The phrase “double-glazed thermal-break aluminum window” can still describe dozens of materially different packages.
A buyer receives three quotations. Each supplier has priced the same window marks, but one has assumed clear glass, another Low-E, and a third has excluded screens and subframes. The totals cannot be compared because the specification never closed the gaps. A useful checklist turns those silent assumptions into decisions before the order.
Define every opening mark
For each mark, record dimensions, quantity, operation, handing, room or elevation and any restricted opening requirement. Reconcile the schedule with plans and elevations before asking suppliers to price.
When documents disagree, issue a numbered clarification instead of letting each bidder choose a convenient interpretation.
Describe the complete system
Name the proposed frame route, thermal-break requirement, glass build-up, spacer, seals, drainage, hardware, finish and screen. Avoid treating the profile series as a complete specification.
Large or unusual units need separate review. A catalogue maximum is not automatic proof of structural, air or water performance at the proposed size.
Separate four performance questions
Thermal transmittance, solar heat gain, air leakage, water penetration and structural resistance are related design inputs but not interchangeable claims.
Request evidence that identifies the tested or calculated configuration, method, specimen size and differences from the project unit.
- Whole-window thermal value
- Solar-control requirement
- Air leakage
- Water penetration
- Structural or wind resistance
- Acoustic requirement where applicable
Close interfaces and scope
Many disputes occur around items that sit beside the window: subframes, anchors, perimeter sealants, trims, flashings, screens, guards, access equipment and making-good.
Put each interface into a scope matrix and name the responsible party. The window price is not commercially complete until those boundaries are visible.
Record approval and change control
State which drawings, samples, colours and documents approve production. Name who can authorise a change and what happens to price and programme after release.
This protects both buyer and supplier from an informal message becoming an unrecorded production instruction.
Questions buyers ask
Can a window be specified by U-value alone?
No. Whole-window thermal performance is one requirement among structural, air, water, safety, operation and interface needs.
Should every mark use the same glass?
Not automatically. Orientation, safety, size, privacy and acoustic needs can differ, but unnecessary variants should be consolidated deliberately.
What should accompany a quotation request?
Provide drawings, window schedule, quantities, location, performance brief, glass, hardware, finish and interface scope where known.
Continue the project review
Connect this guide with the proposed window and door systems, then review how Cavorlen approaches manufacturing and quality control. When your schedule is ready, send it through the project review form.
Primary references
ISO 10077-1 — thermal transmittance calculation ↗U.S. DOE — window types and technologies ↗FGIA — performance class overview ↗Related buyer guides
Exact systems, performance, price, programme, delivery and warranty require authorised project-specific review.