Re: [EnergyPlus_Support] C-Factor for Underground Walls and F-Factor for Slab-on-Ground Floors (ASHRAE 90.1, Title 24 etc)

[Jean Marais <jeannieboef@xxxxxxxxx>]

You have it! The key with (B) and energyplus is to understand that as long as you correctly reverse engineer the physical construction, the physics take care of themselves and you (should) hit the correct rating as per the rating method.


2014-02-18 12:59 GMT+01:00 <<mailto:seanking.1970@xxxxxxxxxxx>seanking.1970@xxxxxxxxxxx>:
> Â 
Thank you very much, Jean. Very detailed and useful reply.

> However, I still cannot come out of this maze, I need a straightforward confirmation to my statements below.
> (A) In EnergyPlus, we can definitely use F-factor, C-factor objects and do not need to care about layered construction at all (E+ does, as you said:Â f-factor c-factor objects create layered constructions internally, which has also been confirmed by EneryPlus support staff).
> (B) As an alternative way, we can also use layered constructions for F-factor (as an example) with the procedures as (1) read F-factor value from Tables 5.5-1 through 5.5-8 depending on climate zone and space conditioning category; (2) calculate equivalent U-factor based on the ground floor area and exposed perimeter; (3) create layered construction (normally a concrete plus an insulation) to meet U-factor calculated by step 2; (4) set outside boundary condition to ground (not FCfactorMethod then). For this setting, we just forget about F-factor (just used as an input to calculate U-factor), but use conventional U-factor instead.
> Best regards,
> Sean
> 
> 




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