You do not need a window in a bathroom, but a well placed one is worth having. Washington's residential code does not require one: it requires an exhaust fan in every bathroom instead. So the window is a choice you make for daylight, a view and fresh air, not for code. If you add one, place it for privacy, use safety glass where the code calls for it near the tub or shower, and plan the wall around it so water and storage still work.
Washington code requires a bathroom fan, with or without a window.
Many older codes let a window stand in for a fan. Washington's does not. The model code section that asked for a bathroom window, R303.3, appears in the 2021 Seattle Residential Code with the note "This section is not adopted," and the state's own rule says the same (WAC 51-51-0303). What the state does require is in the mechanical chapter: "Bathrooms, toilet rooms, and kitchens shall include a local exhaust system" (WAC 51-51-1505, M1505.4.4.1). The minimum rate for a bathroom fan is 50 cfm when it runs on demand or 20 cfm when it runs continuously.
In practice that means the fan does the moisture work in every bathroom we build, and a window is extra. Opening a window helps on a dry day, but in a Seattle winter most people keep it closed, and the fan is what keeps the mirror and the ceiling dry.
A window adds daylight and a view, and it costs privacy and wall space.
Here is how the trade off usually looks in a remodel:
- Daylight. Natural light makes a small room feel larger and is the best light for a mirror. A high window or a skylight brings light in without a view in.
- Fresh air. An operable window airs the room out after a shower in mild weather.
- Privacy. A window at eye level beside a toilet or a tub needs frosted or textured glass, a high sill, or a covering.
- Wall space. Every window is wall you cannot use for a mirror, a medicine cabinet or tall storage, which matters in a small bathroom.
- Heat and condensation. Glass is the coldest surface in the room. Warm, wet air condenses on it, so a window in a bathroom needs a working fan even more.
Glass near a tub or a shower has to be safety glazing.
The Seattle Residential Code treats glass near water as a hazardous location. Section R308.4.5 says glazing "adjacent to hot tubs, spas, whirlpools, saunas, steam rooms, bathtubs, showers and indoor or outdoor swimming pools where the bottom exposed edge of the glazing is less than 60 inches (1524 mm) measured vertically above any standing or walking surface shall be considered to be a hazardous location." The exception is glass more than 60 inches, measured horizontally, from the edge of the tub or shower. Glass in a hazardous location has to pass the code's human impact test (R308.3), which is why a window over a tub or inside a shower is ordered with tempered or laminated glass.
A bathroom window works best over a tub, high on a wall, or as a skylight.
The best spot depends on the layout you already have, because moving a window means opening the outside wall.
- Over the tub. A classic place, with the view above the person in the bath. It needs safety glass and a sill that sheds water.
- Inside a walk-in shower. It can work well when the window already sits on that wall. In the Walk-In Shower Master Bathroom Remodel on our portfolio, the shower runs the length of the window wall, with a long tiled niche set just under the sill so bottles stay off the floor.
- Next to the vanity. Side light on a mirror is flattering, but a window right behind a vanity leaves no room for the mirror itself.
- Overhead. Where a wall window would cost privacy, a skylight brings the light in from above. In the Skylight Wet Room Master Bathroom in Seattle, WA, the tub and the shower share one glass enclosure under a skylight.
The window style matters more in a bathroom than in other rooms.
- Awning windows hinge at the top and open outward, so they can stay open in light rain and sit high on the wall for privacy.
- Casement windows crank open from the side and seal tightly when closed. They are easy to reach over a vanity.
- Sliding windows suit a wide, short opening above a tub.
- Fixed windows do not open, so they only add light. Pair one with a good fan.
For privacy, frosted or textured glass lets light through without a clear view, and it avoids blinds that get wet and grow mildew.
Adding or changing a bathroom window usually means a permit and an energy code check.
A new window or a wider one changes the outside wall. Bellevue's handout P-3 (July 2016) says "A permit with plan review is required for installing or moving an exterior door, skylight, or window, including making an existing window wider. No permit is required for replacements of the same size in the same location." In Seattle, window work is not on the Residential Code's list of work exempt from a permit (R105.2), and the Seattle Energy Code says a replacement window "shall meet the applicable requirements for U-factor and SHGC in Table R402.1.3" (R503.1.1.1). We check the rules for your address before we price the work.
Here is how we decide on a bathroom window with you.
At the walkthrough we look at the outside wall, where the plumbing runs, and what you see from the tub and the toilet. If the window stays, we plan the tile, the niche and the mirror around it. If it moves, grows or goes away, we include the wall, siding and permit work in your written estimate. See Bathroom Remodeling Across the Greater Seattle Area for the service, Window Replacement Across the Greater Seattle Area for window work on its own, and the Bathroom Remodeling Portfolio Across the Greater Seattle Area for finished rooms.
Bathroom window questions
Is a window required in a bathroom in Washington?
No. Washington and Seattle did not adopt the model code section that called for a bathroom window (R303.3 reads "This section is not adopted."). Instead, every bathroom needs a local exhaust system: an exhaust fan rated for at least 50 cfm when it runs intermittently or 20 cfm when it runs continuously (Table M1505.4.4.1).
Can a window go inside a shower?
Yes, with planning. Glass in a wall around a tub or shower whose bottom edge is less than 60 inches above the standing surface is a hazardous location under R308.4.5, so it has to be safety glazing. The sill also has to shed water, which is why we tile the sill and slope it toward the shower.
Do I need a permit to add or replace a bathroom window?
Adding a window or making one wider changes the wall, so plan on a permit. Bellevue's handout P-3 says no permit is required for a replacement of the same size in the same location. In Seattle, window work is not on the list of work exempt from a permit, and a replacement window has to meet the energy code's U-factor.
Planning a bathroom with or without a window? Book a consultation below. By appointment. Limited start dates.
