| 1. Project Application and Performance Requirements |
| Primary application | Common uses include bathrooms, kitchens, utility rooms, plant rooms, stairwells, corridors, and naturally ventilated façades. | Suitable where permanent airflow, screening, or weather protection is required without user operation. | Suitable where occupants need to control ventilation, airflow, and rain exposure. | Define whether the window is intended for ventilation, daylight, privacy, exhaust air, or a combination of these functions. |
| Ventilation control | Ventilation performance depends on the free area, blade angle, blade spacing, opening mechanism, and pressure difference. | Provides continuous airflow but cannot be closed for weather, security, or seasonal control. | Allows airflow to be adjusted or stopped, but moving parts require proper alignment and maintenance. | Choose operable louvers for variable occupancy or changing weather conditions; choose fixed louvers for continuous passive airflow. |
| Privacy and daylight | Blade depth, blade pitch, angle, and finish influence sightlines, glare, and daylight penetration. | Angled or opaque blades can provide permanent screening and reduce direct views. | Offers adjustable privacy and daylight, but open blades may increase visibility and glare. | Review a full-size sample from both the interior and exterior before approving the blade profile. |
| Weather exposure | Wind-driven rain resistance is affected by blade geometry, drainage, seals, frame design, and installation quality. | Can be designed as a fixed weather screen, but the assembly must still be tested or rated for the intended exposure. | Closed blades provide better weather control than open blades; seals and operating hardware become critical. | For exposed façades, request tested water penetration and wind-load data for the complete window assembly. |
| 2. Cost and Budget Planning |
| Indicative supply and installation cost | Typical preliminary allowance: approximately USD 180–350/m² for basic fixed units and USD 250–500/m² for standard operable units. | Usually has the lower initial cost because it uses fewer moving parts and less hardware. | Usually costs more because of operators, hinges, handles, restrictors, seals, and additional fabrication. | Use these figures only for early budgeting. Obtain project-specific quotations after dimensions, glazing, finish, hardware, and installation conditions are confirmed. |
| Thermally improved construction | Thermally broken frames can reduce conductive heat transfer compared with standard non-thermal-break aluminum frames. | Thermal improvement is useful for fixed ventilation panels or screened openings in conditioned spaces. | Thermal breaks and continuous seals are especially valuable where the operable unit separates conditioned and outdoor environments. | Specify a thermally broken system when energy codes, condensation control, or interior comfort are important. |
| Glazing configuration | Single glazing commonly has a center-of-glass U-value near 5.7 W/m²·K, while modern double low-emissivity insulating glass can be approximately 1.1–1.6 W/m²·K, depending on construction. | Single glazing may be adequate for unconditioned spaces, but it provides limited thermal and acoustic performance. | Double glazing can improve thermal comfort and condensation resistance, although it increases weight and hardware requirements. | Confirm the complete window U-value rather than relying only on the glass center-of-glass value. |
| Installation complexity | Cost increases with difficult access, irregular openings, perimeter repairs, waterproofing, and interior finishing. | Generally faster to install because alignment and operation checks are simpler. | Requires accurate setting of sashes, operators, restrictors, seals, and drainage paths. | Include survey, removal, flashing, sealants, scaffolding, testing, and making-good work in the installation budget. |
| 3. Maintenance and Service Life |
| Routine cleaning | Clean exposed aluminum surfaces and blades with mild detergent and clean water; avoid abrasive cleaners and harsh solvents. | Typically requires less routine attention because there are no operating mechanisms. | Requires cleaning of blades, tracks, hinges, operators, and drainage openings to maintain smooth movement. | Provide safe access for cleaning, especially on upper floors and in high-dust or coastal environments. |
| Hardware inspection | Inspect screws, handles, hinges, operators, restrictors, and fasteners at least annually in normal service conditions. | Inspection is mainly focused on fixings, seals, drainage, and perimeter joints. | Inspect moving components more frequently where the windows are operated often or exposed to salt, dust, or moisture. | Specify replaceable hardware and maintain access to adjustment points and fasteners. |
| Finish durability | Powder coating and anodizing can provide durable finishes when correctly specified, applied, and maintained. | Fixed surfaces generally experience less mechanical wear. | Operating contact points may experience additional wear, especially where blades or seals rub during use. | For coastal or industrial locations, specify a finish suitable for the corrosivity level and follow the coating supplier’s maintenance requirements. |
| Corrosion considerations | Salt deposits, standing water, dissimilar metals, and aggressive chemicals can accelerate corrosion of aluminum and hardware. | Lower mechanical risk, but drainage and coating integrity remain important. | More vulnerable to corrosion-related stiffness or seizure in hinges, operators, and fasteners. | Use compatible fasteners, isolate dissimilar metals, avoid blocked drainage, and increase inspection frequency in coastal areas. |
| Expected service planning | Service life depends on design, exposure, coating, hardware quality, cleaning, and installation. Hardware and seals may require replacement before the frame. | Often offers a simpler long-term service profile. | Can provide long service when hardware, seals, and drainage are maintained and replacement parts remain available. | Request maintenance instructions, spare-parts availability, finish-care requirements, and warranty conditions before purchase. |
| 4. Technical and Compliance Checks |
| Air leakage | Air leakage should be verified using the applicable local or project test standard; performance depends on the complete assembled window. | Fixed units can achieve consistent performance when perimeter joints are properly sealed. | Operable units require reliable gaskets, compression, alignment, and locking pressure to limit unwanted leakage when closed. | Request certified air-leakage results for the selected size and configuration rather than relying on generic product data. |
| Wind-load resistance | Required capacity depends on building height, location, exposure category, opening size, and local structural requirements. | Load transfer is relatively straightforward, but blades and frames must resist design pressure. | Hardware, hinges, restrictors, and locking points must resist the design loads in both open and closed positions where applicable. | Have the structural designer confirm the design pressure and anchorage before final fabrication. |
| Water penetration | Drainage paths, sill design, blade overlap, seals, and perimeter flashing influence resistance to water entry. | Fixed blade overlap can improve rain shedding, but it does not replace proper sill drainage and flashing. | Closed blades and compression seals can improve resistance, but blocked drains or poor alignment can cause leakage. | Require water-penetration testing or documented classification suitable for the project exposure. |
| Safety and operation | Window restrictors, opening limits, guards, safety glazing, and fall protection may be required by local regulations. | Often simpler for locations where occupant operation is not required. | Use restrictors or controlled opening devices where there is a fall risk, child-safety concern, or high-wind exposure. | Check fire, egress, fall-protection, accessibility, and safety-glazing requirements before selecting the operating type. |
| 5. Final Product Selection Criteria |
| Recommended fixed-louver choice | Best for simplicity | Choose when continuous ventilation, screening, low maintenance, and lower initial cost are the main priorities. | Not applicable as the primary selection, although fixed panels may be combined with operable sections. | Confirm that permanent airflow and reduced weather control are acceptable for the room and climate. |
| Recommended operable-louver choice | Best for control | Not applicable as the primary selection where adjustable ventilation is required. | Choose when occupants need to regulate ventilation, privacy, daylight, or weather exposure. | Prioritize robust hardware, positive closure, replaceable seals, restrictors, and accessible maintenance points. |
| Preferred frame specification | Use corrosion-compatible aluminum, suitable drainage, adequate wall thickness, and a finish appropriate to the exposure. | Standard frames may be acceptable in unconditioned or low-exposure areas. | Thermally broken frames are preferable where the window is part of the conditioned building envelope. | Match the frame depth and thermal design to structural loads, glazing thickness, condensation risk, and energy requirements. |
| Preferred documentation package | Product drawings, section details, glazing data, finish information, installation instructions, and test reports. | Focus on blade profile, drainage, fixing method, and weather-screen performance. | Include operator details, opening limits, locking method, hardware schedule, and maintenance instructions. | Do not approve the final product until dimensions, tolerances, performance ratings, finishes, hardware, and interfaces are coordinated. |
| Overall decision rule | Select the lowest whole-life-cost option that satisfies performance and code requirements. | Usually the better value where the opening can remain permanently ventilated and accessible for cleaning. | Usually the better value where user control, weather closure, or variable ventilation offsets the higher purchase and maintenance cost. | Compare initial cost, energy performance, maintenance access, replacement parts, durability, compliance, and expected operating conditions together. |
