PROJECT REPORT: SUSTAINABLE BUILDING DESIGN
Hawkins\Brown have also been appointed to deliver Phase 1c – 125 homes across two blocks – one of which they originally designed, and the other being by Mae. The Hawkins\Brown team contains three Passivhaus Certified Designers, including Woodward, and will be collaborating with Max Fordham who are also looking after the PHPP model.
Sustainability
While all new build elements are aiming for Passivhaus status, EnerPhit – the retrofit equivalent – is not currently being targeted for the refurbishment of the tower block; the team are instead aiming to achieve BREEAM Domestic Refurbishment Excellent certification. However, explains Woodward, “Until the structure is stripped back, we are unsure exactly what quality of fabric we have.” It will be taken back to the concrete frame and then extended, in order to minimise embodied energy, he says. Designing for Passivhaus is demanding, and the typology as well as scale at Agar Grove was always going to increase the design challenges. “At the outset this was quite an unusual typology for a Passivhaus scheme,” says Woodward. Despite this, the standard wasn’t amended or revisited by the Passivhaus Institute in order for Phase 1a to receive its certification. A further advantage of the multi-phase approach is that the practice will take lessons learnt from earlier phases and apply them to upcoming ones on achieving the energy efficiency needed. One of the main challenges encountered early on in the project was how to minimise thermal bridging, given heavyweight materials were being used for the facade (brick and stone). Minimising thermal bridging has been key, with masonry support required due to the brick cladding, explains Woodward: “This works hard to support metal balustrades and GRC window linings, so as little as possible bridges back to the primary structure.” Balconies have also been stacked where possible, and the designers “internalised some, to minimise the thermal envelope,” he adds. These internal balconies – or “external rooms,” also offer better privacy and shelter to residents. Air tightness, another crucial element, was achieved through various design measures. “It was a mixture of concrete framing, wet plaster ‘parged’ blockwork infill, triple glazed windows and an array of airtightness tapes for various junctions,” explains Woodward. Blown mineral fibre insulation was “key to ensuring continuity of insulation, with minimal thermal bridging and avoiding a
ADF DECEMBER 2021
25
Interior images © Tim Crocker
resulting performance gap,” he says. This insulation took up an additional 50 mm of space, but this was gained back thanks to the full filled external walls, which removed the need for a cavity.
One of the biggest challenges was avoiding overheating – largely from solar gain. The east and west facing facades in particular proved problematic, explains Woodward, due to the lower position of the sun in the sky. “Getting the window design right was tricky,” he says. “The proportion is key to get maximum daylighting for a given glazed area. We needed to work hard to achieve a balance, especially seeing as Passivhaus does not measure daylighting, but criteria still need to be met for planning.” Windows and balconies on the south facade were particularly important for helping achieve these daylighting requirements and ensuring a pleasant living environment. The balconies have a “dual benefit” Woodward explains, not only providing outdoor amenity space for residents, but also shading during the summer months. “Their depth ensures that low winter sun can still penetrate deep into the plan,” Woodward adds.
The way tenants would use and live in the building was also key to maximising the building’s energy efficiency potential. Expectations of likely user behaviour were modelled in the PHPP software, with one of the “most difficult areas” being overheating, says Woodward, such as “assuming whether residents were likely to open their window if rooms felt too hot and stuffy.” All other elements were kept as simple as possible for
WWW.ARCHITECTSDATAFILE.CO.UK
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68
