Crack a window or install an ERV: the ventilation decision for Lake City's tightest houses, starting with the filter-change schedule
Two ways to get fresh air into a sealed house. One is free and lets in air with a dew point of 72. The other needs its filters changed.
Window versus machine on a June morning
Set the two options side by side on a June morning in Arbor Greene. Option one: crack the bedroom window. Fresh air comes in, free, and brings with it air whose dew point is 72, which condenses on the cold glass, soaks into the drywall around the frame and pushes the room’s humidity past 70 percent by breakfast. The air conditioner then spends the morning wringing out water you invited in. Option two: an energy recovery ventilator, a box in the attic that brings in a measured stream of outside air, passes it across a core that hands most of its heat and moisture to the outgoing stale air, and delivers it filtered into the return. Not free. Dry. Steady. The window wins in October. The machine wins the other eleven months.
The maintenance schedule is the product
Here is where we start every ventilation conversation, because an ERV is only as good as its upkeep. The outside-air filter loads with pine pollen in March, catkins in April and whatever the burn piles produce in winter; it needs changing every few months, more in spring. The core, the heart of the unit, needs a rinse once or twice a year or it loses its ability to shed moisture. The exterior hood screen collects leaves and the occasional wasp nest. None of this is hard, and all of it is forgotten, which is why the units we find in attics that were installed by a builder and never touched are often doing nothing. We write the schedule on the unit and offer to cover it under a maintenance agreement; ask for the agreement specifics. [[CONFIRM WITH JERRY]]
Warranty terms worth reading twice
Ventilation equipment carries a parts warranty like any other appliance, and two clauses matter. One ties coverage to proper installation, which for an ERV means balanced airflow, measured, in and out; an unbalanced unit pressurizes or depressurizes the house and voids more than the warranty. The other ties it to maintenance, which brings us back to the filter schedule. We balance every unit with a flow hood at commissioning and leave the readings on the cabinet so a future technician can verify them.
Ask whether your house needs fresh air
Choosing: a ventilator for the new subdivisions, spot ventilation for the old ranches
Forest Cove, Arbor Greene, Hunter Oaks, The Reserve at Jewel Lake: houses built in the last several years are sealed well enough that bedrooms go stale overnight and windows sweat on the inside in summer. An ERV is the right answer and, in Lake City’s humidity, the energy-recovery type is the one to buy; a plain heat-recovery unit brings in the moisture.
Callaway, Cypress Landing, Summers Ridge (1990s-2000s): these fall in the middle. Most breathe enough on their own; a few, after new windows and attic sealing, cross the line. We test rather than assume.
The 1950s-80s block ranches and the frame houses downtown: these leak enough that mechanical fresh air is wasted money. What they need is spot ventilation that works: a real bathroom fan on a timer, a kitchen hood that vents outside rather than into the cabinet, and a dryer duct that is not kinked behind the machine.
Manufactured homes: nearly always the spot-ventilation case, with the added job of sealing the belly board so the crawlspace stops being the fresh-air intake.
What the install looks like
A day in the attic for a retrofit: the unit hung from the trusses, two insulated ducts to an exterior wall or soffit hood, a connection into the return plenum, a condensate line, a control on the wall and the balancing. New construction is cleaner still, done before drywall. Either way the house breathes on purpose afterward, and the bedroom window stays shut in June.
Ventilation questions from the new subdivisions
How do I know whether my new house is too tight?
Stale bedrooms by morning, condensation inside the windows, cooking smells that linger past dinner and a carbon dioxide reading that climbs overnight are the signs. A blower-door test puts a number on it, and most houses built in the last few years here come in tight enough to need mechanical fresh air.
Will a ventilator pull in pollen in March?
It pulls outside air through its own filter first, which catches most of it. During the worst two weeks we can set it to run less, and the filter gets changed when the season ends.
Does an ERV replace the bathroom exhaust fans?
It can be ducted to pull from the bathrooms and act as the exhaust, which is a clean design in new construction. In a retrofit we usually leave the bath fans in place and run the ERV as a separate balanced system.
What happens to the ventilator in a long power outage like Helene?
It stops, like everything else, and the house slowly goes back to breathing through its cracks. When power returns it restarts on its own. There is no damage risk; it is a pair of fans and a core.
New house, stale bedrooms by morning?
That is a ventilation problem with a known fix. Call and tell us the subdivision.