What is FENSA

FENSA logo

FENSA is an acronym that stands for Fenestration Self-Assessment Scheme. It was set up, with approval from government bodies, by the Glass and Glazing Federation (GGF). The organisation’s prime function is to regulate double glazing companies and ensure compliance with Building Regulations.

If you want to replace double glazing, it needs to comply with the Building Regulations for thermal performance. Now, you can get the permission and certification for this from your local building authorities. Alternatively, you can get an installer who is accredited by FENSA.

A FENSA-registered double glazing installer will be aware of local building regulations. Moreover, he is equipped under the Competent Person Scheme to certify the installation. As a result, you don’t have to get the approval and certification yourself. You can hand over the responsibility to your installers. They will take care of everything from start to finish.

What is the Competent Person Scheme

The short answer is, this is a form of self-governance and regulation. These government-approved bodies register installers. They do so after making sure that their service and installation is up to the mark. Once they are registered, they are given the authority to self-assess and certify their installations.

In April, 2002, the government decided to regulate double glazing installation. However, it is quite a task to manage, monitor, and certify all windows and doors installations across the country. This is why the Competent Person Scheme came about.

There are 6 bodies that were set up under this scheme. Each of them monitors its members. Additionally, each of them equips its members to certify their installation. Since the regulatory bodies manage their own members, it’s a self-governed process.

This makes it easy for building authorities to ensure compliance. Moreover, homeowners don’t have to run around to get paperwork and certifications for their new double glazing.

FENSA approved installers make planning permissions and certification easy

What is the Purpose of FENSA?

FENSA was established due to the change in regulations in April, 2002. This is when Building Regulations decided that double glazing installation needed to be standardised. This was necessary to lower the national carbon footprint.


When we heat up our homes, a certain amount of heat escapes through conduction. The biggest culprits are the doors and windows. Single glazed windows and doors are notorious for not retaining heat inside.

The more heat your doors and windows let out, the longer you have to run your heating. As a result, your home consumes more power. If you could insulate your home better, you would not need as much energy in heating.

By regulating the thermal performance of double glazing, FENSA and GGF are trying to reduce energy consumption. Additionally, these bodies also ensure that regulations for ventilation and fire safety, are also followed.

How Does FENSA Function?

The way FENSA works is by inviting double glazing companies to register. They then screen each applicant for their quality and performance. After they are satisfied that the applicant is up to the standards set by them, they allow them to display the FENSA logo.

Additionally, the installers get a ID that displays their company along with their FENSA affiliation. Once FENSA registers the company, they can assess their own installation. Once they complete the installation, they can issue a certificate of compliance.

In order to join the FENSA network, companies have to prove their commitment to quality. To this end, they need to do more for their clients. As a result, you get an insurance-backed guarantee on your installation. They are also required to provide deposit protection to their clients.

Why Should You Choose FENSA Approved Installers?

FENSA approved installers give quality service and installation

Even though there are 5 other Competent Person Schemes that regulate double glazing installations, FENSA is the most popular. This is because of its high standards and commitment to excellence. As a result, it also has the largest network of approved double glazing companies.

When you choose a FENSA approved installer, you get the benefit of this body’s standards and protection. You can be sure that your installation will be of the highest industry standards. Moreover, the body protects the customer’s interests with compulsory guarantees and indemnities.


You can find FENSA-registered double glazing companies extremely easily. You can find recommended local companies on their website.

Additionally, they provide all accredited installers with a member ID card. The card displays the installer’s name, company as well as the FENSA logo. The card is impossible to fake because of its security features.

This regulatory body demands high standards from all its members. FENSA constantly monitors and re-assesses for constant, ongoing perfection. As a result, you have the peace of mind and the assurance of a regulatory body.


As per the requirements of FENSA, all registered double glazing companies need to provide insurance for their work. This includes the installation quality as well as certain aspects of the performance.

Moreover, an indemnity protects your initial deposit. Essentially, FENSA protects your double glazing and you.

Compliance and Certification

One of the biggest headaches you might face with new double glazing is getting it certified and registered. Suppose you call an unapproved installer to install it. Now you run the risk of it not being compliant with regulations. In such a case, your installation will not be certified. Additionally, the installer and you may face penalties.

With FENSA approved installers, you don’t have to worry about such problems. They ensure that the installation complies with building regulations. Moreover, they can certify their own installation. This way, you don’t have to expend energy getting the certification from local authorities.

Moreover, they will also get your double glazing registered. The best part is, the installation cost covers all these costs. This way, you don’t have to pay extra for the convenience of not having to deal with the paperwork!

Find a FENSA Approved Installer Near You

If you are looking for a reliable double installation, we are happy to recommend a FENSA registered company near you. Simply get in touch with us. Someone from our team will contact you and give you a list of registered local installers.

Alternatively, you can use our online quote generator to get a quick quote. Once you’ve informed it of what you need, it will generate a quick quote. Additionally, it will give you a list of local installers as well.

Frequently Asked Double Glazing Questions

Frequently Asked Double Glazing Questions

Are Double Glazed Windows Good For The Environment?

Once of the best ways of making your home more energy efficient is insulation. Double glazed windows act as another layer of insulation, helping to prevent the loss of valuable heat.

If I Use Double Glazing on the Web Who Will Fit My Double Glazing?

Double Glazing on the Web have a fully accredited network of local installers. Once you have created your free online quote we will put you in touch with up to three reputable local suppliers. Each of these suppliers will offer you a free no obligation quote and who you choose is completely up to you.

How much is double glazing per window?

Double glazing prices per window can vary from around £150 to £600 depending on the specification. The window style, type of glass, frame colour and handles are all contributing factors. To find out the true double glazing price per window it is a good idea to get a number of quotes to compare.

What is the average cost to double glaze a house?

The average cost to double glaze a house will depend on the size of your house and the number of windows. To double glaze a flat or apartment it will probably cost around £2,000. The average cost to double glaze a house is usually between £4,500 to £7,500. If you collect a number of double glazing quotes you will be able to compare companies and prices.

Is double glazing expensive?

Double glazing can be an affordable addition for many homeowners. The price you pay can depend on the quality of the windows and the energy ratings. Other factors are the style of the windows, the colour of the frames and the type of glass. Why not get an online double glazing quote to get an idea of the price.

Is double glazing easy to break?

Double glazing is a strong option for windows compared to single glazing. The frames are durable and there are high security locking options. As double glazing is made from glass it is possible to break however you will have to exert quite a bit of force to do this. This is practically impossible to do without making a noise.

What Does Double Glazing Do?

Double glazing makes your house more energy efficient, keeping heating in and keeping the cold out during winter months. During summer months, it helps keep the hot air out, keeping your house cooler. It also works to insulate sounds from busy areas and roads, leaving your house more peaceful and quieter.

Does Double Glazing Block Sound?

Double Glazing not only provides heat insulation but it also provides sound insulation too. Double glazing is perfect for houses in busy areas and streets.

How Do I Know If My Double Glazing Needs Repaired?

There are four tell-tale signs that your double glazed windows need repair or replaced: There are chips and cracks in the panes of glass; there is condensation (misted windows) between the two panes of glass; the window allows cold air through; water begins to seep through the frame. If your double glazing does any of these things, you may need to get your double glazing repaired or replaced.

Is uPVC Flammable?

No, uPVC isn’t flammable and is actually a fire retardant.

What Can Cause Double Glazing To Crack?

Double glazing can crack for what appears to be no particular reason at all. A sealed window unit faces constant pressure either side of the glass, however, most of the time double glazing is strong enough to deal with this. Winter can be one of the worst time for cracked glass as the difference of temperature on either side of the glass stressing it to the point it can crack.

Should I Double Glaze My Windows?

Double glazing works to make your house more energy efficient saving you money on your heating bills. Double glazing also provides sound insulation which is perfect if your house is situated near busy roads and noisy areas. Double glazed windows are also tougher and harder to break than single glazing windows making your house more safe and secure.

How Do I Know If My Double Glazing Needs Replaced?

Double glazing will need replaced after a while due to the nature of the design – the gas that separates the two window panes slowly leaks out over time meaning the energy efficiency of your window is compromised. If your double glazing allows cold spots; water to seep through the frame; has cracks or chips in the window or has a build-up of condensation between the two panes of glass (misted windows), you should probably look into getting your double glazing replaced or repaired.

How Long Does Double Glazing Last?

It is important to note that the argon gas that separates the panes of gas, giving double glazing its energy efficiency will eventually leak out overtime. Double glazing has an average life span of about 20 years, however, this can vary depending on materials used and the installation.

Is Double Glazing Worth It?

Double glazing helps make your home more energy efficient as it prevents the loss of heat. During the summer, it helps to keep the heat out of your home. It provides your home with sound insulation which is perfect for houses that are in busy areas and streets. Double glazing also makes your home safer and more secure.

Is Double Glazing Easy to Break?

No, double glazing is not easy to break which means your home will be more secure. When attempting to smash double glazing often what happens is that the first pane of glass and the second will remain intact. This is due to the argon gas working as a shock absorber. This will mean the smash is very loud but unsuccessful on the first attempt.

How much does it cost to install a window?

The prices given in our pricing tables, our online quotes and our costing calculators reflect the price of the window itself as well as the cost of installation. For example, a 500mm x 500mm casement window will cost between £150 and £175 including the cost of installation.

How much does it cost to double glaze a 3 bed house?

On average a double glazed window will cost between £350 and £400, with a uPVC door typically costing £600. This means that double glazing a 3 bedroom semi can cost between £3500 and £5000.

Should I replace my old sash windows?

Sash windows are a key feature for many traditional period buildings. Sash windows were traditionally built using timber, which is fairly high maintenance and has a tendency toward rotting and warping. Over time, these windows can become draughty and insecure. uPVC sash windows are a great way to experience the benefits of modern double glazing, without sacrificing the aesthetic of your home. uPVC sash windows will not rot or warp and require little maintenance. They are also thermally efficient, which means that your home will not require as much heating.

Instant Double Glazing Prices