[Equest-users] Modelling Floors with Different InteriorConfigurations

[Nick Caton]

It's my feeling that it is within reason to make the assumption that hourly heat transfer between conditioned floors is not necessary to model to achieve an acceptable level of accuracy, in most cases. 

 

Building on this assumption, I generally select "no exterior exposure" adiabatic roof and floor constructions for custom "per-floor" shells with a shell immediately above or below.  Adiabatic surfaces retain the inter-floor thermal mass properties (they store heat on an hourly basis without transferring heat to/from the associated plenum/space) while slashing the required model inputs quite a bit.

 

The only times I would do otherwise are if:

- a space or level is unconditioned or will be conditioned to very different setpoints (invalidating the above assumption) - in this case I might model adiabatically initially but would edit/assign to be a properly-associated internal partition in detailed edit, for those spaces only.

- a shell of a multi-story building has a mixture of exterior roof surfaces and internal floor constructions on the same plane, in which case I will specify the roof construction for the whole shell, then  delete the "sandwiched" roof surfaces between the floors in detailed edit.

 

Keep in mind:  You should not feel unequivocally 'forced' to create separate shells for each differently zoned floor.  While I also do this most of the time, we should keep in mind that a repeating floor pattern (using a multi-story shell) is potentially a MAJOR time saver and can justified from an accuracy standpoint in many cases:  Not every energy model is created with the intent to accurately model historical consumptions to a tight degree, and if the end-goal is to inform the design process and/or achieve LEED credits (90.1 models), a reasonably "averaged" floor zoning pattern is fine where that can be achieved. The 90.1-2007 User's manual encourages such geometrical simplification and floor multipliers where it makes sense, and gives guidelines for judiciously translating HVAC zones into larger, combined thermal blocks.


~Nick

 

 

 

NICK CATON, E.I.T.

PROJECT ENGINEER

Smith & Boucher Engineers

25501 west valley parkway

olathe ks 66061

direct 913 344.0036

fax 913 345.0617

www.smithboucher.com 

 

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Karen Walkerman
Sent: Tuesday, February 01, 2011 11:26 AM
To: Rob Hudson
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Modelling Floors with Different InteriorConfigurations

 

I think what Rob meant is "adiabatic", which means that there is no heat transfer across the surface.  This is usually an acceptable option for buildings where each space is maintained at the same, or similar temperatures.

 

--

Karen

 

2011/2/1 Rob Hudson <rdh4176 at gmail.com>

There is an option when assigning your roof construction in the wizard to make the space be below a conditioned space, and therefore ambient.  I have used this option before and it works beautifully.  if you need more information or a screenshot of what i am talking about let me know.

 

Rob

2011/2/1 Ömer Moltay <omoltay at mimtarch.com>

	 

	Dear All,
	
	We are encountering this problem all too often and would like to know if anybody has a satisfactory solution. For example, in a two storey building, the interior space configurations in each floor are considerably different, forcing us to create two separate shells that sit on top of each other in eQuest schematic wizard. However, when this is the case, eQuest treats each shell as a separate building and place exterior surfaces (ie. Roofs) between floors (instead of ceilings). The times it takes to manually convert these into interior surfaces with the right intra-space relationships is way out of reasonable limits.
	
	Is there a way to create a shell with floors that each have different interior layouts (even different exterior footprints for that matter)?
	
	Thanks,
	
	Omer Moltay, LEED AP
	Mimta Ltd.
	
	
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-- 
Rob Hudson


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