Sheffield's step-by-step EnerPHit

Nestled in Sheffield, this 1950s Vicarage is South Yorkshire’s first EnerPHit (Passivhaus retrofit) certified home. Dan Bilton, Bilton Design Ltd, homeowner and Passivhaus designer combined his passion and expertise to transform this cold and draughty house into a healthy, comfortable, and energy-efficient home for his family.

The old St Bartholomew Vicarage, a traditionally constructed, brick cavity wall, four-bedroom detached property, has been reimagined as a benchmark for sustainable retrofits. Key upgrades, including external insulation, airtight construction, and solar PV installation, have significantly reduced energy demands. Today, the home requires heat input for just a couple of months each year, keeping bills incredibly low while maintaining year-round comfort.

Key stats

Construction: Traditional masonry overclad with timber
TFA: 158 m²
Build start date: 2017
Completed: 2019
Certified: EnerPHit, 2020

The Passivhaus Standard was adopted because it is the only system that reliably ensures the actual energy performance of a building aligns with the design - Dan Bilton, Passivhaus Designer, Bilton Design, Sheffield EnerPHit

Construction

The rapid-stepped retrofit involved minor remodelling, externally insulating the walls and creating a warm roof. Internally, the building was stripped back to brick, with the airtightness line formed at the internal plaster. The process involved detailed work on joist ends and internal window box junctions before wet plastering and connecting the airtight layer to the internal raft foundation, ensuring a seamless thermal envelope.

U-values

Roof: 0.11W/m²K

New melamine-faced decking forming an airtight line on the original rafters. 240mm EPS + 50mm mineral fibre insulation over

Wall: 0.1W/m²K

Original masonry cavity wall with blown cavity insulation. New external larch cladding over 50mm of mineral fibre and 240mm EPS insulation

Floor: 0.22W/m²K

Original concrete raft overlaid with 100mm PIR insulation and 18mm P5 T&G chipboard

External cladding system © Bilton Design, Sheffield EnerPHit

Further information can be found at the International Passivhaus Database listing

The property’s original features made it particularly well-suited for an EnerPHit transformation. Its raft foundation and higher-than-average ceiling heights facilitated an airtight floor structure with space to insulate over, whilst internal drainage and the detached structure minimized disruption during external insulation works. A southerly aspect further optimizes passive solar gain, boosting thermal performance naturally.

To stagger and reduce costs, the project was completed in stages, with multifunctional components seamlessly integrated throughout. This approach also reduced materials and wastage, lowering embodied carbon.

Learn more about this step-by-step EnerPHit

Sheffield EnerPHit sequencing - Image © Bilton Design

Building performance

Measured energy performance
Airtightness n₅₀ (≤ 1.0 ACH @ 50 Pa)	0.3 ACH @ 50 Pa
Space Heating Demand (≤ 25 kWh/m².a)	18 kWh/m².a
Heating Load	11 W/m²
Primary Energy Demand: (≤ 120 kWh/m².yr)	73 kWh/m².a
Primary Energy Renewable (PER) Demand (≤ 60 kWh/m².a*)	69 kWh/m².a

*+/-15 kWh/m².a allowance if offset by energy generation. See Passivhaus criteria.

Services

The warm roof design freed up space to accommodate the home’s mechanical ventilation with heat recovery (MVHR) system. The MVHR unit continuously supplies fresh, filtered air to living spaces while extracting stale air, ensuring excellent indoor air quality and maintaining a steady indoor temperature. A minimal heating system, active only during the coldest months, meets the family’s needs efficiently. This low-demand heating setup is complemented by renewable energy generation through solar photovoltaic (PV) panels installed on the south-facing roof. Window adjustments further improved the home’s seasonal comfort. Deep reveals were added to south-facing windows to prevent overheating in summer while allowing beneficial solar gain during winter.

MHRV unit fitted in the loft © Bilton Design, Sheffield EnerPHit

South facing window with a deep reveal © Bilton Design, Sheffield EnerPHit

We thought we would miss our old log burner, but when you're not cold you don’t yearn for a cosy room with a fire - Dan Bilton, Passivhaus Designer, Bilton Design, Sheffield EnerPHit

Challenges & lessons learned

Phased execution: Careful planning and phased execution helped to keep the project on track without compromising quality or comfort within ambitious timeframes.
Working to standard measurements: Insulation unit sizes were used to guide the layout of construction elements, such as Larsen trusses and cladding rails. This strategy minimized the need for on-site cutting, reduced waste, and streamlined the build process, saving both time and resources.
Local contractors: Finding qualified local professionals familiar with Passivhaus principles proved to be a challenge, highlighting the importance of building local expertise in sustainable construction methods to support the UKs retrofit transition.
Discontinued services: Some products and service providers became unavailable post-construction, raising the need for easily maintainable systems and future-proofed choices. However, with careful planning, this issue could be mitigated in future projects.
An EnerPHit template: Despite these challenges, the project was a success. Reflecting on the process, the homeowner and designer, Dan Bilton, noted that there’s little they would change if they did the project again.

Key team

Architect, Passivhaus Designer & M&E consultant: Bilton Design Ltd
Structural engineer: Peak Engineers
Passivhaus Certifier: MEAD Consulting

Sheffield EnerPHit - UK Passivhaus Open Days 2024

Six years on, we visited Sheffield's first EnerPHit project at the UK Passivhaus Open Days 2024. The tour sold out immediately, demonstrating the increasing appetite for Passivhaus solutions in the region. Attendees included architects, students and homeowners considering their own retrofits, who were treated to a comprehensive tour and presentation with detailed drawings and the project's PHPP model. The highlight was meeting the homeowner and designer, Dan Bilton, who generously shared his expertise and personal journey through the retrofit process.