English

Rising moisture from the ground has caused quite a lot of damage on foundations of Swedish buildings, in particular for the type concrete slab on the ground. Some of these constructions may be repaired by mechanical ventilation, for example below the floor or below the concrete slab , if there is an air-permeable layer below the slab. Summarized results from a few field studies and tests, which have been going on for a period of 2-3 years, are reported. Different methods with mechanical ventilation systems have been found to work quite well so far, i.e.

Measurements in some dwellings show differences of the absolute humidity as a function of the kind of ventilation (only natural or mechanical exhaust air or balanced ventilation) and the position of the single rooms, especially of the bedrooms. Therefore is investigated into the expected moisture transport in two different ground plans. The main humidity production is in the kitchen and bathroom. If kitchen and bathroom are on the outer side, the dwelling is loaded with this moisture through the main wind direction.

When carrying out pressure tests of models of multi-story buildings in The Boundary Layer Wind Tunnel, the external mean and RMS pressures are measured at 400 to 800 different locations over the building surface. The tests are originally carried out in order to determine the net wind loads for the design of cladding and glazing, but the results can also be used to estimate the internal pressures, and then calculate the air infiltration. Two mathematical models are used to estimate the wind-induced air infiltration in three multi-story buildings.

Laboratory measurements have shown that when pressure differences are applied across wall and roof elements, the majority of the pressure drop takes place across the vapour barrier . Similarly , field measurements have shown that the majority of the leakage in Norwegian buildings occurs at the joints in the vapour barrier , at wall / floor joints , around penetrations of the vapour barrier and through holes in the vapour barrier . Prior to 1980, the standard vapour barrier in Norway was 0.06 mm thick polyethylene sheeting.

The accuracy of tracer gas measurements of building air infiltration rates has been a widely discussed topic. One question that has often come up at past AIVC conferences is the ability of passive methods, such as the Perfluorocarbon Tracer (PFT) method, to accurately measure fluctuation air flow rates. A series of field studies is being conducted to compare the air infiltration measurements of the constant concentration tracer gas (CCTG) and PFT methods and provide recommendations for their proper implementation in the field.

Brookhaven National Laboratory (BNL) in the USA has developed a multiple tracergas technique called BNL/AIMS (Air Infiltration Measurement System) for determination of air infiltration rates. The technique is applicable in occupied dwellings and might be promising for wide-scale measurements. This paper discusses the main results of field measurements made by the Danish Building Research Institute with use of BNL/AIMS. The results obtained are compared with the results of parallel measurements made in the laboratory and by using computer controlled field measuring equipment.

All the findings about indoor air quality is of little use to the average citizen, if they are not applied and and translated into rules incorporated in our building codes for the design, construction, and last but certainly not least maintenance of our buildings. And scientifically based up-to-date coders are not much use if they are not backed by strict , honest, and competent building inspectors. Recommendations are made for improvements in building codes to ensure good indoor air quality by concentrating, but not exclusively, on ventilation.