Marc Nickels, Business Development Manager Kingspan Technical Insulation 

Whole life carbon (WLC) assessments are an increasingly common part of the design process. The specification of Mechanical Electrical and Plumbing (MEP) services is a key factor within these assessments with systems potentially accounting for a significant proportion of both operational emissions and embodied carbon in buildings. This is especially true in office developments, as spaces may undergo numerous CAT-A fit-outs across the building’s lifespan.  

Whilst the detailed specification of these services is undertaken by the M&E consultants or contractors, it is important for architects to have an understanding of how fundamental decisions, such as the choice of heating or cooling emitters, can impact WLC. 

Engineering specialist, Introba, were commissioned by Kingspan Technical Insulation to research how different specifications of MEP systems can impact embodied carbon. This example looks at a typical office development. Its findings suggest that limiting use of metals (such as steel or aluminium) is a key factor in reducing embodied carbon from MEP systems, and that the use of pre-insulated phenolic ductwork over conventional lagged galvanised steel ductwork can be beneficial.  

Research

The research looks at a typical 5-storey office building with a gross floor area of 10,000 m2. Three different HVAC scenarios were assessed:

• Variable refrigerant flow (VRF)
• Air source heat pump with fan coil units (ASHP with fan coil units)
• Air source heat pump with chilled beams (ASHP with chilled beams)

The research considered the total embodied carbon from all three MEP areas for both a Shell & Core and CAT-A fit out. The embodied carbon for each scenario was calculated using the methodology in CIBSE TM65 – Embodied Carbon in Building Services: A calculation methodology (2021) .

Results

Graph 1 shows the outputs from the modelling – these are broken down into the Shell & Core and CAT-A fit outs. The outputs show there are key differences in the embodied carbon associated with the two fit outs for the different scenarios which will have a notable impact on WLC.

In the case of the ASHP with chilled beams scenario, the Shell & Core fit out has the lowest embodied carbon of the three scenarios considered. However, the embodied carbon from its CAT-A fit out is by far the highest. This is largely due to the use of aluminium chilled beams – with the embodied carbon of these emitters being over four times higher than for the other CAT-A fit outs.  

Of the other two scenarios, the ASHP with fan coil units had the lowest embodied carbon for the CAT-A fit outs and the lowest overall embodied carbon when both Shell & Core and CAT-A fit outs were considered together. 

Overall embodied carbon from the VRF scenario was the highest of the three which were examined. Refrigerant leakage contributed to 32% of the overall embodied carbon from the VRF scenario. In a high refrigerant leak emission scenario, the embodied carbon from the VRF specification could increase further.

Ductwork

As Graph 1 shows, across all Shell & Core fit out scenarios, ventilation systems were found to have a high embodied carbon due to the steel used for the air handling unit and ductwork. 

To investigate how reducing the volume of steel could impact embodied carbon, a further analysis was carried out. This involved switching from a galvanised steel ductwork specification lagged with phenolic duct insulation, to a pre-insulated phenolic ductwork system. The pre-insulated ductwork system is fabricated from rigid insulation panels with a foil facing – eliminating the need for galvanised steel ducting.

The results showed a notable impact on embodied carbon from the ventilation system for the ASHP with fan coil units scenario – reducing lifecycle embodied carbon from 100.2 kgCO2/m2 to 88.9 kgCO2/m2 – a reduction of over 11%.

Embodied carbon emissions for the ventilation system in the VRF scenario also fell by 4.7 kgCO2/m2 whilst change for the ASHP with chilled beams was only 0.3 kgCO2/m2 due to the lower quantity of ductwork needed.

Metal focus

The research highlights that notable savings in embodied carbon can be achieved by considering MEP approaches which minimise the quantity of steel and aluminium needed. For architects, this means thinking carefully about the overall approach used to heat or cool a space – particularly on the emitters – and considering technologies, such as pre-insulated phenolic ductwork, which can limit steels needed for ductwork.