Revit 2022 HVAC load and energy simulation results - Validation

[HVAC-Novice]

Did anyone actually validate the HVAC load and energy simulation data of the R2022 features? And do you have enough confidence that it is usable for design and ditched 3rd party software (Trane Trace, HAP, Trace 3D etc.)? 

I had spent quite some time with older Revit versions and concluded the results are more like guesses and at most usable for initial estimates and not for actual design (like where I stamp the results and get in trouble if it is wrong). Some lack of features that scare me was no ERV function, and lack of other features to be set that would have an impact on load and energy calculation.

So I ended using Trace 700 (and now Trace 3D). I'm not really happy with Trace 3D, and also want to do more in Revit as long as it is correct. I looked a bit into the System Analysis features of R2022. But it seems limited and clunky for what details one can decide on. This is sad, since not using a 3rd party software would be much more efficient and would have fewer errors transferring information. If I have a choice for accuracy, I really would like the Load part to be correct over the energy simulation. The load calc is what I actually stamp, and what is needed for every project. 

If Revit is only good for "estimates "and later in design I need to use a 3rd party software, I would just skip the Revit features entirely. But I really wonder if it is good and accurate enough now. 

Yes, I read the help files and they make it sound like it is great. 

So what is your experience with R2022 Load calcs? 

[dyp4f]

This is a good question. I think that almost every Mechanical or HVAC Engineer, who is using Revit and is responsible for cooling and heating loads calculation, is wondering if he/she could trust Revit’s Report output. I mean to trust those Reports, not just as an initial estimation, but as an official submittal document that he/she could sign professionally.

I believe that an independent body like ASME, or ASHRAE, or EnergyPlus, or some committee of HVAC Engineers should do a thorough Study about the accuracy of the HVAC Loads, as they are calculated and reported by Revit.

Every single year we are waiting for a valid tool inside Revit, that we could really trust, but even today with Revit 2022, we are all still wondering whether we can trust it for loads calculations, or not.

[iainsavage]

The calculations are done using EnergyPlus which has, I assume been validated.

My concern in the Energy Analysis in previous Revit versions was the validity and completeness of the input data which Revit sends to EnergyPlus, rather than lack of confidence in the EP calculation.

I waded through a lot of the EP documentation from their website and it is very comprehensive but it relies on a 3rd party interface (in this case Revit) to provide the input.

My own problem previously has been that I couldn’t find a way of seeing the input data, setpoints etc which Revit sends to EP and some users on the forum have said that changing certain values had no effect on calculation results which implied that Revit was maybe ignoring certain user inputs and just sending its own assumed values to the calculation engine. This lowered my confidence in the accuracy of the results.

The newer Systems Analysis tool seems, on the surface, to give the user more control and visibility in terms of the inputs, therefore, maybe a higher level of confidence in the results?

[HVAC-Novice]

Thanks to both for the replies. I agree, the EP engine is fine and is used by all modern 3rd party software. where the quality of all software differs is how user-friendly and adjustable the interface is. and part of a correct design is that I can see what is going on so I can tell errors. 

AFAIK Revit doesn't tell me a lot of what data I enter it actually uses. and it also doesn't have as many options to enter data or detail the systems like a 3rd party software. 

I'm also a bit less concerned about energy simulation results. Because there we don't care that much about absolute values. We really only need to know the differences between scenarios. Energy consumption in real life also depends on the actual usage, proper commissioning etc. 

But load has to be reasonably correct since all systems are sized based on that. Too large, and we waste equipment and operate outside good operating ranges (short cycling etc.), too small and we freeze or sweat. 

I'm not even sure if the 3rd party software (Trane, Carrier) have some sort of certification for the load. I just know all designers use them. I know some energy efficiency organizations (like for energy efficiency tax credits etc.) have a list of approved software. But I'm not aware of an approved list for load calculation. I know the software manufacturers go great lengths to put all responsibility on the designer. 

[dyp4f]

Let say an independent Engineer decides to spend (a lot of) time to make a private research on testing Load Calculations Programs. Let’s say he puts on the test 10 buildings, and for each one building he uses: Trace, HAP, Trace 3D, IES VE, REVIT e2022, etc.

He then receives for each one of the 10 buildings results that differ from each other.

How could this Engineer come to any certain conclusion, after this test?

Which program is closer to the real numbers?

Is TRACE better than REVIT 2022? Is REVIT 2022 better than HAP?

Who knows?  Is there anyone who can judge, and tell the truth?

Who can validate or not a Load Report produced by a Software, since there is nothing already validated to compare to?  If there was a Validated Program we would know its existence, and we would use it!

That’s why I say there is an absolute need for a Scientific Approach. Take for instance ASHRAE. Over the years, several ASHRAE committees have invented several Load Calculation Procedures, but they never go beyond the theoretical point of view: they have never tested and evaluated the relevant “Real World” Software Programs, for True Compliance against their Procedures / Methods. All commercial Programs on the market claim that they accurately implement the ASHRAE procedures, but all these all just commercial claims, since ASHRAE doesn’t validate nor invalidate those claims.

What kind of responsibility can a single Load Calculation Engineer have in this strange situation?

All modern ASHRAE Load Calculation Methods demand the use of computer Software, but no end-user Software is validated. All end-user Programs are proprietary and closed, “Black Boxes”, and you can’t see what Data they are taking as Inputs, nor what calculations they do inside. They just throw numbers at the end, out of the “Black Box”, and you have to trust them blindly.

I am wondering how our Professional Engineers Societies can allow to continue such a sick situation:

Anyone Claims Anything, and Nobody can Validate Anything.

[RSomppi]

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@dyp4f wrote:

you can’t see what Data they are taking as Inputs, nor what calculations they do inside.

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I'm not so sure that is true. I've seen the formulas that are used in more than one program. I was never interested in them as they are above my pay grade and I was only trying to learn to use the programs.

[iainsavage]

@dyp4f 
EnergyPlus is not proprietary software, its an open source initiative: “EnergyPlus is free, open-source, and cross-platform—it runs on the Windows, Mac OS X, and Linux operating systems. Its development is funded by the U.S. Department of Energy’s (DOE) Building Technologies Office”

The comprehensive documentation includes an Engineering Reference describing the methodologies and equations used, as well as an Input and Output reference.

https://energyplus.net/documentation

There’s also information and reports on the methods used to test and validate the software.

https://energyplus.net/testing.

So I think EnergyPlus is fairly transparent.

But again the EP engine can only be as good as the input data which it receives from the 3rd party interface (Revit in this case).