Reducing energy demand

Major building alteration and repair operations provide an excellent opportunity to incorporate energy saving and energy generating measures. all building activities consume energy, so it is important to use 'sustainable' materials, with low embodied energy and from renewable sources

Also see...

Reducing energy demand

Click on headings on list of contents or scroll down the page


Typically slate, clay or concrete tiles on felt and timber rafters. Major source of heat loss, well worth dealing with. Aim for 300mm of insulation in roof space if practical.

 (Adding insulation to existing buildings can cause condensation if not correctly specified –
if in doubt seek expert advice.)

Roof lights

e.g. existing 'original' skylights, typically over stairs. Replace with timber double glazed units, openable for summer ventilation.

Dormer windows

Often lightly constructed un-insulated structures and adjoining roof slopes. Consider stripping down and installing insulation.

External walls

Typically solid, thick, usually brick or rubble stone inside faced with dressed stone externally, with render to side and rear walls. Provide a good heat store, slow to react to temperature change, but exposed north and east facing walls can become very cold particularly when the render is saturated. If doing a major building upgrade worth considering adding external insulation and re-rendering. Internal insulation is a less satisfactory solution, as it does not use the benefits of the wall’s thermal mass.


Concrete floors to ground floors and basements. Difficult to add insulation, unless installing new raised floor, eg, strip flooring, when insulation can be incorporated in some cases. Suspended timber floors, with ventilated airspace under are a considerable source of heat loss, difficult to deal with unless doing major works. See draughts below.


Major source of heat loss and discomfort. Review all external openings, even letter boxes and loft hatches. Create draught lobbies if possible, and draught proof external doors and doors to unheated spaces. Ventilated floor spaces can cause considerable drafts if the floorboards are not closely laid – it is possible to have wide gaps filled as part of a renovation and still have the floorboards left exposed. Alternatively, carpets with underlay on hardboard sheeting will also cut out drafts.

 (Requirements for natural ventilation for gas appliances must be considered when closing draughty openings – if in doubt seek expert advice.)


Timber double hung sash windows are typical. Their relatively modest size in relation to solid wall makes heat loss through them less important than often assumed. Badly fitting timber windows leak heat and cause draughts. First step - have these overhauled by specialist, who can fully weatherstrip against draughts and noise, and make to easy to operate. It is usually unnecessary to renew the whole window.

(Plastic replacement windows never look right and UPVC is now regarded as unsustainable.)

Other window measures

Double glazing
Difficult to install particularly if the windows have slender traditional glazing bars, as the thicker glass needs heavier and often obtrusive glazing bars.

Secondary glazing
Demountable 'winter' glazing in clear acrylic, which can be taken down and stored may be good alternative. Or clear plastic film adhered to the window frame - this needs to be used where the thin film will not be damaged, for example for fixed high level glazing, perhaps the stained glass panels so common in our area.

Many houses were built with folding timber shutters to main windows. Very effective protection against cold radiation . Use if available and consider reinstating if missing.

Consider also insulating roller blinds and thermally lined curtains.