Experience with Wall Convection Heaters?
October 31, 2016 5:56 AM   Subscribe

Do you have any experiences with wall-mounted convection heaters, like this thing? Are they any good? I have a small glass porch I'd like to warm up for winter mornings.

As I mentioned here, I have a three-season room. Three walls are floor to ceiling sliding glass patio doors. The fourth side is french doors that open into my kitchen. We have a small house, and we'd like to be able to use the room more over the winter. It's already really cold in there every morning.

Space heaters are really the only option. We have an oscillating small heater, which does the job after a few hours. We also have a portable radiator, but we have a 2 year old, and don't like using it while she's around. Some respondents to my prior question suggested just leaving open the kitchen doors to ambiently heat the porch with house heat, but that just makes the whole first floor too cold.

Which leads me to things like these wall-mounted convection heaters that purport to stay cool to the touch. Here's one, the Envi and this thing.

Have you used these kinds of heaters? Are they any good? Space is probably 120 sq ft, but it really sucks out heat through the glass (at least until the afternoon, when it gets passable on its own--it's like a greenhouse).

Ability to hook it up to a WeMo would be a plus.

posted by Admiral Haddock to Home & Garden (10 answers total) 5 users marked this as a favorite
I have a small glass porch I'd like to warm up for winter mornings.

We have an oscillating small heater, which does the job after a few hours.

How quickly do you hope such a heater will warm the area to comfortable levels? The porch is going to get thoroughly chilled overnight. Even if you dump a bunch of heat into the air, it will take quite a while for the surfaces (floor, tables, chairs, etc) to soak up enough energy to be pleasant to touch.

You can easily compare the heaters you linked to, to the one you already have, by looking at relative wattage ratings. It's all electrical resistance heating; there isn't any magic technology specific to one design or another. Some heaters will have a better enclosure or fan or whatever, but the amount of heat delivered is straightforwardly relative to the amount of electricity consumed.

If you're willing to suffer high electricity bills then a space heater that you leave on all the time, set to a low temperature, and turn up briefly in the morning is an option that will keep the room reasonable comfortable. If you don't expect to use the room often enough to do that but would like to make the room tolerable on short notice, then a radiant heater might be a better choice than convection. If you've got natural gas at the house then a gas heater would be cheaper to run, albeit more expensive to buy and install.
posted by jon1270 at 6:28 AM on October 31, 2016 [1 favorite]

We have an Envi, as beta-testers of sorts, and a cold basement with a bedroom in it. Initially, we asked if it would be powerful enough to heat the whole basement -- the rule of thumb, they said, is that it will, as long as there's not a lot of air movement from colder areas.

The convection heater could heat up a single room, with just one door (and better when the door is closed) because it's working off cool air falling to the floor and warm air rising. Ours, with a stairway from the upstairs and likely a "waterfall" of cooler air from the rest of the house, wouldn't work; the Envi couldn't keep up with that scenario.

However, we put it in the basement bedroom -- and this is North Dakota, mind you, and it had a large egress window and inefficient furnace ducts -- the bedroom was getting down to the high forties in the winter. After installing the Envi, even at 40-below, that basement bedroom stayed in the sixties. We kept the door closed to help with the heating.

So, from your profile it looks like you do get some real winters where you live; although as you point out the glass does let a lot of coolness in, which is a bit more than my bedroom had, I think the biggest factor is going to be how quickly the three-season room exchanges air with the rest of the house, and how cold that air is. But, if it has a pretty stationary "pool" of air to exchange in, particularly if the room heats itself up during the day due to sunlight so as the evening cools off the Envi just has to fight against cooling, not heat already cold air, it might to OK.

Envi is also quite responsive to emails, you could ask them.

Also: regarding the WeMo -- an Envi isn't like a space heater. It doesn't just start heating up a room when turned on, and when it's warm enough or you're not using the room you turn it off. The Envi has a thermostat, but to keep an even heat it should be left on pretty much all the time, turning it off means a long time before it will heat up the room to the point the thermostat clicks off, so it's less efficient than just leaving it on and letting its thermostat do the work.
posted by AzraelBrown at 6:30 AM on October 31, 2016 [3 favorites]

I have used similar heaters in winter in Australia. They worked fine. It stayed cool to the touch & heated the room it was in with no problems, though winter temps where I was rarely got below 10C. I am not sure how it would work in harsh US winters. They aren't really a turn on & heat a room quickly type of heater though they are more a slow & gentle kind you leave on with a thermostat so not sure how it would work to just warm it up for the mornings unless you put it on a timer and even then it would take an hour or 2 at the very least to heat something like a glass porch in winter even in Australia.
posted by wwax at 6:35 AM on October 31, 2016 [1 favorite]

Check out small ductless mini-split heat pumps. You'll pay more up front but save bigly on electricity — they will run at something like 30-40% the cost of pure resistance space heaters (convection or other) for the same amount of heat. Plus, they'll air-condition in the summer.
posted by beagle at 8:46 AM on October 31, 2016 [3 favorites]

Just asked my electrician and solar panel installer son about the Envi heaters, he approves.

You also need to consider better insulation for this room and maybe thermal shutters that you close as soon as the sun no longer comes in. If you're handy and want to make them yourself you can find instructions online. This kind looks pretty simple.
posted by mareli at 8:48 AM on October 31, 2016 [1 favorite]

I love these things. I have two in my livingroom. I put one in each of the upstairs rooms of the house I built for my parents. I've been replacing in-wall Cadet heaters in my rental with them. I built myself a little garden room, and I'm putting two in there. They're not MASSIVE heat, but they do the trick, especially if they're complementing another system.
posted by humboldt32 at 9:26 AM on October 31, 2016

By the way, those Econo-Heat panels are just an older version of the Envi's. The first ones I installed were Econo-Heat panels, no switch, no enclosure, just the composite panel and a cord.
posted by humboldt32 at 9:29 AM on October 31, 2016 [1 favorite]

We have one in a 6'x 9' room upstairs that for some crazy reason doesn't have a heat vent/register/whatever they're called there's no heat. We got it in March so I don't have a full winter of stats yet but it really does warm up the room. I just leave it on turned up all the way (you have to leave it on all the time for it to work but you can adjust the level). The room is about 63 degrees right now (38 degrees outside). We haven't noticed much of an increase in our electric bill. I think when it gets really cold in a couple of months I may have to also run a small fan heater at night but the convection heater really makes a discernable difference.

Pay attention to all the info in the reviews on Amazon and the Envi website, especially about size of the room. Customer service is very responsive and I bet they can give you advice about the glass walls and whether it will work.
posted by TheLateGreatAbrahamLincoln at 10:29 AM on October 31, 2016 [1 favorite]

All electric heaters are pretty much 100% efficient. So if your small space heater (probably 1500W, but you can check) takes a few hours to do the job, a 450W heater is going to take roughly three times as long. As suggested above, a radiant heater that heats you, instead of the room, might be an option.

You don't need to fuss with the size of the room or any other extraneous details - it really is as simple as how much electricity goes into the room.
posted by ssg at 10:50 AM on October 31, 2016

These heaters are basically just a more elegant version of the oscillating heater you already have, except they're only about 1/3 as powerful (450w) as most space heaters (1500w). You can easily get 3000w in-the-wall heaters installed (by a licensed electrician) with a dedicated circuit that would do a better job and be even more seamless. You can also get a ductless mini-split heater installed, with a flush-mount ceiling vent like what you would have with a regular central air system, which will not only be much more powerful but which will also be cheaper to run and provide cooling as well. My parents got a quote for such a system for their own 3-season room that came in at I think $6500. If you got a "box on the wall" style mini-split that would be cheaper; I've seen quotes in the realm of $4500.

The Envi folks are saying that their heater will heat up to 150sqft. Bear in mind that that is definitely going to assume a well-insulated room with standard eight foot ceilings. 3-season rooms are generally very poorly insulated because they usually have lots of glass—big windows and sliding patio doors and such. A quality double-pane window or patio door of recent manufacture will still only insulate about 1/5th as well as a standard 2x4-framed exterior wall with fiberglass insulation. (R-value 15 vs. R-value of roughly 3.25.)

Also, if you want to use this room in the winter on more than an occasional basis, resistive electrical heat is going to get expensive. That's generally the most expensive way to heat a space by a large margin, which is why even things like the in-wall heaters I mentioned above are best suited for supplemental heat in small spaces like bathrooms, where they're not running all the time. If you want to add heat to a room without extending your house's existing hydronic or forced hot air heating system, a ductless mini-split is a much better option. They're much more efficient and powerful. It's obviously a lot pricier, but it's a true permanent solution.
posted by Anticipation Of A New Lover's Arrival, The at 11:40 AM on October 31, 2016

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