Image Credit: All photos: Joe Nagan Like most first responders, Joe keeps a flow hood handy. This doesn't look good. This is serious! The air flow is zero! Joe needs to act fast. Fortunately, Joe has a bottle of IV fluid. Still no vital signs. This is very worrisome. Time for the defibrillator. Stand back. OK — let's give it a try. We did everything we could. Hello? I'd like to speak to someone at the coroner's office. All the belts are broken. We'll miss you, ERV.
Years ago, when I worked as a home inspector, I was hired to perform a capital needs assessment at a Buddhist retreat center in rural Vermont. In an obscure mechanical closet I discovered a heat-recovery ventilator that the facilities manager didn’t even know existed.
The HRV had been installed at least a dozen years before. The filter, which had never been changed since the day it was installed, was totally clogged. The HRV was no longer working — perhaps the motor had burned out years ago. I advised the owners to call an HVAC contractor to have the unit serviced.
Who’s going to notice when it conks out?
When a furnace or water heater stops working in January, it only takes a few hours for the homeowners to notice that something is wrong. However, when an HRV stops working, the owners rarely notice.
The HRV failure at the Buddhist center raises several questions:
- Are there ways that HRV installers can ensure that ventilation equipment is properly maintained?
- If an HRV can stop working without the owner noticing, is mechanical ventilation even necessary?
I don’t have any ready answers to these questions, but I welcome comments from readers.
An ERV emergency in Wisconsin
Memories of the clogged filters at the Buddhist center came flooding back to me recently when energy consultant Joe Nagan sent me an amusing series of photos by e-mail.
Here’s the story: Joe was walking by his local nature center in Wisconsin — a “green” building equipped with a rooftop PV array — and noticed that the building had a large, commercial-sized energy-recovery ventilator (ERV) mounted on an outdoor slab. Although he could hear the Venmar unit’s three motors humming along, he was surprised to notice that there wasn’t any air flow at the intake or exhaust grilles.
Leaping into action like any good energy consultant, Joe decided to respond to this ERV emergency. “I took a quarter out of my pocket and removed a door panel,” Joe told me. The problem was clear: every belt was broken. All of the filters had been destroyed by flying chunks of rubber as the broken belts were sucked into the ERV wheel.
Sensing an opportunity to stage some photos, Joe rushed home to get some first-aid equipment. “I did as I preach,” said Joe. “I first measured airflow. Nothing.” (Joe later learned that the unit was rated at 1,500 cfm.)
“I immediately went into action with my ‘MacGyver’ medical training,” Joe continued. “I started an IV with a bottle of Seagrams wine cooler. Nothing. I rechecked vitals — nothing. I then took my battery charger and makeshift defibrillator paddles and started treatment. Again — nothing. I finally had to ‘call it.’ Sometimes there’s not much we can do.”
The useless ERV motors ran for years
Once he was done taking photos, Joe got serious again. “This unit must never have been looked at since being installed five years ago,” he said. “The controls were set for continuous operation. Three motors have been running continuously for years, without any airflow through the unit.” It’s fair to assume that the nature center was spending hundreds of dollars a year on the electricity required to run these useless motors.
Joe said, “When I showed the ERV to the building manager, he said, ‘I don’t even know what that is.’”
ERVs and indoor air quality
According to most energy experts, tight buildings need a good ventilation system to assure good indoor air quality. Without a mechanical ventilation system, moisture will condense on windows, odors will accumulate, and rooms will feel stuffy.
It’s easy to imagine that bad indoor air quality might go unnoticed in some buildings — in a bowling alley, for instance. But one might think that the visitors to an environmental center or a Buddhist meditation center would be sensitive to the quality of the indoor air.
You’d think that once the ventilation system stopped working, the nostrils of a visiting environmentalist or Buddhist might twitch. But no one noticed.
Last week’s blog: “Belgian Passivhaus is Rendered Uninhabitable by Bad Indoor Air.”