As a certified HERS rater and ICC Residential Energy Inspector / Plans Examiner I find many builders and even inspectors that get confused when it comes to the Energy Codes (IECC). So with that in mind we have started a new series on the basics not written in code speak, starting with the three means of complying with the code and three key terms to watch for…
Three compliance paths:
Unlike the Building Codes (IRC, IBC, IFC…) that are primarily prescriptive in nature, the energy codes are geared more towards performance and effectiveness. With that in mind they have created 3 means of complying with the code:
- Prescriptive – just like it sounds, you need to follow the code to the letter (while you can do better you can’t do any type of trade-offs – i.e. better windows doesn’t mean you can skimp somewhere else)
- Performance – AKA the UA / insulation trade off option – i.e. architect uses ResCheck or something similar to show compliance (for example skipping under slab &/or exterior continuous insulation in favor of adding more insulation in the attic)
- The ERI Option – AKA the HERS path where one has to meet or be less than a target HERS score where you can use higher efficient appliances to comply (Only applicable to 2015 / 2018 codes – 2009 / 2012 didn’t have this option)
3 Key Terms to Understand:
Generally at the start of an energy code section you will spot the words (Mandatory) or (Prescriptive) shown. While reading through a section you may also spot some Exceptions: which can be quite helpful.
(Mandatory) is a term that applies to all three paths and of course needs to be done – for example all new construction work must have a blower door test done & must be below the permissible ACH limit.
(Prescriptive) is used only for those following the prescriptive path – for example the section on fenestration only applies to those following the prescriptive path while the other two can do other tradeoffs to qualify. So if you would like to have more than 15 SF of stained glass you would need to choose another path.
Exemptions: are just what they sound like, an exemption from that section if XYZ applies completely. For example no duct testing is required if all the ducts are located inside the thermal building envelope. Now if you are going after the tax credit, going after a certification, or trying to maximize HERS points you might still need to do a Leakage to Outside Test but that’s for another piece.
Got any specific questions on this or other parts of the code – please leave a comment below or contact us.