Improving Thermal Performance While Preserving the Original Look
Pyramid Eco installed external wall insulation and replacement windows at a property in Watford in collaboration with Watford and Three Rivers.
The retrofit assessment found that many of the existing windows were single-glazed or had rotten sills, which would have stopped the insulation from sealing properly.
By replacing the windows at the same time, Pyramid Eco could bring them forward, reduce thermal bridging, and create a cleaner overall finish.
Project Snapshot:
Location: Watford, Hertfordshire
Property Type: Residential home
Client: Resident/homeowner
Purpose: Improve thermal performance, reduce heat loss, replace poor-condition windows, and preserve the original appearance
Solution: External wall insulation with window replacement
Funding: Warm Homes: Local Grant
Delivered under: Watford Borough Council and Three Rivers District Council scheme
The Challenge
The retrofit assessment identified external wall insulation as the right measure, but the windows also needed to be upgraded first.
Many were single-glazed or had rotten sills, which would have made it difficult to seal the insulation properly. Replacing them allowed Pyramid Eco to bring the windows forward, reduce thermal bridging, and improve the final finish.
The round front window also required careful detailing, as a standard overhang could not be formed around it. It had to be installed after the EWI was complete and pushed forward to achieve the correct result.
Why Pyramid Eco?
This project needed more than standard external wall insulation. It required joined-up retrofit planning, careful window detailing, and attention to the home’s original appearance. Pyramid Eco worked with Watford and Three Rivers to improve performance while preserving the property’s character.
Retrofit-Led Specification
The measures were selected following the retrofit assessment, ensuring the work was appropriate for the property and its condition.
Window Replacement and EWI Coordination
By replacing the windows alongside the external wall insulation, Pyramid Eco could improve the seal, reduce thermal bridging, and create a cleaner finish.
Preserving the Original Appearance
Watford and Three Rivers wanted the property to look as close to the original as possible. Pyramid Eco used brick slip detailing on the lower half of the property to replicate the previous brickwork, with render above.
Resident-Focused Delivery
The work was completed in just over two weeks with minimal disruption, helped by favourable weather and efficient project sequencing.
Related: Window Replacement Grants: How to Apply
Our Approach: Combining EWI, New Windows, and Brick Slip Detailing
Pyramid Eco installed external wall insulation and new windows to improve the home’s thermal envelope. To preserve the original look, the team used brick slips on the lower section and render above, matching the previous brick-and-render appearance. The windows were brought forward to reduce thermal bridging and help the EWI system seal more effectively.
System: External wall insulation
Additional Works: Window replacement
Finish: Brick slips to the lower section, render to the upper section
Timeline: Just over two weeks
Delivery Partner: Watford and Three Rivers
Key Detailing: Round front window, brick slip finish, window positioning
Related: External Wall Insulation Cost Guide
Overcoming Key Challenges
- Replacing Poor-Condition Windows
Most of the windows were single-glazed or had rotten sills. Replacing them was necessary to achieve a better seal and avoid undermining the performance of the external wall insulation.
- Reducing Thermal Bridging
The windows were brought forward as part of the work. This helped reduce thermal bridging and created a more effective thermal envelope.
- Round Window Detailing
The round front window required careful planning because the usual EWI overhang detail could not be applied in the same way. The window was installed after the EWI was complete and pushed forward to achieve the correct finish.
- Maintaining the Original Appearance
The property previously had a brick-look lower half and a rendered upper half. Pyramid Eco used brick slips to recreate the original look while avoiding altering the home’s visual character.
Results and Benefits
The project delivered a major visual improvement while improving the property’s thermal performance. Because the work was completed in summer, the resident will see the full impact of warmth and heat retention once the property has been through winter. However, the combination of new windows and external wall insulation is expected to make a significant difference.
Key Outcomes:
- External wall insulation installed
- Windows replaced to support a complete EWI seal
- Reduced thermal bridging through improved window positioning
- Brick slip detailing used to preserve the original appearance
- Round front window detail successfully managed
- Major visual improvement to the property
- Project completed in just over two weeks
- Minimal disruption to the resident.
Client Satisfaction
The resident was pleased with the finished appearance of the property. The work delivered a significant visual improvement while preserving the home’s original look.
The full efficiency and heat-saving benefits will become clearer after the property has been through winter, but the combination of external wall insulation and new windows is expected to provide a significant improvement.
Planning a Whole Home Retrofit?
External wall insulation works best when the surrounding details are right. If windows are single-glazed, poorly positioned, or affected by rotten sills, they may need to be upgraded as part of the same project.
Pyramid Eco coordinates insulation, window placement, and finishing details, such as brick slips and render, to improve performance while preserving the home’s character.
