It's cold outside. Really cold. So it's no surprise that interest in cheaper, more sustainable ways to warm your home tends to, ahem, heat up this time of year.

Here are some unusual strategies for keeping homes warm — some of them you can even try at home.

Heat the person, not the house

Some time back, I wrote about permaculture blogger Paul Wheaton's video, explaining how he has slashed heating bills by focusing on heating the person, not the house. He used several contraptions, including a heating mat to warm up dog beds, an incandescent heat lamp, a skirt wrapped around his desk and even a heated keyboard. I suggested at the time that this approach might struggle to get mainstream appeal. That said, the principle is utterly sound and can also be deployed in less extreme forms.

From Jimmy Carter's advocacy for wearing a sweater when it is cold to a push to make electric blankets cool again, we should all look for ways to keep ourselves warm — our houses don't care if it gets a bit chilly.

Warming with compost

When it's made right, compost creates heat. And that heat can be put to good use. Search YouTube for "compost" and "heat," and you'll find plenty of videos exploring compost-heated showers and greenhouses. But permaculture expert Chris Towerton has been experimenting with a heat exchange system to power a radiator in one of his upstairs bedrooms. (There's also a detailed explanation of a Wisconsin compost heating project here.) Sure, this method is probably not practical for heating an entire home for most of us — but it might just provide a little extra heat for the hardcore composter.

Candles as a room heater

Candles may warm small spaces, but they won't have much of an impact on bigger homes. Ansis Klucis/Shutterstock

I wrote about this candle-powered room heater, and while I was skeptical about indoor air-quality concerns and the relative carbon footprint of extensive candle burning, many commenters disagreed. They argued that this is a good source of emergency heat for those living in small, rented homes (which are usually the greenest kind of home anyway). Either way, it's a useful reminder that we can meet our basic needs with a little ingenuity and some simple materials.

Move to Finland

Snow-topped homes in Helsinki, Finland. Aija Lehtonen/Shutterstock

Helsinki, Finland, has been expanding its city downwards, creating subterranean parking structures, data centers and more. Not only do underground data centers stay cooler because of the ambient temperatures, but the excess heat they generate is piped upwards to heat city homes. District heating is actually fairly common in cities around the world. In Paris, for example, they're exploring using excess body heat from the Metro to help heat homes.

Heat with nothing at all

Passive solar homes have been around for some time now. Most use the sun's energy alongside other heating sources like natural gas or wood heat, but some manufacturers and designers are claiming to go a step further. Enertia, a manufacturer of what it calls geo-solar homes, claims that its manufactured solar homes can run on little to no supplemental heating or cooling except what is harvested directly from the sun. The passivhaus movement has also been spreading globally, with many homes built in cold climates that require no additional heat except for that which is generated from solar, body heat, and wasted energy from cooking.