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Description
Double glazing with low emissivity coating.
Unit cost of installation
£2000 - £4000 depending on the quality of the frames.
Bulk cost of installation
Data not available.
Indicative cost and carbon saving
| £/yr saving
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kgC/yr saving
|
| from
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to
|
from
|
to
|
|
|
| 35
|
125
|
120
|
295
|
(the data assumes that single glazed windows are replaced with windows with a U value of 2 W/m2K)
Maintenance
Occasionally the air-tight seal on the glazing units breaks down necessitating replacement of the sealed unit. This is more likely in situations when the sealed units are site-fixed into frames with no provision for draining the rebates (rather than factory applied into new frames).
Lifetime
15 - 20 years for a sealed unit in an appropriate frame.
Technical suitability
Need to check bay windows to check if the window frames being replaced perform a structural function. With some older frames the lower edge of the glass may be lower than 800mm from the internal floor surface, in which case toughened units will be required. Care should be taken to ensure that the replacement glazing does not have a significantly lower U-value than any of the adjacent thermal elements, such as a solid brick external wall, as this could lead to surface condensation preferentially forming on the walls instead of the glazing itself. Attention also needs to be given to the safe egress of occupants in case of fire.
Non-technical constraints
In some areas (e.g. conservation areas), or in listed buildings, double glazing may require planning permission or the consent of English Heritage.
Potential concerns with fuel poor
No specific issues.
Ancillary benefits
Double glazing has a number of non-energy benefits
- Units are usually more secure than older frames
- Inclusion of trickle vents can have a beneficial impact on indoor air quality
- Reduced condensation on inner surface of glass
- Sitting near windows is more comfortable
- Sound transmission from external noise is reduced (this is mainly the result of good draught-stripping which manufactured units have)
Technical Guidance Available
» CE184 - Practical refurbishment of solid-walled houses
» GPG 295 Refurbishment site guidance for solid-walled houses - windows and doors
» Steel Window Association 020 7637 3571 http://www.steel-window-association.co.uk/
» British Woodworking Federation 0870 458 6939 0 http://www.bwf.org.uk/
» British Plastics Federation windows group 020 7457 5000 www.bpfwindowsgroup.com
» Approved Document N Glazing - materials and protection
» Approved Document B Fire Safety - Part B1 Means of warning and escape
» CE66 Windows for new and existing housing
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