. The ceiling mounted panels in my father's home warmed the attic nearly as well as the room intended. Poor insulation in the attic as well as the floor and walls amplified the spotty nature of the "radiant" heat. This is why I mentioned that for your 100 yr old uninsulated brick walls, it might not be the best use of energy to be placing wall or ceiling panels. You seem to indicate that, indeed, the attic may well be in a similar under insulated state.
I did find the notion of combining radiant heat with mini-split heating interesting in that I know the concept has been around for some time. I am acquainted with such an installation and I intend to use a similar hybrid approach on my next project. The motivation is simply to provide a manageable and cost effective way to CMA for heating on the few extreme days when an air source heat pump might be struggling to provide heat. A bonus advantage is being able to size the ASHP in such a way that I can maintain system sizing which will allow for the best dial down of output when it is not so cold.
The cove heaters I use personally are not magical or capable of exceeding physical laws. They do have one very useful feature. The apparent trick of making more energy emanate on the front side is achieved by coating them with a special paint or whatever that has high emissivity of infrared energy. This is why you can't paint them your own colors or touch the front excessively. The back side of the curved extrusion is raw aluminum, which is a comparatively poor emitter. Highly polished aluminum surfaces are very poor emitters and very good reflectors of infrared energy. Radiant foils rely on the principle.
The cove heaters energy "beam" is directed more forward due to the coating, which can be imagined as soft florescent kind of light/heat. It still gets warm on the back and air flows over them and rises to the ceiling. That is not to say that infrared shadowing doesn't occur. It still does, but as my home has above R30 wall and R50 ceiling insulation, the general room temperature ultimately equalizes out at whatever the thermostat says. A less well insulated room would most likely demonstrate obvious cold spots.
The convective flow creating some warm air over the units might possibly be interpreted as a "loss" in some minds, but warm air is warm air. How do these people think air furnaces warm you. Anyway, something elst to note if you are not already aware, choosing 220v over 110v will not save energy either. Make your choices on how your wiring and panel decisions drive things.
Last note, radiant is inherently slow to warm things. Setting back thermostats should only be done if a room is not to occupied for a lengthy period. It can takes days to re-warm a large room with furniture. Everything has mass which needs to be raised. Heating air is quick due to the low mass. You can feel warm with warm air even if the sofa is actually quite cool.
> radiant is inherently slow to warm things
If the thing is a person, then radiant can be quicker to warm. This can be important in a case like a radiant bulb heater on a bathroom switch. I have such a bulb in the shower and am glad that the effect is immediate.
Jon R,
True, a too broad statement based on the discussion of radiant panels not other radiant sources. A radiant paint stripper would certainly not be slow.
>" The second floor is closed off from the first floor, the second floor air has no direct path to the air intake.
The result is that we have to bump up the thermostat to get enough heat to the second floor."
If there is no direct path to the heating return the duct system is EXTREMELY unbalanced and inefficient. With only supply ducts on the top floor it makes "the great outdoors" part of the return path, pressurizing the top floor relative to the outdoors, and de-pressurizing the lower floor(s). Every room with a supply register needs a low impedance return path.
With some 100 year old homes built with a commoned return there is a floor grille return on the top floor, often in a hallway serving as a common return path for all rooms on that floor. But there are variations on the theme. You may be able to figure out a location for installing such a grille. Sometimes a joist bay can be used as a "jump duct" to separate the floor grille and the corresponding ceiling opening below to help mitigate light & noise transfer. A similar approach can be taken for doored off rooms with no returns using partition wall stud bays. When using framing bays as jump ducts it's important to air seal the jump duct section from the remainders of the bays- you don't want to pressurize/depressurize the framing bays to drive other leakage paths. I
It's hard to tell from your floor plan sketch if there would be sufficient wall area to use partition walls or door transoms to the stairwell (rather than a floor grille) as jump ducts.
>"For the two zoned approach is seems that a mini -split is the best option. The first contractor i talked to advised for 3 heads, it has been suggest here that one head is enough."
The "head for every room" approach almost always oversizes the system, often by a ludicrous factor leading to low efficiency & low comfort. Do a room by room Manual-J for those rooms using a freebie online Manual-J(-ish) tool such as LoadCalc (dot net) or CoolCalc (dot com). Those tools tend to overestimate reality by 25% or more even when discounting air infiltration & ventilation to zero, but it's way better than a guess. If the nominal capacity of the head is twice the design load the efficiency will be slipping. It's likely that the upper floor would be better served by a single mini-duct cassette right-sized for the combined loads. With tall walls that COULD be installed at the current ceiling level in the hall at the top of the stairs, creating a service bay by building a new ceiling below the cassette & ducts. If that doesn't work it can sometimes be done with soffited ducts along the edge of the ceiling rather than a whole ceiling. (Fujitsu's mini-duct cassettes can be mounted vertically, if there's enough floor area to give up in the hall area, which also makes servicing the cassette & swapping filters easier.) The mini-ducted approach is a lot more work than just banging in a head per room and is a bit outside the wheelhouse of an HVAC contractor and not usually the first proposal.
The NEEP listings for cold climate heat pumps is a useful search tool for finding the appropriate equipment: https://ashp.neep.org/#!/product_list/ Filter for "compact ducted" if going the mini-duct cassette approach. The 99% outside design temp for Toronto is -17C/+1F and the NEEP pages list the capacity at +5F (= -15C), which is pretty close. Equipment with a +5F capacity of 1.1x to 1.3x your calculated design load would be the most appropriate. An bigger than that would lead to sub-optimal oversizing, since the calculated Manual-J load already has some padding- a 1.3x factor based on the Manual-J is likely to really be 1.5x the real load.