Richard Tol posted at Climate Economics: How much energy do building code save?

Not nearly as much as expected, according to this paper by Arik Levinsohn. California has had building codes for energy since 1978, and they are tightened every so often. Levinsohn compares the energy use of buildings build before and after a code change, compares Californian houses to houses elsewhere in the USA, and compares the weather sensitivity of houses with different building codes. He finds that codes save energy, but the ex post estimates are lower than the ex ante ones on which the regulation was based.

Arik Levinsohn wrote at American Economic Review  How Much Energy Do Building Energy Codes Save? Evidence from California Houses 

Abstract

Regulations governing the energy efficiency of new buildings have become a cornerstone of US environmental policy. California enacted the first such codes in 1978 and has tightened them every few years since. I evaluate the resulting energy savings three ways: comparing energy used by houses constructed under different standards, controlling for building and occupant characteristics; examining how energy use varies with outdoor temperatures; and comparing energy used by houses of different vintages in California to that same difference in other states. All three approaches yield estimated energy savings significantly short of those projected when the regulations were enacted.

Footnote:  From Green New Deal promotional article:

Existing buildings hoover up about 40% of energy consumed in the U.S. and emit about 29% of greenhouse gases. The Green New Deal calls for retrofitting all of them—every last skyscraper, McDonald’s, and suburban ranch home—for energy efficiency within the next 10 years.