Technical Refurbishment
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Improving thermal performance in retrofits 01
Read up on the legislation Approved Document L1B,
Conservation of fuel and power in existing dwellings, gives guidance on what reasonable provisions should be made to comply with energy efficiency requirements for existing dwellings, extensions, conversions and renovations.
Walltite CV 100 injection grade polyurethane foam insulation Crescent Primary School in Selhurst, Croydon
Guy Shackle, senior associate, Curl la Tourelle Architects
Selhurst Boys School is a listed 1913-built Edwardian grammar school that’s undergoing a £5.5m refurbishment to transform it into a modern three form entry primary school. Although Building Control only required
that 10% of the contract sum be spent on improvements to energy efficiency, we decided to aim significantly higher than that and bring it in line with performance levels expected in a new build. The combination of cavity wall
insulation, roof insulation and a complete window replacement are expected to reduce thermal heat loss through the external fabric to a U-value of 0.3W/m²K and help us achieve a BREEAM rating of “very good”. The external wall is an unusual early form of cavity wall with an outer leaf of brickwork tied to the inner leaf using brick stretchers, which can cause moisture bridging and is therefore unsuitable for most blown fibre insulation products.
Product news
THE REFURBISHED Kingsthorpe Grove Primary School in Northampton features automatic glass entrance doors fitted with Geze UK’s Slimdrive SL sliding automatic operators. The bi-parting doors are designed to reduce heat loss or gain and form an important part of architect Ellis Williams’ largely transparent design for the building. The door operators are just 7cm high and can be mounted almost invisibly to the glass.
www.geze.co.uk
42 | SEPTEMBER 2012 | CONSTRUCTION MANAGER
THE INTRICATE details of London’s Tower Bridge will be visible at night for the first time thanks to an LED lighting scheme provided by GE
Lighting. More than 2km of the firm’s
Tetra Contour LED lighting has been moulded around the bridge’s stone and metal work and 90W LED floodlights installed on and around the bridge. The lighting scheme was developed to enhance the aesthetics of the bridge and minimise energy use with controls fitted to allow the lighting to be changed to suit different occasions.
www.gelighting.com
A NEW SOLAR panel support has enabled photovoltaics to be installed on the lead roof of a Grade I-listed church near Chesterfield. The support “pods”, designed by the Lead Sheet
Association and fitted by heritage roofing specialist Martin-Brooks, are built with expansion gaps to allow the natural movement of the lead roof. The installation was completed in conjunction with Derby solar panel installer C-Changes and will enable the church to cut its energy bills and access higher rate feed-in tariffs.
www.leadsheetassociation.org.uk
Walltite was one of the few foams that would work in this application. For the thickness of material – a 3in filled cavity – Walltite has a very good thermal performance and low air permeability compared to other similar products and, in combination with new Velfac double-glazed windows, it will reduce noise transmitted from the school. Boosting the thermal performance of the walls also meant that during the design stage we could reduce the size and power of the radiators and boiler inside. An alternative to blown fibre insulation
would have been to line the external walls with insulated render, but this would have impacted the building’s listed status, and an internal layer of insulation and dry lining would have reduced the available floor area of classrooms, which were already close to the minimum size required for primary school teaching. Pumping foam insulation was beneficial
for the programme and main contractor Kier was able to insulate 3,000m2
of
wall in just two weeks. Post-installation, the foam will not shrink or settle over time, which is great from a building maintenance point of view.
heat transfer through a building product and are measured in watts per square metre per Kelvin or W/m²k. Certain values must be met to comply with the regulations, for instance 0.28W/m²k is required for walls, compared with 0.22W/m²k for floors.
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wall is likely to have a U-value of more than 2W/m²k and require significant improvements, whereas a 1970s house with a cavity wall and basic insulation could have a U-value of less than 1W/m²k and may not need a substantial thermal upgrade.
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economic way of upgrading a thermal element in renovations. Find out what insulation is already included in the wall or roof, in many cases a thermal element may require only a minor improvement.
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Above and beyond? The regulations are minimum
mandatory requirements, but further upgrades in insulation will improve energy efficiency and reduce heating demand. Selecting a thermal board with enhanced performance, such as GTEC Thermal K, provides superior thermal insulation improvement over standard plasterboards.
By Ali Arasteh, technical director at Lafarge Plasterboard. A toolkit on using plasterboard to improve thermal efficiency is available by contacting 01275 377589.
Think thermal Thermal plasterboards are an
Know your project A Victorian house with a solid brick
Understand your U-values U-values are a measure of the rate of
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