How to Insulate a Loft

Nov 06, 2023

Start by lining your cold-water tank with the jacket, following the manufacturer's instructions.

Next, insulate pipes, using a snap off knife to cut the insulation to size.

Secure the pipe insulation with duct tape.

Insulation shouldn't be laid over any electric cables. Where possible, clip them to the roof joists or gently lift them out of the way whilst you install, before laying them over the insulation when it's in position.

If you have recessed lights, now's the time to install down light protectors, being sure to follow the manufacturer's instructions.

Once the insulation roll is in position, measure the width of roll you need to fit between the joists; this tends to be either 400mm or 600mm. Then, cut the roll to size using a panel saw or large bladed kitchen knife.

Position the crawling boards in the furthest corner of the loft. You’ll need to start laying with a minimum gap of 25mm between the eaves and the insulation to ensure a suitable air gap. Maintain this gap along two opposite sides of the loft.

Make sure that the wall plate is covered, then roll out the insulation, moving backwards so you are working towards the centre of the loft to avoid putting your weight directly onto the insulation.

Gently push the insulation so it fits snuggly between the joists, but don't compress it as that will reduce its efficiency.

When you reach a cross beam, use a straight edge or metal ruler and a snap off knife to cut the insulation to fit.

To join two lengths of insulation, simply butt them up tightly.

Continue to lay until the first layer is in position, cutting the insulation as required to fit any awkward spaces.

To reach the recommended loft insulation depth of between 270-300mm, a second layer can be added. Simply unwrap the insulation and lay at 90-degrees to the first layer and ceiling joists.

As before, when joining two lengths, make sure the butt joint is a snug fit. Stagger the joints to avoid them all meeting in the same place.

Continue to lay until the entire loft is covered.

Measure the loft hatch and cut insulation to size. You will probably need two layers to achieve the recommended depth.

Wrap the insulation you’ve cut in some of the insulation packaging, as this will allow it to be secured in position.

Attach the insulation to the loft hatch using a staple gun or large headed tacks.