See all forum discussions about CS-v4 EAp2
 Subscribe to new posts about CS-v4 EAp2 Post a new question aboutCS-v4 EAp2
See LEEDuser’s guidance on CS-v4 EAp2»
FAQs about EAp2 :

Do the required savings for this prerequisite (and credit) need to come only from building energy, or also process loads?

Our project doesn't have enough energy savings to earn the prerequisite. Can we get there by incorporating onsite renewables?

Our proposed design has insulation R-values that are below those prescribed by ASHRAE 90.1-2010. Can we still meet the prerequisite?

View answers »

Forum discussion

CS-v4 EAp2:Minimum energy performance

Purchased Chilled Water in System 3, Different cooling energy types

Default Avatar
Martin K
LEEDuser Basic Member
0 thumbs up

Hi all,

I need help with these three questions:

Case 1) when a proposed building is supplied with purchased chilled water, but a VRV system serving a server rooms is supplied with electricity, what energy source should be used for HVAC System 3 which is serving the server rooms in baseline building? DX or purchased chilled water? The main baseline system is System 7. I am asking due to section G3.1.1.3 of ASHRAE Standard 90.1-2010.

Case 2.1) the proposed building cooling source is supplied with natural gas (gas heat pumps). No additional cooling source is installed. The question is what energy type should be used in baseline? According to G3.1.3.7 Type and Number of Chillers, electric chillers should be used regardless of cooling energy source of proposed building. It is OK to report cooling energy performance within the PRM Compliance Report in two separate rows, one for electricity (zero kWh proposed vs XY kWh baseline) and one for natural gas (XY kWh proposed vs zero kWh baseline)? Or just use different energy rates and provide a narrative?

Case 2.2) if additional cooling source is installed as a support to the gas heat pumps, e.g. an electric water cooled chiller, is there any change in the baseline cooling energy type against the case 2.1? Can be the PRM Compliance Report prepared similarly like in the case 2.1?

 

Thanks in advance for any suggestions.

 

Martin

0
Post a reply

You rely on LEEDuser. Can we rely on you?

LEEDuser is supported by our premium members, not by advertisers.

Go premium for $15.95  »

Profile picture for user sheffer
Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Mon, 02/05/2018 - 18:59

1. Looks like chilled water according to G3.1.1.3.2. 2.1 Electric cooling yes. What you propose sounds correct regarding reporting. 2.2 No change. Yes reporting would be the same.

Wed, 04/23/2025 - 09:48

Hi @Marcus Sheffer,  Sorry to reopen a closed query, but I'm encountering a similar issue in one of our ID+C projects. In this case, the server rooms are served by VRV systems, while the other spaces receive supply air from an AHU connected to a purchased chilled water plant. For the baseline model, we used:
  • System 8 for AHU-served spaces (purchased chilled water)
  • System 4 for VRV-served server rooms
The project was submitted, and we have now received reviewer comments. The reviewer has specifically asked us to substitute System 4 with System 8 for all spaces, referring to Section G3.1.1.3.2(a) of ASHRAE 90.1-2010. However, our energy simulation was performed using HAP software, which does not allow System 4 to be connected to a central plant (such as purchased chilled water) under the Baseline case. Given this software limitation, we are unsure how to address the reviewer's comment. Could you please clarify how we can resolve this issue or suggest any possible strategies to comply with the requirement, especially considering the software constraints? This project is critical to us, and your guidance would be highly appreciated. I've included the reviewer comments in this chat for your reference.   REVIEWER COMMENT: 2. The Water-Side HVAC tab of the MEPC indicates that purchased chilled water has been modeled; however, the
Performance_Outputs_1 tab of the MEPC indicates electric space cooling in the Baseline. Section G3.1.1.3.2.a of ASHRAE
Standard 90.1-2010 indicates that purchased chilled water shall be substituted for the cooling types in Table G3.1.1B. Both
Baseline System Type #8 and #4 must be modeled with purchased chilled water. a. Update the General Information tab of the MEPC to indicate district cooling and Path 1. b. Update the models and MEPC to comply with this requirement.

Tue, 05/13/2025 - 16:10

Just to clarify, it does not appear that the reviewer is asking you to substitute System 4 with System 8, but rather to change System 4 to use district cooling rather than DX, which is correct based on Section G3.1.1.3.2a. I do not use HAP so I would recommend reaching out to their support team for guidance as to how to model this system configuration in their software. 

Add new comment

To post a comment, you need to register for a LEEDuser Basic membership (free) or login to your existing profile.