|  Tel: 020 3475 8049

Member Login

Energy efficiency with steel window style

Dating from the 1930s, One Southampton Street has been refurbished to provide eight floors of flexible open plan office space that average 3,400 ft² and offer superb natural light thanks to some 120 new steel windows installed on three sides. The windows replace the building’s original windows and were manufactured and fitted by Steel Window Association member West Leigh to meet the latest standards of energy efficiency.


One Southampton Street stands in the Strand Conservation Area alongside London’s Covent Garden and has been developed by Aviva Investors. The 1930s marginal pane steel section windows were single glazed and it was necessary for the replacements to closely replicate these to meet planning conditions laid down by Westminster City Council.


West Leigh went to site and surveyed every window opening to ensure each new window would exactly fit within the stone facade. The original profiles were then matched using W20 rolled steel sections and the windows were manufactured to the existing layout with most windows having two openers and two fixed panes. W20 sections offer narrow sightlines and allow hinged casements to be hung at top, bottom or side, and swing windows to pivot horizontally or vertically. The new windows have a factory applied, white polyester powder coat finish.

The building has recently received BREEAM Excellent certification, the highest ever rating for an office refurbishment. To meet the Part L requirements for energy efficiency, the new windows were fitted with 16mm double glazed, krypton gas filled, toughened units giving a U-value of 1.2 W/m2K. This was based on a centre pane measurement as a concession to the planning requirements. After much consideration, it was decided that, rather that forming them separately, the marginal panes would be created using glazing beads applied to the glass, as this helped gain the required U-value and provided a reduction in overall cost.