Analysis of air tightness, water tightness and wind pressure resistance test standards for external doors and windows in Europe.

1. The research background

Products entering the EU market need to have the CE mark, and some products that fall within the scope of mandatory supervision need the approval of the EU Notified Body. Although the UK has entered a state of leaving the European Union, the access requirements for most products are not independent of each other. Only the market access method changes. Building exterior door and window products are such products that need to be recognized. According to the standard requirements of "EN1435L1 Door and Window Product Standard Performance Characteristics-1 Building Exterior Windows and Exterior Doors", exterior doors and windows products belong to the level 3 requirements of compulsory supervision. Manufacturers can only use the corresponding products after passing the test by the EU Notified Body. Use the corresponding CE label. The EN14351-1 standard stipulates a series of performance requirements for external doors and windows of buildings, including but not limited to wind resistance, snow load resistance, fire response, fire performance, water tightness, impact resistance, safety device bearing capacity, acoustic performance, Thermal performance, radiation, air tightness, opening force, mechanical strength, ventilator, repeated opening and closing performance, etc. Among them, airtightness, water tightness, and wind pressure resistance are the basic performance requirements of exterior doors and windows. This article will analyze and interpret the corresponding standards from the perspective of the three performance (hereinafter referred to as the three) tests.

The composition of the three sex test standards in Europe is different from that in the United States, Australia, and China. The American standard is a test method standard for each test and a general product standard including test classification. The Australian Standard is a general test method standard, and a general product standard includes test classification. China GB/T7106-2008 "Classification and Testing of Air tightness, Water tightness, Wind Pressure Resistance Performance of External Doors and Windows of Buildings" is a general test method standard and multiple product standards. The old version of the grading index was in the test method standard, but the new version of GB/T7106-2019 "Testing Methods for Air Tightness, Water Tightness, and Wind Pressure Resistance Performance of Exterior Doors and Windows of Buildings" cancels the classification and is classified by each product standard. Relatively speaking, among the old grading indicators, the overall requirements of the national standard are relatively low, and there is a certain gap with foreign standards. With the gradual improvement of domestic product quality, it should be gradually in line with foreign standards. The European standard adopts that each test corresponds to a test method standard, a classification and judgment standard, and then is summarized by a general product standard. The function of each standard is clear, but the number of standards to be checked in actual operation is indeed quite large. Table 1 shows the corresponding standards of the three-character test of the European standard.

^{Table 1 Corresponding standards of the European three-character test}

2. The test requirements

In the European standard, since the three tests are expressed in different standards, there is no specified test sequence, but the wind pressure test includes repeated air tightness, and the moisture of the sample after the water tightness test will affect the air tightness result, so the usual test The order is airtightness, water tightness, wind pressure resistance (including repeated airtightness test). Generally, the three tests are completed on one set of test equipment, and samples with different installation angles, such as the water tightness test of skylights, may require 2 sets of samples. 

The basic composition of the door and window test equipment is as follows:

① fan; 

② pressure control system; 

③ flow meter; 

④ water flow meter; 

⑤ differential pressure meter; 

⑥ test box; 

⑦ displacement test components; 

According to the installation direction of the sample, the equipment has two forms of internal spraying and external spraying. The European standard mainly conducts experimental design in the way of internal spraying, but external spraying can also be used for testing.

2.1 Air tightness test

The European standard air tightness test first needs to determine the gas leakage of the box (test system). If the leakage of the cabinet is less than 5% of the limit value of the class to which the test sample belongs, the leakage of the cabinet can be ignored. However, it is difficult to estimate the sample leakage before the test, so the conventional test method is generally used, that is, the additional leakage of the box is tested once, and the total leakage (including the leakage of the box and the sample) is tested once. The leakage of the box should be controlled within 30% of the total leakage. The airtightness test procedure is as follows.

(1) When the leakage of the box is ignored, as shown in Figure 1. First, turn on and off the sample, check the function of the sample, apply positive pressure for 3 pulses of 660Pa, and then conduct a formal positive pressure test, the pressure sequence is 50, 10, 150, 200, 250, 300, 450, 600Pa. The negative pressure test sequence is the same as the positive pressure.

^{Figure 1 The air tightness test process without considering box leakage}

(2) When considering the leakage of the box, the test process is shown in Figure 2. First test the additional leakage of the box, open and close the sample, check the function of the sample, add positive pressure to the test box for 3 pulses of 660 Pa, and then perform a formal positive pressure test, the pressure sequence is 50, 100, 150, 200, 250, 300, 450, 600 Pa. And the negative pressure test sequence is the same as positive pressure.

^{Figure 2 The air tightness test process considering box leakage}

Regarding the additional leakage test, the EN1026 standard is marked as test negative pressure. This is considered based on the internal spray test device because the purpose of the additional leakage test is to test the leakage of the tank. The sealed sample is on the outside. If it is sprayed inside, the outside of the sample faces the box. At this time, the negative pressure is sucked into the box, so the additional leak test adopts negative pressure.

If it is sprayed outside, the outside of the sample faces the outside of the box, and the positive pressure is sucked into the box at this time, so the positive pressure is the correct test method for the additional leak test.

The evaluation of the European standard air tightness test is divided into two indicators: unit seam length and unit area, as shown in Table 2 and Table 3. When using the EN12207 standard, it should be noted that this standard evaluates both exterior windows and interior windows, so it is necessary to distinguish them. The former needs to evaluate the airtight performance at the highest pressure of 600 Pa, while the latter only needs to evaluate the highest pressure of 150 Pa.

Table 2 Air leakage rate per unit area

Table 3 Air leakage rate per unit slit length

The air tightness test of the outer window is divided into 4 levels, from level 1 to level 4. Among them, level 4 is the most stringent, and level 1 is the minimum requirement. Satisfying a certain level not only means that the air permeability meets the requirements at 100 Pa but also ensures that each test pressure that does not exceed the maximum test pressure meets the requirements of the level according to the standard calculation formula. For example, grade 4, needs to meet the requirements at 50, 100, 150, 200, 250, 300, 450, and 600Pa. The calculation formula of flow requirements for other grades is shown in formula (1).

Q=Q₁₀₀（p/ 100*Pa）^2/3 （1）

In the formula:

Q is the air permeability (limit value) under the test pressure, m³/h

Q₁₀₀ is the air leakage rate under the standard pressure of 100Pa, m³/h;

p is the test pressure, Pa.

A test grade will be obtained for the unit area and unit seam length, but the air tightness grade has only one value, so it still needs to be judged. When the two grades are the same, the air tightness grades are also the same. When two grades are adjacent (such as a grade 2 and a grade 3), the air tightness grade shall be the better grade (grade 3). When the two grades differ by one grade (such as one grade 1 and one grade 3), the air tightness grade takes the median value (grade 2). When the two grades differ by more than one grade (only in the case of one grade 1 and one grade 4), no rating is given.

Compared with the evaluation methods of other standards, the European standard air tightness rating is slightly more complicated. For non-combined exterior windows, the first two cases are more common. When the grades are adjacent, the best grade is to encourage the outer windows to reduce the opening gap as much as possible. However, it should be noted that the latter two situations generally occur in combined external windows, one part of which is a fixed fan and the other part is an open fan, resulting in a larger sample area and a smaller slit length. Although the sealing of the opening part is poor, because the overall area is large, the leakage rate per unit area can still achieve good results. To avoid such products with an inferior performance from entering engineering applications, it is required that the leakage rate per unit area and unit seam length differ greatly and not be rated.

^{Figure 3 The air tightness test detection equipment 1}

^{Figure 4 The air tightness test detection equipment 2}

For products with a single fixed fan, the European standard does not allow testing, and gives a grade 3 certification, so fixed fan products can choose to test air tightness or directly obtain a grade 3 (indoor windows are divided into grades A and B) level, C level, D level). Compared with the European standard, the American standard does not rate the combined external windows as a whole but adopts the method of grading each type of external window separately. This is more beneficial for the user to grasp the actual performance of the product. The national standard GB/T7106-2019 no longer grades the airtight performance. The old version formulated looser standards due to consideration of the technological level of domestic doors and windows. However, the technological level of doors and windows on the market can completely adopt higher standards and meet the requirements of European and American standards.

2.2 Water tightness test

The European standard water tightness test method adopts the test method of continuous spraying and gradual pressurization. The spraying of the test adopts a row of spraying pipes on the top of the sample, and the spraying amount and spraying angle are fixed. The spray angle setting will change for products with an upper edge.

The specific requirements are as follows. The spray angle of the sprinkler head can cover 120°, the water spray volume of the first row is 2L/min, the water spray volume of the increased sprinkler head is IL/min, the height of the sprinkler head should not exceed 150mm above the opening seam on the top of the sample, and the distance The sample surface distance is 250mm. The distance between sprinkler heads should be 400mm. When the sample height exceeds 25m, a row of sprinkler heads should be added. From 4 hours before the test to during the test, the sample should be in an environment with a temperature of 10-30°C and humidity of 25%-75%.

The sequence of testing is a step by step pressurization. Firstly, no pressure is applied for 15 mm, and then the pressure is tested every 50 Pa for 5 min until leakage occurs. The European standard water tightness test starts from level 0. Level 0 is no water tightness requirement, level 1 is no leakage after spraying without pressurization for 15 minutes, and level 2~9 corresponds to the pressures of 50, 100, 150, 200, 250, 300, 450, and 600 Pa in Figure 3 respectively. When the water tightness of the sample is better than grade 9, you can continue to pressurize, increasing the pressure level every 150 Pa, and the pressure that passes through is directly marked as Ex xx. The water tightness test combing is shown in Figure 3.

^{Figure 5 The water tightness test processing}

2.3 Wind pressure test

The European standard wind pressure test includes 4 test stages, namely, wind pressure deformation resistance, repeated pressurization, repeated air tightness after wind pressure, and ultimate wind pressure test. The details are shown in Table 4.

Table 4 Wind pressure rating/Pa

2.3.1 Wind pressure deformation test

The pressure against wind pressure deformation is Pi pressure. During the test, the pressure needs to be raised slowly (100 Pa/s) to the specified pressure and kept for the 30s, and the deformation of the stressed member is recorded. Then release the pressure to 0Pa, keep it for the 60s, and record the residual deformation of the stressed rod. Calculate the deflection separately.

2.3.2 Repeated pressurization test against wind pressure

The pressure of repeated pressurization test against wind pressure is P2 pressure, p2=0.5pi, repeated pressurization is under soil P2 pressure, reciprocating cycle, a completely positive and negative pressure cycle is a cycle, test 50 cycles, and observe whether the sample has damage. Each cycle is at P2, and the pressure of P2 should be maintained for 7±3s, and the process from P2 to knock2 should also be maintained for 7±3s (that is, the period of each pressure change)

2.3.3 Repeated air tightness test

The process method for this test is the same as the air tightness test. Since the additional air tightness test has been carried out, this item can no longer be performed here (this item needs to be re-tested when the condition of the test box changes)
repeat air tightness

Since it is carried out after wind pressure deformation and repeated air tightness tests, the result may be worse than the first air tightness. It is required here that the repeated airtightness result cannot exceed the required value of the level of the first airtightness result multiplied by 120%, otherwise the judgment will not pass.

2.3.4 Ultimate wind pressure test

The ultimate wind pressure test pressure is p pressure: Ultimate pressure P3=1.5*P1.

After the test is completed, check whether the sample is intact, whether it can be switched normally, and record whether there is any damage, shedding, etc.

3. The conclusion

Among the performance requirements of the three-character test of the European standard, the minimum requirements for airtightness and water tightness are lower than those of the Australian standard and the American standard, but the actual project requirements are all specified by the owner. Under the relatively high requirements of building energy efficiency regulations in Europe, most of the performance requirements of actual projects require higher levels, even exceeding the highest level requirements. At the same time, there are certain requirements for the heat transfer coefficient and acoustic performance of the product. Skylight products will also put forward requirements on hardware performance. The European standard EN14351-1, as the main standard for the performance requirements of building exterior doors and windows, stipulates in detail the performance requirements that door and window products must meet. The three properties of exterior doors and windows are the basic performance requirements of doors and windows. This article describes these testing methods and basic requirements in detail, which can be used as a reference for technicians who implement testing, suppliers of doors and windows, and managers of engineering projects in Europe.

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