Expanding upon what I said on FTL tonight, so that others may benefit.
The “heat bubble” is not my creation, I learned of it from Paul Wheaton. The reality that is overlooked, by the way we heat our homes, is that air is a terrible heat transfer medium. Air has a low heat density, low emissivity, and escapes the ‘envelope’ of the house too easily. But that’s how we use the heated air, not to heat the person directly, but to heat the objects in the home. Because we don’t feel warm or cold (predominately) because of the air temperature, but because of an imbalance of heat flowing into our out of our bodies. That seems overly simple, but what we so often overlook is radiation; which is always around us, moving from us to our environment and from our environment to us. This is invisible to us, and usually in constant balance, so it’s easily overlooked. But the key point to understand is that you’re not comfortable in your home because the air temperature is warm enough, but because the walls (and furniture, etc) around you are warm enough (from the air) and are constantly radiating infrared heat towards you at your balance point.
So what we’re doing wrong is that we’re heating the air, and using it to heat the walls (and furniture, etc) when we should be heating the walls, furniture & humans directly.
Doing this while you are asleep was my example, and the easy way to use this method; as an electric mattress pad (or electric blanket) will directly heat the sleeping person via conduction, before escaping from under the covers to contribute to the heating of the air. But another version of this is, heating your workspace; or heating your couch as you watch television. Wherever you spend a lot of sedentary time, you can come up with ways to heat the objects or people in that immediate space. A heat lamp, like the kind used to keep reptiles alive in a glass cage, can be used to do this; by pointing it at your computer chair or your recliner. An excellent example of this direct heating of the human principle is common these days in the form of heated seats in your car. Even though the heat that comes from your vents are effectively free, since it’s waste heat from the engine anyway; the small amount of wattage that your heated seat consumes is much more effective at heating your back and butt during a cold day; but you are most comfortable (while driving your car) when you use both these methods in a balance that is comfortable for you. This is the idea behind the heat bubble. You’re still going to be heating the airspace in some fashion, just not nearly as much as you would need to otherwise because you’re putting deliberate energy into heating yourself directly.
Another way to do something similar is to use an electric somavoar, which is a small countertop water heater, keeping drinking water near boiling. The heat that the unit uses to keep a gallon or so water hot ends up in the airspace anyway, so it’s not a loss to keep the water hot until you need it. When you use it to make a hot drink, you’re heating your body from the inside, by drinking water that’s warmer than your body temp. This is heating the person directly, but from the inside out. A little hot tea or instant coffee works wonders.