Case Studies

Retrofitting existing buildings is a proven option to reduce energy demand, combat
carbon emissions, and optimize savings in the longer term. Three in-depth case studies across this section explain the revolutionary potential of well‐designed energy efficiency schemes. Every example records accurate data on pre- and post‐retrofit conditions regarding energy bills, comfort levels, and carbon outputs and includes visual links to pre- and post‐photos.

After:

Before And After Visuals:

Terraced Flat, Queen’s Park

Featured Case Study

This case study is about a one-bedroom terraced flat in Queen’s Park that Westminster City Council retrofitted as a pilot project in collaboration with Morgan Sindall Property Services (Westminster City Council and Morgan Sindall Property Services, 2023, pp. 3–5). The flat, which was built in 1890, originally had expensive energy bills (approximately £1,400 per year), a cold and draughty interior, and 2.5 tonnes of carbon emissions; its Energy Performance Certificate (EPC) rating was D.

A four-week £40,000 whole house ‘whole home’ retrofit was undertaken.

Interventions comprised:

Wall Insulation: To reduce heat loss, internal wall insulation was installed using a SWIP system with 100 mm insulated studs and moisture-proof plasterboard. (Retrofit Case Study: Terraced Flat, Queen’s Park, 2023, pp. 11–13): Costs: Approximately £9,000; Savings on energy bills: £269 per annum; Carbon savings: 612 kg per annum.
Floor Insulation: Suspended floor filled with 100 mm Rockwool Flex, significantly reducing heat loss through the ground (Retrofit Case Study: Terraced Flat, Queen’s Park, 2023, p. 12).
Smart Air Bricks & Ventilation: The installation of bright air bricks—with integral humidity and temperature sensors—and improved ventilation systems also helped maintain indoor air quality while reducing heat loss (Retrofit Case Study: Terraced Flat, Queen’s Park, 2023, p. 13).

Secondary glazing was fitted to the living room and bedroom to preserve the historic appearance while improving thermal efficiency. A GRP composite door replaced the back door to eliminate draughts (Retrofit Case Study: Terraced Flat, Queen’s Park, 2023, pp. 15–17).
Figures: Cost: approximately £5,000; Energy bill savings: £102 a year; Carbon savings: 232 kg a year.

The old gas boiler was replaced by an air source heat pump, a new hot water cylinder, new radiators, heat controls, and a waste water heat recovery unit installed underneath the bath. This offered a lower-capacity, more efficient heating system (Westminster City Council and Morgan Sindall Property Services, 2023, pp. 19–21).
Figures: Cost: approximately £13,000 (after receiving a £5,000 Boiler Upgrade Scheme grant); Energy bill savings: £55 per year; Carbon savings: 851 kg per year Retrofit Case Study: Terraced Flat, Queen’s Park, 2023 pp. 8).

Eight Canadian Sola Mono 405W solar panels and a 5 kW Huawei battery storage system were installed on the roof to reduce reliance on grid electricity to near zero (Retrofit Case Study: Terraced Flat, Queen’s Park, 2023, pp. 24–25).
Statistics: Cost: approximately £8,000; Energy bill savings: £1,058 per year; Carbon savings: 802 kg per year (Retrofit Case Study: Terraced Flat, Queen’s Park, 2023 pp. 24)

Since retrofitting, the flat has an EPC rating of B. Energy modelling indicates that annual energy bills are literally ‘near zero’, the interior is warm and cozy, and carbon emissions have reduced to nearly 0 tonnes. The project additionally acted as an open house over the summer of 2022, bringing in more than 300 attendees—council tenants, owner-occupiers, landlords, and housing officers—and receiving the ‘Best Net Zero Carbon Initiative’ award during the 2023 National Housing Maintenance Awards (Westminster City Council and Morgan Sindall Property Services, 2023, p. 27; National Housing Maintenance Awards, 2023)

“

“It was enormously helpful. In 10 minutes, I could see and understand the improvements and the technology, which would have taken me several hours of research on the internet.”.

Susan, Little Venice, resident (Retrofit Case Study: Terraced Flat, Queen’s Park, 2023, pp. 24).

Visuals

Victorian Terrace Retrofit, London

Featured Case Study

This project involves a refurbishment of an existing Victorian-period terrace in inner London, battling the same high energy consumption, cold spots, and energy-thirsty single-glazed
windows—with an initial EPC rating of D and costly heating in winter months.

Install high-performance double glazing to minimize thermal losses.
The installation of thick internal insulation to external walls and ceilings reduces overall heat loss by more than 40% (figures following UK standards according to Gov.uk and the Energy Savings Trust, n.d. pp. 5).

Remove the gas boiler and install a hybrid electric heat pump system that delivers three times the heat energy it needs for its electricity input.
Smart thermostats and efficient radiators were incorporated to optimize heating cycles and reduce energy wastage.

Solar photovoltaic panel installation and battery storage system, akin to the Queen’s Park project, to minimize grid dependency.

Upon retrofit, audits indicate:
• Lowers yearly energy costs by over 35%.

• A shift from cold and drafty to an ever-present warm indoor comfort.
• A carbon output reduction of nearly 2 tonnes, the EPC rating improved to B or higher (Westminster City Council and Morgan Sindall Property Services, 2023)

Conclusion

Together, these two case studies—from Queen’s Park residential terraced flat to a Victorian
terrace in the centre of London—demonstrate that an integrated retrofit approach can transform
the most diverse building types into highly sustainable homes from inefficient ones. Detailed
analysis and before/after infographics confirm these gains by:

Reduced Energy Bills: Comparison charts of energy expenses before and after retrofitting
show considerable savings.
Reduced Carbon Emissions: Graphs display substantial CO₂ reductions—from initial
levels as high as 2.5 tonnes in some cases to near zero.
Enhanced Comfort: Heat maps and comfort indices illustrate graphically the enhanced
indoor climate.

These findings satisfy UK-based sustainability requirements and are supported by evidence
from reliable sources such as Gov.uk and the Energy Savings Trust. As retrofitting programs
evolve and additional empirical evidence is collected, these case studies will continue to serve as
viable templates for sustainable development in the built environment.

References:

Architects’ Journal. (2024) Collective Works completes deep retrofit of north London terrace
house. [online] Available at: https://www.architectsjournal.co.uk/buildings/collective-
works-completes-deep-retrofit-of-north-london-terrace-house [Accessed 9 Apr. 2025].
Energy Savings Trust (n.d.) Home Energy Saving Measures. Energy Savings Trust. Available at:
https://energysavingtrust.org.uk (Accessed: 27 April 2025).
Gov.uk (n.d.) Energy Efficiency in Housing. Gov.uk. Available at: https://www.gov.uk/energy-
efficiency-housing (Accessed: 27 April 2025).
Inigo. (n.d.) A built history of the Victorian terraced house. [online] Available at: https://www.inigo.com/almanac/built-history-victorian-terraced-house [Accessed 9 Apr. 2025].
National Housing Maintenance Awards Judges (2023) National Housing Maintenance Awards. [Award speech/feedback]. 2023.
Retrofit case study: Queen’s Park. Retrieved from https://www.turnerandtownsend.com
Westminster City Council and Morgan Sindall Property Services (2023) Retrofit Case Study:
Terraced Flat, Queen’s Park. April 2023. [PDF] Unpublished internal report, Westminster
City Council. pp. 3–27. (Accessed: 27 April 2025).