Miscalculations in Ecodesigner (shipped with ArchiCAD 17)

[Anonymous]

This pertains to EcoDesigner's Operational Profiles. In my case I have a building that is only open two-days per week for 9 hours per day. When sizing the heat recovery ventilation system and defining its daily schedule, EcoDesigner shows correctly that the vent system will be operational for 936 hours for the year.

All good so far. However, when I define a corresponding Operational Profile for the building (two days per week for 9 hours per day) EcoDesigner calculates the annual hours of operation as 2,496 hours which is patently incorrect. This miscalculation overstates the usage of the building by over 200%, which translates into much higher energy consumption (kWh/cubic foot/annum) than should be the case.

The algorithm doing the calculation of operational hours per annum need to be looked into and fixed.

BTW I use kWh/cubic foot/annum because kWh/square foot/annum can sometimes be misleading. Higher ceilings (10ft-14ft) in a small, 3,000 sf community building will yield a different energy consumption profile than a 3,000 sf building with 8ft ceiling plate for the same number of occupants.

Any thoughts or perspectives on what I think are miscalculations in EcoDesigner's Operational Profiles would be much appreciated.

Thanks

[gpowless]

Don't get too out of shape.

Ecodesigner is not an energy-compliance tool. It is merely a pre-design estimation tool.

On the other hand, all energy-compliance apps are simply estimations in the first place. What we think is accuracy has little bearing on the real-world use of the building. And at the end of the day while we might come in within a few thousand watts it is nothing but a guess masked with calculations & flowery output.

[James B]

Hi Phil,

Just checking if you've reviewed this dialogue in the Building Systems?

[Anonymous]

James B:

Thank you. Indeed YES I have indeed used the Building Systems Dialog for the heat recovery ventilation system operating hours. When I tie the HRVS to the two-day per week, 9 hours per day I get the correct 936 hours of operation. When I go to the Operational Profile and define the same two days per week, same 9 hours per day for occupancy, I get 2496 hours; an incorrect calculation which overstates the potential energy consumption.

I know that actual building use is different from simulation. However, my long years of experience in the field of simulation (system dynamics in particular) dealing with highly complex public health models, tells me that clients want credibility and accuracy. If an arithmetic error of the kind I think I've identified in EcoDesigner and that I thus far cannot explain, then the whole purpose of energy evaluation becomes pointless and frustrating exercise. Moreover the credibility of using BIM models can be seriously compromised in the eyes of clients who can quite readily detect the arithmetic errors that I think I've identified.

I'd be delighted to chat with anyone on the Graphisoft team who thinks that I'm wrong and am missing a critical aspect of the Ecodesigner model

I am also aware that Ecodesigner is not EcoDesigner Star. I was on the beta teat team for EcoDesigner* and am anxiously awaiting its release. Even so, EcoDesigner needs to be accurate even if it is not extensive in its compliance with a variety of energy evaluation systems and standards out there.

Below are some screen shots of what I'm seeing

[Anonymous]

Gpowless:

I'm concerned about the credibility of EcoDesigner in the eyes of clients. See my reply to James B. on this.

Phil
iMac 3.4GHz Intel Core i7, 16GB 1333 MHz DDR3
OS X 10.8.4
ArchiCAD 17

[Karl Ottenstein]

pallsopp42 wrote:
Below are some screen shots of what I'm seeing

Don't see your screenshots. You can attach one per post, and there is a size limitation of 256kb as I recall.. so you'll have to lower the jpeg quality, use gif, etc. Or provide links to an external photo hosting site.

[Anonymous]

Karl:

Thanks - I'll reduce the file sizes later today and re-post

Phil

[Anonymous]

Karl:

per my previous note, I have - hopefully - attached two screen shots that show the large discrepancy between a 2-day-per-week; 9-hour day operational profile for the building's energy recovery ventilation system and the Operational profile of the building (occupancy, temperature ranges etc.).

[Anonymous]

And here's the other screen shot of the energy recovery ventilation system profile showing the correct 936 hours of operation per year.....

[Barry Kelly]

pallsopp42 wrote:
Karl:

per my previous note, I have - hopefully - attached two screen shots that show the large discrepancy between a 2-day-per-week; 9-hour day operational profile for the building's energy recovery ventilation system and the Operational profile of the building (occupancy, temperature ranges etc.).

I don't know much about Ecodesigner but there is nothing in this operation profile that tells it that it is only for 9 hours per day.
2 x 24 x 52 = 2496
Maybe Ecodesigner doesn't allow for hourly usage in an operation profile but only daily usage.

Barry.