How to Spec Windows for a Custom Home Build
Windows are one of the higher-stakes line items on a custom build. They affect the facade, the energy model, the comfort of every room, and — because lead times are real — the schedule. Getting the spec right early prevents expensive changes later. This is a practical checklist for builders and architects, in the order the decisions usually need to be made.
Start with the openings
Everything begins with the rough openings: location, size, head height, and how each window relates to the elevation and the interior. Decide early which openings are fixed (for view and light) and which need to operate (for ventilation and egress), because that drives both cost and hardware.
A few things to lock down up front:
- Egress requirements for bedrooms and habitable basements — confirm the operable style and clear-opening dimensions meet code for those rooms.
- Sightline intent — where you want slim frames and big glass versus where a divided look is wanted.
- Operation direction — inswing vs outswing, and how sashes clear furniture, walkways, and window treatments. Inswing styles like tilt-and-turn need interior clearance; outswing casements need exterior clearance.
Materials and finish
Choose the frame material against the architecture, climate, and maintenance expectations — the tradeoffs are covered in aluminum vs clad wood vs timber. Then set the finish: exterior color, interior finish, and whether they differ. Consistency across the whole package matters for the elevation, so specify the finish once, globally, and note any exceptions.
Custom and oversized sizing
Every Bellevue window is a custom size window by default — there’s no standard-size catalog to deviate from, and no upcharge tier for a non-standard opening. That matters most at the extremes: oversized single units, unusual aspect ratios, and openings that don’t match any manufacturer’s standard range. If a proposed opening is close to a structural or shipping size limit, flag it early so we can confirm feasibility and lead time before the rough opening is framed, not after.
Glazing and performance
Match the glass to the energy model and the climate, not to a default. Decide double vs triple pane, the Low-E coating, and where you need laminated or tempered glass. Our glazing guide covers U-factor and SHGC, the two numbers that drive most of the performance conversation with an energy consultant.
Hardware and operation
Specify the hardware brand and finish, and confirm the locking type on operable units — multi-point locking improves both sealing and security. Note handle style and finish so it coordinates with the rest of the home’s hardware. For large moving glass like bi-fold or sliding units, confirm the operation is rated for the size and weight you’re specifying.
Lead times and delivery
Custom windows are made to order, so lead time is part of the spec, not an afterthought. Build it into the construction schedule and sequence the order so windows arrive when the openings are ready — not so early they sit on site, not so late they hold up dry-in. Bellevue’s lead time is typically around 60 days from order to delivery.
For a direct-to-builder supplier like Bellevue, product ships straight to the project rather than through a dealer network, which removes a handoff from the schedule. Coordinate the delivery window, site access, and who’s receiving and storing the units before install.
A spec checklist
Before you release the order, confirm you’ve specified, for every opening:
- Size and rough-opening dimensions
- Fixed vs operable, and operation direction
- Egress compliance where required
- Frame material and interior/exterior finish
- Glazing (pane count, Low-E, laminated/tempered), U-factor/SHGC targets
- Hardware brand, finish, and locking type
- Grille/divided-lite pattern, if any
- Lead time confirmed against the schedule and delivery coordinated
Working on a build now? Send the opening schedule and intent in a quote request and we’ll return an itemized, configured quote within one business day.
What information do you need to quote windows for a custom build?
Opening dimensions, the operation type you want for each, material and finish, glazing requirements, and your framing schedule. From that we can return an itemised, configured quote rather than a base price that changes later.
When should windows be ordered on a new build?
Once openings are dimensioned and before framing completes, since made-to-order units typically run around 60 days from order to delivery. Ordering against the framing schedule rather than after it is the single most common way to avoid a delay.
Can window sizes be changed after ordering?
Before manufacturing begins, yes. After that, a made-to-measure unit is built to the dimensions given, which is exactly why the measurement step matters more on custom work than on standard-size replacement.