Infill development targeting Passivhaus
An infill development of nine highly insulated and airtight new build houses on a constrained brownfield site for a private developer in Devizes.
The Passivhaus standard was targeted and formal Passivhaus certification was achieved for the larger terrace of six houses to the north of the site.
Formal certification was not achieved for the smaller block, due to its less favourable form factor and the constrained nature of the site, but a similar strategy was applied with highly insulated building fabric, excellent airtightness and efficient MVHR systems.
Greengauge was brought in to provide MEP Design for the project and provided some PHPP support in relation to building services.
Strategy
The mechanical services strategy for the project involved the specification of direct electric heating and hot water cylinders, with solar PV arrays on the roofs. Ventilation was delivered through individual MVHR (mechanical ventilation with heat recovery) units in each home.
Project team
Client: Gaiger Construction & Development
Architect & Passivhaus Designer: PKA Architects
Contractor: Gaiger Construction & Development
M&E Design: Greengauge
Passivhaus certifier: WARM
Key data
“We enjoyed problem-solving on this constrained Passivhaus infill project, to identify the mechanical services required. We were glad to find workable solutions that helped the project achieve Passivhaus certification.”
Gerard Thacker, Greengauge
Challenges & solutions
Space for ductwork
The key design challenge was getting suitably sized MVHR ductwork integrated into buildings with a tight planning constraint on ridge height, which didn’t allow for a service zone. Greengauge designed deeper bulkheads above kitchen cupboards to distribute the main rigid ductwork , without affecting floor to ceiling heights elsewhere. Greengauge designed the final run-outs to supply and extract valves using semi-rigid ductwork which was threaded through open webs of the Posi-joist floor system.
A Passivhaus first for contractor
The project was the first Passivhaus project for the developer and contractor, which now has more Passivhaus projects in the pipeline. The contractors benefited from a diligent on site team and site manager, resulting in the project comfortably achieving the required air permeability results.
Achieving Passivhaus PER requirements
Achieving the Passivhaus Primary Energy Renewable (PER) Demand criteria was quite challenging on the project, as there was not suitable outdoor space to accommodate air source heat pumps. The heating strategy therefore had to be direct electric, but the PER criteria was achieved by means of using more efficient white goods and providing local renewable energy generation from roof integrated solar PV panels.
Video credit: Gaiger Construction & Development