Hi, first off a simple question – when defining the thermal zone, what are the boundaries suppose to correspond to - the exterior facade or interior wall?

I have a house model situated on a sub terrain, meaning a "half-cellar" where the back wall is placed into a ground. How can I define a thermal zone so that the back-wall is set as a foundation? The side-walls are obviously half-exposed to air and the front wall as an exterior wall to the outside air. Any other suggestions how to simulate the energy loads of a sub terrain-level?

Thanks

Tags: definition, level, sub, terrain, thermal, zone

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This is a common energy simulation scenario. You want to make two separate breps for the two boundary conditions of below and above grade. Be sure to make sure the below grade wall is defined as BOTH a thermal zone face (with material) and tagged separately as ground with the boundary rep component.

This may give you the impression that you'll have duplicate objects in your simulation, but the boundary rep component uses its input to 'find' the faces in the zone that should be tagged as ground.

When I have worked on these types of models with students, you have to make sure that you don't have objects with more than 4 vertices (per energyplus). It is best to greatly simplify where the ground is meeting your walls.

Keep in mind the energyplus models archsim use constant ground temps for ground contact boundary conditions. You can put in your own numbers for each month, which may be slightly better, but for models that depend on high accuracy with ground contact it is better to use the secondary simulation tools that come with energyplus which are specifically designed to simulate earth contact accurately, where isotherms are influenced by soil depth and heat transfer over time with the building. Those things get super advanced super fast -- definitely not something your average architect is going to spend time on. If you use the basic ground temps, I would take your results with a grain of salt and think of them as an estimate (as all energy simulations are).

Thanks a lot for the answer. Do you mean like this? Pls see attached png. There is one energy plus component for my simulation. 

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