Is on-site construction really all that bad?.
The heat pump may contain refrigerants with high global warming potential and the MVHR unit will require insulated ductwork.Much of this may be made out of materials with high embodied carbon such as aluminium or blown plastics.
This additional material volume becomes additional embodied carbon.. On the other hand, a Passivhaus design tends to be a more compact shape, thus less materials used.Due to its more efficient envelope performance, a Passivhaus building needs a small heating system, and due to its reduced energy demand, it requires a smaller PV array.These characteristics, when coupled with a focus on procuring low embodied carbon materials and equipment, can deliver objectively low embodied carbon designs, despite the additional material volume.. Based on the above, it can be observed that some of the inherent characteristics of Passivhaus increase embodied carbon whilst others reduce it.
Taking a 200 m2 house, (10 m x 10 m x 2 storeys, 40 % WWR) as an example, Bryden Wood has done a rough estimation of the impact that Passivhaus distinctive strategies have on embodied carbon:.Adding triple glazing instead of double glazing would increase carbon around 6 kgCO2/m2 over its lifetime.
Adding a MVHR and ductwork would increase carbon by 6.5 kgCO2/m2.
Adding a heat pump would increase carbon by 3.5 kgCO2/m2.In other words, you can have two floors for data halls in a 20 metre planning envelope.. A fundamental reassessment of the integration of cooling systems and structure, and optimised M&E services zones through close coupling of electrical and mechanical systems will yield geometric reductions that can reduce floor to floor height.
Constructing less costs less, but this approach has the potential to yield much more.For example, a reduction in floor to floor height to 6.5m would enable a three-storey data centre on that same site – an instant gain of 50% in site yield and significant reduction in cost per kW.. A similar approach to close integration of design and the arrangement of primary plant and ancillary systems will optimise the data centre facility plan footprint.
Again, this maximises yield per m2, with the added benefit of a reduction in costly M&E distribution paths..Deferring CapEx, delivering predictability.