Flow paths in a Swedish single family house - a case study.

The ventilation of a Swedish single family house is investigated by means of tracer gas and pressurization techniques. The ventilation flow plays an important role in this house as it enters through a dynamic loft insulation and exits via the crawl space. This design is said to give preheated and clean supply air, warm floors and good energy efficiency. But to meet these promises, it is essential that the air really flows in the intended paths. A single tracer gas technique is used to determine the air flow rates. The measurements show that actually too much of the supply air by-passes the dynamic insulation by direct infiltration. The measurements also detect an unintended flow from the crawl space to the living area. If there exists radon in the ground soil such a flow must be avoided. Pressurization tests are used to build a pressure drop-flow model. This model describes intended flows, i.e. supply air through dynamic insulation, extract air to crawl space and exhaust air from crawl space to the outside, as well as the unintendedjlows, i.e. infiltration to living area and the two leakages from outside to crawl space and from crawl space to living area. The model is used to explain the present flows and then to tell how to change them. This is done by simulating the model when one of the parameters (e.g. a size of a leakage) is changing. One conclusion is that the crawl space must be made considerably more airtight.