Grade II listed Central London Eco Home


Prewett Bizley Architects

Contract Value

Circa £1.5M

Project Description

Prewett Bizley were seeking a contractor to completely refurbish and thermally upgrade this property. We were approached as we are one of very few London contractors with experience in Passivhaus construction and high-end finishes. When purchased, the building had been used as offices for many years; the client wanted to transform the 1820s grade II listed Georgian town house in Bloomsbury back into a cosy family home and upgrade its energy efficiency in line with the Passivhaus Enerphit standard. They also sought to add a 2 storey extension to the rear, creating more accommodation and an outdoor terrace.

Its years as an office building had left the house in a miserable state with numerous hastily thought out additions and modifications. We sought to faithfully restore and reconstruct this building, significantly improving its ability to retain and circulate heat around the house, maintaining an even comfortable temperature and fresh air throughout this 4,100 sq ft building. It now features MVHR to every room employing two Paul Focus units.

Details such as cornices, handrails and skirtings were painstakingly repaired or recreated as necessary. The windows were one of the most challenging elements of the build. In the majority of the building we had to keep existing single glazed sash windows, and we worked hard with Prewett Bizley to obtain planning permission to install vacuum glass secondary glazing. All shutterboxes had to be disassembled, a middle section built that could take the secondary glazing and then reassembled. This is a one-off project where this technique has been successfully used and this work was closely scrutinised by the local authority conservation officer who insisted that all shutterboxes retain functionality. We were pleased to meet the exacting standards of Islington planning authority and our clients.

We used a Lutron smart home system to automate lights, windows, blinds, ventilation systems, bathroom towel rails. Even though the entire system is quite complex, the client has a very simple interface that allows them to control many aspects of the building. We now design and install Loxone systems as they are more powerful and cost-effective.

A reduced heat demand following thermal upgrade allowed us to employ renewable technologies to eliminate gas from the building using Solar PV, Solar Thermal and an air source heat pump as the sources of heat for the building. Insulation materials employed included Spacetherm aerogel on the ground and 1st floor party walls, Pavadry wood fibre on upper floors, Icynene vapour open and closed expanding foam on all levels.

  • “We’re expecting a dramatic reduction in costs. We now know how much energy we’ve used (in March) and we rarely have the heating on compared to this time last year in our old house.”
    — Toni M
  • “Bow Tie was a pleasure to work with. I think we were very lucky to find them. They gave me a very high level of confidence that all technical aspects were within their control and they knew what they were doing. This was a technical project and it was important for us to be comfortable on those matters. At the other end of the scale, they paid just as much attention to all the niggly, small decorative matters that become very important towards the end of the build. They were impressive right across the range of skills you have to have to get a project like this done well."
    — Francis M
  • “The Grade II listing permission required a lot of flexibility in the building, planning and scheduling and real close cooperation between Prewett Bizley and Bow Tie and they managed it very well, putting in contingencies and safety nets in case planned windows were not approved. There was a flexible approach to managing a dynamic project. In the end we did achieve exactly what we wanted with secondary glazing as a result of Prewett Bizley and Bow Tie’s consistent and careful lobbying of Islington planning department until they agreed with what was proposed.”
    — Francis M

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