Private Client - Harpenden

Deep retrofit of a 1960s detached house in Harpenden and the addition of a small rear extension.

This project is certified as meeting the EnerPHit Plus (Passivhaus) retrofit criteria, the third such project in the UK, and is 'gas free', using an air source heat pump and harnessing renewable energy with an entire roof pitch dedicated to solar pv. 

The existing brickwork walls were externally insulated using wood fibreboard and finished with a painted render and the curtain walls were removed and replaced with new highly insulated timber I beam walls with cellulose insulation and clad in larch. The rear single storey extension was also constructed in this way and finished with either render or timber cladding. The existing ground floor was removed and replaced with a new highly insulated slab with underfloor heating. 

Project Team

Contactor: Jigsaw Design and Construction

Thermal Bridge Consultant: Heatflux

Certifier: Mead Consulting

Lighting Design: Focalglow

Photography: Matthew Smith Architectural Photography


Project article in The Times

Project listing in Passive House Database 

Project listing in Low Energy Building Database

Project in 'The Planner'