Around 25% of heat lost from an un-insulated home goes through the roof. Adding insulation to your loft is one of the most cost-effective ways to reduce your heating bills and increase the warmth and comfort of your house. We recommend using insulation rolls as it is the easiest and least time-consuming method so is perfect for the DIY beginner.
The first decision to make is whether you want a cold loft or a warm loft. A cold loft is where you insulate above the ceiling of your top storey at the level of the lofts floor, with this method no heat gets into your loft. A warm loft is where you insulate under your roof, this results in heat travelling to the loft space. The cold loft option is the cheapest and most straightforward solution and is the method we will be describing in this blog.
Materials Needed:
How much loft insulation you need will depend on how much insulation you currently have down and the size of your loft.
- Loft Floor Insulation (glass or mineral wool) – Buy Here
- Crawl/Walk Boards – use any boards or pieces of wood you have at your disposal
- Duct Tape – Buy Here
- Down Light Protective Guards – Buy Here
- Pipe Insulation – Buy Here
- Cold Water Tank Jacket – Buy Here
- Staples – Buy Here
Tools Needed:
The tools needed for this job are likely ones that you already own, if not then use the ‘Buy Here’ links to browse for the best tools for you.
- Tape Measure – Buy Here
- Hand Saw – Buy Here
- Scissors – Buy Here
- Work Light – Buy Here
- Metal Rule – Buy Here
- Staple Gun – Buy Here
- Drill – Buy Here
- Screwdriver – Buy Here
Safety Kit Needed:
You will be working in tight and confined spaces and on your knees for some time so safety, as well as comfort, is paramount.
Preparation:
Existing Insulation:
First thing to do is check for any existing insulation, if there is previously installed insulation then check its depth. The current recommended depth of glass or mineral wool for a loft is 250mm to 270mm, but this hasn’t always been the case. Previously it has been as low as 25mm and more recently 200mm.
You have two options; you can either keep the existing insulation and add new insulation on top or remove all the old insulation and start again fresh. Modern insulation is sold in standard depths of 100mm and 170mm which can make topping up older insulation installed pre 1980s quite tricky. Installation installed post the 1980s is likely to be 100mm or more which will fit the depth of the wooden joists, this means a much easier top-up job.
The modern standard depths of 100m and 170mm are to be laid between wooden joints and over and across, at a right angle, joints respectively. This results in the recommended depth of 270mm.
With any previously installed insulation measuring below 100mm we recommend removing it and starting again this will make the whole process a lot easier and quicker.
Calculating the materials needed:
The spacing between joists is most commonly 400mm or 600mm, loft insulation rolls tend to be available in a width of 370mm, 570mm and 1140mm.
Most 1140mm rolls will come with pre-cut perforations such that they can be cut into thirds or halves.
Use a tape measure to measure the spacing between two wooden joists: if the spacing is 400mm then use a 370mm roll or a third of the 1140mm: if the spacing is 600mm then use a 570mm or half of a 1140mm roll.
To calculate how many packs of loft insulation you require, you will need to measure the length and width of your loft space; if this is not possible you can measure the storey below given it is the same size. Multiply the length (m) by the width (m) this will give you the area of your loft in metres squared.
For your base layer of insulation, the layer that sits between the joists, you need to subtract 10% from the area, you can do this by multiplying the total area by 0.9.
Divide this area by the manufacturers recommended coverage per pack and round the number up to nearest whole number to give you the total number of packs needed for the base layer.
For the top layer of insulation simply divide the total area of the loft space before the subtraction of 10% by the manufacturers recommended coverage per pack and round the number up to nearest whole number.
Preparing the space:
Ensure your loft space is clear, tidy and well lit. If the light in your loft is not substantial enough you may want to use an additional work light. If you have any floor boards laid down you will need to unscrew and remove them using a drill or screwdriver.
Insulation should not be laid over any electrical or lighting cables as it can become a fire risk. Where possible clip them onto the roof joists; if the cables do not have enough slack for this then when laying the insulation turn off the electric supply to the loft/top storey and carefully lift the cable such that it sits on top of the insulation.
Before beginning laying your insulation you should make sure that your cold-water tank and any pipes are properly insulated.
Line your cold-water tank with the jacket following the manufacturer’s instructions, if your tank is raised at least 100mms above the top layer of insulation then you can indicate the underside of the tank as well.
To help prevent pipes from bursting you will need pipe insulation, use a panel saw to cut the pipe insulation to size and fit it, securing it with duct tape.
Any recessed lights in the rooms directly below your loft can become potential fire hazards if covered by insulation, to circumvent this you need to install down light protective guards to act as a barrier between the two. Ensure that the light’s transformer is placed clear of the insulation and that the light is not touching the inside of the guard.
Step-by-Step Guide:
Step 1:
If you have bought 1140mm insulation rolls then you will need to first cut these to size using a hand saw, either in half or in thirds depending on your joist spacing.
If you have purchased pre-cut rolls of 370mm or 570mm then this step isn’t applicable.
Step 2:
Use crawl/walk boards to reach the furthest corner of the loft, this is where the insulation laying will begin and then you will work your way back towards the loft hatch. Lay your first roll at the eaves and be sure to leave an air gap of 25mm between the eaves and the insulation, this will help to prevent condensation.
Step 3:
Continue to unroll the insulation between the two joists working backwards towards the centre of the loft. Use the crawl boards to avoid putting your weight onto the insulation.
Step 4:
Once the roll is fully laid out gently push it against the joists such that it fits snuggly and no gaps are left, do not compress the insulation as this will reduce its efficiency. The insulation has likely been sat compressed in its packaging so you may want to carefully fluff it up using your hands.
Step 5:
If one roll is not long enough to reach from one side of the loft to another then you will need to use two rolls. Lay out a new roll and butt the joints together making sure to not overlap them.
Step 6:
When you reach a cross beam, use a pair of scissors and a metal rule cut the insulation to fit flush with the beam.
Step 7:
Continue to lay new rolls of insulation in the same way as before, for any narrow or awkward space be sure to cut the insulation to fit and not just compress in the insulation.
Step 8:
Once the first layer is fully laid across the entire loft it is time for the second layer. There is no need to cut the rolls to size, simply lay the new rolls out at right angles to the first layer.
Step 9:
Continue until the top layer is complete and as before butt together any joining rolls until there is a snug fit.
Step 10:
The next task is to insulate the loft hatch. To do so, firstly measure the length and width of the hatch and cut two strips of insulation to size (just like with the rest of the loft you will need two layers of insulation in order to reach the required depth).
Step 11:
Next wrap the cut insulation in some insulation packaging or any plastic packaging. This allows the insulation to be easily attached to the hatch using a staple gun.
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