Ingjutna ventilationskanalers påverkan på luftljudsisolering i flerbostadshus

Sammanfattning: Good sound insulation is highly valued by Swedish tenants. To be able to achieve that, one must look at many aspects, such as room volumes, floor planes, flooring, but also what materials that are to be built with and how it ́s constructed.  The use of cast-in ventilation ducts in the load-bearing structures is a common method in Sweden. This is a method that is well suited when large residential houses in concrete are to be built and you want a flexible way to lead the ventilation ducts in the building without them taking up unnecessary space or having to be led longer distances than necessary.  At present, WSP acoustics in Umeå uses two different methods with reasonable assumptions to calculate the impact of cast-in ventilation ducts on airborne sound insulation, but they wish to verify which of the methods is most reliable. In one method, the wall with the ducts is thought of as a hollow core slab with the same corresponding weight as the actual wall. In the second method, the weight lost at the channels has been calculated and then the wall depth is reduced accordingly. The purpose is to evaluate whether these approximate calculation methods regarding the impact of embedded ducts on airborne sound insulation are consistent with the results of field measurements.  Field measurements show that the airborne sound insulation becomes gradually worse with an increased number of ducts, and this is most clearly seen in the range between 400 and 3150 Hz. The methods do not differ by more than 1 dB in weighted standardized sound level difference compared to the field measurements and can therefore both be used in designs. The comparison between the calculation methods shows that both give equivalent results, but the method with reduced wall depth is recommended.