Window and Exterior Door Maintenance for Washington Homes: Seals, Drainage, and Replacement

A window or an exterior door is a drainage system with a seal around it. Almost every fault belongs to one of four parts — the sealed glass unit, the frame’s drainage path, the perimeter flashing and air seal, or the operating seal at the sash or door edge — and each part fails in a way the others do not. Sort the symptom first. The expensive mistakes are all sorting mistakes: caulking a sill that was built to drain, paying to clean glass whose seal has already gone, or pricing a replacement for water that is entering at the flashing above the frame.

The ordering matters more in Washington than a general maintenance list suggests, for two reasons. The state’s residential energy code puts a floor under what a replacement unit must be, and the federal lead rule treats window replacement differently from almost every other small job. Both are checkable before anyone quotes the work.

Which of the four parts has failed

Two of those rows are routine maintenance. One is weather. The remaining three are not improved by cleaning, and only one of them is a replacement decision.

The sill is a drain, not a seal

The most useful document on this subject is not written for homeowners. Building Science Corporation prepared an information sheet for the Department of Energy’s Building America program that divides window and door installations into two kinds. A barrier installation, in the sheet’s words, “does not provide for forgiveness to water infiltration through or around the window or door opening”; the guidance says such details should be limited to areas of low rainfall potential or openings protected by overhangs or porches. A drained installation is built to collect the small amount of water that gets past the cladding and put it back outside.

Central to a drained opening is pan flashing under the sill, and the sheet lists what it must do: provide a continuous waterproof surface with no holes, tears or wrinkles that could hold water; have a back dam or a positive slope toward the exterior; have end dams at the sides so water cannot run laterally into the wall; and lap over the drainage plane below the opening.

Then comes the sentence that decides the common homeowner repair. The sealing of the assembly into the rough opening, the sheet states, “should be made at the jamb and head of the window, however the sill should be left free to drain to the exterior.”

That is why a bead of caulk run along the bottom of a window frame so often precedes a report of water inside. In a drained unit the sill is the exit. Sealing it leaves the water nowhere to go but into the wall. The Building America Solution Center’s guidance on weep holes makes the same point from the other end: many windows contain small openings that let water out of the frame or the track, and “if weep holes are clogged or accidentally caulked, trapped water can accumulate within the frame and eventually damage the framing, sheathing, insulation, and other building materials.”

The practical rule is narrow and absolute. A slot or series of slots at the bottom of a frame is a drain until the product’s own instructions say otherwise. Do not fill it, widen it, or paint over it.

The glass is the one part that cannot be serviced

Most windows sold now are dual-pane: two panes with a sealed air space between them. That space is the product. When the seal goes, the space is no longer sealed, and the result is the fog or milky haze that will not wipe away from either side. One manufacturer’s published guidance is blunt about all three cases. Condensation on the room side means “the humidity level is too high indoors, not because there is something wrong with the window.” Condensation on the outside face is dew, and the same guidance calls it “a sign of energy efficiency,” because it means the outside pane is well insulated from the room. Condensation between the panes means the seal has failed, and there the guidance says you will not be able to prevent it from forming.

Only one of those three is a window problem.

Indoor humidity is the variable in the first case, and the federal guidance gives both a band and a limit. The EPA’s indoor air quality guidance is to keep indoor relative humidity below 60 percent, and ideally between 30 and 50 percent. Its moisture-control page explains the mechanism: cold air holds less moisture than warm air, which is why water forms on the inside of a window in cold weather, and why showers, cooking, plants and drying clothes indoors all add to the load.

The limit moves with the weather. The same EPA page reproduces ASHRAE’s maximum indoor humidity levels by outdoor temperature: 35 percent at 20°F, 30 percent at 10°F, 25 percent at 0°F, 20 percent at minus 10°F, and 15 percent at minus 20°F. A house sitting at 35 percent is comfortable and clear at 30°F and fogs its glass at 5°F. That is the ordinary explanation for condensation that appears only during a cold snap, and it is the reason a humidity reading taken on a mild day proves little.

Water that reaches a ceiling or an interior wall as well as a window is a different question: whether it is a roof leak or condensation has to be settled before either is repaired.

The manufacturer’s winter recommendation — 30 to 35 percent — sits inside the EPA’s ideal band and above what the federal table allows at 0°F. The two figures are answering different questions: one is a comfort target for a heating season, the other is a condensation limit that falls with outdoor temperature. Where they disagree, the glass is the more reliable instrument for that room on that night.

For a replacement, condensation can be specified rather than hoped for. The National Fenestration Rating Council’s label carries a condensation resistance rating alongside U-factor, solar heat gain coefficient, visible transmittance and air leakage, and a higher condensation resistance number means better resistance.

What to check from inside and at ground level

None of this needs a ladder. The checks below establish which of the four parts is at fault; the repair is a separate decision.

1. Identify the unit before touching it. Open the window and look at the jamb track for the certification label. The care guide for that product governs the cleaner, the tools and whether any opening may be cleared.
2. Test the weep holes with water. The Building America guidance is to pour a glass of water into the interior weep hole or the track, or to mist the exterior surface, and watch whether water leaves through the opening. If it does not, clear it with a soft tool — a pipe cleaner, a small drain brush or a wire hook — pulling debris out rather than pushing it further in. If a slot has been caulked over, that is the finding, and the product’s instructions should be read before any tool goes near the frame.
3. Look at the track, not only the glass. Soil, plant debris and hardened sealant all interrupt the same channel.
4. Inspect the interior perimeter after a rain, not during one. Staining, bubbling paint or soft plaster at the head or jambs points to the perimeter, which is a flashing question.
5. Note where the water is and what the outdoor temperature was. A note that says “inside face, 24°F” separates humidity from a failed unit without any instrument.
6. Check the door’s sweep and threshold contact. A sweep that does not touch the sill, or a threshold with a gap under the door, is the operating seal, not the glass.

Weatherstripping and caulk are not interchangeable

The Department of Energy draws the line cleanly. Caulk is for cracks and openings between stationary components, such as around door and window frames. Weatherstripping is for components that move, such as doors and operable windows.

One caution belongs with any air-sealing work, and the Department’s own guidance puts it first: before sealing, determine how much fresh air the house needs and how combustion appliances are ventilated. A tighter house with a starved furnace or water heater can release carbon monoxide into the living space. That is a reason to treat whole-house air sealing as a project with an assessment attached, not as a weekend of caulk.

Cleaning without driving water into the wall

Exterior cleaning is where a maintenance task turns into a water-intrusion repair. A manufacturer’s care guide for vinyl and aluminum units is specific. A heavy rain is often enough; a garden hose is the next step. It states plainly that the units should not be washed with a high-pressure spray, because the pressure “could crack or destroy the caulking around the window or door,” and adds a warning that catches most people: many operable windows and doors “are not designed to withstand direct, full-pressure, full-volume spray from a typical garden hose,” and may let water penetrate when they get one. The instruction is low volume, moderate pressure and an indirect spray, working from the top down.

The same guide sets the cleaning materials: a soft cloth or a long-handled soft bristle brush, and no chlorine bleach, liquid grease remover, strong soaps, nail polish remover or detergents containing organic solvents, any of which can affect the finish.

Two boundaries follow. Washing a wall or a window with force is the same mistake in a different costume, and how water gets behind cladding and finishes during cleaning is its own subject. Exterior glass above the ground floor is an access problem before it is a cleaning problem, and this page stops at what can be reached safely from the ground or from inside.

Replacement: the code sets the floor, the label proves it

When the decision really is replacement, Washington’s residential energy code has already decided part of it. Section R503.1.1.1 of the Washington State Energy Code, residential provisions, states that where some or all of an existing fenestration unit is replaced with a new product, “including sash and glazing,” the replacement unit must meet the applicable U-factor and solar heat gain coefficient requirements in Table R402.1.3. Where more than one unit is installed, an area-weighted average of the replacements may be used to demonstrate compliance.

Table R402.1.3 sets the fenestration U-factor at 0.30 for Climate Zone 5 and Marine 4 — the zones the state’s code assigns — with skylights at 0.50. The requirement is statewide rather than city by city. The code does allow the local code official to approve an alternative where full compliance is, in that official’s opinion, physically impossible or economically impractical and the design either improves efficiency or is necessary for health, safety and welfare. That is a decision for the building department, not for a contractor’s estimate.

The label is how the claim is checked. NFRC certification is the basis of the ratings, and ENERGY STAR qualification for windows, doors and skylights runs through NFRC’s certification program. The label’s U-factor runs from 0.20 to 1.20, and lower is better; solar heat gain coefficient runs from 0 to 1, and lower means less solar heat; air leakage and condensation resistance are also reported. A replacement unit that meets U-0.30 but carries no label is a claim, not a rating.

Two questions belong in the same conversation. Whether a permit is required is a local question, and the process for checking it is its own subject. And whether the job is a full-frame replacement or an insert that fits inside the existing frame changes what is being bought: an insert leaves the old frame, and whatever flashing and drainage path it has, in place. The federal retrofit guidance is to flash the rough opening before new or rehabilitated windows and doors go in. Ask which of the two is being quoted, and ask what happens to the existing flashing either way.

The pre-1978 rule that catches window replacement

The federal lead rule is the other thing that changes with the age of the house. The EPA’s Renovation, Repair and Painting Rule applies to work in housing built before 1978, and its list of covered activities includes window replacement by name. The rule’s small-job exemption — six square feet or less of disturbed paint per interior room, or 20 square feet or less on an exterior — does not apply here: the EPA states that window replacement and demolition of painted surfaces “are always covered regardless of square footage.”

In practice that means a paid window replacement in a pre-1978 house requires a certified firm, even a sole proprietorship, and a certified renovator assigned to the job. It does not mean the work is dangerous or that the windows should not be replaced. It means the certification and the lead-safe practices are part of the scope, and asking for them is a fair question before work begins — alongside the registration check that applies to any contractor in the state.

What a written scope should describe

A window quote that lists a unit and a price is not yet a scope. The items below are the ones that change the work:

• Which units, by location, and how each is identified.
• Whether each is a full-frame replacement or an insert, and what happens to the existing flashing and trim.
• The U-factor and solar heat gain coefficient of the units offered, and the label that states them.
• Whether lead-safe practices are specified, and which certified firm and renovator are responsible.
• Removal and disposal of the old units, and who pays for it.
• What is excluded — paint, trim repair, blinds, interior finish repair, disposal fees.
• The manufacturer’s warranty and the labor warranty, stated separately.

Comparing those scopes side by side is its own exercise, and the live guide to comparing quotes sets out how.

Start with the water, not the window

Work through the four parts in the order the symptoms appear, and only then decide whether the answer is a tool, a contractor or a new unit. When it is a new unit, the state’s U-factor floor and the federal lead rule are both part of the job.