MRC_Book_CoverPrescriptive Path

This path is the simplest to follow and is where most builders will find the easiest compliance option. As the name implies, this path follows the letter of the code like a doctor’s prescription. Install the insulation to the levels in Table 1102.1.1. Also complete the items listed as “mandatory” and have a blower door test done at the final to show that it meets the air leakage requirements, and that’s pretty much it. No trade-offs and a minimum of paperwork.

Here are your steps:

  1. Construction documents must contain details, such as a section drawing which shows the insulation levels outlined in the code. Other details such as the location of air barriers must also be included in drawings and documents submitted with the permit application.
  2. Schedule an insulation inspection BEFORE DRYWALL but after the insulation is installed. During this inspection, the inspector will look for insulation in areas that will be hidden from view during final inspection. Not only will they look for the insulation and it’s thickness or R-value, but they will also look for air-barriers to be properly installed in locations listed in Table 1102.4.1.1. They should also be looking at the duct locations and sealing methods; remember that building cavities may no longer be used as ducts (N1103.2.3)
  3. Schedule a blower door test to be performed after the house is made air-tight. Typically this occurs about the time the painters are touching up the walls and trim. If you don’t already have a go-to person for blower door testing, you can find one in Michigan at www.MichiganBlowerDoor.com
  4. Post a sticker with the insulation values and blower door test results on the electrical panel door. Some code offices and insulation contractors have pre-printed stickers. They can also be printed from a REScheck file report if you built a file for the house.

Total Ua Compliance Path

Here is where things start getting complicated and you’ll do much better if you have a designer¬† who specializes in code compliance to complete the calculations and prepare the documentation for you. At the time of this writing (January 5, 2016) the Michigan BCC has NOT RECOGNIZED THE IECC 2015 AS AN “ABOVE CODE PROGRAM” that can be used in lieu of the Michigan Energy Code. To see the ACPs that are approved, turn to section N1101.7 Until the state does recognize the IECC 2015 as an above code program, you’re stuck doing the math long-hand to prove that your home “as designed” is as good or better than the code reference home. Nu-Wool insulation is working on a spreadsheet calculator to help do the math.

To understand Total Ua, you first need to understand what Ua means. A U-value is the opposite of R-value and is typically used for assemblies made up of materials with various R-values. For example, a 2×6 wall with R-21 insulation is actually not R-21 because there is framing, sheathing, drywall, paint, siding, and air films that all make up the wall. So the U value of that wall might be .058 which is a little over R-17. After calculating the U value of the wall or other building component, multiply times the area to get Ua. By adding up all the Ua values for all the building components, you should end up with a nice big number like 500 or 600 something for a typical house. Compare your calculated Ua to the reference home Ua and as long as your home is the same or lower, it complies.¬† Now wasn’t that easy?!

If the state does approve the use of IECC 2015 and therefore the handy software tool REScheck, keep in mind that you’ll have to bump the attic insulation up R-49 because that was the original value in the 2015 code before Michigan lessened the requirement and made it R-38.

Performance Path

This path used to offer the greatest trade-offs for many builders. Stated simply, if the estimated energy costs of the proposed home are lower than the estimated energy costs of the code reference home, then it is deemed to comply. Keep in mind that this trade-off as well as the Total Ua trade-off method take steps that do not allow for the trade-off of mechanical equipment (you can’t skip some insulation and put in a more efficient furnace).

The biggest trade-off item from previous versions of the code involved the blower door test to prove that less air infiltration would mean lower energy bills. In this new code however, the air leakage requirement is almost half what it used to be, and so half of the trade-off value is gone.

To calculate the performance path, you’ll need to use a software tool to calculate the energy costs. The most common tool is REScheck.

Energy Rating Index (ERI)

Index 1

If you are not familiar with HERS Ratings, read THIS POST to learn about them. The code states that depending on your climate zone, you can have the house rated by a HERS Rater and if it scores a 53, 54, or 55 (depending on climate zone) then it is deemed to comply. There is a HUGE caveat to this path however; in order to comply, the insulation levels listed in the 2006 Code must be met prescriptively without trade-offs. That means R-10 foundation, R-20 / R-13+5 walls, R-38 attic, etc. If you want to make any trade-offs in R-value, this method is not the choice for you.

There are many other reasons to get a home rated by a HERS rater besides code compliance. In fact, for most HERS Raters, code compliance documentation is a by-product of doing a rating. The code officials look favorably on a builder who is using a HERS rater as well because it takes much of the guess work and inspection checklists off their plate and rests them on the rater.

 

Above Code Programs

ES_logo_3At the time of this writing (January 5. 2016) the only programs approved by the State of Michigan as “above code” are ICC700-2012 Silver (USGBC) and ENERGY STAR 3.0. Since the new code requires blower door testing and mechanical ventilation, as well as many other requirements that are also required by ENERGY STAR, many builders will find that their code built homes are 90% of the way to complying with ENERGY STAR and so should just push the last little bit and have the home certified as such. To learn about ENERGY STAR, visit the Contractor FAQ & Guides section of this site.

MEECA is working hard to get more programs recognized by the state including Passive House, Net-Zero, LEED, and others.

 

Summary

If you’re looking for an easy answer, build prescriptively to the letter of the code or hire a HERS Rater to help you with compliance. If you have a bunch of time on your hands and like to learn new software and argue your points with the code office, try using REScheck to calculate the Total Ua or Performance path….then call a rater!