Coordination Principles Between Curtain Wall Design and Architectural Design
Before starting curtain wall design, it’s essential to follow certain coordination principles to ensure consistency with architectural design.
From the type of curtain wall, window opening method, grid design, to the selection of panel materials and the treatment of structural nodes, to lightning protection, fire protection, ventilation, energy saving, lighting, advertising, cleaning and maintenance, etc., every link is related to the performance, quality and service life of the building. This article will comprehensively sort out the core points of various aspects in the process of curtain wall design and implementation, and provide a systematic reference for architects, structural engineers and curtain wall engineering practitioners.
At the early design stage, it is essential to communicate with architects to select the most suitable curtain wall system. Early coordination ensures technical feasibility and architectural coherence.
① Common curtain wall forms include:
A. component curtain wall, B. unit curtain wall, C. full glass curtain wall, D. point curtain wall, E. double curtain wall, F. photovoltaic curtain wall, etc.
Among component curtain walls, the use of fully hidden frame glass curtain wall has been restricted.
② Usually, the curtain wall thickness of component curtain wall is between 200mm and 250mm. And it can be reduced by adding keel supports at special locations like shear wall and column position. While the thickness of unit curtain wall is above 250mm.
The thickness of full glass curtain wall mainly depends on the height of glass ribs. And it is necessary to consider adding a channel thickness of 500-800mm in the double curtain wall.
③ Unless specified, the curtain wall design area is calculated according to the visible light area.
When it comes to the window opening design, it should be based on ventilation needs, space functionality, safety codes, and user convenience. The position and type of curtain wall windows must be coordinated early with the architectural plan. So that it can avoid conflicts with structure or façade detailing.
① The types of curtain wall window opening usually include: top-hung windows (most commonly used), casement windows, sliding windows, bottom-hung windows, etc.
② When the opening area cannot meet the requirements, ventilation and air exchange devices should be installed.
③ It is not advisable to set up external casement windows in high-rise buildings. And many local regulations prohibit the installation of external casement windows in high-rise buildings. Meanwhile, it is not advisable to set up opening windows in super high-rise buildings, and top-hung windows shall not be used as smoke exhaust windows.
④ For hidden frame opening windows, the silicone structural sealant should be used in the second sealant of insulating glass.
⑤ When designing curtain wall opening windows, the installation height should not be too high. And the opening windows should be set at a height that is convenient for adults to open. If they have to be installed at a very high position, then the mechanical or electric opening should be considered.
⑥ The structural design of curtain wall opening windows should comply with the rain curtain principle:
⑦ External opening windows should not be set within the 2m height range of the first floor.
Curtain wall grids should balance architectural aesthetics with structural beam locations, floor zoning, and interior finishes. Coordinated grid design ensures ease of construction, cost control, and long-term quality.
① Curtain wall grids should be standardized to facilitate material procurement and installation.
② The same curtain wall glass unit should not cross two fire partitions of the building.
③ The standard horizontal grid of the glass curtain wall is 1.2m. When it exceeds 1.2m, the specification stipulates that the main load-bearing wall thickness of the curtain wall transverse keel is not less than 2.5mm. And when it is less than 1.2m, it is 2.0mm. If the grid is too small, according to engineering experience, the weight of aluminum per square meter will increase. Therefore, the horizontal grid is preferably 1.2m. The conventional size of aluminum plate is ≤1.2m. If both sides are greater than 1.2m, the cost will increase significantly. The short side length of the stone curtain wall should not exceed 0.73m. If it exceeds, the cost will increase.
④ The height direction of the curtain wall should be designed at the same time above and below the structural beam to facilitate the setting of curtain wall fire blocking and indoor ceiling decoration and indoor floor skirting decoration.
⑤ The height of the frameless glass spring door should not be greater than 3m.
⑥ Curved glass curtain walls can be designed with smaller folded glass grids because of the high cost of curved glass and poor user experience (the specific horizontal width needs to be simulated to prevent sharp corners at the grids that would make the plane less smooth).
⑦ It is also recommended to make a small section of broken grid for the stone curtain wall with an arc shape, and the grid in the height direction should not be staggered up and down.
Use of panel materials for curtain walls should be in coordination with the building’s function, spatial characteristics, and safety level, so as to ensure structural soundness and operational safety through close collaboration with the architect.
① Laminated glass is suitable for glass curtain walls that potentially get hit and impacted, such as glass railings, glass floors, and glass within 1m above the indoor floor.
② When glass is selected as a supporting structure, laminated glass should be preferred. While the single-piece glass should not be used.
③ Laminated glass is prohibited in emergency exits, evacuation passages and other parts of the building. In those places, it is better to use single-piece glass with obvious marks.
④ In the glass of the point-supported curtain wall, there is generally a large local stress at the support. Ordinary glass has low strength and is difficult to bear. Therefore, high-strength tempered glass and its products should be used. Pay special attention to the edge treatment of the hole edge: fine grinding of the edge & hole, and chamfering of not less than 1mm.
⑤ In order to prevent accidents and terrorist attacks, explosion-proof glass should be used in sensitive parts of important buildings. Explosion-proof glass is a multi-layer high-strength tempered laminated glass. It will not be destroyed or scattered when an explosion occurs. That means, the glass will crack, but remain intact. Explosion-proof glass reduces secondary disasters.
⑥ The door and window glass used for explosion venting shall not be made of laminated glass. Use single-piece tempered glass instead.
⑦ The thickness of the stone slabs of the stone curtain wall should not be less than 25mm for the smooth surface. Meanwhile, the thickness of the burned surface should increase by 3mm, and the area should not be greater than 1.5㎡.
⑧ The minimum thickness of the single-layer aluminum plate of the outdoor curtain wall is 2.5mm.
⑨ Stone should not be used for the curtain wall ceiling. Instead, the lightweight and safe materials such as aluminum plates should be used.
The surface treatment of curtain wall materials should be based on the building facade effect and environmental durability requirements. Besides, the treatment method should be confirmed together with the architect.
① The surface treatment methods of curtain wall profiles are usually:
② Performance: Fluorocarbon spraying is much superior to powder spraying in terms of performance. It is wear-resistant, weather-resistant, UV-resistant, and not easy to fade. Fluorocarbon spraying is mostly used outdoors, and powder spraying is mostly used indoors.
③ If there is no special agreement, the stone should be protected on six sides.
④ Hot-dip galvanizing is usually used for the anti-corrosion of concealed steel keels of curtain walls. Other anti-corrosion measures such as fluorocarbon spraying or polyurethane spraying can be used for outdoor steel.
The connection between curtain wall and structural frame should be planned in coordination with structural systems and construction stages, choosing between pre-embedded and post-installed anchors appropriately.
Curtain wall support embedded parts can be pre-embedded and post-installed.
①Large commercial buildings often have complex structures. Pre-embedded embedded parts are labor-intensive, time-consuming and also with low accuracy. Commercial buildings are often still soliciting investments during the construction process, and merchants usually request modifications to the original building facades. There are many changes in the facades. And so the utilization rate of pre-embedded embedded parts is extremely low. Based on the above situation, it is recommended that commercial buildings use post-embedded embedded parts. For cantilevered canopies or large steel structures, due to the large force at the support, it is recommended to use pre-embedded embedded parts if conditions permit.
②For high-rise buildings, the grid is generally a standard module. And the probability of grid change is extremely small. Pre-embedded construction is convenient and accurate, so pre-embedded embedded parts can be used.
Curtain wall connections to the main structure should be determined in coordination with the building’s structural layout, load paths, and construction conditions to ensure both structural synergy and practical execution.
①The fully hidden frame glass panel is fixed to the curtain wall keel by structural glue. And the horizontal load is completely dependent on the structural glue constraint, so it should be used with caution.
②In the construction of inclined glass curtain walls, the fully hidden frame glass curtain wall is prohibited.
③ If there is a requirement for shielding at the structural position, the architect should consider using stone or aluminum curtain walls. When it is a glass curtain wall, colored glaze glass, frosted glass or transparent glass with aluminum lining can be used to shield the structure.
④ When the first-floor glass curtain wall has a horizontal hidden frame, it is advisable to set the skirting in the outdoor direction.
⑤ The roof parapet wall should be closed with stone or aluminum plates. Stone and aluminum plates should span the top surface of the parapet wall and be turned down for closing. It is not easy to design a seam facing the sky when the stone is closed.
⑥ When downpipes and fire extinguishing boxes are placed inside the curtain wall, sufficient space for placement should be considered.
⑦ When the corridor has a curtain wall ceiling, the architect should coordinate with the heating, electrical, gas, air conditioning and other professionals to determine the ceiling elevation. What’s more, he should ensure that other details such as the ceiling height and the location of the ceiling vents meet the requirements of each profession.
As the building external protective structure, the curtain wall shall not exceed the building red line in violation of regulations.
① The curtain wall construction drawing should be submitted for review with a “Structural Safety Certificate” issued by the design institute.
② Sometimes, the curtain wall drawing already confirmed by the owner and the design institute may be modified too much compared with the original building design. In that situation, the design institute shall adjust the relevant building, structure, and energy-saving drawings according to the modified curtain wall drawing. What’s , more, it should issue a change letter so that the curtain wall construction drawing can be submitted for review.
③ The strength grade of the main structure concrete at the curtain wall connection part should not be lower than C30.
④ The height of the civil structure beam should not be less than 0.8m. This makes it easier to design the curtain wall column into a double-span simply supported beam, reducing the project cost. At the same time, it is also conducive to the setting of fire blocking.
⑤ For curtain walls that exceed the roof, when the height is high, the structural engineer should be coordinated to design the structural support. Or reserve the civil structure as the foundation of the curtain wall steel structure.
⑥ Curtain wall decorative lines can be supported by small steel subframes integrated into the curtain wall system, without the need for additional concrete structures.
⑦ The structure at the anchor point of the cable curtain wall should consider the pre-tension of the cable.
⑧ The curtain wall should be fixed on the civil structure. And the structural design should not make the curtain wall edge line far away from the civil structure. Because when the curtain wall is far away from the civil structure and the conversion steel structure is used for support, the safety performance is reduced.
a. The durability of the steel structure is worse than that of the concrete structure.
b. Factors such as material quality and on-site construction quality.
c. The conversion steel structure support is subjected to large force, and the safety is reduced when post-embedded parts are used.
① Fire blocking should be set up above and below the structural beam. When automatic sprinkler fire extinguishing facilities are installed indoors, the height of the solid skirt wall shall not be less than 0.8m.
② Fire rescue windows should be opened on the curtain wall facade corresponding to the fire truck climbing operation site. The net height and net width of the window should not be less than 0.8m and 1.0m. While the lower edge should not be greater than 1.2m from the indoor ground, and the spacing should not be greater than 20m. Beside, each fire partition should not be less than 2. The window glass should be fragile and set with obvious signs that can be easily identified outdoors.
③ Fire climbing sites should not be set on the side of double-layer curtain wall facade.
④ A protective cantilever with a width of not less than 1m should be set above the outdoor entrance and exit.
① When designing new air vents on the facade of a building, consideration should be given to installing sufficient blinds for ventilation.
② When the opening area of the external window does not meet the requirements, mechanical ventilation devices should be installed inside the building.
③ The curtain wall shall not cover the gas pipeline.
④ In locations where heat dissipation is required, aluminum grilles should be used for curtain walls (areas with hot summers and warm winters).
The energy-saving parameters of the glass and thermal insulation cotton used in the curtain wall should meet the requirements of building energy conservation. And the overall thermal performance of each direction must also meet those requirements.
① Class I lightning protection buildings need to be protected from side lightning strikes above 30m.
And the Class II lightning protection buildings need to be protected from that above 45m.
Class III lightning protection buildings need to be protected from that above 60m.
② The method of preventing direct lightning strikes is usually to set up lightning rods and lightning strips on the roof. On the curtain wall, the location of the lightning strip is usually on the parapet. When there is a single-layer aluminum plate with a thickness of not less than 2.5mm on the parapet, the aluminum plate curtain wall can be used as a lightning arrester. Then, there is no need to set up a lightning strip at this time, just reliably connect the aluminum plate to the main lightning protection system. Then the non-conductive protective layer should be removed from the connection part to ensure smooth conduction.
① For stone curtain walls, you can consider setting spotlights on the top or bottom to highlight the texture of the stone and the momentum of the building. Or make groove lines in the stone and set hidden light strips on the facade.
② Aluminum curtain wall: Like stone curtain wall, the routing of light strips on aluminum curtain wall is also more convenient. While considering the facade shape, the building should consider hidden lights and their responding structure details. Different light types can be set according to different facade requirements.
③ Hidden frame glass curtain wall: It is generally not recommended to set light strips on hidden frame curtain walls. Because on the one hand, the exposed light strips affect the beauty of the curtain wall. On the other hand, the setting of light strips will have a greater impact on the water tightness of the hidden frame curtain wall.
④ Exposed frame glass curtain wall: The light strips should be reasonably connected to the main force-bearing structure of the curtain wall. The setting of light strips cannot destroy the overall effect of the curtain wall. Designing decorative lines with light troughs can effectively hide the light strips.
⑤ Outdoor lighting fixtures must not damage the water tightness of the curtain wall.
⑥ When installing lights indoors, the light strip can be directly fixed on the curtain wall beam at the bottom of the structural beam, without waterproofing requirements.
⑦ The lighting design unit should communicate and negotiate with the owner, architectural design unit, curtain wall design unit and other relevant units on lighting issues.
① For the scope of the advertising opening, the curtain wall should be made of aluminum plate or composite aluminum plate or other metal panel substrate. And waterproof measures should be taken, with the advertising cloth hanging points or light box fixing points reserved.
② Small logos or advertising fonts can be directly extended from the curtain wall keel and fixed with adapters after calculation. Large logos should reserve a logo support frame outside the curtain wall. The frame needs to be fixed with a separate support, and the waterproof structure should be properly designed at the junction with the curtain wall.
① As a non-curtain wall item, the production and installation of LED screens should be designed, produced, installed and maintained by professional manufacturers. And it must have its own independent structural support system.
② Usually the installation space of LED screens needs to be more than 700mm for daily maintenance (this space data is subject to the LED screen manufacturer).
③ Usually the LED screen is surrounded by a metal frame and closed by the curtain wall. When designing and constructing LED screens, the boundary range, installation space, and surrounding closing of the LED screens should be communicated and agreed with the owner, architectural design unit, curtain wall design unit, and other related units. Then the curtain wall contractor and the LED contractor should make handover and closing arrangements according to the contract.
① Large awnings are subject to greater forces at their supports. When designing elevations, try to avoid having no civil engineering structures at the awning supports.
② The drainage slope of glass awnings or skylights should be ≥3%.
③ Laminated glass should be used for awnings. Floating head point glass claws should be used for inverted point glass awnings.
④ When the ratio of the cantilever length to the thickness of the cantilever awning structure is >1/10 (to be calculated specifically), if the building does not allow the thickening of the awning or the reaction force of the support is too large, it is necessary to negotiate with the architect to add a tie rod.
⑤ When the depth of the awning is greater than 2m, it should be designed with an internal drainage. And the path of the downpipe should be reasonably arranged on the facade.
The design of personnel walkways should ensure safety and reliability. The walkway width should generally not be less than 0.65 meters, and the design load should not be less than 2 kN/m. And the load value should be increased based on actual conditions. Guardrails should be installed on both sides of the walkway.
① Cleaning equipment should be installed for curtain wall projects with a height of more than 40m.
② For a single-person Spiderman cleaning system, a safe and reliable Spiderman hanging point should be set at the roof parapet. Windproof locks or other hanging points for fixed cleaning slings should be set in sections in the height direction.
③ When setting up a window cleaning machine system, a special plan for the window cleaning machine should be designed by a professional company. Besides, the special design plan should be negotiated and agreed upon by the owner, architectural design unit, curtain wall design unit and other relevant units.
④ Whether it is a simple Spiderman cleaning device or a window cleaning machine system, the architect should consider reserving the building space required for the window cleaning machine to work when designing. While the structural engineer should consider the relevant structural structure and window cleaning machine load.
① The aluminum plate needs to be folded 25mm at the grid and fixed with a steel keel. Therefore, when the protruding span of the “匚” type aluminum plate line is greater than 300mm, it’s necessary to consider that the line thickness can meet the space required for the upper and lower aluminum plate folding and the installation of the aluminum plate keel.
② The closed curtain wall system has high watertightness. However, the waterproof performance between the curtain wall panels and the civil structure is relatively weak. Rainwater usually penetrates through capillary permeation and then through the civil engineering surface into the curtain wall system. Therefore, when designing a building, it is necessary to avoid the curtain wall closing with the civil structure on the water-facing side, especially the sky-facing side.
③ Behind other non-transparent curtain walls such as stone and aluminum plates, brick walls or other interior decorations are usually required to cover the keel on the back of the curtain wall.
In summary, curtain wall design is a highly comprehensive work that requires a balance in aesthetics, structure, safety, energy saving, operation and maintenance. Only by deeply considering the type selection, material application, structural processing and system coordination of the curtain wall in the early stage of design can the comprehensive performance and user experience of the building be effectively improved. Through the systematic mastery and reasonable application of the key points of curtain wall design, it can not only ensure the smooth implementation of the project, but also help to create a high-quality building facade that is both functional and artistic.
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