Location: 240 Regent Street, London, W1
Client: Bovis Lend Lease
Value: £ 1.2M
Carried out: September 2007 to September 2008
We replaced and upgraded the failed Universal Section 1930s, un-galvanised steel windows with new high-performance replicas from the W40 range - galvanised and powder coated, acoustically and thermally insulated steel windows - on this grade II listed building.
The transformation of the former Dickens & Jones store on London's famous Regent Street has included a £1 million plus contract carried out by Steel Window Service & Supplies (SWS) for the replacement of the original universal section windows.
The combination of traffic pollution and exposure to the elements over many decades had caused the old windows to corrode badly, while the design team for the project was also seeking to greatly improve the future physical performance. Although the use of cold formed box section frames was considered at tender stage, the W40 system was selected on the basis of its slimmer sight lines, strength and the ease with which it meets part L of the building regulations. Acoustic performance was another key consideration and SWS subsequently carried out laboratory tests to determine the sound reduction properties of different glazing arrangements.
The window package manager for Bovis Lend Lease, Melanie King, comments: "These old style windows would not normally be required to achieve such high acoustic performance, but the project architects made the specification because of the commercial office use which the upper floors of the building will be put to.
"The test results on the windows showed that they achieved a good pass throughout the range except for one of the higher frequencies. There has been a huge amount of documentation passing back and forth between the architects [Rolfe Judd], the window manufacturer and acoustic consultants, but everything seems to have been resolved successfully."
Darren Joyce of Steel Window Service & Supplies recounts: "This has been a technically very demanding project as well as a very interesting one, where we have had to work closely with the architects and, in particular, the acoustic consultants Alan Saunders Associates - as well as our client, Bovis Lend Lease with whom we worked on other recent contracts such as the BBC buildings at Western House and Old Broadcasting House.
"In line with the growing trend in high specification schemes, there was a set of some 30 different decibel reductions to be achieved across the audible frequency range with differing performance levels for individual building areas. This included Octave Band Centre Frequencies for the whole window system of between 15-21 dB at 125 Hz rising to a maximum of 32 dB at 1 KHz. A further performance requirement for the project was that almost all the windows have been designed to be openable to allow smoke ventilation."
Interestingly, while the use of concealed multi-point locking mechanisms was used on all the opening frames to offer the best possible weathering performance and deterrent against forced entry, the contract also included the specification of 'Fireman's Axe' locks to provide for emergency escape situations.
The original window sections used were of the Medium and Heavy Universal type making the modern W40 system an ideal alternative offering a similar sightline. By employing soft-coat low emissivity glass and Argon gas filling enables the new windows to meet current requirements of Part L to the Building Regulations. The units are 26.8mm thick incorporating an 8.8mm acoustic laminate as well as a 4mm thick sheet of toughened glass.
Some windows were in excess of two metres high and their safe installation was governed by the main contractor's stringent health and safety guidelines set out in its Incident and injury free (IIF) site working policy.