Conceptual energy modeling, difficulties with U-Values, Insight/Revit

[Anonymous]

Hi,

I have great doubts if revit/insight consider the u-values in my building model correctly.

As in online-resources explained, in Advanced energy settings, material thermal properties are so to consider:
1) conceptual types are defaults, and you have actually very limited choice if you build out of US (for example european energy-efficiency standars are significantly higher)
2) schematic types (if defined, they overwrite conceptuals, and there is a huge library of materials)
3) detailed elements: it takes the u-values from modeled element (this is not what I use in my model).

There are several reasons that support my doubts on Revit/Insight.

Firstly, I cannot verify the input-information about buidling envelope of my model. What Insight shows in results as Walls ("Current Setting: Uninsulated - R38 Wood") and what I defined ("Frame wall with 8 in insulation (U=0,1911)") does not match. Where did he take the info about "R38 Wood" (?)...

Secondly, I doubt on the reliability of results for Energy Use Intensity (EUI). With a very good envelope (based on passive house standards), in southeast Europe climate, you should achieve the building that consume 10-30 kWh/m² for heating and perhaps up to 100-200 kWh/m² for HVAC+Electricty. I researched this field in-depht and done numerous case-studies about it. This are approximate values to expect. What Insight shows are the EUI values in a range of app. 400 kWh/m²... With number of improvements, I come to 380 kWh/m²a or back to 500+ kWm/m²a...

Third, I have no a real overview of all input parameters after the simulation, beside such short sentences like "Wall construction Current Setting: Uninsulated - R38 Wood". No possibility to verify the input-data for a calculation = no reliability on the results. This is a kind of misleading.


How can I verfy the input data for calculation (after calculation) and be sure which U-Values the program considered? If I missed some control settings, I hope there is a solution for this problem. If not, I cannot rely on the results from Insight.

Kind regrads
Vladimir

[Anonymous]

Hi @Anonymous

Just a few questions for you to help determine what is driving the results you are seeing & to help understand what inputs are being used in the Insight analysis:

• When you specified the constructions in your Revit model, did you choose “Use the Detailed Elements” setting of the Advanced Energy Settings dialog? This is how Insight will use your model’s thermal elements (Use Detailed Elements for Thermal Properties).
• Did you remember to choose your location in the Revit Energy Optimization Panel?
• Did you choose a Residential building use-type in the Advanced Energy Settings in Revit?
• What other types of efficiency measures are used by the passive house standards? Are those specified in your Revit model?
• Are all of the intended spaces actually included in the Energy Model? You can confirm that by reviewing the help topic on Energy Models. If there are surfaces that are shades instead of envelope elements (walls, roofs, floors) the enclosed area is not included in the energy model. See Energy Model Contains Incorrectly Located Shades
• If you do not have Spaces and Space Properties specified in your Revit model, Insight will use default values for things like lighting power: References for Energy Optimization. This reference topic also describes many of the other input settings used by Insight if you do not specify them in your model.
• Are there Insight factor options that closely reflect those measures for you to choose from when calculating the EUI? Such as very airtight envelope, high-performing windows, efficient HVAC systems (unfortunately those choices in Insight are limited), very efficient lighting and plug loads, etc. This Insight Widget Settings document has more details about the options on the Insight Factor graphs: Insight Documentation

It sounds like you probably understand most of the Insight concepts, but I’ll just briefly cover them again. Insight automatically runs 9 parametric analyses for Wall Insulation (and calculates all of the combinatorial results with all of the other Insight factors) and R38 is just one of them. Looking at the factor widget graph, the triangle point labeled BIM shows where your specified wall construction falls in relation to the energy performance of the other factor options. At this time, Insight does not show a description of the construction of your Revit BIM model – it just says BIM.  

 The Energy Cost Range (ECR) values shown when you first view the Insight result are the mean, minimum, and maximum of the cost or EUI calculated with all ranges selected for each factor. (The initial Insight mean value result, is not the result of just model’s settings—it is the mean of the range of all the factor settings. If you want to see the result of your model’s settings, in each factor widget choose the BIM value).

These ECR/EUI calculations are based upon the 240+ parametric runs that are automatically generated by Insight. The reason for starting out with such a large range is based upon the idea that early in the design phase of a project there are many specifics that are not yet decided upon or known, such as maybe the architect does not yet know what type of glass they will use in the project—or maybe not even how much glass for each façade of the model.

To see the result for your Revit model, as well as for each of the individual parametric runs, log into Green Building Studio (the back-end service used by Insight), click on your project.

To see the specific values that are used in the analysis, from the Green Building Studio page, click on the specific run you want to understand (probably the base run) and go to the Export and Download Data tab. Here you can look at the gbXML file. Note that you can also download the gbXML file (as well as the DOE2 file and the Energy Plus file) from Insight (go to the gallery page in Insight—open the Insight where you model is stored (it will be in the “All Uncategorized” Insight until you create another Insight gallery to move it into) and expand the menu by the model. However the gbXML file from here will be populated with the input settings selected in Insight and not necessarily the ones used in the initial baseline Insight analysis with your model’s settings. The gbXML file might be overwhelming to review but using something like xml notepad gives you a tree view and you can look for constructions, etc.

Please click the "Accept as Solution" button if this solves your issue or answers your question so that others may also benefit from the information.

[Anonymous]

Hi marjoriestein,

thank you for your reply.

Firstly, here are answers, in order to understand my building model better.

I will adress a second part of your reply in an additional comment, I need to take time to check the sources what you forwarded to me.

Here are the answers on your questions:

• “Use the Detailed Elements” --- No, only conceptual and schematic.
• Location --- Yes, that was defined.
• Passive house --- Concept is with basic principles (passive solar gains, highly insulated und air-tight envelope, overheating prevention and heat-recovery mechanical ventilation), like here described http://www.beattiepassive.com/what-is-passivhaus.php. I did not define air-tightness and HVAC in details, but it is still a good house in terms of energy-efficiency for the region.
• The whole building is only one thermal zone. The building form is very simple, a kind of “simple box” modeling.
• I am familiar with basic setting in Insight, though I thing that “Insight Widget Settings” should be definitely packed in one PDF and be ready for download, not through GitBook…
• What I used for the envelope in “schematic” is following,
  Roof: Super-insulated flat roof (U=0,1769)

Ext. Walls: Frame wall with 8 in insulation (U=0,1911)

Floors: Passive floor, R-30 board insulation, any cover (U=0,1987)

Doors: Solid core wood, wood storm (U=1,6466)

Ext. Windows: Low-E triple glazing SC=0.65 (U=1,4554, SHGC=0.62)

Best regards

Vladimir

[Anonymous]

HI @Anonymous

You probably did, but just to be sure, in your schematic constructions you checked the box to ensure the constructions are overriding the conceptual constructions.

Also did you select the residential building type in the Energy Settings?

Did you review your Energy Model in Revit to make sure the entire space is properly enclosed? 

Go to Green Building Studio and look at the area to make sure it is what you are expecting (may be some minor differences). If there is a big difference then there is a problem with the Energy Model.

Feel free to send me your model in a personal message if you checked those things and are still getting unexpectedly high results.

[Anonymous]

Hi Marjorie,

I checked the model in green builidng studio. This is even more strange. The end results are in a way realistic, but the input is really questionable. Below I listed some issues.

End-results from Green building studio:
Building Type: SingleFamily
Floor Area: 240 m²
Location: Belgrade, Centralna Srbija Weather
Annual Energy
Energy Use Intensity (EUI)     686 MJ / m² / year
Electric     41,566 kWh
Fuel     14,971 MJ
Annual Peak Demand     18.3 kW

I come with that to EUI: 190 kWh / m² / yr

and about 17 kWh / m² / yr.
So far, so good...


Misleading issue No. 1:

In green building studio, these are u-values from the envelope (these are not the same like what I defined, and I have realy no idea where he picked these information from...)
Base Run Construction
Roofs     
R20 over Roof Deck - Cool Roof
U-Value: 0.25 R20 over Roof Deck - Cool Roof Layers
    120 m²
Exterior Walls     
R14.8 8in Concrete Wall
U-Value: 0.37 R14.8 8in Concrete Wall Layers
    364 m²
Interior Walls     
Uninsulated Interior Wall
U-Value: 2.35 Uninsulated Interior Wall Layers
    293 m²
Interior Floors     
R30 Wood Frame Floor
U-Value: 0.19 R30 Wood Frame Floor Layers
    120 m²
Slabs On Grade     
Concrete slab R15 perim
U-Value: 0.07 Concrete slab R15 perim Layers
    120 m²
Fixed Windows     
North Facing Windows: Double Low-E Clear U-SI 1.96, U-IP 0.35, SHGC 0.67, VLT 0.72 (2 windows)
U-Value: 1.96 W / (m²-K), SHGC: 0.67 , Vlt: 0.72     17 m²
Non-North Facing Windows: Double Low-E Clear U-SI 1.96, U-IP 0.35, SHGC 0.67, VLT 0.72 (14 windows)
U-Value: 1.96 W / (m²-K), SHGC: 0.67 , Vlt: 0.72     56 m²


In my model, I checked in "schematic" following U-Values:

☑ Roof: Super-insulated flat roof (U=0,1769)
☑ Ext. Walls: Frame wall with 8 in insulation (U=0,1911)
☑ Floors: Passive floor, R-30 board insulation, any cover (U=0,1987)
☑ Doors: Solid core wood, wood storm (U=1,6466)
☑ Ext. Windows: Low-E triple glazing SC=0.65 (U=1,4554, SHGC=0.62)


Misleading issue No. 2.
On the other hand, Insight End-Results are miles away... and I see no connection between these two...
EUI: 358 kWh / m² / yr
20180406_Einfammilienhaus_simple_2
1749 | 11


What I'm realy missing in energy modeling with revit/insight/greenbuidling studio is "One Single Point of Truth". This make the work-flow unstructured, models very inconvenient, and leave the recommendations about energy-design for clients on a very weak argumentative basis.

[Anonymous]

Hi,

here two screenshots

1) Inconsistency GBS / Insight
2) Inconsistency GBS / Revit

I saw you can control your model my using project templates in GBS, so all U-Values can be defined directly in GBS (my understanding ist, that the GBS will jus ignore the whole input from revit and overwrite the thermal qualities of the budilign envelope with this "template settings"). Is that right?

My next Quesions:
Can I limit the number of simulations from GBS (For example: I want only one, instead of 240+ automaticly generated from revit/insight/gbs)?

[Anonymous]

Hi @Anonymous

From your screenshot comparing GBS with Insight, the Insight selections you have selected are a range & not a single value. The single value in Insight which will represent your Revit model (and also what is shown in GBS) will be the BIM point. To edit the selections for each factor, click on the card you will see the points selected highlighted in blue. Drag the slider bars to select the point, or range of points that you want to use in the calculations and close the window. Once you close the window the graph will be larger and you can see the label for each point. For the BIM settings right now Insight doesn’t show the specific details from your model (except for the Window to Wall ratios).

Unfortunately I can’t tell from your second screenshot of the Insight settings, but in the Advanced section you need to check the box that says “Detailed Elements,” otherwise Insight will use the Conceptual constructions for your model. Sorry this workflow isn’t made more clear.

The templates in GBS don’t work with the normal Insight workflow. Those are a legacy feature from an older workflow, but you can still use the templates with these steps outside of Insight:

1. In GBS create a project
2. Create a Project Template in GBS,
3. Assign the template to the project you just created
4. Export the gbXML file from Revit: Select the “Room/Space Volumes” option for the export
5. Go back to GBS to your project and upload the gbXML file
6. This workflow will only generate one analysis run
7. When the analysis is finished and you open the results look at the top left corner (under “Energy and Carbon Results” tab name) and you will see the Project Template Applied name. You can click on the template name there to confirm the template settings are correctly set

 Please click the "Accept as Solution" button if this solves your issue or answers your question so that others may also benefit from the information.