Roof insulation: info & costs
Insulating the roof is a very smart investment. As heat rises, 25% of the heath in a house gets lost through an uninsulated roof. Considering the high energy costs and grants for roof insulation, you can earn back the investment pretty fast. On this page, you can discover the different roof insulation materials and their prices.
Go to: Materials & prices – Insulate pitched roof – Insulate flat roof
Roof insulation materials
Depending on the available space, your budget and the presence of a roofing underlay, you can choose between several types of roof insulation. Below, you will find the most frequently used materials and their prices and properties:
1. Fibreglass insulation
Glass wool is one of the most common insulation materials for roofs. It is lightweight, has a good insulation value and is quite cheap as well. Glass wool insulation is only possible if there is a roofing underlay. Moreover, the inside should always be finished with a vapour barrier. In this way, the insulation won’t be able to absorb damp from the room.
Cost: £10/m² (excl. installation), £20/m² (incl. installation)
Disadvantages: Takes a lot of space – slightly irritating during installation
» Read everything on glass wool insulation here.
2. Insulation boards / insulation panels
Insulation boards are the best choice when you want to exploit the space beneath the roof as efficiently as possible. They have a high insulation value and they are already available with a thickness of 1.5 inches. When there is no underlying roof, you can also use special boards that stop water and conduct it to the bottom of the roof. One can easily seal the vapour barrier with a special aluminium tape.
Cost: £11/m², excl. installation. – £20-25/m² incl. installation
Advantages: Space-saving & easy to install
» Read everything on insulation boards here.
3. Rock wool
As rock wool has a slightly better density than glass wool, it is able to insulate sound better. This type of roof insulation is made of volcanic rocks that are melted and spun into a woolly substance. Rock wool is especially known in the shape of Rockwool’s Delta boards, which perfectly fit in the roof due to their triangular shape.
Cost: £20/m², excl. installation. – at least £30/m² incl. inst.
Disadvantages: Less protected against vermin – irritation during installation
» Read everything on rock wool here.
4. Spray foam insulation (PUR)
This roof insulation method is by far the easiest and most efficient one. It fills every gap effortlessly and it even allows you to insulate spaces you cannot reach yourself. Spray insulation exists of two components that, after merger, immediately expand and start forming foam.
Cost: approximately £30/m²
Disadvantages: must be carried out by a professional (certain gasses are released during the spraying process)
» Read everything on spray foam insulation here.
Do you want to have your roof insulated with one of these insulation materials? In order to be sure of a correct installation, it is recommended to rely upon an insulation expert. By using our online quote service, you can receive free and non-binding quotes from different experienced professionals. Click here to go to the quote page.
Insulate flat or pitched roof
The price of roof insulation is not only determined by the choice of material. The surface, the thickness of the insulation layer and the difficulty level have an influence as well. You can choose to install the insulation on the inside or outside. Both a flat and a pitched roof can be provided with insulation in both ways. It is more expensive to have the roof insulated on the outside than on the inside.
1. Pitched roof
In case of a pitched roof, the insulation is traditionally installed on the inside of the roof. However, one sometimes chooses to install the insulation on the outside; this is called a ‘sarking’ system. This option is especially interesting in case of renovations, as the interior finishing remains intact. Is the attic not used as a living space? In that case, it is better to insulate the floor of the attic. In the table below, you can discover prices for the insulation of a pitched roof.
2. Flat roof
The approach is different when you have a flat roof. You can opt for a so-called cold or warm flat roof. A cold flat roof is insulated from the inside: the insulation is placed underneath the roof covering and the roof construction. This method is especially applied to existing flat roofs which are restricted to a certain height. A cold roof has some disadvantages, which is why people often choose a warm roof. In that case, the insulation is installed on the outside of the bearing construction.
A price list of both methods:
| What to insulate? | Installation of the insulation | Average cost per m2 | Customised quote? |
|---|---|---|---|
| Pitched roof | On the inside | £15 - £45 (excl. finish) | ✓ Receive quotes |
| Pitched roof | On the outside | £35 - £50 (excl. finish) | ✓ Receive quotes |
| Flat roof | On the inside | £25 - £35 (excl. finish) | ✓ Receive quotes |
| Flat roof | On the outside | £60 - £100 (incl. finish) | ✓ Receive quotes |
| Attic floor | PUR on massive attic floor | £20 - £30 | ✓ Receive quotes |
Note: Check whether you qualify for loft insulation grants. There are many loft insulation grants for homeowners. Thanks to the Energy Companies Obligation Scheme (ECO), you may even be able to recover the full cost of loft insulation (provided that you fulfill a range of criteria). Insulation experts will be able to inform you on this.
Click here to get in touch with professionals and to receive quotes for free.
Insulate the roof – what do you need to know?
Roof insulation makes money
Roof insulation is an investment which can be earned back quickly. Do not just pay attention to the purchase price when you choose the insulation material. You can already earn back the additional cost of better roof insulation (with a higher insulation value) within a few years’ time. It would be a pity to have to take down the ceiling after a couple of years in order to install extra insulation.
A vapour barrier is indispensable!
To ensure the optimal functioning of the insulation and to avoid moulds, it is important to finish the material with a vapour barrier. This can be made of plastic or silver paper and it must be closed completely. Gaps due to nails or tears and openings can be sealed by means of silicones or a special tape.
No rooms in the attic? Only insulate the floor
If the loft is exclusively used as a storage room, you would be well advised to insulate the attic floor. This way, heat won’t escape either and you do not need as much insulation material.