21% of a typical home's heat is lost through the windows and doors, plus 12% from draughts
Around 18% of heat lost from a typical house is through the windows. Double or triple glazed windows will reduce the movement of air, and like reducing window draughts, can make your home more comfortable and in turn reduce heat loss. It is also possible to cut out the draughts and reduce heat loss through windows using various forms of secondary glazing.
The type of glass used in windows and doors makes a real difference to energy efficiency. Low emissivity (Low-E) glass lets sunlight and heat in and also cuts the amount of heat that can get out again.
1. Double or triple glazing
This is a window with two or three panes of glass with the space between them filled with argon gas to reduece heat loss. This could knock around £140 a year off your heating bills. Joinery workshops can make wooden double glazed sash windows which typically have a lower embodied energy than the PVC frames. Look for the energy rating label when purchasing new windows as this tells you about the performance of the window as a whole – including the U value of the glass, the frame, the proportion of frame to window, how airtight the unit is et
2. Secondary glazing
Where a second layer of glass (C) or clear plastic is fitted inside an existing window frame behind the existing pane of window glass; it is cheaper to install but not as effective as double glazing. A second window opening into the room can also be fitted (D). As a temporary measure you can cheaply purchase kits of thin film from DIY stores. This is cut to size and secured to the window frame using tape or a hair drier. Once heated the film stretches taught. This will not improve energy efficiency as well as more permanent systems but can improve the comfort level in the home.
3. Refurbishment of existing sash windows
Many homes have sash windows which are popular and which people do not want to replace. These can be refurbished (E) to reduce drafts by inserting brush strips into the woodwork to significantly cut down heat loss and on external noise too. There are some companies in Bristol who are now going an extra step and replacing the single panes with double glazed units into the original
When you think about replacement glazing, you need to make sure your windows are installed correctly and comply with all the relevant regulations.
Advice - Centre for Sustainable Energy
Advice - Energy Saving Trust
Trade Association - FENSA
Energy Saving Trust