Indoor Air Quality — Duluth, Superior & the Northland

Winter dryness is a real problem here, not a comfort preference

When it is −15°F outside, that air holds almost no water vapour. Heat it to 70°F and the relative humidity collapses — Twin Ports houses routinely sit at 10–20% RH in January, which is drier than most deserts.

The consequences are not trivial: cracked skin and lips, nosebleeds, sore throats, static shocks, and — expensively — hardwood floors that gap and shrink, trim that opens at the joints, and instruments and furniture that crack. It also makes you feel colder at the same thermostat setting, so people run the heat higher than they need.

A whole-home humidifier plumbed into the ductwork and controlled by a humidistat is the answer, not a room unit you refill every day. Target 30–40% RH in winter. Higher than that in this climate and you get condensation on windows and, worse, moisture inside wall cavities and attics where it causes real damage. We set the control to the house and the weather rather than leaving it wide open.

Tight houses need mechanical ventilation

Air sealing and insulation are genuinely good — they are the cheapest way to cut heating bills in a 9,000 HDD climate. But a tight house does not breathe, and everything you generate indoors stays indoors: moisture from cooking and showers, CO2, VOCs from finishes and furniture, cooking particulates, pet dander, and radon.

A heat-recovery ventilator solves the arithmetic. It exhausts stale indoor air and brings in fresh outdoor air, passing them through a core that transfers 60–85% of the heat from the outgoing stream to the incoming one. You get fresh air without throwing your heating dollars out the wall.

HRV versus ERV: an HRV transfers heat only, an ERV transfers heat and some moisture. In this climate, with winter dryness as the dominant problem, an HRV is usually the right choice — an ERV's moisture recovery is more valuable in humid climates. There are exceptions for very tight new construction, and we will explain which your house is.

Radon is worth naming specifically. Northeastern Minnesota and northwestern Wisconsin have substantial radon potential, and a tightened house with a depressurised basement can pull more of it in. Ventilation helps, but if you have not tested, test — it is inexpensive, and mitigation is a known, solvable job.

Filtration: thicker is not automatically better

The common mistake is buying the highest-MERV filter on the shelf and pushing it into a one-inch slot. A restrictive filter in an undersized filter rack starves the blower, drives static pressure up, ices cooling coils, and can crack a heat exchanger over time from overheating. You have made the air worse and shortened the equipment's life.

The right approach is to match filtration to the duct system's capacity. Usually that means installing a four- or five-inch media cabinet, which offers far more surface area — so you get genuinely better filtration at lower resistance, and you change it twice a year instead of monthly.

For households with real needs — asthma, allergies, immune compromise — we can go further with high-efficiency media or properly integrated electronic filtration. We measure static pressure before and after so we know what the change actually did to your system, rather than hoping.