I have an existing envelope that is a complete curtain wall assembly that is to be replaced. The overall WWR for the building is over 70% currently and is being removed and redesigned to be approximately 35% glass when complete. Two questions:
1. Should the baseline model WWR be the original 70% or be set at the new WWR of 35%?
2. Should the baseline glazing and wall assembly values be set at current conditions (single pane glass, low wall R-value) or have to meet the minimum requirements in section 5 of ASHRAE 90.1-2010?
Thank you.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5909 thumbs up
January 16, 2018 - 10:53 am
The standard is certainly not clear. Table G3.1-5 Baseline (f) indicates that you can model "existing conditions". It is not clear that they mean area and window performance values or just window performance values. Looking ahead in the development of Appendix G in ASHRAE 90.1-2016 it appears that they have clarified this to include the area. So I think that you can model the baseline with the original 70% WWR and the existing performance parameters.
Wade Cooper
1 thumbs up
January 16, 2018 - 11:06 am
Thank you Marcus. I appreciate your expert feedback.