Glass wool insulation

Would you like to have your home insulated (better)? If so, glass wool insulation may be a good option. It has a good insulation value, is fireproof and relatively cheap. In this article you will find more information about glass wool, its costs and applications, as well as useful tips and tricks.

What does glass wool insulation cost?

Glas wool insulation is one of the cheaper insulation materials to choose from. Of course, costs vary depending on the size of the part of your home to be insulated, as well as the type of glass wool insulation material you choose. See the overview below for each insulation measure for an indication of the cost per m2. £ 22

Roof£ 20 – £ 25

The exact cost of glass wool insulation per m2 depends, among other things, on the chosen thickness of the material, the material type (blankets, boards or flakes) and, should you hire a specialist, the labour costs.

What is glass wool insulation?

Glas wool is an insulation material consisting of a combination of sand and recycled glass. Like stone wool, it falls under the types known as mineral wool. To make this insulation wool, glass is first ground up. This ground glass is then melted and combined with a binder containing sand. From this, long fibres are spun to form fibreglass blankets or sheets. Glass wool insulation is an environmentally friendly choice.

What advantages and disadvantages are there?

Glas wool is a very light insulation material, especially if you compare it to stone wool, for example. It is also non-flammable, soundproofing, moisture and mould resistant. Glass wool is therefore very suitable to work with.

One of the disadvantages of glass wool is the fact that the material is itchy and can cause irritation if it comes into contact with your skin. Professionals therefore always wear a mouth mask and protective clothing. In addition, glass wool does not dissolve in water, but loses its insulating effect as soon as it gets wet. For this reason, glass wool slabs are often fitted with an aluminium strip called a nail flange, for example. This foil prevents glass wool from coming into contact with water in the event of leakage, for example, so that the insulation value remains optimal.

Shapes of glass wool insulation

Glass wool insulation is available in various forms. In practice, glass wool blankets and slabs are most commonly used. Glass wool slabs are usually used when insulating partition walls, pre-walls or cavity walls. These are all structures that have fixed dimensions. Slabs are also usually suitable for ceilings. Slabs can generally be found in thicknesses ranging from 40 to 150 millimetres.

Does your project require longer lengths, or are the distances more irregular? Then glass wool blankets are a better option. This is because these are easy to cut to size. Think about insulating (prefab) roofs, for example, or specific ceilings, floors and facades. Glass wool blankets can be bought with and without a nail flange in thicknesses from 60 to as much as 260 millimetres.

There are also glass wool flakes, also known as blow-in wool, however. These flakes can be injected into the cavity in already existing houses, eliminating the need to break open the wall and making pre-walls unnecessary. The flakes are gradually distributed throughout the cavity wall, preventing the insulation from collapsing and ensuring optimal heat retention.

How do I calculate the insulation value of glass wool?

For insulation materials, the higher the insulation value, the better the material insulates. Better insulation means higher savings on energy bills. The insulation value of a material is also important for receiving subsidies.

The insulation value of a material is often indicated on the packaging, but can also be calculated. First divide the thickness of the material in centimetres by 100. Then divide that number by the lambda value of the insulation material.

The lambda value

The lambda value of a material indicates how well the material conducts heat: this is the thermal performance of the insulation material. The lower this value, the better the conductivity. The lambda value of glass wool is 0.032 to 0.040. Therefore, for a thickness of 13 centimetres, the insulation value of glass wool is 3.25 to 4.06.

The central government’s website states what the minimum insulation value must be to receive a subsidy. For example, for cavity wall insulation this is 1.1, where for floor insulation and roof insulation a minimum value of 3.5 applies. A specialist will know exactly what thickness is needed to meet these values.

Where do you use glass wool insulation?

As briefly touched upon above, glass wool insulation can be used in several places in your home. It is even possible to insulate most of your home using glass wool insulation. We highlight the most common insulation options of glass wool insulation below.

1. Cavity walls

Glass wool is a popular material for insulating cavity walls. A cavity wall is the space between your inner and outer walls where a lot of heat can be lost. Homes built after 1920 generally have a cavity wall, but homes built before 1980 often lack proper cavity wall insulation or are very poorly insulated. By filling this space with insulation material, you will save a lot on your heating costs. If you choose a material such as glass wool, the insulation also has a sound-absorbing effect.

Newly built houses – when glass wool is chosen – are generally fitted with boards. For already existing buildings, glass wool can be injected into the cavity wall by means of flakes, or blow-in wool. See below the average cavity wall insulation cost per m2.

2. Floor

Your floor can also be insulated using glass wool. This not only reduces the amount of cold air entering your home through the floor, but is also good for acoustic damping. As a result, walking on a wooden floor makes less noise. Because glass wool is made of a breathable material, it works well with wooden floors anyway. Floor insulation with glass wool can be done using boards or glass wool blankets.

3. Roof

An insulated roof is incredibly important if you want to create a more economical and sustainable home. Glass wool is suitable for insulating roofs, even when they are sloped or inclined. Roof insulation is a more expensive form of insulation because it is labour-intensive to install. However, because heat rises, it is also one of the most important insulation projects.

The total cost of insulating your roof will depend on the type of roof to be insulated, whether it will be insulated inside or outside and what preliminary and follow-up work is required. Would you like to leave your project to a specialist and get a more precise price indication? Then request a quote.

Glass wool compared to other types of insulation

If you want to insulate your home, glass wool is not the only type of material you can choose from. Other options include PUR foam, rock wool or EPS insulation. By comparing insulation materials, you can choose the one that best suits your budget and home. See below for a brief list of the types of insulation most commonly used in addition to glass wool insulation.

The average costs mentioned are only the costs for the material. * The lambda value indicates how well a material conducts heat. Here, the lower the value, the better the insulation.

What is the difference between glass wool and stone wool?

Both glass wool and stone wool are known as mineral wool. They share many of the same characteristics. For example, both insulation materials are water repellent, impervious to mould and fire resistant, although the fire resistance of stone wool is just a little higher. With both materials, the insulation value decreases as soon as they get wet; vapour control film is therefore recommended. Also, both glass wool and stone wool cause itching and irritation on contact with the skin: a mouth mask, protective goggles and clothing is strongly recommended.

There are also differences to be found between glass wool and stone wool, however. First of all, as the names suggest, glass is made of glass and stone wool is made of volcanic rock. Stone wool is also heavier and harder than glass wool. The strength of stone wool means it can handle higher loads and slabs sag less easily. In contrast, glass wool has the advantage of flexibility.

The insulation value of glass wool is slightly higher and it is also slightly cheaper than stone wool. On the other hand, however, stone wool has a better sound-damping function. Which insulation material you prefer therefore depends entirely on your situation and preferences. These steps obviously differ from one situation to another and depend on which part of your house is being insulated. Below you will therefore find an overview of how a specialist works.

Step 1: Preparation for installation

Before the specialist starts installing glass wool insulation, he or she will first prepare the room in question. For already existing houses, this starts by checking the gaps.

With cavity wall insulation, small holes are drilled in the joints on the outside of the house. Through these holes, the specialist inspects the cavity of your home. He or she checks whether the cavity wall is wide enough, but also whether insulation has already been placed in the cavity wall and what its condition is. If there is already insulation material in the cavity wall of which the quality is no longer good, this must first be removed.

When installing floor and roof insulation, the specialist will remove the finish and check whether there is already insulation material. Is everything in order? Then they can proceed to install the glass wool insulation.

Step 2: Glass wool protection

Glas wool is a safe insulation material, but it must be treated with care during installation. Glass wool consists of a mixture of ground glass with a binding agent that can cause irritation to the skin and eyes. The specialist therefore puts on protective clothes and wears a dust cap and protective goggles. After installation, he also cleans the area thoroughly, so that no fibres remain that can cause irritation later.

Step 3: Installation

The installation of floor insulation can be done under the floor covering, or on the ground floor in the crawl space. In the case of roof insulation, sheets of glass wool are sandwiched between beams on the inside of the roof, after which the roof is finished with plasterboard, for example.

In the case of cavity wall insulation, this can be done in two different ways. If you are having a new house insulated, the specialist will place sheets of glass wool on the inside of your walls, after which the rest of the wall will be finished.

Would you like the cavity walls of an existing house to be fitted with glass wool insulation? Then they do not break up the outer walls anymore, but fill the cavity wall through the holes already made in the joints during the preparation. The specialist blows the blow-in wool into the cavity wall, so no major rebuilding is required. The holes are then refilled, so you won’t see any of it afterwards.

Tips for glass wool insulation

Subsidies and discounts

The central government is trying to encourage home insulation as much as possible. That is why there is a cheaper VAT rate on labour costs for installing insulation, including glass wool insulation. Do you have a home that is older than two years? Then the VAT rate is 9% instead of 21%.

In addition, there are many subsidies available. Both the government and municipalities come to your aid when you make your home more energy efficient. For instance, there is a national subsidy, called the ISDE, if you take one or two insulation measures. You can get up to 30% of the costs back. Local pots are also often available. Check Energy subsidy guide for the possibilities in your area.

While you must comply with the conditions set for the subsidies. Want to know more? Check our Insulation Subsidies page for all information on subsidies.

Insulate together with your neighbours

Are your neighbours also interested in (glass wool) insulation? And would you like to have the insulation done by a specialist? Then investigate whether you can have both houses insulated at the same time. This can make a significant difference in price. You only have to pay the call-out fee once and for larger projects you can often agree on a cheaper total price.

Insulate your home in the best possible way

You can make your home even more energy-efficient by having it insulated in other ways besides glass wool insulation. Think of various extra options, such as insulating your heating pipes, installing radiator foil or installing special ventilation grids that regulate the temperature in your home extra well. These small adjustments cost little and will give you extra savings.