Closely allied to glazing are heating and ventilation. These pose particular problems in a garden room or conservatory that is intended to be both an extension of the living room, giving scope for relaxation and leisure activities most of the year round, and a display room for, among other plants, exotics that cannot withstand outside temperatures.
Take, first, the human factor. Where the garden room is built out from an existing room, the extension may have to provide all the ventilation for the entire area. Under building regulations basically habitable rooms must have ventilation capacity equal to one twentieth of the room area, in this case possibly the living room and garden room combined. If the garden room is virtually all glass, the ventilation capacity should be increased beyond the one-twentieth requirement to avoid heat build-up on hot summer days. A solution is to have vents or openable windows within something like half the glazed sections of the garden room.
Always open ventilators when the temperature is rising and, during short daylight hours, close them early to retain any solar heat that has been built up.
Living comfort apart, plants in the garden room will, with some exceptions, be harmed by a hot, dry atmosphere. On the other hand, in winter an unheated garden room is no more than a cool greenhouse, a refuge from the frost outside for plants that remain dormant in winter. As such it could be useful accommodation for half-hardy and tuberous plants (e.g. pelargoniums, some fuchsia varieties and begonias) that have to be brought in from the garden to hibernate during the winter. But it would be too bleak for family leisure or entertaining.
If you intend to occupy the garden room as much in winter as in summer and in the company of exotic plants, which require a temperature cf at least 15 deg C (60 deg F), some form of heating is clearly needed, the output depending on the extent of glazing and whether it is double-glazing. Provided the heating boiler has sufficient capacity, in a centrally heated house a radiator or skirting convector could be introduced in the garden room. In an almost fully glazed room, skirting heaters fit unobtrusively. Alternatives include direct-action spot heaters or convectors but central heating best maintains a constant level of heat to suit both people and delicate plants.
Inner doors. Where the garden room is an extension of the living area, installation of an inner partition in place of the original outer wall acts as an insulant layer in the winter and is especially useful if the garden room is only single-glazed. The partition could comprise glass sliding doors.