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Airtightness estimation of wood based residential houses using Blower-door test
Srba, Jaromír ; Böhm, Martin (advisor) ; Trgala, Kamil (referee)
This dissertation analyses airtightness of residential buildings which in many ways influences their energy performance and therefore also their costs of use. Properly conducted airtightening layer can significantly extend the lifespan of the construction. The main objective of the dissertation is to evaluate the construction of newly built buildings in the Czech Republic and to assess the most important parameters which affect airtightness.
The Blower-door test was used to assess air leakage. This method belongs among the most widely used and conclusive methods of analysis. Its advantage is mainly the fact that it can detect construction defects of the airtightening layer in important stages of construction (and possibly enable these defects to be corrected before completion). The core of this method is to create a pressure difference of deltap 50 Pa between the exterior and the interior of the building and at the same time discover the faulty places which are different for positive and negative pressure.
The air leakage was assessed in 345 residential buildings constructed between 2006 and 2016, especially in conventional wood frame buildings or with buildings made from wood panels such as cross-laminated timber. The development of values of air change rate through the building envelope was evaluated according to the Czech standard ČSN 73 0540-2 and the results were compared to previous outcomes of other authors. Analysis and photo documentation of the most frequently detected leakage points are also part of the dissertation. A significant decrease in values of the air change rate was discovered, on average by 40.49% in 2016 compared to 2006, while for passive houses the air change rate values were almost steady. For buildings with wood frame construction, it was the way of ventilation which was determined as the most significant parameter affecting air leakage. For wooden buildings with natural or combined ventilation, the average value of air change rate at the pressure difference of 50 Pa was 1,29 h-1, for buildings with mechanical ventilation and heat recovery it was 1,18 h-1 and for buildings with very low energy consumption for heating with mechanical ventilation and heat recovery it was 0,44 h-1. Other parameters affecting the values of air leakage include the construction company, the presence of a chimney, the place and method of construction of the wood frame construction.
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