Four regimes have governed how homes in this part of the east metro get their air, and they are listed below newest first on purpose. Start at the top and walk down until one describes what is physically in your building today. That regime — not the year on the permit card — is what decides whether the answer is a heat-recovery core, an energy-recovery core, or nothing yet.
Furnace Direct installs recovery ventilators across Maplewood, from the plat blocks along the McKnight and 3M corridor to the older village pockets on the north side. There is no retail inventory behind this page; identifying the regime is simply how a quote conversation gets short and honest.
What it assumed: That air change is a designed, powered, measurable thing, and that the building will not provide any of it accidentally.
You are living under it if: There is a cabinet with two insulated ducts leaving it and two hoods on the outside wall, and the house has been foamed, re-glazed, or built recently enough that you cannot feel a draught anywhere.
How it fails: By neglect and by never having been commissioned. A core nobody has washed moves a fraction of its rating, and an appliance nobody balanced has been half wrong since its first day.
What it assumed: That importing outdoor air is the same thing as exchanging it, and that a timer is a ventilation strategy.
You are living under it if: A six-inch duct comes through the rim and tees into the return with a small motor on it, and there is no cabinet anywhere. Very often the timer has never been adjusted from where it left the factory.
How it fails: In deep cold, invisibly. The damper dumps January air at the furnace and recovers nothing from the air being pushed out elsewhere, so the house runs arid all winter and the owner blames the furnace.
What it assumed: That spot exhaust in the wet rooms is sufficient, because the rest of the building will keep leaking enough to cope.
You are living under it if: Poly behind the drywall, reasonable sheathing, and no mechanical ventilation beyond fans that run when somebody remembers to switch them on. This is the most common regime in the plat blocks.
How it fails: The first winter after somebody improves the envelope. The leakage the design quietly relied on disappears, the fans were never the plan, and the coldest window starts reporting it.
What it assumed: Nothing at all. Air change was a by-product of how houses went together, not a decision anyone made.
You are living under it if: Original windows or early replacements, an attic hatch that has never been weather-stripped, an open rim joist, and a basement that smells of outdoors in a wind.
How it fails: Expensively rather than uncomfortably. These houses usually have no air-quality complaint and a large heating bill, and they stay that way until the first serious sealing project.
Build year predicts how a house was originally assembled, and that was genuinely useful information when most houses still resembled themselves. It is much weaker now, because forty years of retrofit work has scrambled the relationship between when a building went up and how it breathes. In one afternoon on the same street you can find a 1962 rambler that was foamed, re-glazed and air-sealed hard enough to be operating under the newest regime, and a house half its age still running a damper that has never been touched. Asking which regime is in force cuts straight to the variable that matters: whether this building provides any air change on its own, and if not, what is supposed to be doing it instead.
An original house with a newer addition, or a lower level finished to a much higher standard than the floor above it, is two regimes under one roof. They do not average out. Moisture behaves worst wherever the shell is tightest and the surfaces are coldest, so the newer, tighter part produces the symptom and the older part masks how bad it is. When you describe the house to us, describe the tight part first and say roughly how much of the floor area it represents. That one sentence changes airflow sizing and occasionally changes the core.
Regime identified? Add the failure you are actually seeing and we scope the install.
Send my regime and symptomThese houses have usually passed through every regime in sequence, picking up an addition in each. They rarely sit cleanly in one, and the survey matters more here than any framework — we are looking for where the tight volume is and how the chases were left when somebody opened a wall.
Much cleaner. Whole blocks were built under one regime and then upgraded under another at roughly the same time, so the regime is usually unambiguous and the install is usually predictable. These are the houses where a photograph or two is genuinely enough to scope.
Stand in the mechanical room and answer four questions. Is there a cabinet with two ducts leaving it, or is there not? Is there a small motorised damper on the return where a duct comes in from outside? Can you see a poly sheet stapled at the rim joist, or bare joist ends and fibreglass batts falling out? And has anybody replaced windows, insulated the attic, or foamed the rim in the last few winters? Those four answers place your regime within minutes and they are worth more to us than an exact build year, because they describe the building's behaviour rather than its birthday.
Because the question that matters is which regime is in force today, and the fastest way to find it is to start at the newest and walk down until something matches. A house built in 1968 can be running regime four after a deep retrofit, and a house built in 2004 can be running regime three because the damper the builder installed is still the only air-change device in it. Chronological order answers a question about the building. Reverse order answers a question about the house you actually live in.
It is normal, and it is the single most common finding on a survey. An addition built under one regime bolted onto an original house built under another produces a building where half the volume behaves nothing like the other half. The decision then gets made in the tightest part, because that is where moisture will misbehave first and where the complaint will originate.
Whichever one the most recent envelope work implies, not the most recent remodel. Kitchens and bathrooms do not change air behaviour. Windows, attic insulation, rim sealing, and siding with exterior foam do. If the last work that touched the shell was twenty years ago, you are still living under the regime that was in force then, regardless of how new the cabinets are.
The damper itself comes out; it has no job once a balanced core is doing the work properly. The penetration it used is sometimes reusable and that saves a little labour, but we will not force a bad hood location just to keep a hole. It is worth being blunt that the damper is not a partial version of what you need — it is a different thing that has been doing harm all winter.
Not the regime, which is about how the building was conceived. It changes the summer moisture load on a lower level and it changes where we want the intake hood so the exhaust is not re-entrained on a still, damp morning. Both of those are install details rather than selection criteria.
Read it and then wait. A genuinely leaky, unimproved house is already exchanging air, badly but continuously, and adding a recovery ventilator to it wastes most of the appliance. The correct sequence is envelope first, ventilation second. Come back the season after the sealing project and the page will read completely differently.
Which regime, what is physically in the mechanical room, and what the air does in deep cold. A core lean and one flat installed number come back.
Other cities in this batch decide with disqualifier sheets, look-alike symptom pairs, and a transect from the water inland.