Energy Efficient Windows and Doors

Windows and doors allow people, air and light into buildings but unfortunately, they can also allow a lot of heat to leak out. Lost heat means wasted money and inefficient use of energy.

Luckily, you can take action to reduce the amount of heat that escapes through your doors and windows. Some of these actions are cheap and easy to carry out and, as well as saving you money, they can reduce noise from outside, reduce condensation and make your home more comfortable to live in. Simply applying draught proofing to your windows and doors can save an average of £20 every year.

What are the best types windows and doors for Sussex?

There are several ways of making your windows more energy efficient and the option you choose will probably depend on your budget. The most effective (but most expensive) choice is to replace your windows with new energy efficient models that are double or even triple glazed. 

If brand new windows are not an option for you, then you may want to consider installing secondary glazing film.

Cheaper choices include draught proofing and the use of heavy, blackout curtains.

Replacing Your Windows

Although windows themselves don’t produce carbon (other than in their production), the heat lost, which then needs to be replaced within your home, does. The less heat loss that occurs, the less energy is needed to replenish it and so less carbon emissions are produced. 

The Energy Saving Trust estimates that in England, Scotland and Wales an average semi-detached house can save between £85-70 a year by installing double glazed windows, depending on the energy efficiency of the units installed.

Photo: Evan Smogor - UnSplash

Many factors affect the efficiency of glazing units, including the use of gases between the panes, special coatings on the glass and the materials used for the frames. Triple glazed units are not always the most efficient. 

Some window manufacturers show energy efficiency using the BFRC (British Fenestration Rating Council) scale which goes from A++ (the most efficient) to E. The window is assessed as a whole including its frame, making this rating the easiest way to choose an efficient product. Windows last for a long time, usually 20 to 30 years or more, so we advise you choose the highest performing units you can afford.

A list of the most common materials used for modern window frames is shown in the table below along with some points of note.

Depending on where you live there may be restrictions on what type of windows or doors you can install. Several wards of Brighton and Hove, Lewes, and other towns and villages in Sussex are classified as conservation areas so it is advisable to check with the local planning office before making your choice if you:

  • live in a conservation area
  • have an article 4 direction on your property that removes the right of permitted development
  • live in a listed building
Material Can it be recycled? Points to note
Although uPVC frames can last a long time without requiring much maintenance, and are often a cheaper option, they can't always be recycled. They may contain toxic chemicals which can be released into the environment when they are disposed of, and it is possible that their appearance may degrade over time.
Wood is a naturally renewable material so has a low environmental impact, depending on the type and source of the timber used. If properly maintained, wood can last a long time but is initially more expensive than uPVC. If you live in a conservation area you may have to install wooden framed windows.
Aluminium frames are slim, strong and extremely long-lasting, requiring little maintenance (there is no need for paint or preservatives after installation). They tend to be more expensive than uPVC but are less likely to degrade over time, meaning they can be cost-effective over the long-term.
Usually consisting of timber frames coated in aluminium, these are strong, weatherproof and require little maintenance. Although aluminium smelting is energy intensive, providing the timber comes from a renewable resource, composite frames can be a good choice. Aluminium clad frames can be recycled with careful dismantling, require almost no maintenance (removing the need for paint or preservatives after installation) and can last from 30 to 50 years. They offer good thermal performance and their timber locks in carbon and is a renewable resource.

Any replacement windows must meet the Government’s building regulations standards. In England and Wales, the easiest way to make sure your windows meet these standards is to choose an installer who is registered with one of the official Competent Person Schemes. These installers will give you a certificate when the job is complete that shows your windows have been fitted in compliance with the regulations.

If you don’t use a registered installer you must apply to your local council for building control approval before installing your windows.

Secondary glazing

Replacing windows can be costly so secondary glazing may be a better option for you as it is much cheaper. It can be a permanent or temporary solution and involves placing a second pane of glass or sheet of acrylic on the inside of an existing single-glazed window. There is no need to replace the existing window. However, it is only about half as effective at preventing heat escaping from your home as double glazed windows.

You can use a professional to install your secondary glazing or, if you are competent at general DIY, self-installation kits are available. 

If you live in a listed building or a conservation area, check with your local planning office before going ahead with secondary glazing.

One disadvantage of secondary glazing is that it can make cleaning your windows more difficult. You will need to clean the outside and inside of the secondary pane and the outside and inside of the original pane of glass. 

Draught proofing and curtains

Draught proofing your windows and doors is a cheap way of saving on your energy bills. It can be a simple DIY task or can be done by a professional.

If you have windows that open on hinges, then BHESCo suggest getting some draught-proofing strips, which are widely available from outlets like B&Q or John Lewis. This is fastened along the hinged edge of a window or door to seal any gaps when closed.

There are two types of draught-proofing strip: self-adhesive foam strips and metal or plastic strips with brushes or wipers attached. Foam strips are low cost and easiest to install but may not last long. Strips with brushes or wipers are long-lasting but cost a little more.

Make sure the strip is the correct size to fill the gap in your window. If it’s too big it will get crushed and you may not be able to close your window properly. If it’s too small, you will still have a draught.

For sliding sash windows, foam strips won’t work well. Use brush strips or get professional help.

If your window doesn’t open, try using a silicone sealant to stop the draught.

Some windows have a small vent above them to allow fresh air to trickle into your home, so make sure not to block these.

Hanging heavy, black out curtains adds another layer of insulation to your home. Open your curtains to let sunlight in during the day and close them at dusk to keep the heat in. This can reduce heat loss from windows by 15-17%, which is quite a lot considering it’s such a small change.

How Can I Make My Doors More Energy Efficent?

There are several ways you can improve the energy efficiency of your doors, ranging from full replacement to reducing draughts. Don’t forget to consider internal doors as well as external.

Replacing Your Doors

Replacing your door might be a good idea if it is very draughty. A new door will probably be better fitted, with fewer gaps than your old door.

Like window manufacturers, many door manufacturers use the BFRC (British Fenestration Rating Council) scale to indicate the energy efficiency of their products. The scale goes from A++ (the most efficient) to E. The door is assessed as a whole including its frame and glazing, making this rating the easiest way to choose an efficient product. Doors last for a long time, so choose the highest performing door you can afford.

The most common materials used for replacement doors are similar to those used for windows (see the table in the windows section). Check with your local planning office before making your final choice as there may be restrictions. You should also check if building regulations apply to any alterations you are considering.

Draught Proofing Your Existing Doors

If replacing your external doors is not an option for you, you can still reduce heat loss in various ways. BHESCo’s Energy Saving Service has achieved a significant improvement in the energy performance of hundreds of homes across Brighton and Hove using the following techniques:

  • Buy a purpose made keyhole cover that drops a metal disc over the keyhole
  • Install a letterbox flap or brush – measure your letterbox before you buy
  • Plug the gap at the bottom of your door with a brush or hinged flap draught excluder
  • Fit foam, brush or wiper strips like those used for windows around the edges of your doors
If you have internal doors which lead to a room that you don’t normally heat then these should also be insulated. Keep them closed to stop cold air moving to the rest of the house. There is no need to insulate internal doors between heated rooms.

Cloth draught excluders, which look like long, tubular pillows, can be placed at the bottom of draughty doors to provide a cost effective insulation option.

See how to make your own draught excluder here.

Case Study - a Domestic Retrofit

In 2017, BHESCo worked with a home owner called Muriel who was keen to install solar panels on the roof of her home. In order to benefit from the feed in tariff for solar energy sold to the grid, she needed to increase the EPC rating of her property.

BHESCo carried out an energy survey which recommended the installation of eight double glazed windows plus draught proofing of various areas of the property. These measures alone (without the solar installation) saved Muriel an estimated £150 on her energy bills, plus 506 kg of CO2 per year. 

home energy saving - windows and doors - case study - brighton hove energy service co-op - bhesco

Working with property owners across Sussex to improve energy efficiency

If you are interested in further steps you could take to improve the energy efficiency of your home, please explore the Home Energy Saving section of our website.

You may also want to book an Energy Survey which will provide you with a highly detailed report of how to save energy in your property and the most cost-effective solutions to achieve this.

If you have any questions, please  email us at: or call us on 0800 999 6671.

1 Comment

A more energy-efficient alternative to the national grid - Vision Group for Sidmouth · 17/09/2021 at 21:45

[…] an EPC Rating of D or worse. Reducing heat loss by installing measures like insulation and double glazing will improve the warmth and comfort for residents whilst also lowering the capacity required to […]

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