CBECC-Com Nonresidential Compliance Software

Highrise Residential Modeling  (FAQ)

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Highrise Residential and Hotel/Motel Projects Modeling Large Central Heat-Pump Water Heaters

Designs using large central heat-pump water heating systems cannot be currently modeled in the software because performance profiles do not exist. A study by the utilities is underway to help determine the real performance of these systems and once complete it will be part of the software, however, the timing to complete the study for the large equipment is late 2020. Smaller central heat-pump water heating systems may be available in the software by early 2020 after initial tests are complete.

There are other options currently available for modeling heat-pump water heating systems without recirculation loops:

  1. Buildings with one heat-pump water heating system per dwelling unit / guest room can be modeled in the software.
  2. Buildings with one heat-pump water heating system for eight or less dwelling units / guest rooms can be modeled in the software.
Buildings with heat-pump water heating systems with recirculation loops or serving more than eight dwelling units / guest rooms cannot be currently modeled. There is currently no work-around for this and modeling a central gas-fired water heater in place of a heat-pump water heater is not an acceptable alternative for compliance.

CBECC-Com Versions affected: CBECC-Com 2016 (all approved versions), CBECC-Com 2019 (all approved versions)

Highrise Residential Projects Recommended Modeling Methodology for Projects using Forced Ventilation (DOAS/Exhaust Based Systems)

The CBECC-Com support team has recently identified a bug in EnergyPlus that is affecting the modeling of highrise residential projects. This bug affects projects where the residential spaces have cooling & heating equipment and use forced ventilation - either continuously operating DOAS or exhaust based systems. It is recommended that these projects model the ventilation to the residential spaces using the 'Natural' option until EnergyPlus corrects the bug and is incorporated into a new release of CBECC-Com. Please note that the 'Natural' option models a constant ventilation rate with zero fan power for both Baseline and Proposed cases, and does not imply that 'Natural Ventilation' is modeled.

Highrise residential projects which have heating only systems (e.g. baseboards) serving the residential spaces can continue to model forced ventilation.

If there are further questions regarding this, then please send an email directly to cbecc.com@energy.ca.gov.

CBECC-Com Versions affected: CBECC-Com 2013 v3d/v3e, CBECC-Com 2016.2.0 / CBECC-Com 2016.2.1

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