After the install: proving it worked and keeping it working

A new HRV or ERV isn't finished when the installer packs up. Collect the right paperwork on install day, recheck the same bedroom about two weeks later and again around three months, and keep the filters and core on a schedule.

Install-day handoff checklist

Before the installer leaves, go through these together. The Building America checklist for balanced systems says operation and maintenance should be reviewed with the homeowner, so this is a reasonable thing to ask for.

Measured airflow for each room. A balancing sheet showing the measured airflow at each supply and return grille. Take a photo of it before it goes in a drawer.
How to use the controls and boost. Which setting it should run on day to day, and how to boost it. Natural Resources Canada recommends running an HRV on low speed continuously year-round, with high speed for things like cooking, showers, painting, or a full house.
Where the filters are and which part to buy. Some filters can be washed and others must be replaced. Get the exact part number.
Condensate drain and frost protection. Whether your unit has a drain, where it runs, and what the unit does in very cold weather (more on that below).
Warranty registered, paperwork saved. The manual, the model and serial numbers, the equipment warranty registration, and the installer's labor warranty in writing.
Permit inspection. Either a date for the inspection or a clear note that none was needed.

What the unit does in very cold weather

When very cold air meets the warm, moist air leaving the house inside the core, frost can form. Natural Resources Canada says most HRVs have an automatic defrost mode that starts when incoming outdoor air drops below about 23°F (−5°C). One method briefly blocks the incoming fresh air and lets warm house air run through the core to melt the frost. Some units use a preheater instead. ERVs need frost protection too, and your manual describes how yours handles it.

As outdoor temperatures fall, defrost cycles get longer. In cold-winter places, including much of Colorado, expect them on the coldest nights. That's normal, not a fault.

Building Science Corporation notes that in cold climates these systems must be set up to handle condensation. If yours has a condensate drain, Natural Resources Canada suggests checking it and its tubing twice a year to make sure water flows freely, and notes the drain needs a trap.

Prove it: recheck nights

Log recheck nights about two weeks after install and again around three months. Keep everything the same as your "before" nights: the same room, the same people, the door set the same way, and the monitor in the same spot. ASHRAE notes that sensor location and calibration are critical for drawing meaningful conclusions from CO₂ readings, so moving the monitor can muddy the comparison.

The two-week check tells you whether the system is delivering air to that room. The three-month check shows whether that holds up, often in a different season with different window and door habits.

The goal is the same as before the install: a typical night of 800 ppm or less, on average, while you sleep. If the room isn't there yet, start with the basics. Is the unit on, set to the agreed speed, and are the filters clean? If so, ask the installer for a balancing check. Measuring the airflow actually delivered to that room is part of commissioning (the target is about 17 cfm of outdoor air per sleeper; see getting a bedroom to 800), and the Building America checklist calls for that measurement with a flow hood, flow grid, or anemometer. Bring your before and after nights from the app so you're both looking at the same evidence.

Keeping it working

Filters. The app's default reminder is every three months, and you can set it anywhere from 1 to 12 months. Natural Resources Canada suggests cleaning filters every one to three months. Your unit's manual has the final word, so set the reminder to match it.
The core. Inspect and clean it as your manual directs. Natural Resources Canada suggests inspecting it twice a year and recommends a yearly service by a qualified contractor, including a check that the system is still balanced.
Outdoor hoods. Check the intake and exhaust hoods regularly for leaves, plants, or other debris, and for snow in winter.
Seasonal room check. Log a night or two in the same bedroom each season. It's a quick way to catch a clogged filter or a control that got switched off.

If you ever turn the system off, Natural Resources Canada advises making other provisions for ventilation, such as opening windows.

When to call someone

Call your installer if a recheck shows the room is no better than before, if you see water where it shouldn't be, or if the unit is noisy or not running. Bring the balancing sheet and your recheck nights. Those two pieces of paper turn a vague complaint into a specific question they can answer.