air tightness

Museum showcases represent a peculiar confined space were ventilation and indoor climate conditions play an important role. Conservation of the works of arts, in fact, requires a control of the environmental parameters, with a tolerance usually far tighter than that required for assuring the comfort of people.

The average air tightness of the ventilation ductwork in France is rather poor, corresponding toa 3A class. This is mainly due to air leakage in the fittings. Because of difficulties encounteredduring the implementation as lack of space, access problems or short time to proceed theinstallation, these fittings are not sealed enough, with mastic or adhesive tape.In order to limit this risk of leakage and to limit sealing operations on site, manufacturerspropose components equipped with joints. Some years ago, CETIAT has tested in itslaboratories different kind of such components.

The Dutch housing stock consists for about 70% of single family houses with an average N50 of about 7-9 ACH and for 30% of apartments with an average N50 of about 3-4 ACH.New single family houses are much more airtight. In the period 1970 to 2000 the air tightness increased to an N50 of about 3 - 4 ACH. Apartments have nowadays about the same or a slightly better air tightness then before 1970.Another trend is the downward tendency of occupant numbers per dwelling.

For retrofitting as well as for new buildings a good airtightness is an important issue. In Germany, Austria and Switzerland about 1000 persons conduct blower door tests according to EN 13829 in order to characterize the air permeability of buildings. Also, preliminary measurements of the air barrier are made, often by the craftsmen themselves. Early measurements allow to repair leakages more easily than when the building is completed.

It is often discussed about the possibilities that more efficient windows offer to reduce the energy loads in residential buildings. Often such results can be achieved reducing the thermal transmittance or optimising the solar gains, not so often the influence of the air permeability is taken into account. This issue is, on the contrary, very important in countries, as Italy, where the age of the building stock is accompanied by the installation of very old windows, characterised by high air leakage, which causes strong heat losses and discomfort phenomena for users.

The airtightness of ventilation ductwork is an important element of the global performance of ventilation systems.

Sheffield City Council in the UK identified some dwellings of non-standard construction that needed to be refurbished. The refurbishment mainly involved applying insulation and rendering to the exterior surfaces of external walls and replacing old windows. The main aims of the refurbishment for the Council were to improve the condition and appearance of the dwellings and reduce conductive heat loss through the fabric.

This paper discusses how ventilation and air distribution can have a positive or negative impact on chemical, biological and radiological agents entering buildings, on their movement within the buildings and on their removal. It also points out the key role played by the envelope airtightness of the building and its pressurization as a security tool.

In developed countries, the concentrations of indoor pollutants are very similar to those outdoors. 3 basic strategies are proposed to reduce occupant exposure to indoor contaminants : 1. Building air tightening and pressure management2. Ventilation and air filtration3. Contaminant removalIn poor countries, the use of advanced ventilation and filtration techniques is not feasible at all, natural ventilation may be one of the more effective solutions

A manufactured home has been installed on the NIST campus for ventilation, energy andindoor air quality studies. The primary purposes of the facility are to study mechanicalventilation requirements for U.S. manufactured homes and to investigate the systems used tomeet these requirements. In addition, the building will be used to investigate moisture issues,indoor air quality impacts of combustion appliances, and VOC emissions from buildingmaterials and furnishings. The first phase of this multiyear effort has focused on airtightness,system airflows and air change rates.