What Is Make-Up Air, and When Does a Minnesota Range Hood Need It?
Make-up air replaces what a range hood blows outside. What Minnesota's mechanical code requires, why big hoods can backdraft a water heater, and the fixes.
Read the guideAir Quality Guides
Humidity, filters, ventilation and the air inside tight northern houses.
Tight, well-insulated Minnesota houses hold heat well, and they hold moisture, dust and cooking smells just as well. Winter air goes bone dry, spring brings pollen, and a new home with no fresh-air system can end up stuffy. These guides cover humidifiers, dehumidifiers, filters and MERV ratings, HRVs and ERVs, UV lights and duct sealing.
We also cover safety: where carbon monoxide alarms belong under Minnesota law, and what soot on a furnace filter is telling you. For equipment and installs, see indoor air quality.
Does Central AC Bring In Outside Air?
No. Central air recirculates the air already inside. How fresh air really gets into a Minnesota house, whether AC dries the air, and when to add an HRV.
Read the guideIntegrated HVAC Smoke Detection: How Duct Detectors and Fan Shutdown Work
Most homes don't need a duct smoke detector; Minnesota's code applies above 2,000 cfm. How they shut the fan down, and why smoke and CO alarms come first.
Read the guideLennox PureAir vs Other IAQ Systems: What It Does and Who It Fits
What Lennox PureAir and PureAir S actually do: a MERV 16 filter, UV-powered PCO for odors, the yearly parts, and how they compare with a plain media cabinet.
Read the guideWhy Is My Furnace Filter Turning Black?
A black furnace filter usually means soot, not dust. How to tell the difference, the household and furnace causes to check, and when to shut it off.
Read the guideLeaky Ductwork in Minnesota Homes: Symptoms and What Sealing Fixes
Cold rooms, dust, ice dams and a furnace that runs and runs: how leaky ducts show up in Minnesota houses and what sealing them actually fixes.
Read the guideBest MERV Rating for Allergies in a Minnesota Home
MERV 8, 11, 13 or 16? What each rating catches, why filter depth matters as much as the number, and how to upgrade without choking your furnace or AC.
Read the guideWhere to Put Carbon Monoxide Alarms in a Minnesota Home
Minnesota law requires a CO alarm within 10 feet of every bedroom. Where else to put them, where not to, and what to do the moment one goes off.
Read the guideWhole-House Dehumidifiers in Minnesota: When the AC Isn't Enough
Why a Minnesota basement stays damp with the AC running, the signs you need a whole-house dehumidifier, how one is sized and installed, and what it costs.
Read the guideUV Lights for HVAC: Pros, Cons and When They're Worth It in Minnesota
A UV lamp aimed at the AC coil keeps mold and slime off it but does little for dust or airborne germs. What EPA says, what it costs and when one is worth it.
Read the guideIs Duct Cleaning Worth It? What Minnesota Homeowners Should Know
EPA says duct cleaning has never been shown to prevent health problems. When it makes sense in a Minnesota house, what a good job includes and what it costs.
Read the guideAprilaire 5000 vs 2000 Series: Electronic or Media Air Purifier?
The Aprilaire 5000 uses ionizer wires; the 2000 series are plain media cabinets. Filtration, upkeep, airflow and cost compared for Minnesota furnaces.
Read the guideERV vs HRV in Minnesota: Which Ventilator Fits Your House?
Minnesota code requires balanced ventilation in new homes. How HRVs and ERVs differ, which suits a house that runs wet or dry in winter, and the upkeep.
Read the guideWhole-Home Humidifiers for Minnesota Winters: Bypass, Fan-Powered or Steam
Bypass, fan-powered or steam: how each whole-home humidifier works, which fits your furnace or heat pump, and how to set it so your windows stay dry.
Read the guideIndoor Air Quality in a Minnesota Winter: What Actually Helps
Better winter air in a Minnesota house, in the right order: humidity, filtration, fresh air, then CO and radon. What helps, what it costs and what to skip.
Read the guideAir Quality questions
How often should my furnace and AC be serviced?
Once a year each: the furnace in the fall before the first cold snap, the air conditioner in spring before the heat. A furnace or AC tune-up starts at $129, or $219 for both in one visit. A heat pump runs in both seasons and piles up more hours than a furnace or AC alone, so a yearly check matters even more. More on maintenance.
What happens during a furnace tune-up?
A proper furnace tune-up goes after the parts behind most winter no-heat calls. That means checking and cleaning the flame sensor, checking the igniter, inducer motor and pressure switch, inspecting the burners and heat exchanger, checking gas pressure and temperature rise, clearing the condensate trap on a high-efficiency furnace, looking over the venting and checking the filter. See our fall checklist.
How often should I change my furnace filter?
Check it monthly during heating and cooling season. A standard 1-inch filter usually needs changing every one to three months, sooner with pets or during a remodel. A 4- or 5-inch media filter in a cabinet by the furnace typically lasts six months to a year. If you hold it up to a light and can't see through it, change it. A clogged filter can trip the furnace's limit switch.
What indoor humidity should I keep in winter?
Lower as it gets colder outside. Roughly 25–35% works in normal cold weather, and in deep cold it needs to come down further or your windows will sweat and frost over. Water or ice on the inside of the glass is the sign it's too high. A whole-home humidifier with an outdoor temperature sensor adjusts for this on its own. See our humidifier guide.
Where do carbon monoxide alarms need to go?
Minnesota law requires a working carbon monoxide alarm within 10 feet of every room used for sleeping. Adding one on each level, basement included, is a good idea in a house with gas or propane appliances. CO has no smell, and a cracked heat exchanger, blocked flue or backdrafting water heater can produce it. Replace alarms by the date printed on them. Details are in our CO alarm guide.
Do I need an HRV or ERV?
If your house is newer and built tight, it probably already has one, since mechanical ventilation is part of how newer Minnesota homes are designed. Older, leakier houses usually don't need one unless they've been heavily air-sealed. An HRV swaps heat between outgoing and incoming air and tends to dry a house out a little, which helps with sweating windows. An ERV also moves some moisture. See HRV vs ERV.
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