ASHRAE90.1 AppendixG: All conditioned spaces in the proposed design shall be simulated as being both heated and cooled even if no heating or cooling system is to be installed.

asked 2023-03-28 06:39:08 -0500

Keigo's avatar

updated 2023-03-28 09:59:55 -0500

After all this time, I would like to discuss the requirement mentioned in the title. The requrement is in ASHRAE90.1 AppendixG Table G3.1.

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  1. Why do we have to simulate both heating and cooling even if no heating or cooling system is to be installed?
  2. For buildings without heating system in tropical climate, normally I use ThermostatSetpoint:DualSetpoint, but I set the Heating Setpoint Temperature Schedule very low such as -100ºC. Is this the correct approach to comply with this requiremnt?

Answers to only one of the two questions are also appreciated.

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Hi Keigo. Isn't the requirement in (b) limited to conditioned spaces, i.e. cooled spaces, heated spaces, or indirectly conditioned spaces? The requirement would not apply to semi-heated spaces or unconditioned spaces, right?

Denis Bourgeois's avatar Denis Bourgeois  ( 2023-03-28 07:50:17 -0500 )edit

@Denis Bourgeois Right.

It applies to cooled only space, but I'm wondering if there is a reasonable background to this requirement, and I'm not so confident in my modelling approach.

Keigo's avatar Keigo  ( 2023-03-28 08:08:10 -0500 )edit

Hey Keigo. My first comment applied only to Q1 (i.e. NO heating & NO cooling), hence requirement (b) doesn't apply. For Q2 (cooling ONLY, therefore conditioned), requirement (b) does apply : virtual heating system (same as baseline). It's also my understanding that one can set the heating setpoint low enough so heating doesn't kick in (in both design & baseline), as you suggest. It'd be nice to quote an official LEED ruling on this ...

Denis Bourgeois's avatar Denis Bourgeois  ( 2023-03-28 08:56:55 -0500 )edit

For Q2, do you think we should model virtual heating system? For example, VAV with Reheat although the actual design does not have Reheat coils? Even if we should do so, I think we eventually need to set the heating setpoint low enough so heating doesn't kick in because there is no actual heating setpoint and heating energy consumption should be 0. Then, I think there is no point in modeling the virtual heating system...

Keigo's avatar Keigo  ( 2023-03-28 09:43:03 -0500 )edit

It's not what I think, it's simply what's stated in AppG (TG3.1, 10c, v2016, proposed building) : "Where no heating system exists or no heating system has been submitted with design documents, the system type shall be the same system as modeled in the baseline building design and shall comply with but not exceed the requirements of Section 6." I agree that it's pointless if you're setting the heating setpoint below freezing in a tropical climate. Maybe chat with the building official ... :]

Denis Bourgeois's avatar Denis Bourgeois  ( 2023-03-28 10:47:32 -0500 )edit