We are working on a major renovation of an existing building which includes removing the facade and replacing it with a highly efficient and tightly sealed facade system. Has anyone successfully used an exceptional calculation method to account for the difference in infiltration between an existing facade in the baseline model and a new facade in the proposed model? I know ASHRAE 90.1 2007 Appendix G does not allow performance credit for infiltration reduction, so I was wondering if anyone has been able to prove savings through an exceptional calculation and how they went about it. Thanks.
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Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
October 22, 2015 - 9:46 pm
Not that I know of.
Christopher Schaffner
CEO & FounderThe Green Engineer
LEEDuser Expert
962 thumbs up
October 23, 2015 - 12:17 pm
Look at LEED Interpretation #3300, which was updated 7/1/15. It outlines a process for claiming savings from infiltration improvements. It references addendum ag to 90.1-2010. You'll likely need before and after blower door tests to prove it.
http://www.usgbc.org/leed-interpretations
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
October 26, 2015 - 11:06 am
Interesting. Thanks for pointing that out Chris.
The 2014 update makes sense to me since they reference a specific, whole building baseline. The 2015 update makes no sense at all. It only references the window air leakage, has the project team determine an appropriate baseline, and does not specify any particular testing protocol. You could drive a large truck through those "requirements". In my opinion the 2015 update is a regression, not an advancement.
Before and after blower door tests would also be a difficult to defend baseline, especially in this case with the total removal of a facade. IMO the baseline should always be the value required for new construction projects. While there is precedent for existing envelop counting in the baseline all other parameters are the 90.1 minimum value in the baseline including existing HVAC. I think allowing existing conditions for infiltration could open up a large hole for game playing.