Interior spaces can be kept warm in cold weather with minimal need for electric or fuel heaters by obtaining heat from available sunlight and warm outside air when available, and keeping it inside using thermal mass, insulation, draught seals, and double or triple glazing.
Can let in sunlight in to heat the interior of the buildling. The sunlight should ideally fall on thermal mass, which can store the heat for later release. Use curtains, eaves, vegetation to block or filter the sunlight when the heat isn't needed.
Vents and open windows let in warm outside air when available, and should be closed when outside air becomes colder than inside air (unless airing the house).
Captures heat from sunlight and warm air, and slowly releases it to keep interiors warm despite cold conditions outside.
Prevents heat loss through walls, ceilings, floors to cold outside air and earth.
Double and triple glazing on windows. Prevents heat loss through windows to cold outside air.
Keeps warm air in and cold air out.
Recirculate warm air that rises to the top of the room back down to where the people are.
The rooms that are most used should have the sunward facing windows.