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Selecting baseline HVAC system (ASHRAE 90.1 2010)

asked 2023-12-27 01:07:39 -0500

raheel's avatar

updated 2023-12-27 08:43:32 -0500

I am working a highrise residential project. The building is 33 floors with 5 basement levels (dwelling units on each floor from GF to F33). Standard used is ASHRAE 90.1 2010

In proposed case the dwelling units are cooled by the split AC and heated by both Hot water radiators and Split AC.

While the corridors are heated (with ventilation) through the one TFA (heated with the having area more than 1900m2.

My interpretation For dwelling units the HVAC system would be System 1 PTAC For Corridors HVAC system would be System 09 Heated and Ventilated

My doubt : I am confused whether shall I use the System 07 or System 09 for the corridor in baseline case.

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answered 2023-12-28 02:05:23 -0500

Keigo's avatar

updated 2023-12-28 04:36:16 -0500

According to your description, it seems that only the outdoor air is heated by TFA (Treated Fresh Air Unit) and there is no thermostat and no circulating air in the corridors for indoor air temperature control. If that's the case, I think the corridors are regarded unocnditioned zones with preheat coil.

  • Fans for unconditioned zones are regarded process loads, and they shall be modelled identical to the Proposed case.
  • G3.1.2.4 Preheat Coils. If the HVAC system in the proposed design has a preheat coil and a preheat coil can be modeled in the baseline system, the baseline system shall be modeled with a preheat coil controlled in the same manner as the proposed design.

That is, the same system as the Proposed case (i.e., TFA) should be modeled in the corridors in the Baseline case.

...That's my opinion. It would be better to wait for other opinions.


ASHRAE90.1-2010 Performance Rating Method Reference Manual states that "The baseline will be modeled with preheat coil in the mixed air stream controlled to a fixed setpoint 20°F less than the design room heating temperature setpoint."

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However, there is no design room heating temperature setpoint in the corridors, right? That's the problem. I think ASHRAE 90.1 does not specify how to model such zones in detail.

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Thanks @Keigo. I have modeled the preheat coil to the corridor spaces in the building and PTAC units to the dwelling units. Waiting for the response from IGBC.

raheel's avatar raheel  ( 2024-01-04 06:42:48 -0500 )edit

@raheel LEED Certification Reviewers vary greatly in their knowledge levels and there is no uniform interpretation of requirements within the LEED Review team. Different projects often reveive dirrerent comments. Hope a good reviewer will be assigned to your project.

Keigo's avatar Keigo  ( 2024-01-04 21:47:14 -0500 )edit

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Asked: 2023-12-27 00:16:35 -0500

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Last updated: Jan 05