The former Lister Lane special school in Bradford, circa 1914 is an ˜open airâₒ school with lots of ventilation. It also had large windows and glass-walled corridors to contribute to staying healthy at a time when tuberculosis was rife. Although it shut in 2010, it was in Bradford Councilâₒs refurbishment programme to update their properties. Plus, it was to have a new role providing respite care facilities for young people with disabilities.
Upgrading thermal performance
The upgrading was carried out in phases, and an important requirement was that the thermal performance be improved. Since the roof itself was sound, the initial proposal was to install rigid foam board between the joists of the original ceiling, plus some Rockwool to be laid on top of the suspended ceiling below.
Avoiding a potential condensation risk
However, it was realised that having Rockwool on the suspended ceiling would make the void above so cold that there was the risk of condensation occurring, as the moisture produced by the activities in the room below migrated upwards.
Instead, PIR board was used between the joists, with TLX Silver fitted below on the warm side of the build-up, providing air and vapour-tightness. They had to remove the suspended ceiling so as to expose the previously hidden windows. This provides more light into the rooms, and the replacement of windows also improves both the insulation and ventilation.
An additional benefit of TLX Silverâₒs shiny low emissivity outer surfaces is that not only does it reflect the heat back into the rooms below, but in summer it reduces the amount of heat being radiated into them, maintaining a comfortable environment at all times of the year.
The Problem: How to provide insulation that would seal roof-level draughts, and not cause a condensation risk?
The Solution: TLX Silver âₓ the fully BBA-certified vapour control layer âₓ provides airtightness and reflects heat back into the interior, whilst also minimising solar gain in summer
