FAQs

Everything people ask us most about SWERV, the window ERV that brings fresh, filtered air into your room without opening a window. Ordered by what we actually get asked most. If you do not see your question, reach out and Austin will answer you personally.

Window fit

What window sizes does SWERV fit?

SWERV fits sliding windows 23 inches wide and up, with no maximum. That includes vertical sliders (single hung and double hung) and horizontal sliders. The window needs to open at least 6 inches. It does not fit casement or crank-out windows, tilt-and-turn windows, or any slider narrower than 23 inches.

How far does it stick into the room?

About 6 inches. It sits in the window opening and extends roughly 6 inches into your room, so it clears most curtains and does not intrude on furniture. It needs about 2 inches of sill inside the window.

My window is wider than 48 inches.

That is fine, SWERV still works. Wider openings just need more foam to seal the gap, so message us with your measurements when you order and we will include extra foam at no charge. There is no upper limit on width.

I have a horizontal or sideways sliding window. Does that work?

Yes. SWERV works in horizontal sliders, and you can mount it vertically or horizontally. One thing to picture first: with a horizontal window, blinds may not block light as completely as they would in a double hung, since they have to clear the unit.

I have tilt-and-turn or casement windows.

SWERV does not currently fit these. This comes up most with Passive House and European-style builds. We know it is a real gap and we would rather say so plainly than waste your time.

Can SWERV share a window with an air conditioner?

We do not recommend it. Two units in one window are hard to seal well and can make the AC less secure. Put SWERV in a separate window and both will work better.

Not sure if it will fit?

Message us through our contact page with your window type and rough measurements, or a photo. We answer every one, usually the same day.

Price and value

How much does SWERV cost?

$799 for the base unit, or $898 with the sensor package (CO2, temperature and humidity, indoor and outdoor), which unlocks Auto Mode. Replacement filters are $49 each. Free 30-day returns and a 5-year limited warranty either way.

Why does it cost this much?

SWERV starts at $799. That is real money and we are not going to pretend otherwise. Here is the comparison that matters: a ceiling-mounted ERV like the Panasonic WhisperComfort runs $400 to $540, but it needs two duct runs, an exterior wall penetration, hardwired power, and attic access. Installed, that is typically $800 to $1,400. A through-wall unit like the Vents TwinFresh needs a core-drilled hole, which is $300 to $800 if you hire it out and is a permanent modification to your building. A whole-house ERV usually runs $8,000 to $40,000 installed.

SWERV installs in 10 to 15 minutes with no hole, no contractor, and nothing permanent. Compare installed cost, not sticker price.

Will it pay for itself?

If you currently open windows for fresh air while running heat or AC, SWERV typically pays for itself in energy savings in about 1 to 2 years, because the energy recovery core keeps roughly 85% of your heating and cooling instead of throwing it out the window.

How much electricity does it use?

About 10 watts at typical speeds, roughly the same as a Wi-Fi router, and 42 watts at full speed. Running it all night costs about a penny at average US electricity rates, or a few dollars a year.

Why not just buy an air purifier?

Because they solve different problems, and this is the single most common misunderstanding we run into. A purifier recirculates the same indoor air. It can pull particles out of that air, but it cannot lower your CO2 and it cannot bring in anything fresh, because it is not connected to the outdoors. If your bedroom hits 1,400 ppm overnight, a purifier will not move that number at all.

SWERV exchanges the air itself, which is the only thing that actually reduces CO2, radon, and VOCs. And because incoming air passes through a MERV 13 and carbon filter, SWERV also does much of what a purifier does. Full comparison: air purifier vs ERV.

Should I wait for the certified production model?

Honest answer: V3 is the design we're taking through UL 1815 certification. We're finalizing tooling now to move the plastic parts from 3D printed to injection molded, so early V3 units may still have a few 3D printed parts. That change doesn't affect performance or reliability. Certification adds a label, not performance.

Ordering now gets you a unit months earlier, and joining the beta earns you up to $200 off a future production SWERV when you share your feedback and CO2 data. What you give up is the UL label for now. V3 is designed to UL 1815 but isn't certified yet, and we may still tweak small details. Every unit is tested before it ships and carries a 5-year warranty and free 30-day returns either way.

Gases: CO2, radon, VOCs, and mold

Will it really lower the CO2 in my bedroom?

Yes, and this is the thing we have the most data on. Because SWERV physically removes stale air and brings in fresh air, it removes the CO2 your breathing builds up overnight. Customers typically see 40 to 70% lower CO2 in the room it serves. One beta customer measured their average bedroom CO2 drop by more than 600 ppm running the unit at roughly half power, and reported their regular headaches stopped. More in our guide to high CO2 in your bedroom at night.

How much fresh air does my bedroom need?

To hold a bedroom around 700 ppm CO2, plan on roughly 38 CFM of fresh air per person. Two people sleeping with the door closed need about 76 CFM, which SWERV handles at a moderate speed. It moves about 50 CFM at 50% speed and up to 110 CFM at full speed.

Does SWERV help with radon?

Yes, and here is the key thing most people miss: radon is a gas, exactly like CO2. A filter cannot capture a gas, which is why an air purifier does nothing for radon no matter how good its HEPA is. The only thing that lowers a gas concentration is dilution, which means exchanging the air. That is precisely what an ERV does.

SWERV is not a substitute for a proper sub-slab mitigation system if you have severe radon, and we will not pretend it is. But continuous ventilation meaningfully dilutes radon in the room it serves. More in radon and basement ventilation.

What about VOCs, off-gassing, and chemical sensitivity?

Same logic. VOCs from paint, furniture, flooring, and cleaning products are gases. You dilute them by replacing the air, and SWERV's activated carbon filter captures much of what is coming in from outside. This is one of the most common reasons people with chemical sensitivity buy a SWERV.

Does it help with mold and humidity?

It helps by continuously diluting humid, stale air with fresh filtered air, which is what mold needs to grow. The ERV core also moves moisture between air streams. It is one layer of a healthy home, alongside fixing any actual water source, and it is not a dehumidifier. More in mold and humidity ventilation.

What if I run it and my CO2 does not improve?

Tell us. Almost every time it is a sealing issue, a fan speed too low for the number of people in the room, or a sensor placement problem, and we can usually fix it over email. Try ERV mode at 50% speed or higher, check that the foam blocks seal tightly, and run a fan to mix the room air. If we cannot make it work for you, free 30-day returns.

I have several people co-sleeping in one room. Is one unit enough?

Usually yes. Typical operation is 28 to 75 CFM, and our beta units are handling bedrooms with three people and pets. If your room is on the larger side or unusually crowded, tell us the details and we will give you a straight answer rather than a guess.

Filters

What filter does SWERV use, and how long does it last?

A 2-in-1 MERV 13 and activated carbon filter that captures smoke, pollen, dust, odors, and VOCs from incoming outdoor air. It is not HEPA; MERV 13 catches most fine particles, including wildfire smoke, with much less airflow resistance. One long pleated filter handles air moving in both directions. Typical life is 4 to 12 months depending on your outdoor air quality and how hard you run it.

How do I replace it, and where do I buy them?

The filter is on an easy-access tray. No tools, no disassembly, about a minute. Replacement filters are always on our site: $49 for a single, $89 for a 3-pack, $119 for a 5-pack.

What happens to filter supply if SWERV goes out of business?

The fairest question anyone asks us, and we are not going to dodge it. Long-term parts availability is exactly where most ventilation companies fail their customers, and we have designed around it deliberately. If SWERV ever stopped supplying filters, we would give owners the specifications and our filter partner's contact so you could order compatible filters directly. If you want to stock up, the 5-pack is roughly 2 to 5 years of filters.

Cold, heat, and humidity

What temperatures does SWERV operate in?

-22°F to 150°F outdoor. It is built to run year-round across the full range of a real North American climate, not just mild shoulder seasons. We have run it through Boston blizzards at -10°F.

Can I leave it in the window during snow and freezing rain?

Yes. SWERV is built to stay in the window year-round through rain and snow, and it has a condensate drain. Frost-up is very unlikely in normal use.

Does the energy recovery actually work in winter?

Yes. The ceramic core pre-conditions incoming air toward your indoor temperature and humidity. In winter it warms incoming cold air using heat from the air you are exhausting. At 0°F outside and 70°F inside, fresh air comes in at roughly 60°F. In summer it does the reverse. This is the entire difference between an ERV and cracking a window: a cracked window in January dumps your heat outside, SWERV keeps roughly 85% of it.

How does it handle humidity?

The core is an ERV core, not an HRV core, which means it transfers moisture as well as heat. In a humid summer it keeps some outdoor moisture from coming in. In a dry winter it keeps some of your indoor moisture from leaving. It is not a dehumidifier and we will not pretend it replaces one, but it does not make humidity worse the way an open window does.

What is the difference between ERV mode and IN mode?

ERV mode is the everyday mode: fresh air in, stale air out, with about 85% of the heat and moisture recovered. IN mode brings in filtered outdoor air with no recovery, like a filtered window fan. Use IN when it is roughly 50 to 70°F outside and you want that cool air inside. There is also OUT mode for clearing cooking smells fast, and Auto Mode with the sensor package.

Shipping and availability

Is SWERV in stock?

Yes, SWERV V3 is open for preorder now. This is Batch 3, and it's targeted to ship in January 2027. Preorder here. You can cancel anytime before your unit ships for a full refund.

When will my order ship?

Batch 3 is targeted to start shipping in January 2027, and we ship in the exact order orders are placed, so ordering sooner means getting yours sooner. We'll email you before yours ships and let you know right away if anything changes.

Can I pay to jump the line?

No, and we want to be upfront about why. We ship strictly in order. Letting people pay to skip ahead would mean breaking a promise we already made to someone who ordered before them, and that is not a company we want to run. If you have an urgent health situation, email us and we will tell you honestly where you sit in the queue.

Do you ship to Canada or internationally?

Not yet. SWERV ships to the United States only for now.

App and controls

Does every SWERV have a CO2 sensor?

No. Sensors are an optional $99 add-on. The base unit ($799) runs every mode and fan speed from the dial. SWERV + Sensors ($898) adds 7 sensors for CO2, temperature and humidity, indoor and outdoor, which unlock Auto Mode and the CO2 history in the app.

Can I schedule it, or run it only while I sleep?

Scheduling is coming around the time your unit ships. Today SWERV has manual fan control on the unit itself plus a companion app, and with the sensor package Auto Mode adjusts fan speed on its own based on your room's CO2. Every unit receives over-the-air updates, so the app keeps getting better after you own it. If there is a specific control you want, email us. Beta feedback is genuinely what drives the roadmap.

Does SWERV work with Home Assistant, HomeKit or Matter?

Not yet. Home Assistant and Matter support are on our list, but we are not promising a date. SWERV works fully on its own, and the app connects over Bluetooth and Wi-Fi.

Wi-Fi, Bluetooth, and EMF

Is there a radio broadcasting in my bedroom all night?

No. This matters to a lot of our customers and we designed for it deliberately. SWERV's wireless radio is off unless you deliberately put it into pairing mode by holding the dial down for 5 seconds. It is not quietly transmitting while you sleep.

Can I skip the app entirely?

Yes. Wi-Fi is optional. SWERV runs as a standalone unit with manual controls and you never have to connect it to anything. You will not get over-the-air updates or the app dashboard, but the ventilation, the energy recovery, and the filtration all work exactly the same. This is a supported way to use the product, not a workaround.

Coverage, noise, and installation

How large a space does one unit cover?

One unit is designed for a single room up to 1,000 square feet. Units can pair for balanced supply and exhaust across larger spaces.

Can two SWERVs work together for a whole apartment?

Yes. Multiple SWERVs pair with each other to serve a full home with balanced energy recovery ventilation. Air does not travel well under closed doors, so two paired units running slower and quieter beat one running fast.

How loud is it?

About 35 dBA at the lowest setting (10% speed), about 50 dBA at 50% speed, which is where most people sleep, and about 59 dBA at full speed, all measured at 1 meter. At sleep speeds it sounds like steady airflow rather than a mechanical hum. Full speed is meant for short bursts of fast air exchange, not overnight.

How long does installation take? Do I need a contractor?

About 10 to 15 minutes, by yourself, using the included weather-tight sealing kit. No ductwork, no contractor, no renovation, no holes. The unit weighs 19 lb and needs no bracket.

How long is the power cord?

About 6 feet, and it can exit on either side of the unit. A standard extension cord is fine.

Is SWERV renter friendly?

Yes. It installs and removes with no permanent changes, so it works for renters, and it comes with you when you move.

Can it help with wildfire smoke or a neighbor's smoke?

Yes. Incoming air passes through MERV 13 and activated carbon, which captures fine smoke particles and much of the odor. Running SWERV in IN mode also keeps your room at a slight positive pressure, which helps push infiltrating smoke back out. See stopping neighbor smoke and keeping wildfire smoke out.

Returns and warranty

Can I return it?

Yes. Free 30-day returns, opened or unopened. If SWERV does not work for your window, your room, or your air, send it back. Email us and we will send a return label. You can also cancel any time before your unit ships for a full refund.

What is the warranty?

A 5-year limited warranty. If something fails, we repair or replace it. Full details in the Return Policy and Limited Warranty.