One of the easiest ways to augment heat is to use southerly facing windows as passive SOLAR HEAT CATCHERS. This uses a plan similar to the outdoor hot box collectors seen at such sites as listed near the end of the article --but is done indoors and in an existing window. No carpentry needed! My super inventor husband thought this one up.

While outdoor mounted heat boxes do work, 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 or vice versa!

With this method we have cut our winter heating costs (we have all electric heat!!!) by over one half. It is very simple to do and very inexpensive for the benefits reaped. And it uses free solar power! We have heat catchers in all our east, south and south-west windows placed in back of existing drapes and blinds.

Materials:
a roll of heavy duty aluminum foil
duct tape or packing tape, tacks, string or other means of securing foil to the window frame
card board strips cut as wide as window frame (optional)
flat black paint
South facing windows (east and west windows are less effective in their solar gain but OK)

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 lap fold together. Paint the more dull side of the foil flat black paint, and let it dry. Fold over a card board strip for ease of handling. Tie wire or string to the top section if desired.

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 for the air to circulate. Or you can tie it on to the drapery rod to secure.

Your basic collector is done! You will feel that end of the room heating as the sun shines on the black foil. It will warm this end of the room as long as the sun shines. Cover the window to prevent radiant heat loss at night through the glass with a window quilt or solar shutters to make the system even more effective.

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 sunward facing black foil. Remember -- black color attracts heat. 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 any case, a circle of moving air is created pulling air if front of the black painted foil and heating it. It rises to the top of the window frame and goes out the gap warming the room.

IN EMERGENCIES:
You can save time by simply cutting a black plastic garbage bag or put 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 foil. Cover the window to prevent radiant heat loss at night through the glass.


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


Cleardome Solar.com
Which sells solar heat boxes, but has lots of great photos.
https://www.cleardomesolar.com


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

To Add to your ability to Keep Heat IN Your Home please see the articles below:

Winter Heating Success
https://www.bellaonline.com/articles/art7967.asp


Cheap Heating

https://www.bellaonline.com/articles/art6347.asp


Make A Window Quilt to Save on Heating

https://www.bellaonline.com/articles/art34745.asp