So far only two states – Maryland and Vermont – have adopted the 2015 International Energy Conservation Code (IECC). But that doesn’t mean a lot more might adopt it, or important provisions from it, very soon.
In particular, there are two provisions that stand out. One is a clear reference to a blower door standard. This sounds simple enough; nothing ground breaking here. Only, the previous version of the 2012 energy code radically upped the ante for air sealing – going from 7 ACH50 to 3 in climate zone 3 through 8 – without specifying how that requirement should be verified. The 2015 revision provides an important reference to the allowable ASTM standard blower door tests … ones that are rigorous enough, it should be noted, that many builders are unlikely to subsume them into their building process without assistance from home-performance pros.
The other big update that may speed adoption of the 2015 energy code is the ERI – or Energy Rating Index. An ERI provides a simple way for homebuyers to compare the energy efficiency of one house to another. The lower the number, the more energy efficient the home, with zero being a net-zero home. Builders will benefit from this because they now have three compliance paths to choose from: the ERI compliance path, the prescriptive path, and the performance path.
The surprising part – which might be viewed as good or bad, depending on your stance on government-mandated home energy performance – is that meeting the basic requirements of the ERI path yields a home that more closely matches a home built to the 2009 IECC than the more energy-efficient home built to comply with the prescriptive or performance paths of the 2015 IECC. Read more.