In most freestanding houses the bulk of unwanted interior heat is gained through the roof and ceiling. Heat builds up quickly in a roof space with nowhere to go except to be radiated into your home through the ceiling. Ventilating the roof helps to reduce heat gain considerably, but it also increases heat loss at colder times of the year, unless the ventilators are thermostatically controlled. Insulating the ceiling works equally well at any time, reducing heat transfer either in or out of the living space.

 

Many products are available for ceilings. In older homes it's generally easier to move around in the roof space to install ceiling "batts". These are thick blankets of insulation material that sit in position on your ceiling. These need at least 200mm of clear space around them to prevent overheating. In newer homes, with truss-framed roofs, it can be nearly impossible to move around inside the roof space and we may need to insulate the roof with "blow-in" insulation.

 

Reflective foil vapour barriers are also available and while many of these are best installed when the roof cladding is removed, many are intended for retrofitting. Some foils are attached to fibre batts and are designed to be installed on the ceiling, while others are concertina shaped and designed to be fitted between the rafters to reflect heat before it enters the roof space.