Porter Robson was appointed to extend, remodel and environmentally upgrade an existing home in Lee-on-the-Solent, using the refurbishment as an opportunity to address the building’s energy performance as a complete system rather than through a series of isolated improvements.

The existing dwelling has an E-rated EPC, and the project has been developed around a whole-house low-energy strategy intended to create a home that is more comfortable, healthy, durable and substantially less energy intensive. The approach follows a clear hierarchy: reduce heat loss, control air leakage, provide effective ventilation, manage moisture and thermal bridging, address summer comfort, then size the heating and renewable-energy systems to the reduced demand.

A significant upgrade to the thermal envelope forms the foundation of the design. The strategy includes external wall insulation, improved roof performance, upgraded floors where appropriate and high-performance replacement windows and doors, with particular attention given to continuity of insulation around openings, floor edges, eaves and roof junctions. The project performance brief targets external walls at approximately 0.18 W/m²K, roof performance of 0.15 W/m²K or better, and whole-window performance of Uw ≤1.0 W/m²K.

Airtightness is treated as equally important as insulation. A continuous air barrier around the heated envelope and identify the critical junctions where new and existing construction meet. The project is being designed towards q50 ≤2.5 m³/(h·m²), with 3.0 m³/(h·m²) set as the maximum completed-building target. At this level of airtightness, ventilation becomes a deliberately designed part of the building rather than something left to uncontrolled infiltration.

A whole-house mechanical ventilation with heat recovery system is therefore integrated into the proposals, providing continuous fresh air while recovering heat from extract air. The system is coordinated with the building layout and roof space alongside the hot-water equipment and photovoltaic systems.

Heating is also being reconsidered as part of the retrofit rather than simply replacing the existing boiler. An air-source heat pump is proposed, with the system to be sized from room-by-room heat-loss calculations and designed around low heating-water temperatures. The strategy targets approximately 45°C flow temperatures where practicable, improving heat-pump efficiency and ensuring that emitters, distribution and fabric performance work together as one system.

Renewable energy is incorporated after demand reduction rather than used to compensate for a poorly performing envelope. Integrated photovoltaic panels are positioned within the principal roof plane, supporting the transition to an electrically heated home while maintaining a clean architectural composition.
Summer comfort has also been considered as part of the low-energy brief. The strategy prioritises controlling solar gain, external shading where required, practical purge ventilation and MVHR summer bypass before introducing active cooling. This ensures that the measures used to retain warmth in winter do not inadvertently create overheating during warmer months.

Architecturally, the refurbishment gives the house a clearer contemporary identity. White render is combined with vertically expressed dark-grey cladding, dark aluminium windows and doors, and a restrained palette of grey roof finishes. The front elevation is simplified and strengthened through a new entrance composition and cladding treatment, while the wider remodelling reorganises the house around a more practical kitchen and dining space, lounge, study, utility accommodation and improved bedroom arrangement.

Leamington House demonstrates how architectural refurbishment and energy retrofit can be developed together. Rather than treating sustainability as an additional layer of technology, insulation, airtightness, ventilation, heating, solar control and renewable generation are coordinated as part of the architecture itself, creating a more resilient and comfortable home with substantially reduced energy demand.

10 Leamington Cr

Client:

Private

Year:

2026

Porter Robson was appointed to extend, remodel and environmentally upgrade an existing home in Lee-on-the-Solent, using the refurbishment as an opportunity to address the building’s energy performance as a complete system rather than through a series of isolated improvements.

The existing dwelling has an E-rated EPC, and the project has been developed around a whole-house low-energy strategy intended to create a home that is more comfortable, healthy, durable and substantially less energy intensive. The approach follows a clear hierarchy: reduce heat loss, control air leakage, provide effective ventilation, manage moisture and thermal bridging, address summer comfort, then size the heating and renewable-energy systems to the reduced demand.

A significant upgrade to the thermal envelope forms the foundation of the design. The strategy includes external wall insulation, improved roof performance, upgraded floors where appropriate and high-performance replacement windows and doors, with particular attention given to continuity of insulation around openings, floor edges, eaves and roof junctions. The project performance brief targets external walls at approximately 0.18 W/m²K, roof performance of 0.15 W/m²K or better, and whole-window performance of Uw ≤1.0 W/m²K.

Airtightness is treated as equally important as insulation. A continuous air barrier around the heated envelope and identify the critical junctions where new and existing construction meet. The project is being designed towards q50 ≤2.5 m³/(h·m²), with 3.0 m³/(h·m²) set as the maximum completed-building target. At this level of airtightness, ventilation becomes a deliberately designed part of the building rather than something left to uncontrolled infiltration.

A whole-house mechanical ventilation with heat recovery system is therefore integrated into the proposals, providing continuous fresh air while recovering heat from extract air. The system is coordinated with the building layout and roof space alongside the hot-water equipment and photovoltaic systems.

Heating is also being reconsidered as part of the retrofit rather than simply replacing the existing boiler. An air-source heat pump is proposed, with the system to be sized from room-by-room heat-loss calculations and designed around low heating-water temperatures. The strategy targets approximately 45°C flow temperatures where practicable, improving heat-pump efficiency and ensuring that emitters, distribution and fabric performance work together as one system.

Renewable energy is incorporated after demand reduction rather than used to compensate for a poorly performing envelope. Integrated photovoltaic panels are positioned within the principal roof plane, supporting the transition to an electrically heated home while maintaining a clean architectural composition.
Summer comfort has also been considered as part of the low-energy brief. The strategy prioritises controlling solar gain, external shading where required, practical purge ventilation and MVHR summer bypass before introducing active cooling. This ensures that the measures used to retain warmth in winter do not inadvertently create overheating during warmer months.

Architecturally, the refurbishment gives the house a clearer contemporary identity. White render is combined with vertically expressed dark-grey cladding, dark aluminium windows and doors, and a restrained palette of grey roof finishes. The front elevation is simplified and strengthened through a new entrance composition and cladding treatment, while the wider remodelling reorganises the house around a more practical kitchen and dining space, lounge, study, utility accommodation and improved bedroom arrangement.

Leamington House demonstrates how architectural refurbishment and energy retrofit can be developed together. Rather than treating sustainability as an additional layer of technology, insulation, airtightness, ventilation, heating, solar control and renewable generation are coordinated as part of the architecture itself, creating a more resilient and comfortable home with substantially reduced energy demand.