As Secondary Glazing does not involve a change to the external window it is not governed by “Part L” of the Building Regulations. It does, however, provide significant levels of thermal insulation (estimated U-value 2.8 – BS 6262-2:2005, table 9) and allows buildings, particularly listed or within conservation areas, to enhance thermal insulation levels. And, of course, English Heritage and conservation officers prefer the use of sympathetically designed secondary glazing to replacement windows.

With the rapid rise in energy costs, many clients and their specialist advisors are now demanding greater energy efficiency and closer adherence to Part L standards.

In order to meet this challenge, Selectaglaze Ltd., the country’s leading specialist in the design, manufacture and installation of secondary glazing systems, has worked with a number of key clients to develop a range of secondary units which will accommodate Part L compliant sealed units with measured U-values – thus combining the acoustic benefits of secondary glazing with the sealed units’ higher insulation properties.

One of the first uses of this development is at the Department of Biochemistry at Cambridge University. The Department’s laboratory occupies the first floor of the neo-classical Hopkins Building and, as part of the refurbishment, the control of solar heat gain was high on the list of priorities. The nature of the building precluded the replacement of primary windows, so the preferred solution was a double glazed secondary glazing system.

Working closely with architects RH Partnership and main contractors Bluestone plc, Royal Warrant holder Selectaglaze Ltd developed an extended capacity beading system to accept a 24mm sealed unit within their proved Series 40 hinged casement units.

In order to control heat loss and solar gain, sealed double glazed units comprising 4mm clear toughened planitherm (high insulation glass) and 4mm clear toughened safety glass was used in the secondary glazing. 25mm slat Venetian blinds were then sited in the cavity, remotely operated by control knobs mounted in the perimeter frame. The result was high thermal insulation together with effective solar control.

The benefits of Selectaglaze’s secondary glazing systems are not only in energy efficiency. The range offers high levels of acoustic insulation and the company has recently developed a suite of Security units providing protection against bomb blast, ballistic and physical attack. The systems are purpose made and appropriate for staged refurbishment or upgrade plans. The production process is also suited to small runs and installation causes very little disruption to the building or its occupants. Secondary windows are constructed from aluminium sections with permanent paint or anodised finishes to complement the interior decor. A range of operating styles including fixed, hinged, vertical and horizontal sliding, together with the ability to shape and curve selected frames, allows almost any window to be sympathetically treated.

Selectaglaze can be contacted on 01727 837271/email:

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