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Image © Rob McDougall

Engineered to win

Winners of this year’s CIBSE Building Performance Awards demonstrate how innovative engineering and focused post-occupancy involvement can deliver outstanding projects, says Sara Kassam, Head of Sustainability Development at CIBSE

Renovation and renewal emerged as a key theme in this year’s CIBSE Building Performance Awards. The Engine Shed, which won both the Building Performance Champion and Public Use awards categories, is a stunning transformation of an old Ministry of Defence train shed into the centrepiece of Historic Environment Scotland’s (HES) new building conservation and visitor centre. Similarly, the refurbishment of the Bartlett School of Architecture’s 1970s-built home won the Retrofit Project of the Year category, with an impressive 60 per cent reduction in energy use per square meter of floor area.

And the new Institute of Physics headquarters building, winner of the Commercial Project of the Year category has been constructed in London behind a retained Victorian facade.

What these CIBSE building performance winners demonstrate is the quality of low energy design that can be achieved when an innovative building services consultancy works with a progressive architecture practice. These winners also highlight the importance of the continued involvement of the design team after the building has been occupied in optimising the operation of the building to work towards design aspirations being achieved.

HES’s brief for the conversion of the old engine shed into the centrepiece of its new facility in Stirling, Scotland was for the scheme to be sustainable. As part of the conversion, the building’s floor plan was extended with the addition of two new wings, one on each side of the existing shed. In line with the project brief, Building Services Engineer Max Fordham’s design incorporated a variety of low energy technologies including a natural ventilation strategy and an underfloor heating system, supplied by a ground source heat pump (GSHP) connected to three 180m deep boreholes.

Image © Rob McDougall

In summer the boreholes provide an efficient source of cooling for the building by turning the heat pump off but continuing to run the circulating pump to push water through the ground loop to provide ground-cooled water to the fan coil units (FCUs) in some of the spaces. The FCUs have been designed to operate at a raised temperature of 12⁰c flow, 17⁰c return.

An additional advantage of this solution is that heat removed from the building in summer is stored in the ground, raising its temperature, so the heat pumps do not have to work quite so hard in winter to provide heat.

In the case of the Engine Shed, the building’s low energy design was complemented with seasonal commissioning of the BMS, monthly aftercare meetings for two years following its opening and the addition of a post occupancy evaluation after the first year of use.

The aftercare meetings involved Max Fordham, the main contractor, sub-contractors and controls specialists and included a walk-around with the building users. Action points are summarised in quarterly aftercare reports. The final report, produced on 4 July 2019 at the end of the second year of operation, shows the building’s gas consumption down 30 per cent compared with year 1 and that electricity consumption has also reduced Year 1 to Year 2, in response to lighting and plant control improvements.

A similar approach has been adopted with the refurbishment of the Bartlett school of Architecture at University College London (UCL). The refurbishment was based on a deep retrofit, which involved retaining the building’s reinforced concrete structure, replacing the building’s poorly-performing facade, extending its floor plates outwards and reconfiguring the interior to help address its outdated learning environment. These additions have doubled space for teaching and research and helped tackle the building’s poor energy performance.

The deep retrofit also involved the strip-out of the building’s ageing low pressure hot water radiator system and its replacement with new, more energy efficient systems. Engineer BuroHappold’s solution was based on the use of active multi-service chilled beams to provide both heating and cooling as required.

To save energy, the system is designed so that in spring and autumn students can open the windows to ventilate the learning and teaching spaces naturally. A wall-mounted traffic light system indicates when external conditions are suitable to operate the building with the windows open. A window interlock turns off the heating, cooling and fresh air supply to the chilled beams.

The building was occupied in January 2017. Seasonal commissioning was carried out in winter, mid-season and during peak summer conditions. A Building Use Studies (BUS) survey was also carried out with staff and students a year after the building was first occupied. The study identified two areas where user comfort needed to be improved: air quality in the basement was found to be poor and there were issues relating to thermal comfort on the upper floors.

About Sarah OBeirne


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