Laborationsmätning av vindtäthetens betydelse för en väggs U-värde
WindpoofnessThermal insulationHot boxHeat flowDarcy´s lawPoiseuille?s equation and AirflowVindtäthetIsoleringsmaterialHot boxVärmeflödeDarcy´s lagPoiseuille ekvation och Luftgenomströmning
To fulfill the climate target that EU and the Swedish government have decided to apply, it becomes increasingly important that the energy efficiency of existing buildings and making new buildings energy efficient as possible. Of Sweden?s total energy consumption in 2011 was 40% used by residential and service. Of the 40% of the energy consumption was 60% used for heating and domestic hot water. A report from year 2012 shows that one reason why the heating volume is so great could be due to underestimating on the energy consumption for the heating in the planning of the building. This may be due to culvert losses, higher ambient temperature than the theoretical calculations and airing. Another reason that the underestimation could be due, and that will be addressed in this report is windproofness and how it can change the U-value of an exterior wall construction when airflow occurs in the thermal insulation layer.The concept of windproofness is in the current situation a word in the building sector which is rarely used. Instead, the word airproofness with the assumption that it is the same but the differences are many and the biggest difference is that the airproofness describes how air change environment which means that the outdoor air goes through the building envelope. Windproofness instead describes how the outdoor air enters the structure and then gets out of the structure in a different location, meaning that the air never changes environment.The purpose of this report is to examine how much impact airflow in an insulating layer has to the U-value of an exterior wall construction. The two of the most common insulation materials are mineral wool and XPS were tested to find out which of these is most changed in U-value by the airflow. The airflow through the test model was created by a pressure difference over the test model. The report is based on the data gathered during the testing of materials, using thermocouples and heat flow meter.The results of the empirical study showed that the U-value changed by a few tenths percent of the mineral wool and the results of XPS was almost negligible at the velocities that occurred at the various pressure differences created in this study.