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February 11, 2015

Thermal Values within Tensile Fabric Structures

Thermal values within Tensile Fabric Structures have not historically caused architects or tensile engineers too many problems. However, with tensile fabric buildings becoming more and more popular due to their cost savings and the design freedom which they offer, such fabric structures are increasingly being used within architecture where Thermal Values are proving to be problematic.

Thermal Values, also known as U-Values, covered by Part L of the Design and Build Regulation had a massive upgrade in 2013; however, tweaks and upgrades are continuingly coming through………especially within commercial buildings where Tensile Fabric Structures are predominantly being used.

With commercial buildings roof U-Values currently being aimed at 0.2W/m2k, traditional Tensile Fabric Buildings are struggling to meet such ecological thermal values. A single membrane layer of PVC or PTFE/glass  weighing in at around 1200gm per meter square has a U-Value of approximately 4.4W/m2k. With this in mind we can quickly see that such a PVC or PTFE fabric membrane building offers a similar U-Value to that of glass. If we then add a second internal membrane layer, also known as a double skin and, create an air gap of 200mm, it will reduce the U-Value down to around 2.6W/m2k, without reducing the fabrics translucency benefits. But this still doesn’t help us achieve a thermal value or U-Value which Part L of the Design and Building Regulations can and does ask for on certain commercial buildings.

Use of Tensile Fabric Construction within Modern Architecture

With more and more architects wishing to push the boundaries of design, form and function within their craft, Tensile Fabric Architecture is increasingly being used to help realise the architect’s vision. And why shouldn’t it, after all membrane structures can last upwards of 30-years – Just as long as most traditional forms of roofing structure. Additionally, with advancements in fabric technology this longevity is set to increase significantly. Add this to the free flowing ‘clear span’ design function which only tensile engineering can offer and you soon see why Fabric Architecture is helping architects design the future.

A current and emerging trend we are seeing at Shade Sculpture is the amalgamation of traditional construction and tensile construction. This is allowing architects to develop some truly amazing, practical and cost efficient design solutions. However, this trend in design is highlighting the potential conflict with Fabric Architecture whilst achieving the ever lowering Thermal Values.

What Affects Thermal Values within Tensile Fabric Buildings?

We could write an entire book trying to answer this, what seems to be a relatively simple question; however, the best way of answering this is with another question………..what is the building to be used for?

For instance, if you want to have a tensile fabric structure to cover and protect goods or property, such as a Temporary Fabric Warehouse, U-Values don’t really come into it, unless you need to keep the goods at a certain temperature that is. However, if you add an office area or toilets within the tensile fabric building, it dramatically changes not only the Thermal Value / U-Value regulation requirements but also the planning regulations. A good example to demonstrate this on would be a fabric building such as a Tensile Fabric Sports Hall. If the Fabric Sports Hall contained nothing but Tennis, Badminton or Basketball courts etc., all you need to think about how to keep the temperature even throughout the year. Add ventilation together with a form of heating matrix and you’ve practically sorted this out with M&E (Mechanical and Electrical). However, add changing room facilities with showers and toilets and suddenly the structure is then deemed as a permanent building. In such instances your U-Value requirements would drop to that of around 0.2W/m2k which falls in line with the same U-Values / thermal values which are found with traditional permanent steel and brick forms of commercial buildings.

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How to Lower U-Values within Tensile Structures

One way is by suspending a quilted insulation layer such as Rockwool between the air gaps which have been created by adding an internal membrane. With such an approach you could potentially get U-Values down to meet practically any building regulation requirements. However, with this approach you would need to use an extremely dense insulation layer, resulting in the loss of natural lighting benefits which translucent tensile fabric buildings offer. Quilted insulation layers therefore only offer part of the solution to meet the ever lowering U-Values within modern Building Regulations.

At Shade Sculpture we have seen the need for Tensile Fabric Designs and engineering to evolve and meet this U-Value challenge head on. This is why we have been working on developing workable solutions to help our fabric buildings achieve and surpass the latest U-Value requirements.

A particular design and build project which we at Shade Sculpture have been working on, with such U-Value stipulations, is a sports hall in Lowestoft. Once built this project is set to see Shade Sculpture delivering the first Tensile Fabric Building in the UK to surpass 0.2W/m2k U-values for a roof. Although, we cannot provide specific details on how we have achieved this U-Value breakthrough, as it would provide our competition with our intellectual property, we can say that we have achieved this by utilising a thermal dynamic air flow and layer system, unique to us and us alone. Such advancements with U-Values within Tensile Architecture will soon see membrane buildings becoming one the most environmentally sound, and, economical forms of commercial building constructions around.

To find out more about U-Value changes and the challenges they pose within Tensile Buildings, please feel free to contact us on +44(0) 1249 848649 or email us at info@airsculpt.co.uk

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