Cooling included in the ERI value when none is selected?

asked 2018-07-06 18:50:55 -0500

Ben Thrun
11 ●1

updated 2018-07-09 18:21:24 -0500

shorowit

10911 ●180 ●9 https://www.nrel.gov/b...

Hi, I am doing standard, new construction simulations using Hawaii as a location in BEopt, and I was wondering if anyone could explain to me why a significant amount of the ERI (or any at all, really) is contributed to cooling when all space conditioning options have been turned off. All other output graph types (source/site energy, utility bills, etc) do not include cooling, but ERI consistently shows cooling. I'm assuming it is not a bug because it has repeated the same results over multiple runs and machines. Could anybody shed some light on why this happens?

Thanks, Ben

answered 2018-07-09 13:45:01 -0500

shorowit

10911 ●180 ●9 https://www.nrel.gov/b...

When calculating an Energy Rating Index, the Rated Home and the Reference Home are always modeled with cooling systems. For example, the RESNET/ICC 301-2014 Standard says "For a Rated Home without a cooling system, an electric air conditioner with the efficiency provided in Table 4.2.2(1a) shall be assumed for both the Energy Rating Reference Home and the Rated Home."

So you're seeing the result of a SEER 13 AC in both the Reference and Rated Homes.

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Thank you for the response, Scott. For calculation of the Energy Rating Index of a naturally ventilated house, am I able to just subtract off that cooling portion from the total? Otherwise I'm not sure how a house could obtain a very low ERI, let alone an ERI of zero. Sorry for the basic questions! I'm very new at this.

Thanks again for the help. Ben

Ben Thrun ( 2018-07-09 14:06:57 -0500 )edit

The Standard says: "Natural ventilation shall be assumed in both the Reference and Rated Homes ...". In other words, ERI does not give credit to homes for natural ventilation. As far as I can tell, the only way you can reduce the cooling contribution to the ERI is to 1) use a more efficient cooling system, or 2) reduce the cooling load through better insulation, air sealing, etc.

Since you're new at this, it sounds like you should reach out to a HERS provider in Hawaii that can help provide more information/context for ratings in your state.