The Guys recently spoke about energy conservation codes and their application to new homes.
What we did not speak of was the nuts and bolts regarding the code application, specifically.
The codes require minimum insulation values, rated windows and doors, total building performance, and high-efficiency mechanical systems.
The United States is divided into eight zones based on climate, from extreme hot in Key West to the subarctic cold of the far north.
Most of Michigan falls into either zone five or six, which classifies us as a “heating design” state.
This determination is made, in part, by historical data that shows we are most often below a mean daily temperature of 65 degrees; so, we require artificial heat sources for most days.
You can access heating degree days, HDD, for various parts of the country through the International Energy Agency, IEA, where we find that North Dakota is one of the coldest states in the country, while Texas is one of the warmest.
We calculate HDD on a daily basis using 65 degrees as the assumed temperature where neither heating nor cooling is needed. If you calculate the mean temperature for a twenty-four-hour period, then subtract the mean from sixty-five, you arrive at the total HDD for that single day.
On January tenth, we had a high of 30 degrees and a low of 10 degrees, so our mean was 20 degrees, based on the total of 30 plus 10 divided by 2. Sixty-five minus 20 equals 45 HDD for that period.
Michigan, as a state, averages around fifty-four hundred HDD every year, while a state like Florida is designed for a cooling climate, and would calculate cooling degree days, CDD.
The more heat we require in a year, the more insulation is required by code, as well as higher efficiency mechanical installations.
For thermal insulation, we use a measure of the material’s resistance to heat transfer through it, called R value. The higher the R value, the better the thermal insulation.
For the exterior wood frame walls of a new home in Michigan, we would be required to have a cavity insulation of either R 20 or R 13 with a corresponding insulating sheathing over the walls with an R 5 or R 10.
The sheathing, or continuous insulation, is required because we have a wood stud in the wall approximately every 16 inches, with the wall cavity occupying 14 1/2 of those inches. Wood studs, due to their low R value, would act as a thermal bridge between outside and inside where heat could move, so we require the continuous sheathing to negate this movement.
Windows and doors, what we refer to as fenestration, are rated differently. While R value measures resistance to heat transfer, U value measures the amount of heat actually transferred in a controlled environment by a single material or assembly.
So, while we seek high R values where required, we look for low U values in windows and doors, like 0.3 for instance.
There is also an air leakage requirement in the code regarding the uncontrolled movement of air through cracks and gaps in the thermal envelope.
This leakage is calculated as unwarranted air changes per hour, ACH. The thinking here is that we consume energy and spend money to condition the air in the house, so we don’t want that conditioned air leaking out of the building only to be replaced by unconditioned outdoor air.
The level of air sealing must be tested upon completion of the project to measure no more than four ACH under the old code and three ACH under the 2021 International Energy Conservation Code, IECC.
This “tightens” a home. When we build to such a standard, we risk creating a contaminated indoor environment, so it becomes critical to remove toxins, dust, excess humidity, etc., and introduce fresh oxygen.
One method used for this is to install devices called energy recovery ventilators, ERVs, that exhaust stale air and bring in clean air that is preconditioned. The ERV will extract heat from exhaust air and infuse the incoming air with that heat.
Builders have some flexibility under the current codes in terms of compliance. The Prescriptive Compliance Path simply requires that every component meet or exceed required minimum insulative values, whereas there is also a Performance Path that allows greater design flexibility, where an energy simulation demonstrates that the proposed design uses no more energy than a code-compliant reference building.
Houses are scored with an Energy Rating Index, ERI, with lower scores indicating higher efficiency.
The best way to ensure a safe and healthy living environment is to only let professionals work on your home or office. Pros like those you can find every day at Insideoutsideguys.com
Listen to the Inside Outside Guys every Saturday and Sunday on AM 760-WJR from 10 a.m.-noon or contact us at insideoutsideguys.com.
This article originally appeared on The Detroit News: The Inside Outside Guys explain why energy codes matter for a new home
Reporting by Ken Calverley and Chuck Breidenstein, The Inside Outside Guys / The Detroit News
USA TODAY Network via Reuters Connect
By Ken Calverley and Chuck Breidenstein, The Inside Outside Guys | USA TODAY Network
