Minnesota slams door (and insulates it) on drafty homes with new energy code

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The new residential energy code will include some exciting opportunities for builders and homeowners. One of the most impactful changes: an air tightness requirement for new homes of 3ACH(50). This means that a house with a 20-mile-an-hour wind blowing against it can only be so leaky to allow three housefuls of air to cycle through the house in a one-hour period.

To help demonstrate what this means, imagine a one-story 1,866 square foot house (the size of the average American home) built to the new code with an air tightness test of 3ACH(50). This would be equivalent to allowing a 9.7 inch by 9.7 inch hole in an otherwise perfectly-sealed wall. The current Minnesota residential energy code—roughly  estimated to be at 7ACH(50)—would allow for as much space as a 14.75 inch by 14.75 inch hole in the wall for air and heat to escape through. Homes built to the highly efficient Passivhaus standard require a tightness of 0.6ACH(50), allowing only a 4.3 inch by 4.3 inch hole. In other words, the smaller the number preceding ACH(50), the more energy efficient the house.

9_14_HouseGraphic2The code’s new air tightness test will give builders an opportunity to showcase how well-built their homes are. Not only will this new requirement for tighter homes lead to lower utility bills, but Minnesota has also added balanced ventilation requirements to balance moisture and bring in fresh air, improving comfort and air quality for homeowners.


But why do we need a new energy code? Isn’t Minnesota already a leader in building energy-efficient homes? While we do build more energy-efficient homes than some states, this is in large part due to our climate zone—our codes typically require that we build more tightly insulated buildings for our cold weather.

However, we have fallen behind in the adoption of new, updated energy codes compared to other states. For example, in 2014, we are currently operating under an energy code equivalent from 2006. Minnesota recently adopted the IECC 2012 with amendments, which will go into effect in 2015, making Minnesota already three years behind by the time the code is implemented. The IECC is updated every three years and the IECC 2015 has already been released. Some states—not including Minnesota—are moving toward adopting it.

Energy codes set the bare minimum requirements for energy use in buildings. Because buildings make up 40 percent of our nation’s energy use they’re a key strategy in reducing our energy consumption. It is critical that we have standards in place that ensure buildings are energy efficient when they are built, rather than requiring owners to make upgrades later. By adopting the newest codes, we give builders a chance to enhance their building skillsets and knowledge while ensuring that homeowners receive comfortable, energy-efficient homes built to the best-available building practices and technology.

Code compliance also plays a key role in the effectiveness of energy codes, and Minnesota is already taking steps in the right direction. Fresh Energy is working with key stakeholders to ensure high levels of compliance in Minnesota. Stay tuned for more details; feel free to contact Alison Lindburg with questions.

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