Forest of Dean retrofit





Passivhaus consultancy, Retrofit, Triple glazed windows
About This Project

A retrofit project adding in low energy products and practices by upgrading materials in the property and extending to give extra room for the clients.


The house was stripped back to a bare shell. All details and elements were modelled to comply with the Passivhaus renovation standard EnerPHit (not certified).


The floor was excavated to allow for floor insulation before internal stud-work could be rebuilt featuring internal wall insulation and an internal wrap of airtight membrane to stop those unwanted draughts associated with old cottages.
A blower door test (air-tightness test) was carried out near the end of the project with an outstanding 0.89ach achieved on such a tiny house… the equivalent of a 50mm square hole/leak path in the entire building. Building regulations requirements would have accepted a 450mm square hole in this building!


With electricity bills of £50 a month (including heating and hot water usage from Air Source Heat Pump) and a renewable heating incentive payment of £65 per month this house was not only comfortable but kind on the wallet also.


The clients were shocked that after 10 months of occupancy neither fell ill or experienced common colds during that time and are adamant this was due to the constant fresh air from the ventilation system. CO2, temperature and humidity levels were monitored during the same period which provided data of utmost levels of comfort and a healthy living environment.
We supplied and fitted our low energy triple glazed windows which made the adjacent road noise a distant memory.

Key features:


– Air source heat pump

– High performance triple glazed timber windows

– Mechanical ventilation system