A Georgian townhouse is remodelled to meet the highest energy performance standards.

An historic Listed Georgian townhouse in London’s Bloomsbury has been renovated into a peaceful, comfortable and energy efficient home that adheres to Passivhaus EnerPHit standards.

This was attained by using state of the art insulation techniques including an innovative secondary glazing system from Selectaglaze that significantly improves the performance of the traditional, single glazed sash windows.

The client wanted a home with low energy usage and offered the most comfortable environment. Robert Prewett of Prewett Bizley architects took on the challenge of convincing conservation officers that a Grade II Listed building could be successfully fitted with a variety of energy saving measures whilst respecting all the historic features.

The large single glazed sash windows were a particular task to overcome as they represented a major proportion of the wall area and could not be replaced. Secondary glazing was the solution; but the exceedingly high levels of insulation necessary, the aesthetics and the need for working shutters in particular rooms called for a bespoke solution.

Robert approached Selectaglaze and initially suggested a totally new design but coincidentally the company was both developing a new sash window design and trialling Pilkington’s Spacia thin vacuum units which have a centre pane U-value of 1.0. The resulting Series 25 window proved perfect for the project due to its high sealing efficiency, a very low U-value and a discreet frame with a specially developed slide catch that allowed shutters to fully close. Today, the house has air tightness close to 1 air change per hour at test pressure which demonstrates that the secondary glazing is performing very well.

The complications of the project and the time taken to receive consents meant that part of the building had to be occupied before the secondary glazing was fitted. As a result, the owner experienced the change in comfort levels offered by the original window and with the secondary glazing in place. There was a remarkable change and what was also apparent was the almost complete removal of road noise. This was not initially perceived as a major issue but the absence of noise positively added to the comfort. 

Monitoring tests will now measure the efficiency of the scheme overtime but meanwhile there has been a transformation that delivers a modern comfortable home setting within an historic building. 

With a successful history spanning over 50 years and a Royal Warrant Holder since 2004, Selectaglaze is the leading specialist in secondary glazing.