Home Contractor's Corner Flexibility in design: the importance of compressive strength when specifying insulation

Flexibility in design: the importance of compressive strength when specifying insulation

by Jennie Ward

By Joan Ferrer, Technical Sales Manager at Ravago Building Solutions.

Joan Ferrer, Technical Sales Manager at Ravago Building Solutions.

Sustainability is a primary consideration in building design, and high-performance insulation has proved to be increasingly important in recent years, making an invaluable contribution to structures that have been hailed for their energy-efficient credentials, including the Stirling Prize winning Bloomberg Building in London. Minimising heat loss and reducing the use of heating and cooling systems through optimal thermal performance are primary drivers for sustainability. But an insulation material’s mechanical properties, especially its compressive strength, can also make a significant contribution to the circular economy.

Truly sustainable buildings are designed for longevity and this includes being able to serve different functions over their lifespan. Architects are increasingly expected to make sure that buildings can be easily repurposed without extensive structural works.

Designing commercial buildings that can be successfully adapted to ensure longevity requires making key choices at an early stage. Choosing insulation with high compressive strength, and therefore able to handle a variety of different loads over time, is a vital part of circularity. This is true of its use in both flooring and inverted roofs.

Variable loadings on floors
A self-evident function of a floor is to support the loads placed on it, but this must be true throughout the life of the building. With some types of building, loadings are easy to predict and unlikely to increase with time. With others, particularly with industrial buildings, change of occupancy or developments in production may require floor strengths to be increased from those originally considered adequate.

Any material will compress when a load is placed on it. The choice of insulation in the floor will need to take this into account and whether there will be static point loads, such as a rack of shelves in a warehouse, or dynamic loads, for example, forklifts and trucks working in a cold store.

Extruded polystyrene (XPS) offers different grades of compression strengths to suit the design and use of the building. Compressive strength – a measure of the reduction in thickness caused by a point load – and compressive creep – a measure of a long term load – are standard mechanical properties of the XPS which the manufacturer declares as part of the CE Marking under EN13164.

As an example, at B&M’s new 1 million sq ft distribution centre in Bedford, ISD Solutions, the cold store specialist contractor, used 760m3 of Ravatherm XPS X 300 SB in the creation of temperature-controlled zones for chilled and frozen stock. These boards combine low moisture uptake and exceptional thermal performance with the ability to withstand 130 kPa of permanent loadings over 50 years with only a 2% reduction in thickness, resulting in a product ideally suited for a range of applications with variable floor loadings, including cold stores.

Efficient use of roof space
An inverted roof can do a lot more than just shield the top storey of a building from the elements, and repairs to the deck and waterproofing are much easier than on a warm roof. Using insulation with high compressive strength, a roof is transformed into a versatile space that can be used for pedestrian terraces, car parking, hosting heavy plant equipment and green or blue roof systems. Provided a roof has the necessary structural strength from the outset, it can easily be retrofitted with additional equipment, for example, air conditioning equipment in response to ever warmer British summers.

In the Westfield Centre in West London, which in 2019 attracted 31 million visitors, new rooftop car parking facilities for its £1m extension project in 2017 was made possible thanks to XPS insulation with 500 kPa of compressive strength. More recently, an under-construction datacentre in Brent Cross for Pure Data Centres Group provides another example where heavy static weights would be in place over a long period due to the roof needing to host a large quantity of machinery to cool the server rooms.

Green and blue roofs build on the existing thermal benefit of an inverted roof while capturing carbon dioxide in plants and creating habitats for urban wildlife. For example, The Forge, award-winning development in Upton Park, used a mix of green and blue roof systems to overcome the challenge of its location in a Critical Drainage Area, meeting Newham Council’s strict attenuation and flow rate requirements. Green and blue roof systems are playing a vital role in supporting the sustainability agenda, but they increase roof loadings, meaning that once again compressive strength of the insulation comes into play.

Designing for tomorrow as well as today
When specifying insulation, we must consider potential future uses for a building and allow tolerances in design to account for the advent of new technologies. By choosing tried and trusted solutions that offer high compressive strength as well as exceptional thermal performance we can help meet sustainability objectives, helping to ensure a building has a long life thanks to flexibility of use inherent in its design.


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