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. Use the aluminum window systems page to frame the product-level discussion, but 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.
Separate confirmed requirements from open decisions
Use three states in the RFQ: confirmed requirement, supplier proposal requested and decision pending. A blank field is ambiguous: one bidder may select a standard component while another prices an upgrade. Tell each bidder which assumptions may be proposed and which must not change.
For every pending field, record an owner and the information needed to close it. For example, if a glazing build-up awaits design approval, request a clearly identified provisional option rather than presenting it as the final configuration. Keep the approval revision beside the field when the decision is made.
- Confirmed: requirement, unit, source document and revision.
- Proposal requested: function needed, constraints and evidence expected.
- Pending: unresolved question, decision owner and required response date.
Build a compact package around the opening schedule
Issue a marked plan or elevation, a schedule and an interface sketch that use the same opening identifiers. Label dimensions as rough opening, frame size or clear passage as applicable. A supplier should not have to infer which dimension convention was used from the drawing scale.
Then add the configuration choices, applicable project performance requirements, evidence requested, finish references and delivery scope. Avoid copying every possible option into a mandatory specification: distinguish the base offer from alternatives so the returned prices remain comparable.
Where the package also contains interior sliding partitions, identify them separately from exterior windows and doors. Review the application boundary and track conditions before carrying an interior product into an exterior schedule. Explore: Interior versus exterior sliding-door selection; Top-hung versus floor-track conditions.
Check the returned offer against the same three states
Ask the supplier to return a marked schedule identifying compliance with the requested configuration, proposed alternatives and remaining assumptions. Check that a later email has not silently changed the glass, quantity, track or finish without updating the schedule.
Close the technical baseline before ranking totals. Send the current package for a project review and use the quotation comparison guide to keep inclusions and allowances visible. Explore: Compare supplier quotations; Send your specification brief.
FAQ
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.
Official sources used
ISO 10077-1 — thermal transmittance calculation ↗U.S. DOE — window types and technologies ↗FGIA — performance class overview ↗Related buyer guides
This buyer guide provides a review method, not project-specific engineering, legal or compliance approval. Confirm the governing specification, applicable requirements and authorised project decisions before acting.