Factsheet 3: Reducing heat loss through windows and doors
within business premises
Energy efficiency should be a priority for all businesses trying to reduce their environmental impacts
and energy costs. Making efficiency improvements should be a continuous process of review and
action. There are many ways in which you can improve the environmental performance of your
business and the Live & Work Rural Programme may be able to help you to do this.
Ensuring that heat loss from your building is minimised can help you to use energy more efficiently
and is preferable to other measures such as installing renewables. This is described in the energy
hierarchy:
Priority 1: Reduce the need for energy
Priority 2: Use energy more efficiently
Priority 3: Use low carbon and renewable energy
Background
At least 10% of heat escapes from typical buildings through windows and doors so upgrading them
can significantly reduce the energy lost. The improvement of glazing should be considered in
conjunction with other energy efficiency measures such as insulation and boiler upgrades.
Improvements to housekeeping should also be considered so that heat is not allowed to escape
through open doors and windows, and buildings or parts of buildings are not heated when
unoccupied.
Windows
The installation of double or secondary glazing can halve heat loss through windows by reducing
draughts and heat flow through the windows. Heat loss from windows can also be significantly
reduced by drawing heavy curtains or blinds across them at night. As well as reducing heat loss,
improved windows can reduce noise and internal condensation on window panes.
When selecting glazing units, advice should be sought regarding which panes need to be made
from safety glass. Advice should also be taken on condensation to ensure that it does not become a
problem due to the reduction in ventilation. Any required cross ventilation can normally be achieved
through the use of glazing units including trickle-vents.
Windows are expensive to replace so the payback (in terms of money saved on heating) on the
investment is quite long. As well as the cost of the windows and the amount of energy saved, the
payback period depends on the cost of the fuel used for heating. Payback periods of over ten years
are typical for the installation of double glazing.
Secondary glazing
The addition of a second pane of glass within the building is known as secondary glazing.
Secondary glazing has the advantage that the property’s external appearance can be retained.
Whilst secondary glazing reduces heat loss, it is not as effective as double glazing. Secondary
glazing ranges from temporary plastic films to custom built systems comprising opening panes.
Double glazing
The most cost effective time to replace windows frames is as part of a standard maintenance
programme. Based on best practice guidelines from the Energy Saving Trust, windows with a
British Fenestration Rating Council (BFRC) rating of band C or better should be selected when
Whilst reasonable steps have been taken to ensure that the information contained within this publication is correct, the authors, the Peak
District National Park Authority, its agents, contractors and sub-contractors give no warranty and make no representation as to its
accuracy or suitability and accept no liability for any errors or omissions or for any loss or damage arising from the use of or reliance on
the information.
August 2010
specifying windows. Units made from low emissivity glass with an argon filled gap of over 16mm will
generally offer the best insulation properties.
Windows frames are available as wood, uPVC or metal. Wood and uPVC frames normally offer
better thermal properties than metal frames.
Wooden window frames can have longer design lives than uPVC frames but these can only be
achieved if the frames are well maintained to prevent rot. To minimise the environmental impact of
window frames only good quality wood from certified sustainable sources is recommended.
Aluminium and uPVC frames offer a lower maintenance option than wooden frames but also have
environmental impacts associated with their manufacture.
Doors
Heat is lost from buildings through doors and their glazing as well in draughts around the frames.
However, a more significant loss of heat is normally through the hot air which escapes each time
the door is opened. Whilst improving glazing and installing draught proofing can significantly reduce
heat loss, the greatest savings can be achieved by ensuring that doors are closed when possible.
To ensure that doors are only open when required, automatic door closers should be installed
where appropriate. Where possible, entrance lobbies should be used as they reduce the cold air
entering the building when people enter (assuming both doors aren’t open at the same time). When
choosing doors they should be chosen with their thermal properties in mind e.g. glass units should
be double glazed. Installing draught-proofing on letter boxes and under doors can significantly
reduce draughts and therefore heat loss from a building.
Draught proofing
Given the long payback of replacing windows it can be preferable to draught-proof their frames as
much as possible and only replace them when they start to fail. Existing panes can be sealed
around their edges to limit draughts and systems are available which comprise sealing strips which
fit into grooves cut into the frames. Windows that open should be checked to ensure that they have
as airtight a closure as possible. Air leakage can also be reduced by installing draught seals around
doors and on letter boxes and by blocking chimneys.
Planning permission
Any significant change to a building within the Peak District National Park is likely to require
planning permission. In the case of listed buildings or structures, even very minor alterations may
require listed building consent. In all cases it is best to seek advice from the Peak District National
Park Authority.
Secondary glazing and timber frames are generally considered more appropriate than double
glazing or uPVC on most buildings within the Peak District National Park.
Whilst reasonable steps have been taken to ensure that the information contained within this publication is correct, the authors, the Peak
District National Park Authority, its agents, contractors and sub-contractors give no warranty and make no representation as to its
accuracy or suitability and accept no liability for any errors or omissions or for any loss or damage arising from the use of or reliance on
the information.
August 2010