Upgrading Roof Insulation in the Urban Landscape

06/09/2021

  • Different types of housing stock require different approaches to refurbishment
  • There may be instances where a change in roof height is not permitted
  • An insulating breather membrane can help reduce U-Values even further

tlx gold urban propertyEngland has a vast variety of buildings, old and new, with many different types of roof build ups to show for it. This makes for a beautifully varied building stock, however when it comes to upgrading the insulation of this landscape, there is no standard ‘one size fits all’ method of doing so, and therein lies the difficulty for builders and roofers alike... Furthermore, the tightening of building regulations over the past few decades has made it even harder to achieve U value requirements, especially in older buildings where shallow rafters are a typical feature, alongside restricted head height. Owing to this, a combination of traditional types of insulation such as mineral wool or PIR board is required alongside the use of a multifoil to satisfy building regulation requirements.

How TLX Gold multifoil insulation can be used:tlx gold roof height

Our two-in-one insulating breathable membrane is a versatile product which can be used in one of two ways, enabling you to make a judgement as to the best installation method suited for your project.

The draped solution: If you cannot raise the roofline, whether it be a listed building or a terraced property, then TLX Gold can be simply draped directly over the top of the rafters requiring no change in roof height. It’s ease of installation is particularly useful in older properties where irregular rafters would otherwise pose a challenge when it comes to adding insulation. A minimum 10mm unventilated air layer is required beneath TLX Gold, ideally 20mm, for the reflection of heat, therefore, the TLX Gold plus the air layer will occupy the top 50mm of rafter space. As a single layer, based on a 75mm rafter depth, it achieves a U value of 0.69w/m2k.

The counter-battened solution: If raising the roof is permitted, Gold can be pulled taut across the top of the rafters and counter-battened above to save on internal space, since it’s thickness will occupy less of the rafter space below it. Even if counter battening is necessary, because it will compress to only 3mm, the height increase is minimal. If the rafters are sufficiently deep, then PIR board can be fitted between them to achieve a U value as low as 0.13W/m2k.

This was the case for a rambling family home in the affluent Didsbury suburb of Manchester. When it was scheduled to be re roofed as part of the complete refurbishment of the property, the roofers were hesitant to use PIR board alone as they feared it would occupy too much space within the rafter and still not meet building regulations. TLX Gold was the obvious choice since it offered the greatest thermal performance without having to compromise on space.

tlx gold pulled taughtThe original rafters were only 75mm deep, however, there was sufficient head height to introduce insulation below the rafters, and it was also possible to raise the roof slightly by using Gold pulled taut with a 38mm counter batten. With 50mm of PIR between the rafters and 50mm below, this achieved the target U value of 0.18 W/m2K.

Compared with the use of PIR board only which would have achieved a U value of 0.23w/m2k in the same space, this solution gave an excellent thermal energy saving and enabled the construction to conform with building requirements with minimal disturbance to the structure of the roof. Additionally, since it is fully breathable, there is no risk of condensation.

In summary:

  • BBA Approved – TLX Gold holds a BBA Certification, a prestigious mark of quality
  • Ease of Installation – Simply rolled out over the top of the rafters, TLX Gold is lightweight and can be easily sealed with integrated tape on the overlap flap
  • Requires no change in roof height ­– When used draped over the top of the rafter, the original level of the roofline can be maintained.
  • No risk of Condensation – Even without the use of a vapour barrier, using TLX Gold poses no risk of condensation as it is fully breathable, allowing water vapour to pass through it.
  • LABC Registered Detail status – A range of pre-calculated solutions can be found in the Approved Solutions guide

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