How different is the Stretch Code from the existing Base Code?

The Stretch Code requires new homes to meet a Home Energy Rating System (HERS) target of 55, and the Base Code requires a HERS rating of 70.  (With HERS ratings, lower is better.) 

On January 1, 2017, both the Base Code and the Stretch Code were updated.  With these changes, the difference between the two codes is now much smaller than in the past.  Additional details about the Base Code and Stretch Code can be found here:  https://www.mass.gov/files/documents/2017/11/21/stretch-energy-code-over...