[EnergyPlus_Support] ground heat transfer modeling for unconditioned spaces

["Spencer, Justin" <Justin_Spencer@xxxxxxxx>]

I'm looking for a good way to model ground heat transfer from
unconditioned spaces.  The basement and slab programs require an input
temperature for the space.  This isn't too hard to provide when you have
a conditioned space - you should be able to get close.  Since the ground
transfer is driven by a small temperature difference between the space
and the ground temperature, getting this temperature wrong will have a
big impact on the resulting ground temperatures and energy balance in
the space.  

 

In particular, a ventilated crawlspace with some amount of duct leakage
into the space creates a real modeling conundrum, since the ground
transfer is one small part of the temperature in the space.  I can think
of 2 possible solutions:

1.	Use an iterative approach.  Run the basement model with a guess
at the temperatures in the space, then run the resulting ground
temperatures in the full simulation, make a new guess at the
temperatures in the space, run the basement model, until convergence is
reached.  (iterative approach)
2.	Abandon the basement model.  Ignore ground transfer through the
floor.  Model the walls with regular 1-D walls, with wall properties
that approximate the soil and wall performance.  (Perimeter conduction
approach)

In the long run, if the basement model ran with the actual building,
instead of needing space temperatures as an input, then the basement
model could be run once, instead of requiring exhaustive iteration.  

 

What's the best workaround to use in the short term?

 

Justin Spencer

 

 



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