Slab-on-grade Floor 90.1 baseline model

asked 2019-06-17 14:49:37 -0600

EnergyPlus question
269 ●11

updated 2020-01-13 16:41:08 -0600

__AmirRoth__

4436 ●5 ●17 http://bleedinggreenna...

Dear all, I have a question regarding how to create the slab-on-grade floor for the baseline model. Below are my questions and the research I have done so far: 1. 6" concrete floor. It seems that 6" concrete floor (density 140lb/ft^3) normally be used for the baseline model.
2. Created the slab-on-grade floor based on F-factor.
Through EnergyPlus/OpenStudio, we can create the floor with the F-factor that required by ASHRAE 90.1. However, EnergyPlus/OpenStudio uses the F-factor to generate the slab-on-grade floor zone by zone. It might require extra work to so since it depends on how people zone their first floor.
Here is the link regarding creating the F-factor floor: https://leeduser.buildinggreen.com/fo... Please correct me if I am wrong. If the project has an underground floor, 0 will be the perimeter input in EnergyPlus.
3. For software that cannot do F-factor floor, it is recommended to calculate it from Appendix A of ASHRAE 90.1.

If you have come across this before, what you recommend an approved methodology to create the slab-on-ground floor.

By the way, the energy consumption difference between the model with 6" concrete floor and the model with the floor that is calculated by the F-factor is more than 5%.

answered 2019-06-20 08:36:17 -0600

JasonGlazer

6835 ●26 ●12 http://www.gard.com/

Seems like the simplest approach is to use the Construction:FfactorGroundFloor object. It is described in general here. I would also recommend reading the details of this approach in the Engineering Reference.

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Thank you, but I checked the report that PNNL documented. It seems that they recommend using both methods. (https://www.pnnl.gov/main/publication...) However, there is around 5% difference (for energy consumption) between them. What is more, the measures that NREL creates for OpenStudio "Create Baseline Building" (https://bcl.nrel.gov/node/83661) do not use F-factor to generate the slab-on-grade floor. That is why I got confused. Could you please give more advice? Thank you.

EnergyPlus question ( 2019-06-20 10:35:57 -0600 )edit

There are multiple ways to get things done. If you are including added insulation in your proposed model compared to the baseline than you probably want the most accurate approach but if you are not then it is your judgment which approach to use.

JasonGlazer ( 2019-06-20 10:39:16 -0600 )edit

Thank you, I totally understand that there are multiple ways to get things done as far as their results are similar. However, as I mentioned above, there is around 5% difference between the F-factor method and 6" concrete floor method (F-factor method consumes more energy from my test). And my question here is only for the baseline model. Both methods that I referenced from PNNL are for baseline models as well. And could you please clarify what is the most accurate approach(F-factor or 6" concrete floor)? Thank you.

EnergyPlus question ( 2019-06-20 10:43:08 -0600 )edit

For this particular topic "most accurate" is difficult to determine. I think I would probably use the Kiva approach which will probably give you yet another answer.

JasonGlazer ( 2019-06-20 10:58:11 -0600 )edit

Thank you Jason.

EnergyPlus question ( 2019-06-21 08:52:31 -0600 )edit

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