The first “Spot ERV” installation seems to be a success!
In our article on Spot HRV’s, we talked about “decentralized ventilation” and how to ventilate a home where it’s difficult to impossible to connect a ventilation system to existing ductwork, because there’s no ductwork, or adding it would be too expensive, or you’re renting and can’t alter the building. At the end of the article, we concluded that spot HRVs can be useful for those living in dry areas like Arizona, but if you live in a humid climate at least part of the year, you’ll want an ERV. Until now, I hadn’t heard of a “spot ERV”, but one enterprising renter (Alex Kessler) did install his ERV without centralized ductwork, and made an excellent video all about it: DIY Energy Recovery Ventilator Installation (For Homes Without Ducts!)
At first I thought this guy would be running ducts along ceilings and through doors, making his home look like a silver octopus had taken over. That’s not aesthetically pleasing to most people. But no, he figured out how to get circulation in his 2-story, 1489 square foot condo using only fans, and decided to situate the ERV itself in his office (2nd bedroom), where he said the noise was tolerable to him and sounded like a large air purifier running at medium fan speed. This video was well worth watching because I believe it’s the first time anyone has thoughtfully designed and installed an ERV without using centralized ductwork. Even the manufacturer could not answer any questions he had on this type of installation, probably because it had not been tested in this way! So as a true “renegade” (his YouTube channel is Healthy Home Guide and he has a free Air Quality course at renegadeairquality.com), he planned it out and jumped right in.
Although he probably did this in the planning stages, Alex described the circulation path he would use to get fresh air into the home and stale air out at minute 24:41. He set up a series of floor and table fans and advised using the Coanda effect wherever possible, which assists airflow by directing it along a wall, ceiling or floor. Planning the airflow is extremely important for this type of ERV installation, so we would advise setting up fans before ever purchasing an ERV for this purpose, and measuring the CO2 with and without the fans on to find the optimal “circuit” for ventilation. He used an Aranet 4 CO2 sensor and recorded the results in a chart starting at approximately minute 28:27. If you look at the far right columns of his chart with Fans On/Off and ERV Off, he discovered that just using fans could lower the CO2 in his living room by 259 ppm (1313-1054, 20%) and master bedroom by 408 ppm (1521-1107, 27%). Your own tests using just fans may improve the CO2 enough that you may not need to buy an ERV! You never know until you try–and measure. The measurements are averages of several readings. In this air circulation trial, you will also want to plan where you’ll place the ERV, because this will be near the fresh air intake and stale air exhaust. It can be a single window, and Alex shows a genius hack to get around the recommended “10 feet apart between intake and exhaust” rule of thumb.
Next, if you decide to continue, you’ll need to select an ERV for your particular space (minute 4:00). Hopefully you’ll plan to be there for a long time, or plan on purchasing a home of similar size later, because good ERVs are kind of expensive ($1000 and up) but can last for many years if maintained well with new filters. He selected one that can handle MERV 13 filters (thumbs up for this!), and can automatically commission itself with internal dampers and fan speeds, with a little input from the user. Also, we noted it has variable speed fans so that he could balance it toward a slight positive pressure (he noted that he set his unit to 55cfm intake and 45cfm exhaust at minute 27:56). Slight positive pressure in a non-airtight home is a great idea, especially because he shares walls with his neighbors. Positive pressure in your unit of a multi-family building is the best way to keep out odors and pollution from neighboring units!
After purchasing the ERV, Alex situated it in his office and placed vents for the inlet/outlet in his window with the vanes facing away from one another. Using insulated flex duct, he connected the inlet and outlet of the unit to the vents, and proceeded to start up the unit. He then made a bunch of CO2 measurements inside and even outside to verify how the unit was working and whether there was cross-contamination from the inlet and outlet (not much!) His ERV and fans ended up reducing CO2 by 757ppm (1521-764, 50%) in the master bedroom and 540ppm (1313-773, 41%) in the living room. If you just look at the % reduction, it’s amazing, but most importantly the end numbers are landing below 1000 ppm, which is the healthy home limit for CO2 that a lot of scientists have agreed upon. In both cases, we’d say that his experiment is a big win! The only requirement to achieve these figures consistently was keeping the exterior doors and windows closed and the interior doors open–meaning that if you had guests, closing doors for privacy will have an impact on the air quality in the closed rooms, of course.
Kudos to Alex Kessler for trying something that no one has done (at least publicly) before–installing an ERV without a permanent duct system in his home. He was determined to improve his indoor air quality, and by introducing fresh air and expelling stale air via an ERV, it’s a maintainable shift even in humid seasons (he also uses a Santa Fe dehumidifier). He’s related some of his experiences with mold illness, eczema, and IBS and also says he feels a lot better since the ERV installation. We would encourage anyone on a similar quest for health to check out his videos and air quality course for inspiration and a lot of good tips on making your home healthier.
Photo by Toshi Kuji on Unsplash
