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  • Can make a big difference to comfort levels
  • Can cut heat loss in the rooms below too

What it is 

If you have had your loft converted into a room, or if your house was built with a room in the loft, with at least some sloping ceilings, then you have a roof room or “room in the roof”. If this roof room is not insulated then you will find it very difficult to heat. You will be losing heat to the outside world through all the walls and ceilings, and you could be losing heat from the rooms below as well. Insulating your loft room could make a real difference to your comfort and energy bills. 

How a room in the roof can be insulated

Roof rooms lose heat in lots of different ways. You will need to insulate every part of the walls and ceilings to help keep the heat in and avoid cold spots. 

To insulate a roof room properly you have to make sure there is a layer of insulation covering every surface between the heated parts of the building and the unheated outside or remaining loft spaces. There will usually be a flat surface above the room, like a mini loft, and one or more flat surfaces in the voids beside the room – the remaining floor of the original loft. These can generally be insulated with mineral wool just like a standard loft, though you may need a firm to blow the material in if access is limited. 
The vertical and sloping surfaces will need to be insulated with rigid material that won’t sag – usually high performance foam insulation board is used to avoid taking up too much space and making the room smaller. The board is fitted between and behind the studs that make up the vertical walls, and between and below the sloping rafters. 
The plasterboard will need to be removed first, and new plasterboard fitted over the insulation before re-plastering and redecorating. 
If your room has an external gable wall, or one shared with next door’s loft, then this will need to insulated. This usually involves fitting rigid insulation board to the internal surface of the wall and re-finishing. 

Things to look out for 

It is important to make sure that the unheated loft voids are well ventilated. Insulating the roof room will make the loft voids colder, which will increase the risk of condensation occurring in the loft. Adequate ventilation at the eaves and the ridge, and a good air gap between the sloping insulation and the roof layer, will help ensure that this isn’t a problem.