The completed project is currently undergoing a 2-year period of energy and environmental monitoring. The predicted CO₂ emissions after retrofit are 16kg/m²/yr – a reduction of 79% from the 1990 baseline for average UK social housing.

Without extending the house, the internal environment has been transformed by the creation of a ventilating lightwell within the existing loft space to provide fresh air, daylight, amenity space and a clothes drying area. Accessible temperate storage is provided in the residual loft.

Innovations include:

• Triple-glazed windows with ventilating panels and louvers for secure day and night ventilation;
• A new product developed by Penoyre & Prasad and the window manufacturer;
• A ‘breathing’ roof to dissipate moisture, using natural insulation products (wood fibre slab and hemp quilt) with an intelligent vapour control membrane;
• Vacuum insulation panels in the floor for high thermal performance with minimal (25mm) rise in floor level.

1. Existing masonry cavity wall with facing brickwork

2. Existing suspended concrete floor with screed finish

3. Existing brickwork parapet with concrete copings

4. Existing timber trussed rafters adapted

5. Timber beams inserted between party walls

6. Existing roof tiles retained to lower parts of roof

7. 90mm rigid PIR foam internal insulation to front wall

8. 120mm rigid phenolic foam external insulation to rear wall

9. Gypsum plasterboard on battens and vapour control layer

10. Silicone render finish to rear wall

11. 20mm vacuum insulation panels (VIPs) with cellular polyethylene foam sheet protection

12. Thin galvanised steel sheets as puncture protection to VIPs

13. Wood floating floor

14. 300mm hemp-flax quilt insulation to existing ceiling

15. 100mm rigid wood fibre insulation above rafters

16. 75+225mm hemp-flax quilt insulation between and below rafters

17. Intelligent vapour control layer with moisture vapour permeable lining

18. Existing roof tiles re-laid to area of raised roof

19. Triple glazed aluminium rooflight with automatically opening lights

20. Triple glazed composite wood aluminium windows with secure ventilator panels

21. Composite wood aluminium front door

22. Triple glazed composite wood aluminium rear door

23. Solar ventilating lightwell with mezzanine, space saver stair and clothes drying space

24. Loft storage space

25. Solar photovoltaic panels to front roof

26. Solar thermal panels to rear roof

27. Existing gas combi boiler fitted with flue gas heat recovery system

Elements not shown for clarity: Party walls with cavity fill insulation, insulated dry linings to party walls in mezzanine and loft spaces, solar thermal storage tank in roof.