Openstudio has the option for ASHRAEClearSky versus ASHRAETau, which i am trying to use to compare to TRACE 700 but when i set the option to ASHRAEClearSky i get zero fenestration solar load. Has anyone else ran Clearsky and not Tau?
I'm assuming you're talking about the SizingPeriod:DesignDay object, specifically the Solar Model Indicator.
You're seeing no fenestration load because when you switch to ASHRAEClearSky it will look for the Sky Clearness (instead of the two tau values, $\tau_b$ and $\tau_d$). You probably left this field blank, which will default to 0, meaning no solar gains.
Clearness may range from 0.0 to 1.2, where 1.0 represents a clear sky at sea level. Values greater than 1.0 may be used for high altitude locations. Traditionally, one uses 0.0 clearness for Winter Design Days.
Edit:
Considering that the Sky Clearness field isn't exposed in the OpenStudio App, you could do something like this to change all your summer design days (the winter ones are usually already as Clear Sky, with clearness of 0) to Clear Sky with a value of 1.0
model.getDesignDays.each do |dd|
if dd.dayType == 'SummerDesignDay'
dd.setSolarModelIndicator("ASHRAEClearSky")
dd.setSkyClearness(1.0)
end
end
So plug in a value in the Taub and Taud location within a range of 0-1.2?
No, plug a value in the "Sky Clearness" (Taub and Taud is used when selecting ASHRAETau). Try with 1.0 for summer design day for example.
I see, the field isn't exposed in the OpenStudio App (which seems weird...)
I had the same issue. It's very confusing that you can select the model but not set the sky clearness. It seems to default to zero, because it's used for the heating load calc.
I opened an issue (feature request) on OpenStudio Github here
Comments
I would help if you could post the link to the documentation of the object you're manipulating and the resulting object too (from your idf)