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Difference between Climate Zone 5 and 4 Marine

We are working on a 5 story wood framing over concrete podium senior living facility in Thornton, Illinois. I am trying to understand the difference between Climate Zone 5 and Zone 4 Marine.

Looking at the Blog Post on this website, "Calculating the Minimum Thickness of Rigid Foam Sheathing", the table on the second page lists the recommendations for Foam Sheathing Thickness, and there is a considerable difference between the Climate Zone 4 Marine, and Climate Zone 5? But, each map I have looked at shows that Cook County, Illinois is both/the zones are the same?

Any feedback would be great.

Thank you

Asked by Andrew Buck
Posted Jul 1, 2014 10:44 AM ET


2 Answers

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First of all, you are correct that Illinois is in two climate zones. The northern half of the state is in Climate Zone 5A, and the southern half of the state is in Climate Zone 4A (not Zone 4 Marine).

I will post an image below to help you decide whether you are building in Climate Zone 4 or Zone 5.


Climate zone map for Illinois - 2.jpg
Answered by Martin Holladay, GBA Advisor
Posted Jul 1, 2014 11:11 AM ET


Here is the link to the Climate Zone Map for the entire country:
Climate Zone Map.

Answered by Martin Holladay, GBA Advisor
Posted Jul 1, 2014 11:14 AM ET

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