| Thermal performance | Compare whole-window U-factor and solar heat gain coefficient (SHGC) for the specified size, glazing, frame, and configuration. Lower U-factor indicates less heat transfer; SHGC describes how much solar heat enters. | Performance affects heat loss or gain and should be matched to local climate, building design, and applicable energy requirements. | Test reports or product labels identifying the rated configuration, test method, and applicable market standard. |
| Air and water resistance | Review tested air leakage and water-penetration performance, including the test pressure and window type. Confirm requirements for the project’s exposure and building height. | Inadequate resistance can contribute to drafts or moisture intrusion; results depend on product design, installation, and site conditions. | Independent test documentation and installation details for the proposed system. |
| Durability and maintenance | Check frame and hardware specifications, finish-care instructions, drainage design, and availability of replacement components. | Maintenance needs and access to compatible parts can affect ownership costs and repair time over the product’s service life. | Written care guidance, component lists, spare-parts policy, and repair procedures. |
| Customization and project fit | Confirm available dimensions, opening styles, glazing options, finishes, and tolerances against drawings and local code requirements. | A product that fits the opening and project specification reduces redesign and coordination risks. Custom options should be assessed alongside lead time and replacement feasibility. | Approved shop drawings, technical data sheets, and a documented change-control process. |
| Supplier reliability | Assess production capacity, quality-control procedures, order tracking, communication practices, and how nonconforming products are handled. | Reliable processes help manage delivery, specification changes, and corrective actions, especially on projects involving multiple shipments. | Quality records, sample inspection reports, production schedule, and written corrective-action procedures. |
| Warranty and after-sales support | Compare warranty coverage, exclusions, claim process, response arrangements, and responsibility for freight or replacement parts. Terms vary by supplier and market. | Clear, practical support terms help buyers understand how defects and service issues will be addressed after delivery. | Full written warranty, service contact details, and a sample claim workflow. |
| Total cost of ownership | Evaluate purchase price together with installation, shipping, duties, maintenance, expected energy effects, repair access, and warranty conditions. | The lowest initial quotation is not necessarily the lowest-cost option over time. Energy savings should be estimated using local rates, climate, and building conditions. | Itemized quotation, stated assumptions, delivery terms, and a project-specific cost comparison. |
| International shipping and compliance | Verify packaging, shipment terms, import documentation, destination-market testing, and responsibility for damage in transit. | Import rules and building requirements differ by destination. Compliance and logistics should be confirmed before production and dispatch. | Destination-specific compliance documents, packing specifications, and agreed shipping terms. |