What's the difference between new-construction and replacement windows?

New-construction windows have a nailing fin that integrates directly into the wall's weather-resistive barrier before siding goes on, giving a fully continuous drainage plane. Replacement windows get inserted into an existing finished opening, which limits how much of the underlying flashing can be redone. New construction is the better opportunity to get water management right from the start.

What should I ask a contractor before hiring them for new-construction window installs?

Ask specifically how they sequence sill pan flashing, WRB integration, and head flashing on new openings, since that sequence is where most future leaks originate. Also ask whether they coordinate directly with your framer and siding crew, since window and siding details have to line up. A contractor who can walk you through their exact flashing order without hesitation has done this enough times to trust.

Why don't you recommend bare aluminum window frames for homes near the water?

Unprotected aluminum is prone to pitting and corrosion when it's regularly exposed to salt-laden air, which is a known trade-off of the material rather than a defect. It's our professional standard to steer clients toward vinyl or fiberglass in salt-exposed locations because they hold up with less long-term maintenance. Coated or thermally broken aluminum systems exist and behave differently, and we're glad to discuss those separately if you have a specific design reason to want aluminum.

What's a sill pan flashing and why does it matter so much?

A sill pan is a sloped, sealed barrier installed at the bottom of a window rough opening that gives any water that gets past the window a path back out instead of into the wall cavity. It's one of the most commonly skipped details on older builds, and it's cheap to do right during framing but very expensive to add later. We install one on every new-construction opening as standard practice.

Does Semiahmoo's coastal weather actually change how windows should be installed compared to other parts of Whatcom County?

Yes — homes closer to the water see more wind-driven rain hitting openings at an angle, not just straight down, which puts more demand on flashing and drainage details than a flashing job that would be adequate further inland. We also see more salt exposure on hardware and frame materials near the Semiahmoo waterfront. The build sequence is the same everywhere, but the margin for error is smaller this close to the water.

Peace Arch New-Construction Windows | Semiahmoo Local Crew

Building New in Peace Arch: Windows Are a Weatherproofing System, Not Just Glass

If you're framing a new home or an addition near Peace Arch, the windows you choose and how they're installed will do more to determine your long-term maintenance headaches than almost any other exterior decision. This close to the Strait of Georgia and the Semiahmoo waterfront, homes take on a steady diet of salt-laden air, wind-driven rain, and a moss season that can stretch from October into May. New-construction windows give you one real advantage over a retrofit: you get to build the water management right the first time, instead of working around whatever a previous builder did.

This page covers what a correct new-construction window install looks like specifically for Peace Arch homes, what the climate demands of the materials and flashing details, and how our process works when we're brought in during the framing stage rather than called back years later for a leak.

What "New Construction" Actually Means for a Window Install

New-construction windows have a nailing fin (or flange) built into the frame that gets integrated directly into the wall's weather-resistive barrier (WRB) before siding or trim goes on. That's different from a "replacement" or "pocket" window, which gets inserted into an existing rough opening after the exterior is already finished. On a new build, we're not working around old trim or matching an existing reveal — we're setting the window as part of the wall assembly itself, which is the only way to get a fully continuous drainage plane.

The trade-off is that new-construction installs demand more sequencing discipline. The window has to go in at the right point in the build — after the WRB is up, before siding — and every layer around it (sill pan, flashing tape, head flashing, siding) has to lap correctly so water sheds outward and down, never inward. Get the sequence wrong and you won't see the consequence for a year or two, which is exactly the kind of mistake that's expensive to diagnose after the walls are closed up.

Why This Matters More Here Than Inland

Whatcom County's coastal exposure means wind-driven rain hits window openings at an angle, not just straight down, and it hits often. A flashing detail that would be marginal but survivable in a drier inland climate can fail within a few winters this close to the water. We treat every opening as if it will see sustained wind-driven rain, because around Semiahmoo, it will.

The Climate Factors We Build Around

Salt air: Airborne salt accelerates corrosion on unprotected fasteners, low-grade hardware, and some aluminum components. It also degrades certain sealants faster than a standard product data sheet assumes.
Driving rain: Storms off the Strait push rain sideways into wall assemblies, so passive drainage (not just sealant) has to be part of the design — sealant alone always eventually fails.
Moss and constant dampness: Long stretches of overcast, damp weather keep exterior surfaces wet longer than they'd stay wet elsewhere, which means anything that traps moisture against wood trim or sheathing becomes a rot risk over time.
Temperature swings: Not extreme here, but enough seasonal movement that frame materials and sealant joints need to flex without cracking.

Frame Material Comparison for Coastal Whatcom County

There's no single "correct" frame material for every Peace Arch project — it depends on budget, the home's design, and how much upkeep you want to take on. Here's how the common options hold up specifically against salt air, moisture, and our maintenance expectations.

Material	Coastal / Salt-Air Behavior	Maintenance	Typical Fit
Vinyl	Doesn't corrode; UV-stable formulations hold up well in PNW light	Low — occasional cleaning	Most budget-conscious new builds
Fiberglass	Excellent salt-air and moisture resistance; very stable dimensionally	Low	Higher-end builds, larger openings
Wood-clad (composite exterior)	Good if cladding is intact; interior wood face still needs protection from interior humidity	Moderate — depends on clad integrity	Homes wanting a wood interior look
Bare/uncoated aluminum	Prone to pitting and corrosion in salt air over time; we don't spec this near the water	Higher — needs monitoring	We generally steer clients away from this in Semiahmoo

We don't install bare aluminum frames in salt-exposed locations as a matter of our own standard — not because it's a bad product everywhere, but because unprotected aluminum's corrosion behavior in marine air is a known trade-off, and there are better options for this specific environment. Thermally broken, factory-finished aluminum systems exist and perform differently, but for most residential new construction here, vinyl or fiberglass gives you the better cost-to-durability balance.

Glass Packages Worth Specifying Here

Glass performance matters as much as frame material in this climate — mostly for comfort and condensation control rather than raw heating-bill savings, since Whatcom County winters are mild but persistently damp and gray.

What We Recommend Discussing With Your Builder

Low-E coatings: Reduce heat loss and help manage the glare off overcast coastal skies; standard on most quality window lines now.
Argon or krypton gas fill: Improves the insulating value of the sealed unit; argon is the typical cost-effective choice for this region's mild temperature range.
Warm-edge spacers: Reduce condensation risk at the glass edge, which matters in a climate where interior humidity plus cool glass is a near-constant combination.
U-factor and SHGC targets: Washington's energy code sets minimums by climate zone — we work within those, but for west- or water-facing rooms we'll also talk through solar heat gain trade-offs with you directly.

Our Installation Process

When we're brought in during framing, the sequence looks like this on every opening:

Rough opening check: Confirm the opening is square, level, and sized correctly before the window ever arrives on site — catching a framing error now is far cheaper than after siding goes on.
Sill pan flashing: Install a sloped, sealed sill pan so any water that gets past the window has a path back out, not into the wall cavity. This is the single most-skipped detail we see on older Whatcom County builds we're later called back to repair.
Window set and shim: Set the window plumb and square, shimmed correctly so it operates smoothly and doesn't rack over time as the structure settles.
Fin integration with the WRB: Tape and lap the nailing fin into the weather-resistive barrier in proper shingle-style order — sides first, then head flashing lapped over the top so water always sheds down and over, never behind.
Head flashing: Install a dedicated head flashing above the window, not just tape, for extra protection against the wind-driven rain this area sees regularly.
Interior air seal: Seal the interior side of the rough opening for both energy performance and to control interior condensation at the frame.
Siding and trim coordination: Work with the exterior finish (whatever siding is going on) so the drainage plane and any rain screen gap stay continuous around the opening.

Rain Screen and Drainage Gap Details

On most new builds in this climate, we recommend a rain screen gap behind the siding — a small ventilated space that lets any moisture that gets past the cladding drain and dry out instead of sitting against the sheathing. Around window openings, this means the flashing and trim details have to account for that gap rather than sealing it shut, which is a detail that's easy to get wrong if the window install isn't coordinated with the siding install. This is one of the reasons we prefer being involved from the framing stage rather than only doing windows in isolation.

Site Checklist We Actually Use

Rough openings verified square and correctly sized before delivery
Sill pans installed with positive slope to the exterior on every opening
WRB integration follows proper shingle-lap order (sides before head)
Dedicated head flashing installed above each window
Rain screen gap maintained and not accidentally sealed shut by trim
Fasteners and hardware rated for coastal/marine exposure
Interior air seal completed and inspected before insulation covers it
Final operation check — every sash opens, closes, and locks smoothly

Why Hiring a Crew That Already Works Peace Arch Matters

Window performance in a coastal Whatcom County climate isn't something you can fully judge from a spec sheet — it comes down to installation details that either hold up against driving rain or don't. A crew that's done multiple builds in and around Semiahmoo has already seen what actually fails here versus what's fine, which flashing sequences hold up through a wet winter, and which shortcuts show up as callbacks two years later. We also work regularly with the permitting and inspection expectations local builders deal with on new construction, so we're not learning the process on your project.

There's also a simple logistics benefit: being local means we can respond quickly during the build if a delivery is delayed, a rough opening needs adjusting, or the schedule shifts — all common on new-construction timelines.

Cost Factors on New-Construction Window Projects

Every project is different, but these are the main variables that move the number up or down. We'll walk through actual figures for your plans during a site visit rather than quoting blind.

Factor	Effect on Cost
Frame material (vinyl vs. fiberglass vs. wood-clad)	Fiberglass and wood-clad run higher than standard vinyl
Number and size of openings	Larger and more numerous openings scale cost directly
Glass package upgrades	Triple-pane or upgraded Low-E/gas fill adds cost per unit
Custom shapes or oversized units	Special-order sizing and shapes cost more than stock sizes
Site access and scheduling	Coordinating tightly with a framing schedule is more efficient than isolated retrofits

Maintaining Your Windows Once the Build Is Done

Even a correctly installed window needs some basic upkeep in this climate. Rinse frames and sills periodically to clear accumulated salt residue, especially on units facing the water or exposed to prevailing wind. Keep an eye on moss and organic buildup around sills and trim — the same dampness that grows moss on a roof will hold moisture against window trim if it's left unchecked. Check exterior sealant joints yearly for cracking or separation, and don't ignore a sticking sash or a musty smell near a window frame — both are early signs worth a quick look before they become a bigger repair.

Let's Talk About Your Project

If you're framing a new home or addition near Peace Arch and want windows installed correctly the first time, we're happy to walk the plans with you and give you a straightforward, no-pressure estimate — just fill out the form below.