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Kiva vs F-factor Ground Method

asked 2023-10-26 13:01:19 -0500

apdavis's avatar

updated 2023-10-28 13:53:43 -0500

I've been modeling buildings using the Kiva foundation method with the default Kiva settings and I'm seeing a big difference in the annual heating when the building has cooling versus when there's no cooling. Here I used create typical to make a 1-story 30,000 sqft office building and this graph show the zone temperature of the building's center zone which seems to be where the biggest problem is. Red is with cooling, blue is without cooling. Zone Temperature cooling v no cooling

When I switched the foundation to F-factor I don't seem to get the same problem. This graph shows zone temperature of the building's center zone when modeled with no cooling where blue is Kiva and orange is F-factor. Zone Temperature Kiva v F-factor

I tried running the model in OpenStudio v1.6 based on other posts, but I'm still seeing the same issue. Any ideas what could be causing this?

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answered 2023-10-26 18:50:41 -0500

Have you tried explicitly setting the Initial Indoor Air Temperature input for Kiva?

EnergyPlus did have a bug (fixed in E+ 23.2) where the default value could be calculated incorrectly. Kiva also defaults to 22 C (71.6 F) for unconditioned zones, which can be a really poor assumption for, say, a vented crawlspace or unconditioned basement.

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Asked: 2023-10-26 13:01:19 -0500

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Last updated: Oct 30 '23