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Near-Roof Air Temperatures: Modelling the Implications for HVAC Performance and Cool Roofs

Conference Paper


Abstract


  • Conventionally in building performance simulations

    (BPS), it is assumed that air entering outdoor HVAC

    equipment is at the outdoor ‘ambient’ temperature,

    obtained from a weather file. However, significant spatial

    variations exist in outdoor air temperature fields,

    especially within the thermal boundary layers that form

    near exposed surfaces like roofs.

    Experiments were conducted at three large-footprint

    shopping centre buildings, to characterise the above-roof

    temperature field. An empirical model was derived from

    the experimental data, and applied in BPS of a shopping

    centre with rooftop HVAC equipment in seven Australian

    climates. In these cases, the electricity savings and gas

    ‘penalties’ attributable to cool roofs would have been

    underestimated by 44–85% (61% on average) if near-roof

    air temperature variations had not been modelled

    accurately.

Publication Date


  • 2019

Citation


  • Green, A., Ledo Gomis, L., Paolini, R., Haddad, S., Kokogiannakis, G., Cooper, P., Ma, Z., Kosasih, B. & Santamouris, M. (2019). Near-Roof Air Temperatures: Modelling the Implications for HVAC Performance and Cool Roofs. 16th IBPSA International Conference and Exhibition (pp. 1342-1348). United States: International Building Performance Simulation Association.

Start Page


  • 1342

End Page


  • 1348

Place Of Publication


  • United States

Abstract


  • Conventionally in building performance simulations

    (BPS), it is assumed that air entering outdoor HVAC

    equipment is at the outdoor ‘ambient’ temperature,

    obtained from a weather file. However, significant spatial

    variations exist in outdoor air temperature fields,

    especially within the thermal boundary layers that form

    near exposed surfaces like roofs.

    Experiments were conducted at three large-footprint

    shopping centre buildings, to characterise the above-roof

    temperature field. An empirical model was derived from

    the experimental data, and applied in BPS of a shopping

    centre with rooftop HVAC equipment in seven Australian

    climates. In these cases, the electricity savings and gas

    ‘penalties’ attributable to cool roofs would have been

    underestimated by 44–85% (61% on average) if near-roof

    air temperature variations had not been modelled

    accurately.

Publication Date


  • 2019

Citation


  • Green, A., Ledo Gomis, L., Paolini, R., Haddad, S., Kokogiannakis, G., Cooper, P., Ma, Z., Kosasih, B. & Santamouris, M. (2019). Near-Roof Air Temperatures: Modelling the Implications for HVAC Performance and Cool Roofs. 16th IBPSA International Conference and Exhibition (pp. 1342-1348). United States: International Building Performance Simulation Association.

Start Page


  • 1342

End Page


  • 1348

Place Of Publication


  • United States