Clarification on Modeling Solar Hot Water Systems in ASHRAE 90.1-2010 Baseline

asked 2025-07-08 05:13:59 -0500

Anurag_G
101 ●1 ●4

For a LEED energy model following ASHRAE 90.1-2010 Appendix G, we're modeling a domestic solar hot water system with:

3 flat plate collectors Solar storage tank Showers as primary end-use

Proposed Case: Modelled the actual solar thermal system

Baseline Case:

Does ASHRAE 90.1-2010 require the baseline to: a) Include an identical solar thermal system? b) Use a conventional system (electric/gas water heater) instead? c) Follow some prescriptive solar requirements?

Reference to specific sections in ASHRAE 90.1-2010 would be greatly appreciated.

edit retag flag offensive close merge delete

add a comment

2 Answers

Sort by » oldest newest most voted

answered 2025-07-10 13:20:39 -0500

Greg Estep
1149 ●38 ●7

updated 2025-07-10 13:21:15 -0500

Hi Anurag, I'm finding ChatGPT to be excellent at answering 90.1 questions. https://chatgpt.com/share/e/6870044e-...

edit flag offensive delete link

add a comment

answered 2025-07-10 22:22:18 -0500

Anurag_G
101 ●1 ●4

Hi Greg, I found the below comment on chatgpt. My point is we have a 100% solar hot water system without any backup systems like electric water heaters. Do we only realize the complete savings by modelling the solar hot water system on proposed model and not modelling anything on baseline model? Appreciate your response!!

*"The baseline building shall use the same service water heating system type (e.g., electric resistance, gas-fired storage, etc.) as the proposed design, except that renewable energy systems (e.g., solar thermal) shall not be included in the baseline building design. *Interpretation for Your Case Proposed Case: You correctly modeled the actual solar thermal system. Baseline Case: You should not include the solar thermal system. Instead, model a conventional system (e.g., electric or gas water heater) that meets the minimum efficiency requirements specified."**

edit flag offensive delete link

Comments

Ah, interesting. I think you should take the largest credit you can. For LEED, points are based on energy cost. Thus, I would set the baseline service water heating system as electric resistance and meet the minimum efficiency requirements. This is because electricity is so much more expensive than fossil fuels (at least in the Northeast of USA). This way, you will maximize points. Does your model show that the solar hot water systems always meets the demand?

Greg Estep ( 2025-07-11 15:40:51 -0500 )edit

Hi Greg, thanks for your response. The domestic hot water are serving mostly the showers and some kitchens. In India, hot water requirement is quite less, mostly during the winters. So, demands are quite meeting. What I had approached was considering the solar hot water system in proposed case while not considering any service hot water system in baseline since this case is not well defined in LEED. Though the savings wouldn't be maximized as you said, but I would atleast not be missing on the solar hot water savings.

Anurag_G ( 2025-07-12 08:29:08 -0500 )edit

add a comment

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Clarification on Modeling Solar Hot Water Systems in ASHRAE 90.1-2010 Baseline

2 Answers

Comments

Your Answer

Training Workshops

Question Tools

Stats

Clarification on Modeling Solar Hot Water Systems in ASHRAE 90.1-2010 Baseline edit

2 Answers

Comments

Your Answer

Training Workshops

Question Tools

Stats

Clarification on Modeling Solar Hot Water Systems in ASHRAE 90.1-2010 Baseline