Selectaglaze: North London Collegiate School

  • 29 Feb 2024

Two Grade II Listed heritage buildings in the London Borough of Harrow have been home to the prestigious North London Collegiate School since 1929. To meet its ambitious sustainability targets (and create a warmer, more restful environment to improve its 800 students’ wellbeing) the school decided to invest in Selectaglaze glazing solutions.

This old mansion house features a collection of stylish arched frames and a Georgian Palladian window, some measuring up to three metres high. While stunning, they were anything but energy efficient. Due to age, the framework of the leaded windowpanes had revealed draughty gaps where heat could escape. A sympathetic glazing solution was necessary, but it needed to preserve the building’s architectural beauty and heritage. 


Lessons learned 

NLCS’s initial plan was to replace the original ornate windows and doors with double glazed versions. However, Heritage England ruled that this would not preserve the building’s heritage and recommended secondary glazing. It was time for Selectaglaze to go back to school… 

Tough tests 

Before NLCS committed to a complete retrofit, the school decided to test out secondary glazing’s thermal insulation qualities and aesthetics. Seventeen windows were chosen, and Heritage England agreed to re-inspect the school once work had finished.

Dave Harris, Estates Manager, comments: “Selectaglaze were very professional from beginning to end. We had some tricky windows to deal with, but their technical input and experience was extremely valuable. The programming and installation worked really well with Selectaglaze fitting during the school breaks minimising any impact on the operation of the School.

“All the products were manufactured bespoke providing a really neat and pleasing installation and they look great. We are delighted with the final installation and are already experiencing the thermal benefits we wanted.  Overall, a great company to work with.”

Outstanding results 

Selectaglaze selected toughened low e-glass to improve heat retention. Combined with the secondary glazing’s excellent sealing qualities, this would stop heat escaping and reduce energy consumption (and bills). Slimline horizontal sliding (Series 10) and side-hung casements (Series 41 & 45) were chosen so they could be opened for ventilation, cleaning and maintenance. Finally, slimline fixed light curved frames (Series 46) were installed for the lunette arch windows. All of this effortlessly complemented the striking exterior features, thanks to jet black (RAL colour 9005) semi-gloss specified on the aluminium frames. 

Conserving energy, preserving heritage 

After a successful inspection by Heritage England, the school felt that the secondary glazing made the environment significantly warmer and quieter. So, having passed the test, a further 99 units were installed, each custom made to match the numerous window shapes and sizes. For the traditional curved windows, slimline fixed lights (Series 46) neatly covered full circle formations. 

Heavy-duty hinged casement systems (Series 41), coupled with horizontal sliding units (Series 10), filled the openings of tall, curved head casements and provided an aesthetically sympathetic treatment of these large windows. In the classrooms and faculty rooms, discrete slimline 2 pane horizontal sliding units (Series 10matched the traditional steel casement windows. 

Sympathetic solutions, enhanced comfort, greater energy efficiency. All in all, an excellent school report. 


Alban Park,
Hatfield Road,
St. Albans,

Phone: 01727 837271
Fax: 01727 844053

Visit Selectaglaze's website

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