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IECC Performance Path

asked 2018-03-19 12:18:54 -0500

Tim Johnson gravatar image

There is an apparent contradiction in the IECC performance compliance calculations for commercial buildings. Section C401.2.3 essentially says the proposed model energy cost should be 85% or less of the baseline energy cost. Section C407.3 says the proposed model should be less than or equal to the baseline model. This seems to appear in 2012, 2015, and 2018. Has anyone seen a clarification?

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answered 2018-03-19 15:35:58 -0500

The IECC 2015 Commentary/User Manual indicates '...Section C401.2 requires that the building's energy costs be 85 percent or less of the costs of the standard reference design building. Section C407 provides the methodology to make the determination of compliance with the 85-percent requirement." C4-123.

Which doesn't necessarily clear that completely up. I think the point they're trying to make is that C401.2.3 is the requirement and C407 is the method(s) to demonstrate compliance. I've see a few local codes that have modified the amount, but none that eliminate it to 0%. (Not saying there aren't any, I just haven't run into them, yet)

This can be a factor for us to move to ASHRAE CH11 for compliance. Different method(s), but no question that ASHRAE is just a flat 'equal or better'. Also have different mandatory elements, so be aware of those impacts as well.

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Thanks, that helps. It seems like C407 ought to be updated to match, but the commentary helps. Unfortunately, the client is insistent on IECC for code compliance and 90.1 for green building certification on this one, so we have a couple slightly different baselines.

Tim Johnson gravatar image Tim Johnson  ( 2018-03-20 09:38:19 -0500 )edit

answered 2018-03-19 15:56:36 -0500

To expand on @dradair's answer, I like this handy reference:

image description


Summary: if you need to comply by just beating the standard, your best bet is ASHRAE ECB.

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Appendix G is not applicable at all for IECC 2015 compliance?

keb gravatar image keb  ( 2021-07-02 11:53:02 -0500 )edit

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Asked: 2018-03-19 12:18:54 -0500

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Last updated: Mar 19 '18