Performance and Tests
The curtain wall project designed for each building is unique. Every design; It is a combination of glass, metal, stone or different materials in different compositions.
However, no matter how many kinds of materials or different designs the building envelope consists of, all elements must act as a whole against environmental conditions, provide the desired comfort level in the interior and maintain this feature throughout the life of the building. In order for the building to maintain its performance in a good way during the use of the building, first of all, it is necessary to pass the necessary tests at the design stage of the building, and accordingly, the system and material to be used for the facade should be decided.
Firms producing curtain wall or applicators applying this system; They think that the building is waterproof and airtight, the elements that make up the façade are properly combined, the seals are placed properly, and the insulation is done correctly. However, the installer or architect often leaves it to the last to resolve the intersections between connections and do not need to check the performance of the intermediate components of adjacent systems. During the life of the building, possible damages occur in these areas and can create serious problems for the building. This can cause problems such as irreparable results and greater costs than rebuilding the building envelope in large-scale buildings. In order to prevent the formation of possible problems from the beginning, in order to evaluate how the building envelope will react depending on the current climatic conditions, the system must be subjected to various tests before manufacturing and application. These tests are very important in determining the use of the right material and how healthy the connections are.
When deciding on the system for the curtain wall system of a building, the solution that actually seems logical, especially for large-scale projects, is to perform curtain wall tests on a sample prepared in accordance with the design before bidding. However, every company avoids incurring such a cost without getting the job. Even if the manufacturer adds the test cost to the bid amount, the building owner avoids paying this cost. For this reason, usually, after the customer decides on a company and the system of that company, a sample is prepared from the constantly repetitive part of the facade in certain dimensions for the experiment, suitable for the project, and appropriate tests are carried out. However, there are two issues that are not considered important in the tests and can be a problem. First; What if the design fails these tests? in the second problem; how well the masters working in the field know this job, their mastery degrees and the knowledge level of the project consultant on the facade.
The effect of movements caused by the building or temperature changes should also be considered. Buildings expand, contract and move. The building does this to live loads; It responds to wind, earthquake, heat, freezing and other forces. Curtain wall elements; It should be designed to provide thermal insulation, sound insulation, waterproofing, tolerance for deflection and structural safety against various loads (thermal, wind and seismic). How healthy these decisions are should be decided according to the results of the tests to be made.
If it is not a large-scale project, a waterproofing test can be performed with an on-site setup, at least to test the workmanship during on-site application. This test can be done in two ways; The first way is to spray high pressure water on the surface, and the second way is to spray water by creating a pressure difference between the indoor and outdoor environment.
With the right decisions and application at the right time, both user comfort and building health are not endangered during the use of the building. For this reason, even if the right material decision is made for a building, critical issues that may cause problems in the future should be determined and how the building will behave in these issues should be determined by passing standard tests. These critical problems are; the maintenance of the building, its structural safety and possible (water, rain, air infiltration, condensation, water vapor, etc.) issues. Although these problems are identified under separate headings, all three are completely related to each other. The unsuccessful results of one may affect the other. As a result, it is necessary to control and ensure the continuity of all these factors before starting the use of the building.
Certain criteria are taken into account when making evaluations for the facade cladding sample of any building that has been subjected to the tests described above. According to the results obtained, either the facade system is changed or the detail improvement is made in the system. However, even if the sample is replaced or repaired, the same tests must be applied to the sample again. After the experiments are completed, the final action on the sample; The parts forming the test sample should be disassembled again and if any water is found in the system in this process, it should be noted and if there are any changes different from the design, it must be determined. Apart from this, each experiment should be evaluated on its own according to certain criteria. According to this;
Air permeability: Allowable air blowing rate (Qo), maximum test pressure (po) for the sample should not exceed 1.5m3 per hour (per hour) per m2 for fixed panels.
Medium pressures (pn), blow rates (Qn) Based on this, calculation can be made: Qn = Qo (pn / po )2/3
Water impermeability: During the test, no water should leak on the inner surface of the test, and when the test is completed, there should be no puddles in the areas where it is desired to remain dry.
Structural performance of frame members at design pressure: The deflection (bending) should not exceed 1/200 of the gap between the connections in the building, or it should be 20mm, or whichever is the lower of these two values. The deflection of the frame members supporting the insulated glass unit should not exceed 1/175 of the length measured along the glass edge, or be 15mm, or whichever is the lower of the two. Excess deformation should not exceed 1mm in the 1 hour period for repair.
Structural performance at 1.5 times the design pressure: There should be absolutely no permanent damage to panels, anchors or frame members. Frame elements must not be bent or twisted. Panels, glass and decorative spaces must remain hung and applied and the wicks must not come off. Permanent deformation of the frame members should not exceed 1/500 of the span between the points attached to the building in the 1 hour period for improvement and repair.
seismic motion; There must be no permanent deformation after and during the test, except for the sealing areas.
Temperature differences: In order to make the right profile and glass selection, outdoor and indoor temperatures must be taken into account. For instance:
Outside temperature: winter minimum -30°C / summer maximum +50 °C
Indoor temperature: winter maximum +40 °C / summer minimum +10 °C
Thermal Permeability Coefficient (U Value-EN 673): In order to make the right profile and glass selection, the U Value, which is also taken into account in building air conditioning and ventilation calculations, should be determined. The unit of U Value is W/m2K, Uf is used for frame, Ug is used for glass, Uw is used for frame+glass whole window (window).
Daylight (EN 410) Transmittance %, Reflectance % should be determined.
Solar Energy (EN 410) Total Permeability (Solar Heat Gain Coefficiet-SHGC), Shading Coefficient and Solar Factor-G Value (Solar Factor) values should be determined.
Condensation calculation is made by taking into account summer-winter, indoor-outdoor air temperatures and relative humidity. Condensation can be prevented by choosing the right profile and glass.
Tests Applicable on Curtain Walls
The standards to be followed in facade tests are CWCT (Centre for Window and Cladding Technology), ASTM (American Society for Testing and Materials), AAMA (American Architectural Manufacturers Association) and TS EN standards.
In general, water impermeability, air permeability, displacement tests due to wind and seismic movements are performed in curtain wall systems. For static testing; ASTM E-331 uses AAMA-501.1 standards for dynamic water testing. The tests should comply with CWCT (Centre for Window and Cladding Technology) standard test methods for curtain walls. In general, the tests that can be done for a high-rise building facade are listed below. This ranking may differ for each building. These are respectively;
Water impermeability (static),
Wind resistance (endurance)
Water impermeability (static),
displacement of the design, seismic movement,
Water impermeability (static),
Water impermeability (dynamic),
Water impermeability (hose),
Wind resistance (safety),
seismic action (1.5 times the design pressure),
Disassembly and reassembly.
The tests to be applied may vary according to the conditions of the region where the building is located. Below are the tests that should be applied on the prepared sample for a building in general. However, apart from these tests, some aging and thermal motion tests can be applied to understand the performance of the materials at the end of a certain process. Aging test; In the stability cabinet, the prepared sample is aged under the influence of certain temperature and humidity during the specified periods. In the ultraviolet cabinet, the ultraviolet effect of the sun’s rays is simulated, and the material is aged under a certain temperature and time. At the end of the aging tests, a tensile test is applied to test the strength of the material. The material tested here is silicone, which is of paramount importance for safety in structural silicone curtain wall systems. The silicone, which is stuck to two different surfaces, becomes unusable by either leaving the surfaces or breaking off within itself. This test is done by gradually increasing the force in the tensile testing cabinet. The thermal motion test is; Six times heat exchange is applied from -20°C to +80°C on the outer surface of the panel, while the temperature and humidity are kept constant on the inner surface.
In order to make any curtain wall ready for testing, a one-to-one sample is prepared, including one or more modules that are constantly repeated in the building. This sample, which is prepared exactly according to the building facade, is mounted on one side of the test room. Other parts of the test chamber, other than the area where the sample will be hanged, may be made of steel or plywood. In addition, the test chamber must have a door for entry and must be completely insulated from external conditions. The figure shows a typical test rig system.
The static pressure test chamber must be positioned to measure the pressure and have readings that are not affected by the velocity of the air outside or inside the chamber. The air supply system should consist of centrifugal fan, control valves with common hose and different negative and positive pressure. It must be able to blow air continuously at a fixed pressure during the test period and must have a pressure capability of approximately 600 pascals in 1 second.
The wind generator should contain an aircraft engine type piston with a 4000mm diameter, counter-rotating propeller, capable of creating different positive pressures during the dynamic test. The generator should be installed close to the outer surface of the example. The water spray system is a uniformly spaced grid system no larger than 700mm. The system should be mounted approximately 400mm from the outside of the sample. The nipple or nozzles should be able to act on a square area not less than the 80º spreading area. The water temperature should be between +8 and +25ºC. The spray system must properly transport water to the outer surface of the sample.
Water for hose testing is done using brass-head teats that continuously produce water granules with a nominal 30º spread. There must be a pressure gauge and valve control between this hose or nipple and the valve. The system should be adjusted so that it can produce 22±2 liters per minute when the pressure is 220±20kPa from these nozzles.
Air Permeability (CWCT)
Infiltration or leakage of air is the passage of air from outside into the building through the curtain wall. Air is filtered through faulty connections or wicks between horizontal and vertical profiles. Air leakage is the main cause of energy loss in buildings. In the regulation applied for buildings in the UK after 2002, certain limits of air tightness are mandatory in large-scale buildings. In 2006, certain limits of air tightness will be mandatory in all buildings, large or small. According to the energy calculations made in the whole of the finished building, the air infiltration must be less than 10 m3/hour/m2.
A high rate of air infiltration in a building will increase the heat loss in the building and impair the material and moral comfort of the building owners. The pressure inside and outside the building is at different levels. This test is applied to determine whether there is frontal air passage or at what levels. Air pressure of 600 Pa in air-conditioned places and 300 Pa in non-air-conditioned places are taken as limit test values. The amount of pressure applied in the tests according to CWCT is Table 1 ;
Water permeability test pressure
Air permeability test pressure
Su geçirgenlik test basıncı
Hava geçirgenlik test basıncı
< 800 Pa
300 / 600 Pa
801 – 1200 Pa
300 / 600 Pa
1201 – 1600 Pa
300 / 600 Pa
1601 – 2000 Pa
300 / 600 Pa
2001 – 2400 Pa
300 / 600 Pa
> 2400 Pa
0,25 x Rüzgar basıncı
Table 1. Pressure levels according to CWCT
In the air permeability test; Three different positive pressures of 660 pascals are applied to prepare the test sample prepared according to the building for the test. Then, airflow measurements are taken at different positive pressures; In pascals of 50, 100, 150, 200, 300, 450, 600, 450, 300, 200, 150, 100 and 50. With each pressure increase, the sample must be held for at least 10 seconds. The air permeability test first looks at its behavior with the insulated sample to determine the airtightness of the test chamber. Then it is checked with the non-insulated sample and the difference between the readings indicates whether there is air passage in the sample. Accordingly, it is decided with limit values.
Water passage refers to the passage of water from outside to inside in the curtain wall system. A small amount of water that can be controlled indoors is acceptable. However, the main principle is to obtain perfect sealing in all curtain walls. In order to determine the ability of the building to withstand water penetration, a test is performed on the sample. Especially in large-scale curtain wall projects, such an application must be made. According to the test sequence above, after the wind and displacement tests, a static test should be applied again. The reason for this is to see if the waterproofing performance is affected by structural movements.
Scientific tests cannot be used to measure the water impermeability of a real building. These values can be used as a reference to identify the weak points of the proposed system. Because the scale of the system built for the example and the scale of the actual building are very different. Here mastery of the actual scale of the building is crucial. In addition, the test time and test pressure are also different according to the climatic regions. For example, is the static test period of 15 minutes sufficient as a representative in all areas in different climatic conditions in the world? Is 20% positive wind load sufficient in storm conditions, temperature changes, earthquake, wind in the world? With these questions, ASTM E-331 is quite appropriate in the water test protocol. Accordingly, according to the wind load given in the standards of the country where the façade is located;
In temperate climatic regions;
Test pressure: 20% of the maximum design positive wind load, Test duration: 30 minutes. In stormy areas (hurricane);
Test pressure: 80% of the maximum design positive wind load, Test duration: 60 minutes.
If a possible water leak occurs during the tests, repairs cannot be allowed at all. According to the test result obtained, either the system or the system detail should be changed and a new sample should be prepared according to the solution and a new test should be performed.
A successful test in accordance with the standards can be defined as the determination of imperfect leaking areas and repeating the test until water leakage occurs during the test, or the determination of damaged or deteriorated leakproof areas at the end of the test period. If there is no water leakage in the sample during the test period, the test is successful. If water leakage is observed during the test period, the water test should be stopped. Water impermeability test; It is applied in three different ways as static, dynamic and hose. According to this;
Watertightness (static) (CWCT): For testing, the water grid is placed in front of the facade specimen and sprayed with positive air pressure. This refers to a heavy rain with wind on the façade surface. Research tests are also tried on the installed façade, rain hose can also be used at special times.
Three different positive pressures of 660 pascals are applied to prepare the test sample for testing. At zero pressure, at least 3.4 liters/m2/minute of water is sprayed onto the sample for 15 minutes. As the water spray continues, the pressure is increased as indicated; It is applied for 5 minutes at 50, 100, 150, 200, 300, 450 pascals, and for 15 minutes at 600 pascals. During the test, it is constantly checked whether the water passes through the inner surface of the sample. If water leakage is observed , the test is stopped .
Water impermeability (dynamic) (CWCT): Water is sprayed onto the sample at a rate of at least 2liter/m2-minute. The wind generator is used to create a positive pressure of 600 pascals across the sample for 15 minutes and is mounted close to the outside of the sample.
The pressure is determined by increasing the wind speed until the amount of deflection in the periphery and its elements, which can be measured in the central axis of the air jet, reaches the amount of deflection recorded at a static pressure of 600 pascals. Absorption (suction) can be applied on the inside of the sample to achieve the required test deflections. However, suction should be limited to 25% of the maximum static pressure. The tightness is checked on the inner surface of the sample throughout the test. If water infiltration is observed, the test is stopped.
Water impermeability (hose) (CWCT): If the test sample is considered as a wall section, this wall section is wetted by moving upwards from the horizontal connection at the lowest elevation. Then intersecting vertical connections, then the next horizontal connection, and so on upwards. Water is supplied directly to the environment and connections on the outer surface of the sample. The water spray is moved slowly back and forth over the port. At a distance of 300mm, the connection is continued by keeping the connection in 5 minutes at every 1500mm. Long or short connections are tested proportionally. During the test , it should be checked whether there is any water leakage on the inner surface of the sample .
It is generally known that the wind exerts direct pressure on the façade. On the contrary, while the wind creates pressure in the areas where it acts perpendicular to the façade, it creates a vacuum, that is, suction pressure, in these parts of the façade by changing the direction of the wind towards the top and the sides. The wind coming on a building creates a positive pressure effect in the middle of the facade on the blowing side and a negative pressure (suction) effect at the corners. The wind, which slows down on the front, accelerates as it passes through the sides and the roof, creating a strong pressure effect in these areas. The wind swirling at the back of the building creates less strong pressure compared to the side sections. Tall buildings are constantly under the influence of wind. Sudden and very fast breezes occur due to air compression and turbulence, especially in places where tall buildings are located close to each other. In high-rise buildings, the durability of the curtain wall should be designed considering this strong wind effect.
The wind test is a test applied to evaluate the structural strength of the curtain wall. Both positive and negative pressure winds are created alternately in the test. The bending limits should be determined according to the construction conditions, vertical and horizontal loads. These bending limits should not be affected by the resistance capacities of the profiles. The healthiest one should be designed according to the bending limit of the glass. Because the glass will break under excessive deflection. Deflection limits are also important to control movements inside the curtain wall. The building construction may be very close to the profiles and excessive deflection may cause damage to the carriers and the building by the profiles hitting the building. The deflection limits are specified as the distance between the anchor points divided by the fixed number. The L/175 deflection limit is common in curtain wall conditions. Allowable deflection should be 246mm in a 4320mm floor height structure. This means that the façade allows a maximum deflection of up to 246mm inside or outside at maximum wind pressure. The deflection in the profiles is controlled by the curtain wall elements in different ways. The curtain wall system is usually controlled by the moment of inertia required to maintain the deflection limits under building conditions. Another way for limited deflections in a given cross-section is to insert steel reinforcement into the profiles. Because the modulus of elasticity of steel is three times that of aluminum. Thus, the steel system will be able to absorb some of the deflection at a lower cost.
Wind resistance (Service capability) (CWCT): To prepare the test sample for testing, three different positive pressures of 500 pascal are applied by resetting the displacement transducers. The sample is then subjected to five positive pressures at different strokes (0 to 500 pascal, 500 pascal to 0). But pressure should be applied as fast as possible, between 1 second and 3 seconds.
To prepare the test sample for testing, three different positive pressures of -500 pascal are applied without resetting the displacement transducers. The sample is then subjected to five negative pressures at different strokes (0 to 500pascal, 500pascal to 0). Pressure should also be applied as quickly as possible, maintained for a maximum of 3 seconds and not less than 1 second.
Wind resistance (safety) (CWCT): The sample is subjected to the pressures specified below. Each application should be as fast as possible and should last no less than 1 second, but no more than 3 seconds.
To prepare the test sample for testing, 3 positive pressures at 500 pascals are applied, followed by 2340 pascals of pressure once (1.5 times the design pressure).
Then, to prepare the test sample for testing, 3 negative pressures at -500 pascals are applied, followed by -2340
Pascal pressure is followed by application (1.5 times the design pressure). As a result of the tests, the displacements determined at the maximum pressure are taken.
Seismic loads must be determined beforehand for the design of the anchors and the curtain wall system. Generally, the façade can naturally withstand seismic and wind loads as the required space is provided between the profile and the glass. In tests, standard curtain wall systems can withstand 75mm of floor movement without leaking water and breaking glass. However, for large floor-to-floor openings, the anchor design must be reviewed as the anchors will take a large load.
Apart from seismic activity, accidental explosions and terrorist attacks are also increasing. It is expected that the curtain wall will make the first defense as the shell of the building against this blast load. These loads are quite large and of short duration. In order to determine the response of the curtain wall to such a large impact, it is necessary to make a dynamic load analysis by making a sample of a certain size of the facade. Laminated glass should generally be used in this type of buildings.
The curtain wall system consists of various cladding panels, frames supporting the panel and a carrier connecting the frame. Thermal load and wind load directly affect the façade. These direct effects can be easily avoided with adequate safety measures. For example, where the curtain wall system is located
According to the climate data of the region, it can be designed with sufficient safety for the wind load that may be caused by the maximum wind speed in the last 50 years. However, the same cannot be done for a seismic movement. Because the time, size and number of seismic movements cannot be predicted.
Seismic events damage the building environment, which undergoes various displacements in relation to the horizontal and vertical components of seismic motion. It is impossible for the curtain wall system to oppose the internal moment of inertia due to horizontal and vertical movements, as the building’s frame and floor slabs are quite large compared to the curtain wall mass. For this reason, the curtain wall system should be designed not only according to the seismic zone estimation, but also according to the strength of the building and the displacements caused by the seismic effects in the building carrier.
Seismic movement at displacement of the design (AAMA 501.4-00): The intermediate steel support beam is moved ±xxmm from the origin and returns to the origin. This movement transformation is repeated a total of 3 times. During this time, the movement is recorded. Movement is measured at the support beam, not in the example. Seismic movement at 1.5 times the displacement of the design (AAMA 501.4-00): Likewise, at the intermediate level, the steel support beam is moved ±xxmm from the origin and returns to the origin. This movement transformation is repeated a total of 3 times. During this time, the movement is recorded. Movement is measured at the support beam, not in the example.