| Thermal performance | Look for the whole-door thermal transmittance value, commonly stated as Ud or U-value, in W/m²K. Check that the stated figure applies to the complete door set, not just the glazing or frame. | For comparison, a lower U-value indicates less heat transfer. A project may set a target around 1.4 W/m²K or lower, but the appropriate requirement depends on local regulations, climate, door size, and the calculation method. | Better thermal performance can reduce heat loss and help improve indoor comfort. Results depend on the complete assembly, including panels, glazing, frame, threshold, and installation. | Is the quoted value for the complete door configuration and size? Was it calculated or tested using a recognised method? Does it include the threshold and glazing specified for my project? |
| Thermal-break construction | Check whether the aluminium profiles use a thermal break between the exterior and interior sections, and ask how the door’s edges and threshold are insulated. | Thermally broken profiles are generally preferable for conditioned spaces. Compare documented performance rather than relying on a product description alone. | Aluminium conducts heat readily. A thermal break reduces direct heat flow through the frame and can help limit cold interior surfaces and condensation risk. | What thermal-break system is used? Are the frame, door leaves, and threshold designed to work together? |
| Glazing and solar control | Review the glazing build-up, centre-pane U-value, solar heat gain information, safety-glass specification, and whether low-emissivity coatings or gas-filled cavities are included. | Choose glazing to suit orientation and climate. Low-emissivity glass and insulated glazing units can improve thermal performance; solar-control glass may be useful where unwanted solar gain is a concern. | Glazing can make up a substantial portion of a double door’s area, so its specification affects heat transfer, comfort, and solar gain. | Does the stated whole-door value use the exact glazing option? Is safety glazing required by local building rules for this location? |
| Locking and hardware | Assess the lock type, number and position of locking points, cylinder protection, hinge security, and the quality of the handle and keep components. | For projects seeking tested burglary resistance in Europe, ask whether the complete door set has been classified under EN 1627, such as RC2 or RC3, where appropriate to the risk and local requirements. | Security depends on the complete installed door, including the frame, glazing, locks, hinges, and fixings—not on the lock alone. | Is any security classification supported by documentation for this exact configuration? Are the locks, glazing, frame, and installation details included in the tested specification? |
| Security glazing | Check whether the glass is safety glass and, where increased resistance to attack is needed, whether laminated security glass has been specified and tested as part of the door system. | In Europe, EN 356 classifies resistance of security glazing; the appropriate glass type depends on the required level of protection and must match the door system’s tested configuration. | Glass type and fixing method influence how the glazed area performs. A security-glass specification alone does not establish the security rating of the complete door. | What standard and class apply to the proposed glazing? Is the glass retained securely by the door frame and compatible with the specified security classification? |
| Air permeability | Request the tested air-permeability classification for the complete door set and check that the test covers the relevant size and configuration. | EN 12207 classifies air permeability; higher classes indicate better performance within the standard’s test framework. Confirm the class required by local codes and the project specification. | Reduced uncontrolled air leakage can improve comfort and energy performance, particularly in exposed or heated spaces. | What is the documented air-permeability class? Does the test include the opening arrangement, seals, and threshold being supplied? |
| Water penetration | Check the water-tightness test result, threshold design, drainage paths, weather seals, and the installation detail at the sill. | EN 12208 provides water-tightness classifications. Select a rating suited to local wind-driven rain exposure and the building’s location; confirm the applicable class from the test report. | Water performance depends on the door design and the way the frame and threshold are integrated with the surrounding construction. | What water-tightness class was tested? How should the sill be drained and sealed? Is the installation detail suitable for the expected exposure? |
| Wind resistance | Review the wind-load classification, door dimensions covered by testing, structural supports, and the fixing requirements for the project opening. | EN 12210 classifies resistance to wind load. The required class depends on factors such as building height, location, exposure, and local design requirements. | Appropriate wind-load performance helps limit excessive deflection and supports reliable operation of the leaves and seals. | Does the tested size match the proposed door? What frame anchoring and surrounding support are required for the site’s wind conditions? |
| Configuration and installation | Confirm the opening direction, active and passive leaves, threshold height, drainage, frame anchoring, perimeter sealing, and adjustment access. | Use the manufacturer’s installation instructions and ensure the installer follows the tested system details. Performance ratings may not apply if the door is altered or installed differently. | Even a well-rated door can underperform if it is poorly installed, incorrectly sealed, or out of adjustment. | Who is responsible for installation and commissioning? Are the fixing, sealing, drainage, and maintenance requirements documented? |
| Documentation and warranty | Request product specifications, relevant test reports or declarations, maintenance guidance, and written warranty terms for the complete door set. | Compare like-for-like documents for the same frame, glazing, hardware, dimensions, and opening configuration. Check local code requirements before purchase. | Clear documentation helps verify performance claims and supports correct installation, operation, and long-term maintenance. | Can the supplier provide evidence for the specified thermal, security, and weather performance? What maintenance is required to keep seals and hardware working correctly? |