Ecodesigner R-values

[Anonymous]

I've just downloaded Ecodesigner (using w/ Archicad 14, North American units) and cannot figure out the outputs I'm getting from the R-value calculator. For a simple example, let's take one assembly that is just 11 1/4" of cellulose insulation. When I go into the composite structures and assign an insulation material to the fill (choosing "Ecofiber" as it seems closest and I don't see cellulose as a choice), the thermal conductivity assigned seems accurate at 0.0231/foot, which works out to a R-value of 3.6/inch...

But the calculated assembly R-value doesn't seem to match: the calculator gives an R-value of 5.64 in the grayed out box. The units imply that this is for the assembly, not per inch. Either way it doesn't make sense.

And then if I override this value and put in my own intended value of 40.5, Ecodesigner automatically sets the value back to 8.07. My guess is that this is a maximum value? Despite this field clearly being ft2-F-hr/Btu, I try 3.6 as the R-value per inch to see what happens. If I then click OK and get back to the Structures tab, I see that my assembly has a value of 20.44, which doesn't seem to have anything to do with anything.

So I'm baffled. I can't seem to make the sophisticated-seeming calculator work, and even if I override the values, the override input is then itself somehow overridden or transmuted in the main Structures list. Does anyone know what's going on? Am I just getting confused somewhere trying to flip between European u-values and American R-values?

[Anonymous]

I'm not really familiar with the American system (we use the international one).

As far as I remember from the time I tested Ecodesigner, once you build up your envelope structure (wall, roof etc.), the software automatically calculates the total transmittance of that structure (U value).

U = sum(1/R interior air + 1/R1 + 1/R2 + ... + 1/Rn + 1/R exterior air)

In the IS, the unit of the U value is W/m2K (W=watt, m2= square meter, K= temperature difference Kelvin degree between inside and outside).

So yes, I think your problem is trying to work in R values in a U values software.

[Anonymous]

But the problem is really much more complex than that. Even if choose U-value rather than R-value, the problem stays. And anyway, R-value is just the inverse of U-value, so I shouldn't be getting such wacky and inconsistent results.

Does nobody in North America use Ecodesigner?

[Graham Whipple]

Molly,
we are in the US and have Ecodesigner and have dabbled in it, but honestly didn't get results that made sense at the time we dabbled. We may have an opportunity to explore the functionality again soon and when I do I will look closely at the issues you have mentioned.
I am not sure that my post really even helps because I don't have any answers for you, but I wanted you to know you aren't alone here either in the US or in the "baffled" state of just how Ecodesigner is working.
I can only hope to delve back in soon and see what we can learn here in our office because this is indeed real functionality we need out of Ecodesigner.

Graham

[Anonymous]

Thanks for the response, Graham. It's good to know we're not the only ones. It seems likely that this is another case of Graphisoft dropping the ball on the US version.

[Graham Whipple]

I've assumed that our difficulties were related to a first effort with the software and the challenge of learning the intricacies that surely impact the results of the analysis. Honestly we just didn't have time to learn the full functionality in the crunch time and so we need to devote more time to learning assessing and inquiring about the functionality and output before we were willing to pass an early and unfair judgement about the software.
I will certainly be exploring it more, but may wait until AC15 arrives so I can see the full functionality of things with the new tools.

Graham