Fresh air in an apartment or condo

An apartment shares its air with a building. Some of it is meant to come down the hallway, some leaks in through the walls and windows, and the bathroom and kitchen fans push some out. The bedroom, at the far end of the unit with its door shut, often gets the least.

How apartments are meant to get fresh air

Many mid-rise and high-rise buildings blow outdoor air into the corridors, expecting it to flow under each front door into the units. In a 13-storey Vancouver building, researchers found only about 8% of that air reached the suites. Ventilation varied about tenfold from one suite to another, and suites on lower floors drew air from the garage.

Building America's work with Steven Winter Associates found the same pattern in US buildings: exhaust ducts that leak or are blocked, and wind and the stack effect overwhelming small fans. Its conclusion was that each unit does best with its own ventilation, such as a small ERV with short ducts.

Since 2016 the ventilation standard for homes (ASHRAE 62.2) has covered apartments in buildings of any height. Whether your building meets it, and whether its air reaches your bedroom, is what a monitor shows.

What a renter can do now

None of these needs anyone's permission:

• Measure the bedroom. Three ordinary nights against the 800 ppm goal tell you whether there's a problem.
• Crack the window, where it's safe and quiet enough. In a Danish study it lowered overnight CO₂ from about 1,820 to 760 ppm.
• Try a night with the bedroom door open, as a test. It shares the bedroom's air with the rest of the unit; if the night is lower, the bedroom is short of outdoor air. Fire-safety researchers recommend sleeping with the door closed, so it's a clue rather than a fix.
• Run the bathroom fan while you sleep, if it's quiet and vents outdoors. It pulls stale air out of the unit, though it reaches a closed bedroom only a little.

Free fixes and Door shut? have more.

A window unit. One window ERV, SWERV, sits in an open double-hung or sliding window, with no hole in the wall. It's early: waitlist only, not yet UL-certified, and its heat-recovery figures are the maker's own. Check your lease before putting anything in a window.

What needs the landlord's yes

Anything through an outside wall, such as a through-wall unit or a new fan duct, needs the landlord's permission. Brick Underground's guidance for New York renters says the same of bathroom fans.

What the codes ask of the landlord. Property-maintenance codes usually require each habitable room to have a window that opens, or mechanical ventilation instead:

• The International Property Maintenance Code, which many cities adopt, asks for an openable window area of at least 45% of the room's required glazing, with mechanical ventilation allowed as a substitute, and a window or an exhaust fan vented outdoors in each bathroom.
• Some cities go further. Tempe, Arizona requires an openable window in bedrooms even where there's mechanical ventilation. New York City accepts a smaller openable window where a room has 40 cfm of mechanical ventilation.
• Colorado's habitability law covers mold and dampness, and windows, but doesn't name ventilation.

These set a floor for the room, not the 800 ppm goal. If your bedroom runs high with the window and door shut, your nights are useful evidence to bring to the landlord, along with a specific ask: a quieter bath fan that can run all the time, or a through-wall unit.

Condo owners: the board first

In many condos the outside walls are common property. A hole through one needs the board's written approval before any work. A typical alteration agreement, like the New York State Bar Association's template, asks for:

• the board's approval of any opening in an outside wall, roof or foundation, and any change to heating or ventilation;
• review by the building's engineer, sometimes with licensed plans;
• your permits, insurance, fees and deposits;
• your promise to maintain the work.

Ask early whether the building allows wall openings at all, whether the wall is fire-rated (if it is, the building's engineer decides whether an opening is allowed, and how), and whether a compact ERV with short ducts inside your unit would be easier to approve. One New York installer prices a room at about $2,000 to $3,500 and a whole apartment at about $3,500 to $6,000, installed.

What to ask for

1. How much fresh air reaches each bedroom, in cfm, against about 17 cfm per sleeper.
2. Where the outside openings go, how big they are, and who approves them.
3. How loud it is in the bedroom at night, at a stated distance.
4. How air leaves the bedroom with the door shut.
5. The filters: which ones, how often, and who changes them.

Room-by-room units lists the units on sale in the US, and the room planner works out what each bedroom needs. Fresh air without ducts compares the options in more detail.