Skylight >5% of roof area

If the proposed skylight area is greater than 5% then it is modeled as designed and the baseline skylight area is reduced to 5%. Then use the skylight values for the baseline in Tables 5.5-X.

Hi Marcus,

I have a similar doubt for an airport project. The WWR is coming to be more than 40%. Also,the skylight area % is coming to be around 42%.

Can you suggest which table to be followed to refer to the baseline U values for the vertical glazings and skylights in this scenario?

So the baseline WWR is reduced to 40% and the skylight area is reduced to 5%.

The U values and SHGC to use are in the 5.5-x tables. Which one you use depends upon the climate zone associated with your project. You can find your climate zone in 90.1-2010 Appendix B. 

Hi Marcus,

we are basically trying to establish compliance of actual design in an early stage project based on baseline values in ASHRAE 90.1 2010. So ,for an actual design with WWR>40% and skylight>5%, can we still refer to the baseline value based on the climatic zone?

Or, do we go with the envelope trade off method or COMcheck tool?

Are you trying to establish code compliance? If so then you likely need to follow the performance path in Section 11. 

Are you trying to establish LEED compliance? What you are trying to do is still unclear to me.

Hi Marcus,

we are trying to establish code compliance for building envelope. Instead of energy cost budget method(since at this early stage we dont have most of the inputs for energy modelling), can we explore the envelope trade off option as per Appendix- C, which allows us to compromise on single envelope parameter given other envelope parameters meet the prescriptive values.

Or, use the COMcheck DOE tool for checking the compliance.

Any suggestions on the above?

If only trying to demonstrate envelop compliance you can certainly use the Appendix C trade off method. I think the COMcheck tools just follow that same procedure.