How can heritage windows be energy-efficient at the same time?

Making replicas of heritage timber windows is a necessity when an old building has to be renovated. In such a case the new window joinery must be the same as its historic original. Heritage windows are, however, made more and more often to special order for people who dream of houses styled on earlier eras. In both the first and the second case the highest quality of the new windows and their performance are exceptionally important. They should have high thermal insulation properties. Thanks to this the building will be able to meet the new energy-efficiency standards.

Can replicas of old windows be energy-efficient?

When planning the renovation of an old building, it is worth seeing to the replacement of the old window joinery with new. In the case of historic houses it must be made with the greatest precision and care for the decorative details. New timber windows should look exactly the same as the original ones from earlier times. Modern technologies should, however, be used to make them, allowing windows to be produced that meet today’s strict energy-efficiency standards.

Replicas of heritage windows must be airtight and give interiors an appropriate level of thermal and acoustic insulation. When choosing them, pay particular attention to the thermal transmittance. The lower it is, the better – because less valuable heat will escape through the windows. Under the regulations, from 2021 the value of this coefficient should be at most 0.9 W/m2K. Such performance of timber windows gives much better energy efficiency for the whole building, because the escape of heat from its interiors is limited.

Although energy-efficient windows are most often associated with modern designs of passive houses, in which large glazed areas are readily used, they can also be replicas of heritage windows preserving the former ornamentation and glazing bar patterns. The use of insulating materials of the highest quality, thermally insulating panes, warm edge spacer bars, laminated timber and seals will mean that interiors are perfectly separated from the noise and cold prevailing outside, and the house will become energy-efficient.