Home heating can easily be augmented by a number of means. These do not supplant the need for adequate insulation and blocking drafts with caulk, etc. that we all know about. While we have found in our Zone 4 winter climate that these will not completely heat a home, they do lower heating costs. Additionally, they can be used as emergency heating methods in times of power outs and brown-outs.

INDOOR Window Heat Collector

One of the easiest ways to augment heat is to use south facing windows as passive HOT BOXES. This uses a plan similar to the outdoor hot box collectors plans seen at such sites as listed in the end of the article.

However, a much easier heat collector can be constructed with aluminum foil, tape and flat black paint using your south facing windows. We adapted the concept to fit a cheap budget. Just tape the collector over the window! If you want to leave the bottom of your windows exposed for light, just make your collector on the top of the window!

Materials:
a roll of heavy duty aluminum foil
duct tape or packing tape or some other means of securing foil to the window frame
flat black paint
South facing windows (east and west windows are less effective in their solar gain)

Directions:
Take the roll of foil and tear to fit the window leaving a space of two inches at the top and two inches at the bottom open. If your windows are wider than the foil tear several pieces and tape together. Paint the more dull side of the foil flat black and let dry.

Once the foil is dry, you tape it to the interior window frame -- Black side facing outdoors.  Leave a space of an inch at the top and bottom open.

Your basic collector is done!

HOW IT WORKS:
The collector works by creating sort of a thermosiphon. The cold from the room passes into the bottom of the collector and  is heated by exposure to the black foil. Then since hot air rises --- passes out the gap at the top into the room heating it. My husband jokes that the way it helps with heating bills is to heat that top of the room so your paid heat doesn't have to do it.

IN EMERGENCIES:
You can save time by simply cutting a black plastic garbage bag or putting a black piece of cloth over the window leaving the gaps at the top or bottom for air flow. This will produce some solar gain and heat in emergency situations, but is not as efficient as metal like black painted aluminum. See photo below.
 

If you want to build an OUTDOOR HOT BOX check out these sites below:
Self Sufficiency:
 http://www.jrwhipple.com/sr/

NoSelft sure:

Which sells solar hot boxes, but has lots of great photos.

And
Bettertimes.org
 http://www.bettertimes.org

If you look at  these sites, you should be able to build an outdoor solar hot box with minimal building skills.