Sheppard Robson’s design team set out to create a specific design aesthetic for the Bechtel House facade, optimise it for good energy and daylight performance whilst working towards high regulatory goals for the project as a whole.
Quick StatsLocation: London, UK Floor Area: 30,000m2 (322,917ft2) Use Mix: New Build Office Number of Floors: 9-12 Storeys Project Goal: UK Building Regulation (Part L, Criterion 3) & Building Performance Rating (BREEAM Excellent)
By calculating the impact of several shading device types and depths, the team was able to choose an optimum design that reduced energy use, bad south solar gains and cooling loads. Using Sefaira for SketchUp’s real time analysis, Sheppard Robson were able to understand the impact of shading types and depths, streamlining from about twenty different options to an optimised design that combined high performance, good daylight and a coherent design aesthetic.
Process & Approach
The team started by focusing on the south block, as it suffered from more solar exposure than the north block. They created simple models of the south block starting analysis on a fully glazed base case (image 1) then testing options with reduced glazing ratios (image 2). Comparing energy use, cooling loads and daylight levels, the team settled on an option with the optimum glazing ratio (image 3).
Image 1 Cooling Load: 403, 987kWh South Solar Gains 388, 050kWh Daylight Level (sDA) 87%
Image 2 Cooling Load: 386, 465kWh South Solar Gains 322, 581kWh Daylight Level (sDA) 86%
Image 3 Cooling Load: 386, 465kWh South Solar Gains: 322, 581 Daylight Level (sDA) 86%
Next, the team focused on reducing south solar gains and the cooling load by testing selected shading options; 0.5m horizontal projections, 0.5m vertical projections, a combination of 0.5m horizontal + vertical projections and a 1.0m Horizontal projection.
Narrowing down to even more bespoke shading solutions, the team tested a tapered vertical fin, a tapered vertical fin with double horizontal shading and double height chamfered panels.
The optimised tapered vertical fin, tapered vertical fin + 2 horizontal projections and double height chamfered fins were most effective for reducing cooling, energy use and bad south solar gains.
Impact on design
The team selected the optimised tapered vertical shading device for the north facade and the tapered + 2 horizontal projections for the south facade.
Taking it one step further, sun path diagrams were made to understand how different building services systems would affect daylight levels within the interior spaces. Comparisons were made between daylight penetration when a “chilled beam + exposed soffit” air delivery system is used and when a “suspended ceiling” system is used.
Results & Final Design
The team selected the chilled beam & exposed soffit option, opening up sightlines to the sky and allowing daylight deeper into the room. Upstands at window level offer additional insulation but are kept to a level that does not reduce daylight levels.
By testing several design options and optimising the final outcome for daylight and energy performance, Sheppard Robson were able make a clear case for their preferred design and confidently steer conversations with their M&E engineer.