Routing HVAC is possible, but it's expensive and requires a system big enough to handle the increased load. Worst of all, it means breaking into walls and ceilings. But there is a certain little metal box which costs $100 to $200, is fully DIY-able, and requires no wall demolition--and it can heat that room, toasty-warm.
It's called an electric wall heater.
These little metal marvels are a convenient way to bring heat into the most far-flung room. But make no mistake: these devices have significant drawbacks when compared to other types of heating.
Like Space Heaters But Better
Electric wall heaters are like those portable space heaters you plug in to heat up a chilly office or bedroom. The difference is that wall heaters are permanent--recessed inside a wall.
The other difference is that they do not plug in; they are hard-wired into an electrical branch circuit (the wire that runs through your walls).
Powered by either 120V or 240V, wall heaters usually have thermostats on the devices. However, some models do have detached thermostats to allow for one thermostat to control multiple heaters within a single space.
Devices rated for 240V can be connected to either 240V or 120V. If 120V is chosen, though, the heat output will be halved.
Note that the reverse will not work: a 120V device connected to 240V power will blow out and be ruined.
Some wall heaters (like the Pic-a-Watt) can be adjusted to run on a wide variety of different wattages.
One Per Room
Wall heaters can heat up an entire room, and quickly, too. These heaters are perfect for single rooms, not for entire floors or multiple areas.
If you have several rooms on a floor, you'll need one heater per room, plus one or more for each hallway or common area.
They work best on interior, rather than exterior, walls.
Why Are They So Great?
- Easy Installation. Installing an electric wall heater is little more than cutting a square hole in the wall, running 120V or 240V wiring into the device, securing the device to the wall, and turning it on. If you have wire access, you can have a heater.
- Spot Heating. Wall heaters are point-of-service heating at its best. You can target a cold area with one of these devices, and heat up that area without heating up the rest of the house.
- No Ducting. These heaters are entirely self-contained. Cold air is drawn into the heater through the front, and then hot air is blown out without ever leaving the heater.
- Inexpensive. Quality wall heaters cost far less than extending HVAC ductwork or even installing electric hydronic baseboard heaters. Installing a complete modulating 97.5% furnace may make you $5,000 (or more) poorer. And that doesn't include ductwork. For that price, you can install wall heaters in every room of your house, have it done by an electrician, and still have money left over to go to Hawaii.
- Energy-Smart. They use energy wisely in the sense that they are designed to heat specific spaces.
Now, What About Those Drawbacks?
- Not So Energy-Smart. Electricity is not the most efficient way to produce heat. Plus, when these heaters turn off, they radiate very little heat. By contrast, steam or water radiators or hydronic baseboard heaters are far more efficient because after the heating element turns off, internal fluids continue to emanate heat.
- Noisy. Wall heaters push hot air by means of "paddle" or "squirrel cage" fans, which can be noisy, especially in smaller spaces.
- "Brown Out" Your Lights. It's a conundrum: run a separate circuit just for this little 1000 W bathroom heater? Or patch it into an existing circuit with lights? While it's recommended that you run a separate circuit for every heater, this is often not practical and it defeats the "easy in" purpose of these devices. Homeowners often patch into lighting or outlet circuits. This can brown out the lights or worse. When the circuit overloads, it will flip off.
- Considered Lower Quality. Subsequent buyers of your home may appreciate that the basement bathroom has some form of heat. But they will not be impressed by the fact that it is produced by a wall heater.
- Maintaining Spacing. Wall heaters contain orange-hot metal heating elements. Though they tend to be recessed a few inches back in the metal wall can, they are still close enough to the surface that they can ignite nearby flammable items. So, you'll always want to keep the manufacturer-recommended buffer zone between the heater and floor, other walls, towels, toilet paper, etc.