Beattie Passive Project
email       01953 687332

TCosyTM Retrofit for Great Yarmouth Borough Council

Project Outline

Location: King Street, Great Yarmouth

Client: Great Yarmouth Council

Project Description: The King Street retrofit in Great Yarmouth was undertaken on a block of six flats owned by Great Yarmouth Borough Council. This block was chosen for the project due to its traditional 1950s style, a common typology across the UK, and thus any solutions to the challenges presented by this R&D project will be able to be rolled out across the country more widely.

For this retrofit we have developed and trialled a new bracketed system that we believe is a fast, efficient, and cost-effective solution to deep retrofit that can be adapted to suit any of the UK’s mixed typology of housing. The results have been excellent, and the system’s versatility has been proven.

New triple-glazed windows have been installed within the cladding system, along with an individual Mechanical Ventilation with Heat Recovery (MVHR) system for each flat, to maximise the benefit of the retrofit with regards to achieving target CO2 and energy bill reductions. The aim is to reach the Passivhaus retrofit standard (EnerPHit), meeting a space heating demand of 25 kWh/m2 and an airtightness of less than 1 ach-1 @50Pa.

The main challenges we faced:

  • The retrofit was carried out on terrace style flats, therefore the way that the newly retrofitted structure interacted with the neighbouring properties required further innovation
  • How to deal with the existing balconies on each flat – and whether our system can incorporate them into the new design, or if they would have to be removed
  • We wanted the design to be aesthetically outstanding, to showcase our vision for the future of housing in Great Yarmouth.

We implemented a number of new innovations to ensure the success of the retrofit, including:

  • GRP brackets and aluminium angles were used to create a frame upon the existing building. The GRP brackets prevent a thermal bridge from the aluminium angle back to the existing building. A fireproof board is fixed to the frame to form a cavity, into which high performance insulation was injected, forming a continuous layer of insulation around the building. The project’s airtightness strategy involved, at one point, the whole building being sprayed purple, using airtightness paint Purple Passive.
  • We located the six MVHR units within the roof space, with ducting running down to each flat inside the wall cavity.

Over the lifetime of the new building, we expect a 75% reduction in heating demand and subsequently energy bills for residents. We will be working with Oxford Brookes University to monitor energy use and air quality in the building for the next year.

Project Benefits:

  • Lifting tenants out of fuel poverty - Expected 75% reduction in space heating requirements
  • Expected air-tightness result of less than 1 ach-1 @50Pa
  • Limited Disturbance to residents – Residents remained at home for the duration of the retrofit
  • Healthier, more comfortable homes – individual MVHR system for each flat providing filtered, fresher air
  • A new look home – completely new, modernized external façade
  • Enhanced fire safety – Non-combustible materials, horizontal and vertical fire barriers between floors, all services are fitted with fire collars and extra fire safety around windows and doors.

Technical Specification:

Wall U value: 0.11 W/m2k

Roof U value: 0.11 W/m2k

Perimeter Floor U value: 0.12 W/m2k

Air Tightness: Below 1/hm2@50pa

Project Team:

The Retrofit Research Project was a collaboration between Beattie Passive, Oxford Brookes University and Enhabit under the BEIS Thermal Efficiency Fund.

Great Yarmouth Retrofit
Great Yarmouth Retrofit
Great Yarmouth Retrofit
Great Yarmouth Retrofit

Tenant Feedback

“I haven’t had to use my heating all year. I’ve even had my energy provider call me up to enquire why my energy use is so low.” – Paul, King Street Resident

“I used to have mould and condensation in my living room, kitchen and bedroom, but now that’s all gone. I don’t have to use the heating very much now either, and when I do its only for an hour or so.” – Lina, King Street Resident

“I used to get condensation on my windows, so much that I had to use a dehumidifier, but since the retrofit I’ve been able to put that away as it doesn’t happen anymore. It’s also much warmer in the flat.” – Mrs Mitchell, King Street Resident

To find out more about the time, cost and environmental benefits of the Beattie Passive Build System, contact us via email, telephone 01953 687332 or visit



The UK’s first certified Passivhaus build system. Visit to find out more.


AECBLABCPassivhaus TrustIPHA