Baseline Fan power pressure drop adjustment clarification

3 posts / 0 new
Last post

Hello Everyone,

Recently we received a LEED review comment related to EAc1 for one of our projects and we would like to get some of your opinions on this issue in case anyone else experienced this problem before. The project is a laboratory building and we are filing under LEED NC v2.2 using ASHRAE 90.1-2004. We implemented addendum ac to ASHRAE 90.1-2004 to claim the baseline fan power pressure adjustments found in section 6 of 90.1. The comment is as follows:

"It appears that a pressure credit is being taken for exhaust air heat recovery for fan power in the Baseline Case. However, while exhaust air heat recovery is present in the Proposed Case, it is not present in the Baseline Case and therefore the pressure credit for fan power cannot be taken. If appealing this credit, remove all Baseline Case fan power pressure credits for exhaust air heat recovery, and update the model and template results."

Based on our modeling methodology, heat recovery is not required in the baseline and this seems to have been accepted. However, what we don't understand is why the baseline fan pressure adjustment cannot be used for heat recovery elements present in the proposed design if the baseline does not require it. Our understanding was that baseline fan power pressure drop adjustments were mutually exclusive of any requirement of baseline system components (e.g. heat recovery).

We are also aware that in ASHRAE 90.1-2007 Appendix G, underneath table G3.1.2.9 the following text is included:

"Do not include pressure drop adjustments for evaporative coolers or heat recovery devices that are not required in the baseline system by Section G3.1.2.10."

However, such sentence is not included in any addenda to ASHRAE 90.1-2004 as far as we can tell, and it should only be considered for projects filing under ASHRAE 90.1-2007. Any thoughts? Is it not acceptable to claim the baseline fan pressure credits for system components not required in the baseline model?

Thanks in advance.


Eduardo Galeano, LEED AP

Eduardo Galeano's picture
Joined: 2011-12-07
Reputation: 0


I have not received this comment but would accept what the reviewer
says. Even if it is not in ASHRAE 90.1 2004 Appendix G, the reviewer has
final authority on items not directly stated in ASHRAE Appendix G.

You can try to argue it but I don't see the reviewer accepting it since
there is not a clear answer to how it should be modeled. Usually you
need documentation if you are going to try to change the reviewer's
mind. Since the baseline model does not include energy recovery it does
not make sense to take the pressure drop for energy recovery into the
fan consumption for the baseline model.

Good luck,


Otto Schwieterman's picture
Joined: 2011-09-30
Reputation: 200

I'm trying to figure out if/how folks approximate scaling in regards to Open Cooling Towers for reduced airflow/heat transfer.
Thanks in advance.


Nikola Kravik3's picture
Joined: 2011-11-12
Reputation: 0