What factors need to be considered in the design of metal roofs?

　　Metal RoofRefers to a roofing form that uses metal sheets as roofing materials, combined with structural and waterproof layers. There are many types of metal sheets, such as galvanized sheets, aluminum alloy sheets, aluminum-magnesium alloy sheets, titanium alloy sheets, copper sheets, stainless steel sheets, etc. The surface of the sheets can be baked, mainly with PE/PE, SMP/PE, HDPPE, PVDFPE. Baking can extend the service life of the sheets, which are 5-8 years, 10-15 years, 15-20 years, and over 20-25 years respectively.

　　Metal RoofWhat factors need to be considered in the design? Let's briefly understand together.

　　1. Load-bearing capacity. It must bear construction loads, rain, dust, snow pressure, and maintenance loads.Metal RoofThe load-bearing performance of the sheet is related to the cross-sectional characteristics of the sheet type, the strength and thickness of the material, the method of force transmission, and the spacing of purlins (auxiliary purlins).

　　2. Wind pressure resistance. To resist local high wind pressure.Metal RoofThe sheet will not be pulled off by negative wind pressure. The wind resistance capability is related to the clamping force between the metal roof panel and the fixing base, as well as the arrangement spacing of the fixing bases.

　　3. Sound insulation. To prevent sound from propagating in or out. The metal roof layer is filled with sound insulation materials (generally soundproof cotton), and the sound insulation effect is represented by the sound intensity difference in decibels on both sides of the metal roof layer. The sound insulation effect is related to the density and thickness of the sound insulation material. Note: Sound insulation materials have different blocking effects on different frequencies of sound.

　　4. Waterproofing. To prevent rainwater from seeping into the metal roof panel from the outside. Rainwater mainly enters the metal roof through overlapping seams or joints. To achieve waterproofing, sealing washers should be used at the screw holes and then concealed fixed, and sealing glue or welding should be used at the panel overlap. Use solid panels to eliminate overlaps and carry out strict waterproof treatment at each joint.

　　5. Lightning protection. To direct lightning to the ground and prevent it from penetrating the metal roof into the interior.

　　6. Daylighting. Improve indoor lighting during the day through skylights, saving energy. Lighting panels or lighting glass are installed at specific locations on the metal roof. The lifespan of the skylight should be coordinated with that of the metal roof panel, and the connection between the skylight and the metal roof panel should be waterproof.

　　7. Safety. Fixed facilities should be set up on the metal roof to protect the safety of construction and maintenance personnel.

　　8. Ice column prevention. To prevent rain and snow from forming ice columns at the eaves.

　　9. Aesthetics. Metal roofs have a good texture and pleasing colors.

　　10. Control thermal expansion and contraction. Control the shrinkage displacement and direction of the metal roof panel. Ensure that the metal roof panel does not get damaged due to stress caused by thermal expansion and contraction in areas with large temperature differences.

　　11. Insulation. To prevent heat transfer between the two sides of the metal roof, stabilizing the indoor temperature. The insulation effect is achieved by filling insulation materials (commonly glass wool and rock wool) under the metal roof panel. The insulation effect is represented by the U-value, with units of W/M2K. The insulation performance is determined by the following factors: the raw materials, density, and thickness of the insulation cotton; the humidity of the insulation cotton; the connection method between the metal roof panel and the lower structure (to prevent 'cold bridge' phenomenon); and the repeatability of the metal roof to thermal radiation.

　　12. Sound absorption. To reduce sound reflection and echo in the room. The sound absorption function is achieved by laying sound-absorbing cotton on the bottom layer of the metal roof and perforating the base plate. The sound absorption performance of the metal roof is represented by the sound absorption coefficient a.

　　13. Moisture prevention. To prevent water vapor from condensing in the bottom layer and the metal roof layer, and to discharge water vapor from the metal roof layer. The solution is to fill insulation cotton in the metal roof layer, lay a waterproof membrane on the metal roof base plate, and have ventilation nodes on the metal roof panel.

　　14. Fire prevention.

　　In the event of a fire, the metal roofing material will not burn, and flames will not penetrate the metal roof panel.

　　15. Ventilation. To facilitate the exchange of indoor and outdoor air. Ventilation openings are provided on the metal roof.