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E+ vs. IES: Loads Results comparison

asked 2019-01-04 06:01:54 -0600

Angeliq gravatar image

updated 2019-01-04 08:58:51 -0600

I am trying to do a comprehensive analysis between the two software, IES VE and E+ (Grasshopper), regarding the Zone Loads. I know that a diffrent method is used for IES (CIBSE) while E+ uses other standards. So far I managed to model and simulate a test building, with the same inputs in both. The results I am getting are diffrent by 9%. I am trying to compare the inputs/outputs and for that I need to get from E+ the following:


-Air temperature (°C)

-Dry resultant temperature (°C)

-External conduction gain (kW)

-Internal conduction gain (kW)

-Air system input sensible (kW)

-Aux vent gain (kW)

-Infiltration gain (kW)

-Natural vent gain (kW)

-Space conditioning sensible (kW)

-Steady state heating plant load (kW)

-DHW heating demand (kW)


I am guessing that:

-Air temperature (°C) --> Setpoint

-Aux vent gain (kW) --> Heatgain rate from DOAS

-Infiltration gain (kW) --> Infiltration Heat addition (IES has negative values for certain rooms while E+ has zeros)

But I am missing the rest ..

Hope this makes sense :/

Thanks in advance!

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answered 2019-01-06 21:47:04 -0600

lutinfr gravatar image

You can change IESVE calculation methodology to ASHRAE to check so. As I know, CIBES is more on steady state methode, ASHRAE is true dynamic simulation, so it's different. IES also suggests that after sizing with CIBSE methodology, users need to check unmet hours to ensure heating capacity is enough, no need this checking with ASHRAE.

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First of all thank you for taking the time to reply! Yes, I know that I can do the calculation using IES VE, but the purpose of this exercise is to identify the main diffrences between the two software (IES vs. EnergyPlus (using OS for GH)). I know they use a diffrent method to calculate (IES using both ASHRAE and CIBSE) while OS only ASHRAE but according to CIBSE Guide A: This is essentially only an issue of computational efficiency and does not affect validity. Among other things I want to estimate the margin between the two, should I decide to only OS for/and GH, from now on.

Angeliq gravatar imageAngeliq ( 2019-01-07 11:31:53 -0600 )edit

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Asked: 2019-01-04 06:01:54 -0600

Seen: 118 times

Last updated: Jan 06