Energy-efficient windows and doors: what are the options?

If you are working to make your home more energy efficient, a number of different approaches can be used. The most important measures involve evaluating your heating system, insulation and any known sources of heat loss in the home. Heating accounts for over half the overall energy consumption of households in the UK. At the same time, poor insulation around windows and doors can lead to heat losses of up to 25%.

This heat loss can be caused by a number of factors including the glazed surfaces themselves (especially when it comes to single glazing), thermal bridges around the connections between the window frame and the walls, a lack of airtightness as the frame and joints age or even the material of the frame (the thermal properties of which can vary).

It is estimated that you will save about 15% on your heating bills in one season after replacing single glazing with double glazing.

In terms of openings in the home, the biggest culprits of heat loss are windows, French doors and sliding patio doors as they are directly exposed to the elements. So it's important to start there when setting out to make a home more energy efficient.

Front doors and other exterior doors are second only to windows in terms of heat loss. As a reminder, the front door is one that opens directly outside (potentially even on to a street) while other exterior doors include garden doors and doors that separate heated and unheated areas of the home.

If you live in a conservation area, be sure to check if you need to secure planning permission before replacing your windows. You may be restricted in terms of the style of window you are allowed to install.

There are a few different types of window, each of which is designed to work with the installation requirements and the needs of the home. Windows come in standard and custom sizes. The basic categories of windows are as follows:

• fixed windows that don't open;
• windows that feature one, two or more openings;
• windows designed to open fully.

Casement windows

Casement windows are the oldest style of window and can swing open on one or two sides. This type of window is suitable for any type of room. Casement windows allow the most amount of air to enter a room and are easy to clean.

Tilt-and-turn windows

Tilt-and-turn windows are designed to open like a casement window and also to tilt open. They can be closed fully or left partially open making them ideal for use in kitchens or bathrooms.

Sliding windows

Sliding windows are good for saving space since they don't need any clearance to open. This system is often used for patio doors for access to a garden. They are also ideal for small spaces such as above a kitchen worktop.

Top hung windows

Top hung or bottom hung windows offer secure partial opening and are suitable for rain-exposed areas. These windows are often used in basements and garages. Top hung windows are often installed in bathrooms.

Front doors offer a range of options depending on the security needs of your home and the type of installation required. Bear in mind that a front door that is secured by an exterior gate won't have the same safety requirements as a front door that can be directly accessed by the street.

Solid doors

Solid doors are front doors that do not feature glazing. These doors should provide maximum security, but this also depends on the material used to make them.

Glazed doors

Glazed doors provide a generous amount of natural light. They must be made of safety glass for security reasons.

Partially glazed doors

Partially glazed doors combine the advantages of both solid and glazed doors providing natural light and the security of a solid material.

Just like front doors, other types of external door can be solid, glazed or partially glazed. However, the style, materials and safety features of the door must be chosen to match the room in which it is being installed and whether it leads to a garage, garden or even a street.

Windows, French doors, front doors and exterior doors all come with a range of characteristics and it's important to consider each carefully before making your choice. Among the most important characteristics are:

• thermal insulation: which is measured using various coefficients, the most common of which being the Uw coefficent for windows and the Ud coefficient for doors;
• acoustic insulation: measured in dB and using the Rw coefficient;
• materials: most commonly uPVC, wood and aluminium;
• protection against break-ins: this means PAS 24 certification for doors and windows and the use of laminated glass for windows;
• performance and durability: this means the doors or windows have passed tests for air permeability, water tightness and wind load.

Windows have a number of other characteristics that must be considered; for example, the type of glazing (e.g. single or double), the type of filler gas used between the glass and the window's Uw values (for heat loss) and G values (for solar transmission).

High-quality windows and doors can be used to make your home more energy-efficient alongside measures such as improving your hot water system and insulation, and installing whole house ventilation and a high efficiency heating system. All together, these measures aim to lower energy consumption and reduce household greenhouse gas emissions.

• What is the energy transition?
• Home energy efficiency grants
• Home energy efficiency standards and certifications
• Energy-efficient heating systems: what are the options?
• Energy-efficient ventilation systems: what are the options?
• Energy-efficient water heaters: what are the options?
• How to improve energy efficiency with insulation