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 had a lot of people stay over Christmas, some quite elderly, who were concerned about being in a big old house in Winter and being cold and we received a lot of complements on the comfort and easy warmth. There is no higher accolade than complements on your house from your mother-in-law!”

    – Toni M
  • “My projects with Bow Tie are the only ones where I’ve left the contractor to follow my airtightness details and the projects have passed the 1st airtightness test.”

    – Justin Bere
  • “Your guys did a very good job on the [window] installation, nice and precise and the assemblies fitted perfectly….Very good silicon application too, with a nice 5mm joint. So please do thank them on behalf of Cristina and myself. We are very pleased.”

    – Stephen M
  • “I was delighted with Bow Tie Construction and have recommended them to several friends and neighbours.”

    – Toni M
  • “It quickly became clear that Bow Tie want to do a good job, they want their work to be to a high standard, no problem is too small to discuss and identify solutions, they really want to get it right.”

    – Francis M

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