Green Building Store is now 21°

Huddersfield low energy retrofit

Architect Ron Berry has undertaken a thorough low energy retrofit of his 1930s Huddersfield bungalow. The home was gutted internally and an extensive refurbishment was undertaken.  A kitchen extension was added to the back of the house and a large glazed entrance area added at the front of the house to create space for a new staircase which enabled bedrooms to be inserted into the pitched roof space.

All the windows were replaced with PERFORMANCE triple glazed timber windows and doors. The house is finished with a white render with cedar boarding used on the extensions. The windows are painted externally a slate grey colour (RAL 7024) and internally white (RAL 9016).

Insulation and airtightness strategy

Ron wanted to make the house as energy efficient as possible within the budgetary and physical constraints of the house. The insulation and airtightness measures at the property included:

  • 120mm EWI insulation (as much as could be added within the depth of the existing eaves of the roof) with 20mm render finish on the external cavity wall
  • 75mm XPS insulation + 28mm Gutex Topboard with Intello Super intelligent vapour control layer and airtightness tapes to the inside of the warm roof
  • 150mm XPS insulation on the external face of single leaf blockwork extension wall. 200mm EPS insulation on the extension roofs and beneath the concrete floor slab
  • 50mm insulation plus intelligent vapour control layer on suspended timber floor with airtightness tapes around the perimeter
  • Triple glazed timber windows and doors, with additional insulated frame
  • Triple glazed rooflights incorporating insulated collar surround.
Triple glazed timber windows and doors

21° supplied PERFORMANCE triple glazed timber windows (with additional insulated frame) with fixed and tilt & turn windows , inward opening front door and outward opening French doors at the rear. Airtightness tapes were applied around each frame.

21° also installed the windows and helped with detailing to ensure optimal performance. The windows and French doors supplied to the Kitchen extension were fitted in plywood boxes to enable the windows to be installed within the insulation zone outside the line of the blockwork wall. The windows supplied to the existing house were also fitted in line with the external insulation layer outside the face of existing cavity wall, with the external wall insulation overlapping the frames.

An architect friend recommended 21° to us. Initially we weren’t sure whether to go for triple glazed windows. As with the rest of the project, we wanted to go as far as we could afford with incorporating energy efficient measures. We’re absolutely delighted with the PERFORMANCE triple glazed timber windows and doors. They are a very high quality product. In addition to the excellent energy performance they also provide very good sound insulation. We’ve been really pleased with the service from Green Building Store. They provided technical support during detail development, installation was carried out very professionally and post contract service has been great – everything went really smoothly throughout.

Ron Berry

Project details


December 2015

Case study

August 2017

Life changing homes