A conservatory is the hardest room in a British house to cool and the most commonly cooled badly. It is a glass box with a glass or thin roof, usually facing the sun, with very little thermal mass to absorb anything. The heat gain per square metre is several times a normal room's, and a unit sized by floor area will lose to it every August afternoon.
Deal with the gain before the machine
Cooling is the last step, not the first. Roof shading or a solid or insulated roof, blinds on the sunward elevations, and ventilation that lets the hottest air out at the top all cut the load the system has to fight. Every kilowatt of gain removed this way is a kilowatt the equipment does not have to buy, install and run.
Sizing an air conditioning unit for conservatory rooms: why area fails
A sizing rule per square metre assumes an average room with an average window. A conservatory is mostly window, and often mostly window facing the sun, with a roof that admits heat rather than resisting it. The correct approach is a heat gain calculation that counts the glazing area, its orientation and its shading factor, and the result is usually far above what area alone suggests.
Where conservatory air conditioning units can go
This is the practical difficulty. There is often no solid wall high enough for a wall head, because the elevations are glazed to the eaves. The usual answers are a low level console under the glazing, a unit on the one dwarf wall or the house wall, or a cassette where the roof structure allows. It is worth deciding this before ordering anything.
The winter half
A conservatory that is too hot in July is normally too cold in January, and a reverse cycle system answers both with one machine. That changes the economics considerably, because the equipment is then earning its place across two seasons rather than three weeks, and it is the argument that persuades most owners the installation is worth doing.
Questions people ask about conservatory air conditioning
Will one small unit cool my conservatory?
Only if the heat gain calculation says so, and for an unshaded glazed room it usually does not. The commonest outcome of choosing a small unit for a conservatory is a machine that runs at full output all afternoon and never reaches the set temperature.
Is it worth insulating the roof first?
Almost always. The roof is the largest single gain in most conservatories, and replacing or insulating it reduces both the equipment size and the running cost. It also fixes the winter problem, which cooling alone does not.
Does a conservatory need building regulations approval for air conditioning?
The cooling installation brings the electrical work into scope, and the wider position depends on how the conservatory is separated from the house. Where a conservatory is exempt from some requirements, that exemption normally relies on it being separated and independently controlled, which is worth checking before you condition it.
Can the outdoor unit go inside the conservatory?
No. The condenser rejects heat and needs open outside air. Putting it in the room being cooled, or in an enclosed space beside it, means the heat has nowhere to go and the system will cut out.