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When an established local architectural practice was commissioned by Manchester Metropolitan University to provide a Lifecycle Upgrade to their Grosvenor Building, they didn ¢t hesitate to contact us in the hope we could offer an effective solution to their tricky project. The building is Being II listed. So building control had specified that any work undertaken must not alter the level of the existing roofline. Yet with shallow rafters, concerns were raised about the level of insulation which could practically be achieved.
Initial obstacles
Limited access made for a challenging first inspection of the existing roofline. 1F felt was found installed in the roof. So a 50mm ventilated air gap occupied the rafter space below it. Therefore, the insulation was virtually inexistent. Owing to the frequent usage of the building, particularly during term time, a fast and effective solution was required to keep the daily occupants comfortable, whilst maintaining a sympathetic approach to the historic value of the building.
What to do with 75mm rafters
TLX Gold 2-in-1 insulating breathable membrane was specified and installed draped over the rafters. A 20mm unventilated air layer was beneath it allows for heat to reflect from its shiny, breathable under surface. This allows for no change in roof height. This is a priceless advantage when the original roofline needed to be preserved. TLX Gold drapes into the rafter space by its thickness, plus the air layer underneath. (amounting to approximately 50mm). Leaving space for 25mm of PIR board just above the plasterboard. The benefit of using TLX Gold is that it has an integrated breathable membrane, thus the 1f felt was removed and replaced by the single layer of TLX Gold.
U Value achieved?
In listed buildings, U value requirements are waivered in favour of preserving a buildings ¢ history, however, it was still a necessary upgrade to ensure the longevity of the building for decades to come. The resulting U value came to 0.45w/m2k. Although this doesn ¢t meet building regulation requirements of 0.18w/m2k, due to the limitations of the upgrade, a significant energy saving was achieved, compared with the original build-up.
Installation:
When fitting the material, the ease of installation was a welcomed surprise. Simply roll TLX Gold multifoil insulation out over the top of the rafters. Then join to the next section with the help of integrated tape for a seamless finish.
Since TLX Gold is fully breathable, you don’t need a vapour barrier to ensure there is no risk of condensation. The reason for this is that any water vapour entering the roof space from below can easily escape through the breathable layers of TLX Gold, whilst the shiny reflective under layer reflects and retains heat.
The result:
TLX Gold installed above the rafters provides an excellent thermal energy saving. It contributes a considerable saving on heating bills. A welcomed benefit for a building of this size.
BBA approved, TLX Gold is a trusted product that guarantees quality. It has a lifespan of that of the roof in which it sits, giving peace of mind that it will serve the building for years to come.
Further case studies detailing the use of TLX Gold can be found HERE
