Hello,
I got a simple question and read most comments here and in NC, but it seems I cannot find a similar question.
In my understanding, the regularly occupied areas in IEQ 8.1 and 8.2 must be consistent to each other, and that should be net floor areas.
Also, to fill out the supplemental spreadsheet, you'll need to know the floor area, not only the ratio of daylight area between 10-500fc.
Now, if you use simulation method for 8.1, do you model a building with thick walls to get the result in net area? i.e. modelling the rooms and extra wall spaces? Or is it OK to model the building with single lines and run simulation (wall thickness = 0: gross area), then estimate the result in net area in any ways like; 1) multiplying the each area's result daylit ratio to its net area or 2) counting the calculation points within the net area space (excluding the points within walls/furniture/shelves) and re-calculate the daylit area? Is there any established method for that?
Alternatively, is calculating the gross areas for both credits in this case all right? - that may affect the result in negative way though.
I haven't submitted any project using IEQ8.1 simulation method yet and I appreciate to hear any thought about that.
Thank you.
TODD REED
Energy Program SpecialistPA DMVA
LEEDuser Expert
889 thumbs up
May 1, 2014 - 8:51 am
The coordination that needs to occur is between the credits and PIF 3.In PIF 3 you have a gross area and the regularly occupied area. The regularly occupied area is the area used in your simulations. That area is not the net, do not consider the thickness of the wall, its the space between the walls that is modeled, the actual space that someone can stand in. Disregard your thoughts of estimating results vs. net. One last time, the regularly occupied column in PIF 3 in table PIF3-1 is the only area you need to worry about with 8.1 and 8.2. That area must be the same as that which is modeled.
As modeling goes, the thickness of wall should be considered when you have an opening, such as the exterior wall. Walls between adjacent spaces can be just one plain, and that is typical modeling protocol. The more surfaces, the more errors, the longer run times.
Takayuki Hirota
izumi CONSULTING, Inc.7 thumbs up
May 1, 2014 - 9:25 pm
Thank you for your prompt answer, Todd.
I thought the thickness of wall are not considered in simulation. Thank you for your clear explanation, that's really helpful for me. Thinking about that, it's really time consuming to model and calculate a building...
In the credit forms, there are "Total regularly occupied area" where figure is linked to Pif3 and "Total regularly occupied area documented in Upload L-8" that you fill in manually. I thought the former is a gross area and the latter is a net area (excluding space between the walls and other objects occupants do not stand in), and when I did so in my previous project, that was accepted by the reviewer.
The other areas we fill in in PIF forms are gorss, so it is little uncomfortable to use net area only for regularly occupied area in PIF3. I think it is not a problem if we use gross area in PIF3 and net area in 8.1 and 8.2, if you can show the suggested spaces correspond to each other. But of course it's easier to use net area in PIF3 than explaining precisely about the different areas if the reviewer asked.
Has anyone ever had problem when using gross area in PIF3 and net area in 8.1/8.2?
Greg Collins
December 15, 2020 - 12:19 am
I do not agree with Todd's answer above. I know this post is old, but it showed up as a top search result while I was looking for net vs gross areas while doing ventilation calculations using an energy model. I think that's a very similar situation to the "regularly occupied" floor area for daylighting and other calcs. It seems to me that the answer to the net vs gross question has one answer that is more appropriate for the specific use case, and potentially another that is easier to use and/or maintains consistency with other calculations.
In my opinion, energy models typically use gross area and most other calculations (ventilation, daylighting, etc.) should use net areas. However, if you have a good energy model, why not use it for ventilation calcs as well? My question is whether it's appropriate to apply a net-to-gross factor to the area-based component of a 62.1 ventilation rate.. I feel like it's reasonable to do so, if substantiated in some way.