Conservatories - not very efficient use for living spaces of a house extension

Conservatories seem to offer inexpensive accommodation with the bright, ‘airy’, almost external feel of a highly-glazed space. However, solar heat gains are more than offset by the high rate of heat loss through glazing, especially if the conservatory does not have a southerly orientation ( - + 45°).

An unheated, southerly-oriented, highly-glazed conservatory will provide comfortable accommodation during spring and autumn, and on a few sunny days in winter. At other times in the winter it will be cold, and in the summer it will overheat. Comfortable periods can be extended by the use of shading, blinds and ventilation, but conservatories should never be heated because this leads to excessive fuel use, fuel costs and carbon dioxide emissions. Leaving an unheated conservatory open to another heated space such as a living room is equivalent to heating it.

Therefore the incorporation of a conservatory in a proposed extension should be approached with great care. A ‘sun room’ space with an opaque, well-insulated roof (perhaps incorporating some roof windows) and partly-glazed walls will often provide bright and airy accommodation that is much more useable and comfortable than a conservatory.