Hi All,
Greetings!
Hope you all are safe.
Our energy model analyst facing issues for one of our projects to meet the energy modeling compliance under LEED v4.1. The proposed project is designed with air cooled chiller and baseline HVAC system is water-cooled chiller.
The % improved beyond code should be calculated based on the following formulas.
1. Performance Cost Index = Proposed Building Performance/ Base Building Performance
2. Performance Cost Index Target = ((BBEUC+(BPF.BBREC))/BBP
3. % Improvement Beyond Code = 100 * (PCI Target - PCI)/PCI Target
From the above it is understood that, the Building performance Factor (BBF) is playing vital role to estimate the energy performance of building.
As per Dubai climate zone & our project type, the BPF factor is 0.62. So, our proposed building energy consumption is too much higher than baseline energy. Even considering the water-cooled chiller in proposed case, the project is unbale to meet the minimum energy savings.
To overcome the issues mentioned above, our team has decided to meet only the minimum energy performance with air cooled chiller by following Section 11 Energy Cost Budget Method.
Q1. I hope that the above approach is acceptable and just a positive energy saving is enough to comply. Is this correct?
Q2. The proposed chiller is air cooled chiller & heating is electrical resistance. So, the baseline system will be system 03 or system 08 or system 09. Is this correct?
Q3. Whether COP of proposed chiller must be higher than baseline COP of system 03 or system 08 or system 09.
(OR)
Q4. Whether COP of proposed chiller must be higher than baseline COP mentioned in Table 6.8.1-3
your support is highly help us to move further.
Thanks in advance.
Jamy Bacchus
Associate PrincipalME Engineers
20 thumbs up
October 25, 2020 - 1:16 pm
Amal,
ECB method per Chapter 11 of 90.1 is not permitted for the prerequisite (EAp2) or the credit (EAc2) for documenting optimized energy performance. So HVAC systems mapping per Chapter 11 is irrelevant to LEED. That's only used for energy code compliance.
If the BPF for your project creates an issue, you should stick with v4 methodology while you still can.
Amal Venugopal
Project Manager7 thumbs up
October 26, 2020 - 2:19 am
Jamy,
The follwing requirements are copied from the link: http://www.usgbc.org/credits/new-construction-core-and-shell-schools-new-construction-retail-new-construction-healthc-170?return=/credits/New%20Construction/v4.1/Energy%20&%20atmosphere
Requirements:
Comply with ANSI/ASHRAE/IESNA Standard 90.1–2016, with errata or a USGBC-approved equivalent standard. ASHRAE 90.1-2016 Compliance pathways in Section 4.2.1.1 include compliance with all mandatory provisions, and compliance with one of the following:
Jamy Bacchus
Associate PrincipalME Engineers
20 thumbs up
October 26, 2020 - 3:07 pm
Amal,
My bad. Yes you can use ECB just for the prereq and forgo any optimize energy credits (you can also just use the prescriptive requirements too provided you can meet those).
Q1: Yes, but no credits.
Q2: Yes, Systems 3, 8 or 9 depending on space and system type.
Q3: Your chiller COP won't be held directly up against the baseline COP. Systems 3, 8 and 9 are not chilled water systems. They each have packaged DX systems. So those won't have pumping energy. Their minimum efficiencies will come from the 6.8.1-x Tables. But the COP of your chiller is not exactly apples to apples with a PTHP's COP for System 8 for example. Your proposed central plant may have to compete against a lot of smaller localized systems with small compressors and limited to no duct distribution and no pumping. Your COP may have to overcome a lot to show parity with the baseline.
Q4: Yes. All of your HVAC needs to be per the mandatory Section 6.4 requirements which includes the min efficiencies in the Tables 6.8.1-x. For your air-cooled chiller that's in Table 6.8.1-13 as you noted (Paths A or B). But as noted above in Q3, you will likely need to find mechanical or lighting or envelope measures which exceed the baselines in order to show you are equal or better than the baseline.