Temperatures in January dropped to -24°F and an air source heat pump kept it comfy and cozy.
There was a "polar vortex" even in Chicago at the end of January, where the outdoor temperatures sank to -24°F (-31°C) at night and got all the way up to -18°F in the daytime. For many people, this would be a problem, but as the Mayor of Chicago said once, "You never let a serious crisis go to waste." Mike Conners certainly didn't; he is the builder of the Ellis Passivhaus, a renovation and reconstruction built to the EnerPHit (renovation) standard and he wanted to see how well his house did. He writes:
The 2019 polar vortex produced -24 F lows that averaged approximately -17 F for 34 consecutive hours. Ellis Passivhaus maintained an interior temperature of > 71 F throughout, far above the required 68 F comfort standard. The ERV (energy recovery ventilator) continuously delivered fresh filtered air while retaining > 84% of the energy in the extract air stream. Despite the heating system’s 140 kW per hour rated capacity (48K BTUs), actual use averaged 7,5 kWh per hour (< 26K BTUs) during the 48 hour event or ~ 90% less than comparable Chicago stock all else equal. All systems performed flawlessly.
And this is while using a Mitsubishi air source heat pump, when everyone has been saying for years that heat pumps are not efficient at such low temperatures and can't cope.
Conners notes that "occupancy of Chicago’s buildings leads to 73% of Chicago’s total annual C02 emissions." Most of that is from burning natural gas for heat. Going Passivhaus reduces the energy consumption by 90 percent, and is useful in events that last longer than the vortex, which caused a spike in the price of electricity:
The polar vortex price spike could have been longer and more pronounced and event driven spikes can turn into secular shifts. For instance, a natural disaster, plant failure or regulatory event like a carbon tax might induce a secular price shift. That’s why it’s always beneficial to need as little energy from the grid as possible.
This is the main reason I am such a fan of Passivhaus. You put your money into the stuff that just sits there and works, the Passive stuff like windows, insulation and careful design and construction. Then the active stuff, like the heating system, gets smaller and cheaper and becomes almost superfluous. Conners noted that a couple of cheap space heaters could have done the job, had the heat pump not worked.
Another thing I have come to admire about Passivhaus is the air quality. I used to go on about natural ventilation, but these days you wonder about opening a window. According to the American Lung Association, Chicago gets an F grade for pollution. A major active piece of hardware in a Passive House is the Energy or Heat Recovery Ventilator, required to provide “continuous balanced mechanical ventilation with energy recovery.”
Ellis Passivhaus uses a Zehnder ERV that removes 90% of particulate matter greater the 1.0 microns and 75% that is < 1.0 microns. It runs 24/7 at 84% efficiency and uses < 2 kWh per day of electricity.
Steve Mann of Passive House Buildings noted that there were other considerations besides the usual Passivhaus requirements, involving what I call Upfront Carbon Emissions. For instance, I didn't know this:
In addition to pursuing Passive House certification, the project team paid equal attention to the carbon footprint and greenhouse gas production of the project. It sourced local materials whenever possible. For instance, realizing that most hardwood floor products are made from North American hardwoods that are shipped to China for finishing and then shipped back to the United States, the team located an urban-forest mill that sources felled hardwood trees from local park districts and arborists. The mill supplied rough-sawn white oak that was finished into tongue-and-groove hardwood flooring.
You don't give anything up on the appearance and the amenities for Passivhaus, this house has every comfort.
The Vortex analysis is just the latest addition to an extraordinary website that covers the design and construction of the Ellis Passivhaus. Conners is president of Kenwood Construction, but also is Passivhaus certified as a tradesperson and design consultant. Credit also to architects Richard Kasemsarn, Consultant ZeroEnergy Design, and Certifier Andrew Peel.
A lot of people try and document their Passivhaus- building experiences; some, like Chie Kawahara, even write books about it. But I have never seen a job documented like this. Every calculation, every detail, every catalog cutting of every piece of equipment, this is a gold mine.
The house is for sale and is pitched as being "planned, optimized and verified. Wellness, sustainability, resiliency and maximum energy efficiency converge in this meticulous reconstruction." And, as is found in most Passivhaus designs, it's "comfy, cozy and quiet!"
Come in and get lost at Ellis Passivhaus.