Ask the experts: How to insulate your loft
PUBLISHED: 08:00 21 December 2017
As the chill sets in, Richard Burr reveals how to warm up your house and slash your heating bills.
If you have a loft, there’s a fair chance it’s under-insulated, which is bad news, as heating is expensive, and a lot of it is completely wasted as it floats up and out the roof. Save yourself some cash and make life generally cosier by following Richard’s top tips on insulating your loft...
What you need
1. A dust mask
4. Knee pads
5. A cagoule, preferably with the hood up - rock wool can be really itchy when it gets down your back!
6. A torch (if you don’t have a loft light that reaches everywhere in the loft)
7. A panel saw
8. Stanley knife
9. Staple gun
10. Measuring tape
11. Plastic sheets (lofts are dirty, so you’ll need these to put under the open hatch and in any room used to store what’s currently in your loft)
12. A draught excluder strip - the self-adhesive kind
13. Rolls of blanket insulation (use a tape measure to work out the dimensions of your loft in square metres and source your insulation. According to the Energy Saving Trust, you need 270mm depth of standard loft insulation to get the full benefit, so this usually works out as a 100mm layer laid between the joists and a 170mm layer over the top. You can buy this from most DIY stores, or in many cases get it subsidised or even free)
14. Pipe/tank insulation (if you have water tanks and pipes in your loft, you will need to get lagging for them too - you can get tank insulating kits from your local DIY store)
15. Heat diffusers (if you have spot lights on your first floor, the chances are they poke up into the loft space - they should already have heat diffusers on them, but if not, you can get them from somewhere like Toolstation, from around £9, depending on size)
16. Wooden staging (if you intend to store things back in your loft, you will need to build a wooden platform, as just laying your things directly on your insulation will compress it and reduce its insulation value. Use 50 x 100mm wood for making your staging, screwed to the side of the joists to give an area big enough to take all of your storage. Lay your insulation inside this area, then screw chipboard sheets on top of your frame)
Prepare your loft
Most lofts (mine included) are dusty, itchy repositories of old Christmas decorations, holiday stuff, childhood treasures you don’t have the heart to throw away, and spiders. If you intend to use your loft for storage, now is the time to get all this stuff out and give it a sort, clean and re-bag. Try using vacuum bags - they save loads of space and keep your stuff airtight, clean and dry.
Before you empty the loft, clear a room and lay a plastic sheet down - things are going to be messy! You are going to need a clear run and plenty of space if you’re going to crack on with insulating your roof. Be careful to only tread on the wooden joists in your loft, or on the wooden staging if you have some. If you tread anywhere else, you risk putting a hole through the ceiling underneath.
Insulate the fiddly bits
You will most likely have a water tank and some pipes in your loft which, if installed correctly, have a jacket for the tank and pipe insulation for the pipes.
Once you have finished insulating your loft it will be much colder up there, as you will have trapped all the heat in the house where you want it. It is vital that all the pipes and tanks are properly insulated. Tank insulating kits are very straightforward. There is usually string to tie it in place, and the foam pipe insulation has a deep cut already in it that you can open and then wrap around the pipe.
Any spot lights you have poking up through the ceilings should already have diffusers on them, but if they haven’t, pop the diffuser hoods on them, and remember to cut around them with your insulation, so you don’t crush them.
Lay out the insulation
When you take the outer packaging off the rolls of insulation, you’ll find some pre-sliced perforations cut into them - these usually correspond with the widths of your joists, so you can lay the bottom layer of insulation between them. Use your saw to cut the insulation while it’s still rolled up and compressed.
Measure the length of your loft allowing for 100mm of gap at the eaves (the bit where the roof touches the walls) for air flow, and cut lengths of insulation accordingly. Roll these into place starting from the space furthest from your loft hatch.
Once you have finished laying the bottom layer of insulation, you will need to lay the top. Lay this across the joists (rather than in line with them) so the top layer is perpendicular to the bottom layer, once again leaving a 100mm gap at the eaves to allow for air flow. If you want to use your loft for storage, build wooden staging as described above.
Don’t forget the hatch!
You’re nearly done now. You’re probably itchy, hot and ready for a celebratory bucket of tea - but don’t give up just yet!
Whether your loft hatch is hinged, or just rests on the frame, you’ll need to first attach some draught excluder to the hatch frame to stop hot air whistling up in to space. Next, you’ll need to lay insulation on the hatch itself.
For the resting (non-hinged) type, this is easy, just cut the required shape and lay on top of the hatch, then take some of the plastic casing your insulation was delivered in, lay it over the insulation and staple it in place on the hatch, being careful to stick neatly to the edges. For hinged hatches, the method is much the same, just make sure your insulation is cut small enough to fit through the hatch frame as you close it.
Now have a long shower, a cup of tea, and enjoy your nice warm house for the rest of the winter. Happy building!