Squire and Partners’ PV mansard revealed
Footprint tours a PV-clad central London rooftop
Shortlisted for this year’s AJ100 ‘Practice of the Year’, Squire and Partners are currently working on a range of high profile central London developments including the Bulgari Hotel which will open this summer, a residential development at One Tower Bridge and the Shell Centre redevelopment masterplan.
Project architect Nick Munro recently toured me through another central London project, an 8400m2 mixed use project at 5 Hanover Square. Completed last month, the six-storey newbuild scheme includes an art gallery on the ground floor, offices on first to sixth storeys and residential in an adjoining block on Hanover Street.
Sited on the southeast corner of Hanover Square, the project replaces an existing 1960s building. Its black brick façade punched with deep window reveals replicates the proportions and scale of Georgian buildings fronting the square.
From the outset, the brief from client Mitsui Fudosan with Stanhope, called for an ‘exemplar sustainable city centre building’ which makes use of renewable energy. AECOM was appointed early in the project to explore renewable energy options.
AECOM services engineer Sophia Negus joined us on site and explained that early feasiblity studies, including wind simulations, showed that the site was not suitable for wind energy. Photovoltaic panels were chosen as the most appropriate renewable technology for the location and massing of the scheme. A top floor mansard roof was designed specifically for the PV installation.
The feed-in tariff was not in place when the decision to go with PVs was made. In fact, the project squeaked through just in time to take advantage of the scheme, so this was a well-received bonus for the client.
The building exudes quality throughout, but the real gem is the top floor. To achieve the complex geometry required to achieve optimum orientation for the 130 panel-installation, the architects opted for a saw-tooth roofline to maximise the collection of solar rays.
Visible from the square, the PV box sits cleanly above the building and avoids the usual PV aesthetic of ‘slapped-on’ panels. Sunpower PV panels (Model: SPR-225E-BLK-D) were chosen especially for their ‘sleek uniform matt black surface’.
The south and west mansard facades are clad in PV’s, the north and east elevations which receive significantly less sunlight, are clad in identical panels but without the PV capacity.
Each residence is allocated eight of the ‘best performing’ PVs, leaving the office with a total of around 90 panels. The engineer estimates the payback period (including the feed-in tariff) to be between 10 and 15 years.
Other green technologies used in the building include rainwater harvesting for flushing the WCs, a heat recovery system, and daylight sensors and presence detectors for lighting. Natural ventilation was not viable due to the city centre location and depth of floor plan.
The EPC B-rated office and CSH Level 4 development is predicted to provide 18% Co2 savings when measured against the 2006 Building Regulations Part L2A.
It was disconcerting to learn that the estimated percentage contribution towards electricity-use generated by the PVs is only 3.4%. This low yield for an entire floor and roof clad in PVs demonstrates the challenge of PVs as a viable technology in urban locations. There is just not enough south-facing surface area.
On a plus note, the architects say that the current PVs could be easily upgraded when more powerful and efficient PVs are available on the market.
Find out how Squire and Partners fare in this year’s AJ100, on 17 May 2012.
Client: Mitsui Fudosan with Stanhope
Structure: Ramboll UK
Planning Consultant: DP9
Quantity Surveyor: Gardiner & Theobald
M&E Services: AECOM
Quantity Surveyor: Davis Langdon Engineering Services
Construction Manager: MACE
Value: £26 million
Construction time: 14 months
Status: Completed April 2012