CARBON AND ENERGY REDUCTION
equipment shared across different hospital zones through heat exchangers, and ground and air source heat pumps. To achieve a Net Zero Carbon design, it is important to undertake early detailed real-world operational energy efficiency modelling, using the CIBSE TM54 or similar methodology, of MEP systems at RIBA stage 2, in addition to what is required for Building Regulations compliance. This early modelling will ensure that key MEP design decisions are tested and included within the concept design.
Choosing low carbon materials The greatest reductions in embodied carbon can be achieved by choosing innovative low carbon materials for foundation, superstructure, and façade, that form 70% of the overall embodied carbon content. Use of tools such as OneClick LCA and EC3 that source certified materials embodied carbon databases can help us evaluate different options for low carbon material design choices very early on – from the concept stages – and develop to detailed design stages, in our endeavour to meet the RIBA 2030 target of 750 kgC02
e/m2 .
Using locally sourced materials that have a low transportation carbon footprint, low embodied carbon materials such as stone and GGBS concrete, and timber finishes where reasonable to use for carbon sequestration, are some of the aspects one must consider to reduce the embodied carbon footprint of our buildings.
Parametric modelling
Through parametric modelling in Rhino/ Grasshopper for the Whipps Cross Hospital design, Hoare Lea evaluated two design options in terms of form factor, annual, and peak energy demands. Early solar studies revealed that the linear ‘Petal’ option with the slightly higher form factor would have higher energy consumption for heating and cooling than the ‘Pinwheel’ option, because the façades were more exposed to solar energy, and the heat losses were greater.
The studies revealed that the ‘Pinwheel’ option had a more efficient form factor that could achieve the most reductions in peak and annual cooling demand by approximately 30% and 15% respectively, with improved thermal comfort inside. Similarly, peak and annual heating demand was reduced by approximately 20% and 40% respectively in this option. This enabled the designers to choose the optimum building massing, and improve its energy performance further through thermal envelope performance, efficient zoning, and spatial planning, along with low carbon energy sources and energy generation.
68 Health Estate Journal September 2021 Peak cooling energy demand W/m2 kWh/m2 Annual cooling energy demand
Optimising building form to reduce operational energy at Whipps Cross Hospital. 4: Re-use and generate
Once the preferred design with highest carbon and energy savings is developed, it’s important to consider aspects that promote the principles of circular economy through reuse, recycle, and regeneration, to further reduce the embodied carbon, and offset carbon through its on-site renewable energy generation capacity. Integration of renewable on-site energy generation on hospital campuses, such as PV cells and geothermal energy, can significantly help in offsetting building energy use – by as much as 20% subject to available space.
Digital tools such as Insight and Rhino simulations help estimate incident solar radiation on the building envelope, and the potential for solar photovoltaic energy generation. Opportunities to integrate other renewable energy sources, such as ground source and air source heat pumps, can also be simulated and quantified for pre-heating air, and reusing waste heat generated from people and equipment within the hospital.
Water efficiency
Another key resource to consider within hospitals is water efficiency. There are
A Whole Life Carbon Approach that embodies the principles of circular economy is key to achieving a Net Zero Carbon Target.
Climate-sensitive building massing based on optimal solar and wind orientation can establish passive design measures that support occupant health and wellbeing, and also reduce a building’s energy demand.
©NBBJ
©NBBJ
©Hoare Lea
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