How to

4 November 2016

Installing Roof and Loft Insulation

Heat rises, and without insulation the heat from your home is rising straight out of your roof. All this leaking heat represents bundles of lost cash in energy bills, cash that could be trapped in with a simple installation of roof or loft insulation. Relatively inexpensive, this kind of insulation can last decades and repay the money spent on it many times over. Indeed, it could even go some way to solving the country’s current fuel poverty problems.

Img source: Martin Pettitt / Flikr
Which type of roof insulation you choose will very much depend on how you use your attic, and how easy it is to access. In this article we will cover the different types and methods, and any possible snags along the way. As long as your loft is accessible and doesn’t suffer from damp or condensation problems it can be effectively insulated. You can even do it yourself if you’re relatively handy at DIY!

Here are the different types of loft or roof, and the insulation they require:


Storage Space Loft

If your loft is used primarily for storage, then it is probably the easiest job, as the insulation doesn’t need to be completely hidden and sealed. Usually storage lofts consist of boards placed over the joists in the roof to provide a storage platform. The area between these joists can be filled with insulating material, usually mineral wool.

However, this doesn’t usually provide enough insulation by itself, so you should add insulating boards on top of the joists, then flooring boards on top of that. Alternatively, you can raise the level of the flooring and fill the space underneath with mineral wool. Just be sure not to squash the wool, as this reduces its insulating efficiency.

The recommended depth for insulation is 250-270mm.

One thing to bear in mind when you perform this type of insulation is that as the loft space will now be significantly cooler, there may be new issues with encroaching damp or condensation, or existing issues can be made worse, so this must be monitored. Any issues can be rectified with proper ventilation.

A cooler loft space could also lead to problems with your pipes or water tanks getting too cold and freezing during winter if they are present in your loft. In that case, the exposed plumbing should be insulated using foam. You could also have cold drafts coming from the loft hatch, so it should also be insulated.


Living Space Loft

Sometimes the loft space is used as an extra living area. In this case, you can’t just insulate the joists and floor, as it will leave the living space above feeling rather chilly. Instead, you must insulate the roof itself, which can prove slightly trickier but still doable. Usually insulation boards can be cut to size and then fitted between the rafters, then covered with plasterboard. If the rafters are quite shallow, you may have to insulate over them as well, but ensure that they still receive some ventilation.

The walls of the loft room should also be insulated, as should any dormer windows (windows that stick out of the roof). This can be done with insulating boards as well.


Flat Roof Lofts

Lofts that have a flat roof can be a little harder to insulate as there is less spare space to fill. Usually the roof instead has to be insulated from above, with insulation board laid either on top of the weatherproof coating, or between that and the roof itself.

It’s not usually economical to remove the weatherproof layer just to install insulation, so you’re best waiting until it needs changing anyway, and fitting insulation at that point. You may have to do it anyway, as if the whole roof is replaced, building regulations dictate that you do.

You can also insulate a flat roof from below, but this can be difficult to do and lead to condensation problems. Flat roof insulation should always be carried out by a professional.

The good news is that flat roof insulation can save you as much on heating bills as loft insulation.


Difficult to Access Loft

If you have trouble getting into your loft, you may need to call in the professionals, who will use their specialist equipment to blow loose, flame-retardant cellulose fibre or mineral wool through the loft space. This can be done in a day.


Already Insulated Loft

If your loft already contains insulation, you could have to replace it or bring it up to modern recommended levels (250-270mm). If it is very thin, around 25mm, it might date back to the 70s. Anything under 100mm is probably old enough to need replacing anyway, and this is good as it is difficult to top up given that modern insulation usually comes in 100mm and 170mm depths. Anything approaching 150mm is therefore fine to be topped up to modern depth levels.


All of these options not only save you money on your heating bills, but also reduce the carbon emissions of your home, so it’s a win-win. If you want to keep on the environmental good side, though, make sure you use properly manufactured insulation materials.

If you’re going for any of the more advanced options, or just don’t feel like crawling around in the rafters, you will need to find a decent local installer. The best way to do that is to use the website of the National Insulation Association (NIA).

Also, one final tip, make sure when insulating that all electrical cables and light fittings have some space so that they don’t overheat.


Now that you know what to do, pick your roof-type and insulate your way to cheaper fuel bills and a better environmental conscience as soon as you can!


Sam Franklin

With a master’s in Literature, Sam inhales books and anything readable, spending his working hours reformulating the info he gathers into digestible articles. When not reading or writing, he likes to put his camera to work around the world, snapping street photography from Stockholm to Tokyo. Too much of this time spent in Japan teaching English has nurtured a weakness for sashimi, Japanese whisky, and robot caf├ęs.