Check U-value of roof instance (element)

[szymon.szewczyk]

Hello everyone, 

I'd like to check U-value of roof which consists of layers of defined materials. I've noticed that Revit calculates the U-value related to thermal conductivity correctly for regular partitions with even layers. 

However in the model there is a roof with a slope created by insulation. 

In a real scenario for preparing energy characteristics of a building I would calculate U-value using average thickness of each layer. 

To conclude - I'd like to know if there is possibility to see U-value computed by Revit for each instance like I can see computed volumes, areas. example below. 

[GaryOrrMBI]

A fairly simple formula in a schedule should give you a rough average thickness:

Volume divided by area = thickness

-G

[barthbradley]

What about Calculated Values in a MTO Schedule? 

you can compute the "average" thickness via this formula: =(Material: Volume/1)/(Material: Area/1) 

Then pull this Calculated Value into another Calculated Parameter to compute U-Value.  

[barthbradley]

Actually, I don't know how that could be done. I don't think the "average" thickness will help you here in calculating the U-Value of the layer.  Frankly, I don't see how "average" thickness could be of any value here.  

Following...   

[szymon.szewczyk]

Hey, thank you for replies. I agree with you. 

Looking at pics from my original post it appears like Revit computes surface area, because both of those roofs have same dimensions in horizontal plane. So approach with volume/area wouldn't give true result. 

My main point is not about that thickness (it can be helpful for approximating U-value according to ISO 6846). Sorry for not making that clear in the post.

The question is about displaying U-value as an instance parameter, not as type parameter because in two of those roofs the insulation layer is of different thickness/shape so actual U-value should be smaller than the one displayed in type parameters.  

[barthbradley]

I'm not following. Instance vs. Type Property? Why would it matter?  The U-Value of a variable thickness roof -- if it can even be calculated, which I don't think it can -- would have to be calculated in a Revit Schedule via Calculated Parameters.   

[szymon.szewczyk]

thank you for explanation. To summ up it does matter, can be calculated manually and makes difference for heat loss calculation. 

It can be computed by Revit with couple of steps using schedule etc. 

[barthbradley]

---

@szymon.szewczyk wrote:

thank you for explanation. To summ up it does matter, can be calculated manually and makes difference for heat loss calculation. 

It can be computed by Revit with couple of steps using schedule etc. 

---

I asked what does it matter that the information come from an Instance Property. I'm not questioning the value of the information.  

[szymon.szewczyk]

Similarly to volume of 2 different roofs shown in first post, their U-value (for each instance) is different (due to different thickness of insulation), therefore in my opinion sould be accessed easily (e.g. in instance parameters).