Uncertain of Sefaira's results

We are working on a new construction project. A residential duplex. We are looking to use an IFC (Insulating Concrete Forms) for the wall assembly. Our goal is to show the client how much better an IFC wall would preform compared to a standard wall construction. We have ran Sefaria and generated some results. We are curious about the results and their accuarcy. We thought a great difference in the numbers. E.g Annual Energy Cost. We are in the Design Development phase and are trying to pin down a the type of wall construction. Based on case study of wall with High R values from Building America we are uncertain if we are interpreting the result of Sefaria properly. We are looking for some guidance or if you could point us in the right direction to figure out a clear solution. We are using Sketch up 2020. Attached are the combined result of the 3 wall types we ran and double and triple glazing for each wall type. And also have attached the inputs. Thank you so much in advance.

There aren’t any attachments.

And you use IFC (wrongly and confusingly I think) for Insulating Concrete Forms. IFC means something else in SketchUp. I think you meant ICF.

Did you analyse in the web browser after the initial setup in SketchUp? Maybe @niraj.poudel could help in interpreting. (if you attach the model :slight_smile:

Edit: changed category

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Here is the model and results. And, yes correct. Meant ICF. Transposed it. Thanks for any insight or input in advance! Cheers!

1903 - DDs - Sefaira - Opt 1.skp (2.3 MB) 1903 Dupont - Sefaira - COMBINED RESULTS 20.08.03.pdf (101.0 KB)

Hi @mardavm144,

Thanks for sharing this scenario. I’m out of office this week but should be able to take a look at what might be going on early next week. Maybe my colleagues @HNatarajan and @AlexG might be able to take a look in the meantime.

Good Morning,

I just wanted to follow up. Has @HNatarajan or @AlexG or yourself been able to take a look at the model or results. I have not heard anything back for anyone. Please respond at your earliest convenience.


HI @mardavm144, thanks for following up. Apologies for not getting back to you sooner. Would you mind sharing the web app project with me as well? Simply copying and pasting the web link should suffice. I would like to see the inputs that you have set up for these studies.

Another thing to keep in mind is that this model has a couple of issues with it.

  1. There are floors overlapping, as you can see in the .gif below there is Z-fighting where the overlap occurs. Sefaira will count the floor area twice and will service the area with twice the airflow requirements.

  1. You only want to tag areas with floor designations where you want the design loads applied, along with the HVAC to service on a per sq footage basis. Some of the indentations and undulations on the facade need not be tagged as floor. A good rule of thumb is, if people are going to be occupying that area or can walk on that surface then tag that as a floor, otherwise tag it as “shading”.

  2. The railing on the roof is tagged as a floor as well. Sefaira will try to service that area. Another best practice to keep in mind is that you will want to ask whether a surface encompasses conditioned space? If so then tag it as a wall, floor, roof etc otherwise either tag it as shading or ignore it (if it does not participate in blocking the sunlight reaching your project).

I hope this helps. Once you correct the issues listed above >> re run the analysis >> please share the project along with the updated SketchUp model here so that I can check to see what might be going on.

Thanks for your reply. The web app used is https://sefaira.sketchup.com/page/project/314533.

This is our first run with Sefaira. Thanks for your input and help. We’ll go ahead and correct the issues you mentioned and re-run analysis and see if that solves the problems. And also share so you might be able to confirm that our results are accurate.

Thank you.

Hi @mardavm144, very welcome. In the meantime you might want to go through these videos as well.

Will set you off on the right foot. The majority (99%) of the errors stem from how the building is modeled for energy and daylight analysis.

@mardavm144 - there is a case study over at the Iowa Nest which is worth looking at. A passive home built entirely of Insulating Concrete Forms (ICFs) and designed entirely in SketchUp, Sefaira and LayOut.

The results? The energy consumption is actually LESS than the Sefaira prediction. We’re talking under $3/month if I remember.

The website was www.iowanest.com