By Beth Okogba

As the UK moves toward higher building performance requirements through the Future Homes Standard, local authorities are facing increasing pressure to deliver climate action and more affordable homes. In North Somerset, the local council is demonstrating that these twin goals are attainable. Elm Grove, its new 52-home development that opened in late 2025, shows that Passive House can be delivered at scale through a proven and reliable route to compliance.

The Elm Grove development in Nailsea consists of 44 houses and 8 bungalows, distributed across 20 blocks. The scheme represents a major step forward for North Somerset Council’s ambition to embed Passive House into their future housing delivery. Designed to respond sensitively to its ecologically rich setting, more than half of the site’s existing green space has been retained, with community gardens, orchards, foraging paths, and ecological corridors woven throughout. In total, 56% of the site is dedicated to landscape and biodiversity, delivering a measurable biodiversity net gain.

Early-stage modeling proved critical to the project meeting the Passive House goals. “Initial proposals for the site had dwellings facing close to east-west and were mostly in blocks of two,” explains Mitch Finn, building physicist at Greengauge Building Energy Consultants. “We did PHPP modeling at an early stage and showed that by having dwellings facing north-south and having them in blocks of more than two, that would significantly reduce heating demand and therefore reduce reliance on thermal performance elsewhere.”

A Passive House‑certified timber frame provided low embodied carbon, predictable thermal performance, and suitability for rapid, high‑quality installation. Because the system’s U‑values and thermal bridge details were pre‑calculated, early‑stage modelling was simplified and uncertainty reduced.

Form factors across the development range from 2.56 to 3.99. The eight bungalows sit at the higher end of this range, explaining their PHI Low Energy certification. Although they follow the same construction specification as the houses, their less favorable form factor results in a higher heating demand. Across the development, space heating demand ranges from 14 to 30 kWh/m² per year, reflecting differences in form factor and certification level. 

All dwellings are equipped with highly efficient PHI‑certified MVHR (mechanical ventilation with heat recovery) units that have an automatic summer bypass mode. Space‑heating demand is extremely low, so air‑source heat pumps were not required. Instead, heating is provided by direct electric radiators, with hot water supplied by an individual hot‑water heat‑pump cylinder in each dwelling.

Dynamic overheating modelling informed the summer comfort strategy, which includes modest glazing areas to limit solar gain, natural ventilation through operable windows, and MVHR with summer bypass.

Each home also includes 3.44–6.075 kWp of PV, providing at least 90% of predicted energy demand. Two blocks achieved Passivhaus Plus certification due to their larger PV arrays.

Lessons Learned

Delivering Passive House at this scale within local authority constraints required careful coordination of design, procurement, and construction. The project benefitted from an integrated approach. This enabled simple, cost‑effective solutions that supported certification across all blocks.

• Early optimization pays off: The near north–south orientation optimizes winter solar gain while limiting summer overheating, reducing space‑heating demand and avoiding the need for excessive insulation thicknesses.

• Choose high‑quality, Passive House‑ready products early: Having certified or well‑modeled components allowed accurate energy modeling from the outset.

• Keep systems simple: With minimal heating demand, direct electric radiators and hot‑water heat pump cylinders proved efficient and cost‑effective.

 “It has been great to be able to offer an integrated approach, combining both building physics and mechanical services design for the project. Greengauge has been able to help provide simple and cost-effective solutions for the development,” notes Finn. He also points out that the client’s commitment to Passive House certification helped ensure that the project reliably met its performance goals. “With certification, a project is going to achieve what it’s been designed and modeled as,” says Finn, and avoid the performance gap that has characterized many UK homes. When questions inevitably arose during the project’s construction, the contractor would always check with Greengauge to make sure that the project stayed on track to meet its Passive House goals. 

Elm Grove demonstrates how local authorities can deliver certified Passive House homes at scale, combining high performance, comfort, and affordability, while addressing both the climate emergency and local housing need.