Default ASHRAE 90.1 envelope parameters - Additional options?

Hi all
I noticed that I am sometimes getting unintended values for both Roof insulation R-value and Window U-factor when selecting various Construction Types using the ‘HB Construction Set by Climate’ component, and I wonder if additional options on this component could be added to differentiate between the following:

Roof type options (ability to select between IEAD, Metal, or Attic for Roof R-value)
Fenestration type options (ability to select between Non metal, Operable, Fixed, etc for U-factor)

For example, for this Steel Framed building in Climate zone 6 using ASHRAE 90.1-2016, it looks like the component is pulling the U-factor for Metal Framed Entrance Door (U-0.68) instead of the value I would like to use, Metal Framed, fixed window (U-0.36) or Non-Metal fixed window (0.30). I assume that this 0.68 value is being applied to my window geometry in the analysis and as a result I will be getting inaccurately high heat loss through my glazing?

When I select different Construction Types, I get various other energy code values. For example, when I select a Wood Framed building, I get a window U-factor of 0.30 (which aligns with the ‘Non-metal framing’ value in ASHRAE 90.1-2016 for CZ 6, however, I the Roof insulation is 0.47 (defaults to the ‘attic’ value), while my intention is to the IEAD value of R-31.

I understand that I can make a custom construction set using the ‘HB Construction Set’ component, but I appreciate being able to quickly set the envelope parameters to code values. Is it possible to add a few additional options to the ‘HB Construction Set by Climate’ component to allow control over the Roof type and Fenestration type defaults being pulled from the library (in the same way that we can select between the wall types)?

ASHRAE 90.1-2016 values below for reference:

Roofs (ASHRAE 90.1-2016 table 5.5)

Fenestration (ASHRAE 90.1-2016 table 5.5)

Thank you!

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I agree. Selecting between residential and nonresidential defaults would also be useful.

I recently pushed a fix related to fixed windows in 2019:

It looks like I will need to push something similar for ASHRAE 2016 and thanks for bringing this to my attention. This probably explains why you’re getting the metal framed entrance door U-value and I’ll post back here once the fix is implemented.

I would rather not change the “ConstructionSet by Climate” component since it’s helpful to have various construction sets organized by SteelFramed/ WoodFramed/ Metal/ Mass categories. Most of the time, these 4 construction types dictate which of the ASHRAE 90.1 fields get used and I’d rather not let edge-case combinations affect the most common cases.

However, if it’s painful to edit these construction sets with the current components, it would only take a few lines of code in a new Python component to edit the base construction set and replace the attic roof with an IEAD roof, for example. All that you have to do is:

  1. Get the construction set by identifier from the honeybee_energy.lib.constructionsets library.
  2. Duplicate that ConstructionSet and output the duplicate from the component.
  3. If you want to change a certain construction, get the construction set by identifier that has the construction that you want (eg. Get the WoodFramed version if you want attic insulation).
  4. Adding that construction to the duplicated constructionSet.

I’ll see if I can out together a sample of this later but it’s not very difficult to do this with the LBT SDK.

I also wanted from make sure that you knew that you don’t need to start from scratch when using this component. You can use it to edit an existing ConstructionSet by plugging in a base_constr_set_. Let me know if this addresses a lot of your concerns and maybe we can put a custom Python component on the back burner.

I added a fix for the U-values in 2016:

You should be able to get it with the LB Versioner in ah hour or so.


Much appreciated, Chris! I see the glazing U-factor changes incorporated in the updated component.

A smaller issue, but something I also just noticed…skylight SHGC values for both 2016 and 2019 are incorrect, as are skylight U-factors in climate zones 1 and 6-8 for ASHRAE 90.1-2019.

I would be interested to see a custom Python component as you mentioned that replaces all ‘Attic’ roof insulation values with ‘IEAD’ if you get around to it (or a similar option that allows users to select either ‘Residential’ or ‘Non residential’ assumptions). I have been slowly learning Python so I will be sure to share something if I get to it first!

Thanks again,

Thanks @molly ,

It seems that these skylight issues might actually be bugs in the openstudio-standards gem from which we derive all of these construction sets. I can see that NREL seems to have the wrong values in its massive spreadsheet:

You’re referring to these values for Climate Zone 1 in ASHRAE 90.1 2019, right:

If so, this bug is on NREL’s side and I’ll open up an issue on their GitHub repo to see if they can fix it.

Hey @molly ,

I opened the issue on the openstudio-standards repo:

Let’s see what NREL has to say about this case.

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Hey @molly ,

NREL was pretty quick to get a fix together for the skylights so I just updated the LBT plugin with their fix:

So this should all be addressed now. Thanks again for bringing this to our attention.

Excellent, thank you!