Many families decide to extend their properties rather than move house and a loft conversion is one way to get more living space and increase the value of your home. But not all lofts are suitable or economically viable for conversion.
You’ll need the following to be sure that a loft conversion is viable in your home:
Most lofts will only have ‘cold loft’ insulation immediately above the ceiling of the top storey. This is aimed at stopping the 25% of heat from your home that can escape through the roof and should be sufficient if you just want to use your loft for storage.
Converting a loft into living space requires ‘warm loft’ insulation, where you insulate the walls (internally or externally) and immediately under or over the rafters, so that the loft space retains heat and draughts are minimised.
The amount you’ll need depends on the type of insulation you use, the breathability of the structure, the installation and the finish.
In this video Superhomer Maria Hawton-Mead talks about the eco-conversion of her loft which exceeds current regulations to achieve a high level of insulation.
The Building Regulations set out general standards which your insulation must achieve, measured in U-values. U-values determine how effective a material is as a heat insulator: the lower the U-value, the better the insulation.
Building Regulations in England require that the U-value of insulation on pitched or flat roofs, for example, be 0.18W/m2 or lower. So, to insulate a pitched roof, this can be achieved with any of the following materials installed between the rafters:
You might want to think about environmentally friendly insulation materials.
Getting the insulation installed correctly is also important to save energy and prevent condensation:
If you do not have the height in the room to insulate under the rafters, then insulating above the rafters, by taking off the roof tiles and insulating beneath, is an option. It is also an expensive option, unless you are already having the roof covering replaced. External wall insulation is also an option to reduce loss of floor area.
While the loft insulation will stop heat escaping from the loft, warm moist air from human activity, such as cooking and showers, can condense on cold surfaces and cause unhealthy mould. If the loft is not airtight moisture can also get into the roof structure and cause damage to the structural components.
You can prevent this by
The vapour control layer may be integral to the insulation material you use, for example many foam insulation boards will have a foil VCL. If not, as in the case of mineral wool, a separate polythene membrane should be fixed under the plasterboard. You can get insulated plasterboard but it may not have the VCL.
In older properties which are designed for the moisture to evaporate through the structure, for example those built before 1919, then the breathing elements should be reinstated using breathable materials. For example, a Victorian house should have lime render externally and lime plaster internally. Wood fibre insulation used internally works well with breathing walls.
If you have an existing loft conversion or attic room there may not be much insulation in place, but increasing the amount of insulation can be expensive and disruptive, so you will need to balance the costs and benefits.
You could add an extra layer of insulated board to the existing walls and ceiling, but this will result in a loss of floor space and head room.
If you are putting a new roof on the house then this is a good time to add insulation between the ceiling of the loft and the new roof. It is also a Building Regulations requirement in some cases.
Maria Hawton-Mead also wanted to install solar panels and she recommends you:
Converting your loft to living space is a major building job that can affect the appearance, structural stability and fire safety of your property. Here are four things you will need to check before you finalise your plans:
If your loft shares a wall or floor with another property then you will probably need to install sound insulation.
If you live in Wales, Scotland or Northern Ireland, the Building Regulations may have different U-value requirements.
Check out Maria’s SuperHomes page
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Written by Trish O’Flynn with thanks to Tony Gwynne of Forest of Dean Council for his input and supporting guidance.