Heat loss DTD by climate zone or state?

Gcracker · October 2018

Can anyone tell me if there is a reference or even a generally-accepted rule of thumb for DTD in a heat loss calculation by state/climate zone? I have had trouble locating this specific resource, and could use something more than my layman's assumption that you look at climate data and go from there.

Specifically, in climate zone 6, what DTD would be considered prudent?

Zman · October 2018

https://www2.iccsafe.org/states/virginia/plumbing/pdfs/appendix d_degree day and design temperatures.pdf

Gcracker · October 2018

Thank you so much!

According to this, then, if we go by -13F, then an 80-DTD isn't that far off.

We had some -20F days last year, and in a perfect world, I would hope the calculation included the coldest possible day, but 97.5% is pretty close, I guess.

GBart · October 2018

You can change it just check with your building inspector first, those are minimums for your area, climate IS changing, units last 20 years so plan carefully.

You could size your heat for -20 and your cooling for 100 if your town will let you

GBart · October 2018

Actually that chart is 2006 and seems off, in my area we design for 0F heat and 95-100 cool and that chart says 7 and 88 ?? compare to this one, seems to me the older numbers were better, with climate change your design numbers should be changing so you winter temp should be lower and your summer temp higher to compensate not the other way around.

https://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Design_Temperature_Limit_Reference_Guide.pdf?8fd5-1967

Heat loss DTD by climate zone or state?

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