The study of a window dating from the 1880s found that even the most basic repair had a major impact on energy efficiency.
HISTORIC PRESERVATIONISTS, eager to preserve the "look" of old building elevations, undertook this study of antique windows, dating from the 1880s, because too often, new windows are not detailed carefully, and can ruin a home's architectural integrity. They wanted to show that replacement is not the only option. The windows were authentic, recovered from an old ship.
Among the report's key findings:
Caulking Works. Simple repairs to mend cracks and eliminate gaps can significantly reduce the amount of air infiltration or draughts. On the window that was tested, air infiltration was reduced by one third.
Sash Repair Works. infiltration through a sash window in good condition can be reduced by as much as 86% by adding draft proofing.
Curtains and Blinds Matter. Heat loss through contact with the glass and frames can be significantly reduced by adopting simple measures like closing thick curtains and plain roller blinds. In the test, heat loss was reduced by 41% and 38% respectively.
Combined Efforts Stack. More elaborate measures reduce heat loss even more and can improve windows to meet modern Building Regulations, which target a U value for windows of 2 or below. In a test with good quality secondary glazing, this value was 1.7. Well-fitted, closed shutters, also produce similarly good results. The best result is when the two methods are used together, resulting in a 62% reduction in heat loss and a U-value of 1.6.
The study was based on an analysis of 2-inch sash windows from the 1880s.
Full report in PDF form HERE