Loft Insulation

Insulating a loft

Up to 30% of heat loss occurs as a result of poorly insulated roofs. By properly insulating your loft you could save a lot of energy and a lot of money. Loft insulation is an easy DIY job – but can be time consuming.

Loft insulation materials are made of mineral wool or cellulose fibres. They prevent the heated air moving through the material. There are two main types of insulation for roofs -  blanket insulation & loose fill insulation..

Blanket insulation

Blanket insulation is compressed into rolls – they are normally 16in (400mm) wide and 4-8in (100-200mm) thick. The rolls expand when rolled out so they should only be opened up in situ. Roll insulation can be installed by most DIYers.

Loose fill insulation

Loose fill insulation is normally made of mineral fibres such as vermiculite or fibreglass. It can be bought in bags and poured or blown between the joists. It is easier to use than rolls in awkward corners, irregular shapes and around obstructions

Preparation

Before you lay the insulation, prepare the working area by making sure that you have a good platform to work from – if necessary lay boards across the joists. Also make sure you have sufficient lighting and wear protective clothing – particularly gloves and goggles. Seal larger gaps around pipes, vents, wires etc with flexible mastic.

Laying insulation

It is recommended that the total thickness of insulation should be between 6-10 in (150-250mm). If you already have some insulation in your loft you can just add another layer of the insulating material. If you’re using loose fill insulation and the depth of joists is less than the required depth of cover, the joists will need first to be raised. If you’re using rolls, a second layer can be laid on the top of the joists, across them.

Blanket

Measure the distance between the ceiling joists. Rolls come in standard sizes and should fit between the joists. Trim the ends of each roll to a chamfer shape – this will allow airflow from the eaves – then roll them out starting at the eaves. Cut the matting to fit around obstructions and pipes. If the distance between the ceiling joists is larger than the roll width, you’ll need to fill the gap with loose insulating material. If required, lay a second layer over the joists at right angles to the first.

Loose fill

When laying loose insulation, strips of cardboard or plywood should be put between the joists to avoid clogging up the eaves. Cover pipes with a bridge made of cardboard and keep all electrical wires above the insulation. Then simply fill the space with the insulating material, using a piece of wood to level the insulation. The insulation must not be spread across the top of the joist – so if the joists are not deep enough they have to be raised.

Notes

• Water tanks and pipe-work must be insulated separately, but do not insulate under the tank
• Do not cover electric wiring with the loft insulation – it could cause fire
• Light fittings protruding into the loft should not be covered either -  trim the insulating material closely around them 
• Make sure that there is sufficient ventilation in the roof to avoid condensation
• Don’t forget to insulate the loft hatch -  attach some insulating matting with PVA glue and fit foam draught-proofing to the edges

Before you start any DIY job, make sure you have a first-aid kit, you’re wearing comfortable & sensible clothing – and you’re covered by proper home insurance! Click here for building and contents insurance quotes!