How to Install Insulation Boards
So, you’ve decided to insulate your home. Insulating it from the inside with insulation boards is one of the most cost-effective and simple ways, to add an exceptional layer of thermal protection to your property.
These affordable, high-performance sheets are installed on battens or walls directly, (more on this below) and are a great way to avoid condensation and cold spots.
We’re going to take a look at every aspect of installation. Below, you’ll find a comprehensive step-by-step guide to installing insulation boards. We’ve also put together a list of the tools you’ll need to carry out the job, as well as things to consider before you start.
There are a couple of common methods used when installing insulation boards, these are:
- Dot and dab - in which you bond the sheet directly to a wall
- Batten - in which you attach the sheets to wooden frame battens, creating a gap between the wall and your insulation.
Which one you decide to go for is entirely up to you and usually depends on the type of wall. The batten method is slightly more labour-intensive. We will outline below the best way to install battens should you wish to use this method.
Install Insulation Boards Using the ‘Dot and Dab’ Method
Once your tools are gathered and the radio is on, there is nothing left to do except install those insulation boards!
Step 1: Clean and prepare surfaces
First things first; remove all wallpaper and paint from the wall. This includes skirting boards and any dust or debris.
Step 2: Remove render
This is where your dust mask comes in handy. Take all of the render off the wall and clean away the dust. Get that wall looking as smooth and clean as possible.
If you detect any damp spots during this step, find the source before you continue. you could have a water leak.
Step 3: Measure and cut boards
Measure your wall and then cut the boards to size. When cutting your boards make sure to leave a 15mm gap between the board and floor.
Dry fit the boards as you go. this ensures all of the boards will fit when actually attaching them to the wall and avoid any annoying complications.
Step 4: Apply bonding agent to the wall (optional)
This step is not recommended by every brand of insulation board, but some - such as Kingspan - recommend applying some diluted bonding agent to the wall before putting it on the board.
This further helps adhesion and is especially useful if you are putting boards directly onto old brickwork, which tends to stay dusty no matter how thorough you are when preparing it.
Step 5: Apply bonding agent to the back of your insulation boards
In 15mm bands around the edge of the board and a line down the middle, add the undiluted bonding agent to the back of every board.
Step 6: Prepare your adhesive
Follow the manufacturer’s instructions carefully and mix the adhesive to your desired consistency.
Step 7: Apply adhesive to walls
Add the adhesive to the perimeter of your walls and ensure you put it around any cracks or holes. Take your time, applying the adhesive in 50-75mm wide strips that are around 250mm long. You can achieve this by using 10-25mm thick daubs and spreading the adhesive as you go.
Step 8: Fit boards onto walls
Fit each board into position carefully. The adhesive should support the edges of the board, covering them as much as possible. At least 20% of the board needs to be covered with the adhesive to be effective.
Push the boards firmly into place. Get someone to help you with this step if you can, it’ll make it much easier!
Step 9: Install fixings
You will usually need to add at least 6 fixings to each board. Applying fixings is important because it helps to prevent the boards from falling off the wall in the event of a fire. The amount of fixings needed will vary depending on the manufacturer, so consult the instructions to be sure.
Step 10: Seal the gap between floor and board
Almost done! All you need to do now is seal the 15mm gap between the insulation board and your floor. Use a flexible polyurethane foam or flexible sealant to fill the space. This prevents thermal bridging and heat loss through your wall.
And there it is - the ten steps to perfect wall insulation. But what about the batten method?
Installing Insulation Boards Using Mechanical Fixings
This method relies on mechanical fixings to attach the boards to walls but it doesn’t vary massively from the method outlined above.
Let’s have a look at where it deviates, and what you’ll need to do to install insulation boards to battens on the wall.
Step 1: Clean and prepare surfaces
Firstly, remove all wallpaper and paint from the wall. This includes skirting boards and any dust or debris.
Step 2: Remove render
Put on your dust mask. Take all of the render off the wall and clean away the dust. Get that wall looking as smooth and clean as possible.
If you detect any damp spots during this step, find the source before you continue, you could have a water leak.
Step 3: Measure and cut boards
Measure your wall and then cut the boards to size. When cutting your boards make sure to leave a 10mm gap at the top and bottom of the board.
Dry fit the boards as you go, this ensures all of the boards will fit when actually attaching them to the wall and avoid any annoying complications.
Step 4: Apply flexible sealant to the wall
Around the entire perimeter of the wall, apply the flexible sealant. Be careful to ensure you also add the adhesive around any doors and windows.
Step 5: Install the timber battens
Measure your wall and mark it so you know where the battens are going to go before attaching them to the wall. Each vertical batten needs to be placed about 600mmm apart and the horizontal battens go at the top and bottom of the wall and also around any openings.
Add 100mm strips of Damp Proof Course to the back of each batten. This prevents damp from rising into your walls over time.
To fix the battens to your wall, drill holes through the timber into the brick behind, then fix them in place with wall plugs and wood screws. The fixings need to go in about 45mm into the wall.
Step 6: Fit insulation boards onto battens
Secure the boards onto the battens with drywall screws at 300mm centres. For windows and doors, we recommend 200mm centres.
The screws need to go at least 25mm into the battens to provide a firm, long-lasting hold. These screws should not penetrate the brick wall behind the batten.
Step 7: Seal gaps between the boards, floors, and ceiling
All you need to do now is seal the 10mm gap at the top and bottom of the board. Use a flexible polyurethane foam or flexible sealant to fill the space. This prevents thermal bridging and heat loss through your wall.
The Tools You'll Need Before You Begin
Depending on which method you opt for, the tools you need will vary slightly.
Damp proof course
What to Consider Before You Start
U-value: In general, the lower the U-value, the better your walls are at keeping heat inside your home. The thickness of the insulation affects the U-value. If you increase the thickness of the wall with high-density insulation, then your U-value will decrease, and the thermal conductivity of the wall will be lowered.
The reason you need good insulation on your walls is to help avoid something called thermal bridging. Thermal bridging occurs when heat is directly transferred through building elements like studs, beams, and metal framework.
Naturally, the quality of your insulation installation affects the U-value of your home. Any gaps or improper seals will allow for thermal bridging and increase the U-value, meaning your will lose heat faster out of the walls.
Most insulation boards will have the thermal conductivity listed on them. Be sure to discover the U-value of your walls before deciding the thickness and density of insulation you need.
To calculate U-value there are a number of handy calculators online. You will also need to know some structural information about your house and the thickness and cavity filling of your walls.
Building regulations: Something to consider before installing new insulation as building regulations vary for different locations in your home.
- Loft Insulation – The recommended U-value for insulation in the UK is 0.16 W/m²K which equates to a 270mm thickness of mineral wool insulation approx. Important to keep in mind when insulating your loft.
- Cavity Wall Insulation – To meet building regulations in the UK you need a U-value of 0.18 W/m²K for new builds and 0.30 W/m²K for existing properties. These are legal minimums to ensure heat loss is minimised and energy efficiency is improved in all buildings.
Insulation brand: When it comes to insulation, there are multiple brands to choose from. Here are the most popular manufacturers of insulation boards in the UK and what makes them distinct from one another.
- Celotex – Insulation for commercial and domestic use. Popular with professionals and DIYers, their insulation is extremely versatile and has exceptional thermal efficiency.
- EcoTherm – Manufactures very lightweight insulation boards with an extended lifespan.
- Recticel – Made from end-of-life PU foams, they have one of the lowest environmental impacts, helping to reduce waste.
- Xtratherm – Low thickness due to slim profiles makes their insulation ideal for smaller spaces.
- Kingspan – Outstanding U-values and innovative vacuum technology make their insulation some of the thinnest possible while ensuring great heat retention.
Hiring a tradesperson:
If you don’t fancy doing the work yourself or are unsure of your skills, then consider hiring a tradesperson to do the job for you.
A tradesperson will be knowledgeable on the various compliances and building regulations you need to be aware of, and they will also have an experienced eye to spot any potential safety problems.
A labourer will generally have a day rate of between £150 - £200, so will have to weigh up whether the increased cost is worth the investment.
Insulation Installation Made Simple
As you can see, the steps necessary to install your insulation to a high standard are actually quite easy. Doing the job yourself is well within your skillset, no matter how experienced you are!
With that in mind, if you do not have the inclination and it is within your budget, don’t hesitate to hire a professional.