Axis wins new Pilot Retrofit contract with Cambridge City Council

Via the Greener Futures Partnership framework managed by Pretium, Cambridge City Council awarded Axis a Net Zero Retrofit Pilot Project contract for 45 houses and 4 flats on Ross Street and Coldhams Grove.

The works, which commence in May 2023 and are expected to last 40 weeks, include:

• Insulation measures: external wall insulation, rafter level insulation
• Replacement windows and external doors
• Replacement building services for heating, hot water and ventilation
• Photovoltaic panels

10 houses will receive external wall insulation under a separate SHDF funding stream.

Cambridge City Council aims to use the outcomes of the Net Zero Retrofit Pilot Project to inform retrofitting the housing stock at a larger scale, to significantly reduce energy use and carbon emissions.

The benefits to residents will be warmer, healthier homes that are energy efficient and economical to run.

About the properties

Ross Street and Coldhams Grove were developed in the 1930s as a mix of 2 storey semi-detached houses and two storey terraces, all of solid brick construction with pitched tiled roofs. Extensions to most houses were added in 1988 and have cavity masonry walls.

Surveys and modelling

EPC surveys show the majority of properties are in Band D, with two Cs and one E (for retrofit of social housing, the Government has set a target for all social homes to be minimum EPC C by 2030).

Energy modelling has been carried out in the Passivhaus Planning Package (PHPP) on five archetypes to show what level of performance can be achieved by the proposed measures.

Air tightness surveys show a range between 4.72 and 14.13 m3/m2/hr at 50 pascals, with a large number of properties at between 6 and 9 m3/m2/hr. CCC’s target is for all houses is to achieve an air tightness of below 2 m3/m2/hr, and in order to meet EnerPHit standards, the post-works airtightness test will need to be below 1 m3/m2/hr.