This project is presented by The Loft Shop
Summary: Insulating your loft information and how to stop the heat escaping through your roof
There are a few types of loft insulation available for the DIY enthusiast to place in the loft or attic. This is a very worthwhile job as you can see from the table below. The main type of insulation used by the house owner is mineral fibre or glass fibre matting. This is dealt with in detail below. There are also sections on loose fill materials like mineral wool, vermiculite and mineral or cellulose fibres. All are effective insulators, as is reflective foil insulation, also dealt with later.
Loft Insulation
Using less than the recommended amount of insulation will cost you money. As much of 15% of your heating can be lost through the roof with no insulation in place. This represents about £155.00 per year wasted not to mention the tonne of CO2. The table below shows the savings that can be made with proper loft insulation. The data in the table was provided by The Energy Saving Trust
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Loft insulation |
Loft insulation |
Annual saving per year (£) |
Around £155 |
Around £45 |
Installed cost (£) |
Around £500 |
Around £500 |
Installed payback |
Around 3 years |
Around 11 years |
DIY cost |
From £250 |
Around £180 |
DIY payback |
From 2 years |
Around 4 years |
CO2 saving per year |
Around 1 tonne |
Around 300kg |
The easiest form of insulation to install is a mineral fibre insulation or fibreglass matting. Both types come in rolls. It works by trapping warm air between the fibres of the mat and stopping it rising further to escape.
The rolls are usually 400mm (16in) wide. Thicknesses range from 100mm (4 in) to 200mm (8 in). This is because this distance is the distance specified between ceiling joists in most modern homes. The full thickness of insulation in the United Kingdom should be a minimum of 200mm. Loft roll, given time, will settle and become thinner. This will have the effect of collapsing the tiny gaps between the fibres which trap the heat and it soon becomes useless as the heat can pass straight through it.
Use the following instructions to make insulating your loft as easy as possible
Access to your loft is usually through a loft hatch in the landing ceiling, If this hatch is not big enough take a look at our project on enlarging a loft hatch. Make absolutely sure you have a solid ladder, or better still a loft ladder, to give you safe access in and out of the loft. Click on links to buy the appropriate products.

Gloves Goggles Tape Measure Craft Knife Dust mask
Make sure that you are wearing all the protective clothing. Fibre insulation contains many small fibres which, when worked loose, will get into eyes, mouths and noses very easily. Mineral insulations can cause irritation to the skin so wearing gloves is also important.
How much insulation?
Measure the area of your loft floor. Rolls of mineral insulation will state on the roll what area they cover. A roll of mineral insulation is cut into smaller sections which are designed to roll out between the ceiling joists so measure between your joists to make sure you buy the right insulation.
Make sure all cracks, gaps and holes in the ceiling are filled with either a standard filler or decorators caulk.
Loose fill insulation comes in two forms, blown and placed. The blown insulation is usually done by specialist loft insulators and is comprised of mineral or cellulose fibres such as rock wool. Rockwool is a man made fibre with excellent soundproofing qualities as well as good insulative qualities. Rockwool is usually placed mechanically into the roof space by specialists and the ceiling joist height very often needs to be raised to accommodate the correct thickness of loose fill.
Vermiculite is another often used loose fill insulation. Vermiculite is a natural mineral which expands (not hugely!) with heat. This expansion is called exfoliation. Vermiculite is fireproof and is often used to insulate new flue liners placed in chimney stacks as well as laid loose in lofts. It is also used as a very lightweight aggregate for floor screeds when mixed with sand and cement. Vermiculite and rockwool have an advantage over mineral or glass fibre insulation in that they do dot have fibres which can irritate the skin. Reflective foil insulation is made from layers of aluminum foil surrounding a wadding or layer of wool material. Usually reflective foil insulation is about 25mm thick and gives a very good U value for its relative thickness. It is easily cut and placed and reflects heat rather than absorbing it.
Much more construction information is available in our bookstore. All the tools and fittings you need in the toolstore.
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