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The Tale of The Zero Energy Ready Home That Survived Sub-Zero Temps Without Heat


In January 2019, energy usage, uncomfortable homes, high heating bills, and broken pipes became top of mind in the wake of the polar vortex. We all received tips on what to do to best prepare for and maintain our homes during this arctic blast that closed schools and offices and left us cuddled together in our homes.


So what did we do? We shut off the furnace at one of our completed, Zero Energy Ready Homes. With an average starting temperature of 70 degrees throughout the home, we monitored the time it took for the temperature to drop below 50 degrees, triggering the furnace to turn back on. We called this the H.E.A.T. (Home Endurance And Temperature) Challenge and publicized the results across Facebook


To many eager viewers’ surprise, the home lasted 34 hours from Monday January 28th, to Wednesday January 30th without dropping below 50 degrees. During that time, outdoor temps plummeted from 17 degrees (felt like 2) at the beginning of the challenge, to -23 degrees (felt like -52). This record-shattering low temp (the previous record of -15 was set in 1966) is what caused our furnace to finally kick on at 3:25 am Wednesday morning. 


Our own Scott Sanders documented the journey with videos to track the home’s progress and break down some of the features that helped us maintain the heat in this new construction home. 


Breaking Down The Walls: How to Insulate a Better Home


It all begins with a wall assembly that is this well-insulated and airtight. A proper wall assembly will retain heat and create a weather barrier from the outside - keeping your home cool in the summer and warm in the winter. Our wall assemblies are made up of 5 primary components:




A staggered stud wall assembly consists of 2x4 studs spaced 12 inches apart on center, sitting on a 2x6 bottom and top plate. This creates a "serpentine" style of framing. As the insulation is blown in, the staggered stud system allows the insulation to form a continuous flow throughout the wall, creating a 'serpentine' effect. This is special to BrightLeaf homes because standard board insulation techniques result in wall assemblies where the board is against the wall there is no insulation to protect from exterior elements. Our staggered stud assembly setup costs about the same as a standard assembly and is just as easy to build for a skilled carpenter. 




Exterior Sheathing

This home is built with a highly engineered exterior wall sheathing structural board. The “skin” on the outside is a high performance Zip System by a company called Huber. Using sheathing and adhesive tape to seal any points and seams in the wall, we create a sturdy building envelope that maintains the home's structural durability and a built-in, water resistant barrier to protect the home from moisture buildup. Most importantly to this experiment, the Zip System reduces air leakage to minimize heating and cooling costs and keep the home comfortable. 




The windows in this home are triple pane vinyl frame windows made by Sierra Pacific.  Triple pane windows are more resistant to condensation, and in colder climates like Chicago, they make your home more energy-efficient. They've even been known to noticeably reduce outside noise. Triple pane windows aren't standard on many new construction homes in the U.S., but installing these over single or double pane windows in our climate will save your home on energy costs and can add value should you decide to sell. 





We insulate the walls in our homes with a dense packed cellulose from Nu-Wool. Using pre-consumer and post-consumer content (including 86% recycled paper), the material is ground into bits and blown into walls so it sticks to the wall assembly and fills every nook and cranny. Not only does this dense packed cellulose slow air flow to save heating and cooling costs, it is non-settling, pest-resistant, fire resistant, and much better for the environment. 




Attention to Air Sealing Detail

We pay close attention to air sealing - both on the outside and on the inside - to make a better performing wall. An airtight drywall approach pays particular attention to any leaky areas. Anywhere possible, electrical boxes, switches, outlets, and pipe setups are put on interior walls to stop holes that lead to the outside. When an electrical box or other component is placed on an exterior wall, it is sealed up with high performance adhesive tape to the backside of the drywall to cut down on drafts and heating costs.




To get an even more in-depth look at the make-up of our walls, check out our Inside the Walls tours that show all the cool stuff behind our walls.


Infrared Camera “Ghost Hunting”

To check our work, Scott used an infrared (IR) camera on loan from Craig Matteson of Arc Insulation in Romeoville to view the real-time performance of our insulation and sealing.



This camera marks hot and cool surfaces with color. Think the movie Predator. Blue and green colors reflect cooler areas and yellow and red identify heat. As we saw, areas around windows and doors show a bit of leakage, which is typical and impossible to seal completely. Looking at an interior bathroom wall, the IR camera shows the wall as one uniform color, meaning the wall is well insulated; there are no hot spots or cool spots. 



Moving into the basement, the IR camera shows that it was actually warmer than the main floor. As the basement is mainly underground, it is protected from the outside air. The walls in the basement are also made up of a lot of concrete, creating a giant thermal mass that holds in heat and acts as an insulator. 

Certifiably Better Homes

Using these building practices in all our homes earns certifications that prove our homes are up to snuff and perform better than a standard new construction home. 



EPA Energy Star Certification

The Energy Star certification follows homes that  are built with better energy efficiency and performance to generate lower utility costs. Energy Star homes are at least 10 percent more energy efficient than new construction homes built to code. You may see this certification on washing machines, refrigerators, dishwashers, or other products that are more energy-efficient than other products on the market. In this case, our homes are certified to be more energy-efficient when compared to other new construction homes. 


Indoor Air Plus Certification

Building on the Energy Star Certification, Indoor airPLUS is a voluntary program awarded to homes that improve the quality of the air through construction practices and building materials that cut down on airborne pollutants and contaminants. It also ensures homes are protected from moisture, mold, pests, combustion gases, and airborne pollutants. Having a home with this certification verifies that the building materials are low in or contain no VOC content. As Scott explains, that “new car smell” is not good for your health or the environment - it’s the smell of chemicals and doesn't belong in your home. 




DOE Zero Energy Ready Certification

A Zero Energy Ready Home certification recognizes builders that strive to increase energy efficiency, improve air quality, and make homes zero energy ready - meaning a home has a renewable energy system that offsets all or most of it's energy consumption. It’s an achievement not just about energy, but making sure you have a better built home that costs less to maintain.


Find out more about how the advancements in our building techniques produce healthy, energy-efficient homes on our Healthy Homes page

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