Which input location do I use?

[Anonymous]

I am looking at getting us future ready for when Eco-Designer is available again in North America and also to use the built-in modelling functionality a bit earlier in our design process. As I was digging through the window parameters I noticed that there are 2 locations to input the u-value of the window, one in the "Descriptions..." section of the Windows Settings Tab and the other in the Classifications and Properties Tab and they aren't linked. My question is which one do I use so that my BEM comes out with the proper results.

Second kind of related question, anyone know how to convert Thermal resistance per mm (RSI) to Thermal Conductivity (Btu/hr.ft.f)? My provincial and National building codes have a bunch of values for what is common in the jurisdictions I work in and it would be nice to use that information do avoid headaches a the permit desk or later in the process.

[poco2013]

The U value under descriptions is a object parameter and can be used to fix the U-value as a default for a particular type of window object. The U- value under classifications is a property and can be used to set the U-value on a individual basis. You need to decide if you want to use a general default for a type of window verses on a individual basis.

U value and R value are generally considered to be the reciprocal of each other -- but they are not the same as they consider different parameters, at least, as concerns windows. R values are more popular, in usage, since a higher R value is more desirable and easier to understand.

You can get the R value of a U value by just creating a expression and returning the reciprocal -- R = 1/U

However, expressions do not have access to object parameters so the description U- value would not be available to be inverted by a expression -- Only the property value.

The two values are not linked because they may be different depending on use. I agree they should be named different if used for different reasons?

[Anonymous]

Yeah, our codes and industry in Canada are all over the place when it comes to units. Code is in metric units, my framers still working in imperial, my surveyors work in metric, I get material data in both; my window supplier specs the U-value, my insulation packaging has an R-value on it, and all my calculations for opaque assemblies for permits have to be done with RSI values... it is all over the place.

Then there is ArchiCAD asking for a Thermal Conductivity (Btu/hr.ft.f) value. I am okay with converting all the values to put in the software but trying to find the right conversion factor is proving to be troublesome and updating the database to use the these accepted local values is proving to be a bit more difficult than it should be.