Thermal Performance of Traditional Windows Prepared for Historic Scotland Corrections and Clarifications Thermal Performance of Traditional Windows Improving the Thermal Performance of Traditional Windows Prepared for Historic Scotland by Summary of Report by the Thermal Performance of Traditional Windows

Corrections Page 17, Table 6: The in situ U-value from Lauriston Place for single glazing with secondary glazing has actually been 1.6 W/m 2 K instead of 2.3 W/m 2 K. Clarifications The U-values in this report are measured at the centre of the glass pane, and are not whole-window U-values; except for the U-value measured by the National Physical Laboratory, refer to Appendix 1, which is a whole-window U-value. The double glazing tested in the laboratory has been a slim-profile double-glazed unit, in which the cavity was filled with a krypton-xenon mix. The Scottish Government has set a target of reducing Scotland's carbon emissions by 80% by the year 2050. This is an ambitious target that requires a series of energy saving measured to be implemented across the country. Just under one fifth of Scotland's dwellings are traditionally constructed, and have significant value to Scotland's built heritage. The key issues for these buildings is how to make them energy efficient, in a way that does not detract from their character or damage the building fabric. To tackle this question, Historic Scotland's Technical Conservation Group commissioned the Centre for Research on Indoor Climate & Health at Glasgow Caledonian University to carry out a series of tests on traditional window performance. Windows are the most targeted building element for replacement to reduce heat loss in dwellings. The window that was tested, provided by Historic Scotland, was a typical timber single paned sash and casement window. The thermal performance of the window was tested at the National Physical Laboratory using a guarded hot box system, in order to get an industry-standard measurement of the window's properties. The thermal transmittance of the window (known as the U value) was measured as being 4.5 W/m 2 K. Draught proofing is a common practice to prevent wind from blowing in through traditional windows. The test window was draught proofed, and although the U value of the window was not improved, the airtightness of the window was improved considerably, reducing the air leakage by 86%. The window is tighter than the recommended 4,000 mm2 trickle vent for domestic new build. A series of heat loss reduction measures were tested. These measures are all standard steps that people can take and are widely available, including the use of curtains, shutters, blinds, and secondary glazing. All the options were tested on the window in the Environmental Chamber at …