air tightness

Deals with a code providing directives for design and construction of cold stores, drafted by the Foundation for Development of Refrigeration Technique (Stiftung Ontwikkeling Koeltechniek). Gives threshold values for admissible pressure difference and admissible measure of non-tightness, and values forthe required pressure equalizing opening, depending on nature and size of the cold room.

Describes a method used for measuring the local air tightness of sections of buildings. Notes its superiority to a previous system developed by Siitonen V. in 1982. Illustrates the device schematically and explains its operation.

In 1981 Norwegian building regulations introduced quantitative requirements to air leakages in different types of buildings. The requirements were formed as maximum allowed air changes per hour at 50 Pa pressure difference according to the pressurization method. To evaluate the consequences of these new requirementsimposed to Norwegian building industry a model proposed by the Nordic Committee for Building Regulations (NKB) was used. The average air leakages of residential buildings , built before the new requirements,are known through a research project performed i n 1979.

The situation in Canada with regard to building regulations affecting the airtightness of buildings is reviewed with emphasis on a new standard test method for measuring airtightness which departs somewhat from methods used inother countries. The purpose of this test is held to be primarily to determine an important aspect of building envelope quality, namely the degree to which unintentional openings have been avoided, rather than to determine energy conservation potential.

Air change rates were measured in one two-storey detached house with five basic types of passive ventilation systems: an intake vent in the basement wall, an outdoor air supply ducted to the existing forced air heating system, an exhaust stack extending from the basement to the roof, and two combinations of the supply systems and the exhaust stack. An expression was developed for estimating house air change rate from house airtightness, neutral pressure level and indoor-outdoor air temperature difference.

The Swiss performance standard for energy conservation in buildings SIA 380/1 is explained. This standard leaves air infiltration and other detail decisions to planners if minimum performance levels are met. Calculation procedures for heat balances based on a standard occupancy are described. Tools to achieve optimum space heating and ventilation rates are explained. Instrumentation for checking the thermal performance of the house in operation is defined.

Increased attention to the reduction of energy consumption in buildings and greater awareness of the need to maintain acceptable standards of indoor air quality have led to the development of new or revised standards of building airtightness and ventilation requirements. In this review of the existing standards of twelve countries, an attempt has been made to compare their main features and criteria. In many cases, direct comparison is not possible because of different ways of expressing the significant parameters.

ASHRAE is preparing a standard which addresses the maximum air leakage associated with good construction. This standard, 119P, links Standard 90, which addresses energy conservation in new residential construction, and Standard 62, which specifies the minimum acceptable ventilation to achieve adequate indoor air quality. Within Standard 119P there is currently a classification scheme that groups building tightness into categories depending on envelope leakage, floor area and building height.

The air tightness of 15 detached houses was measured firstly immediately after erection and secondly after a period of 1.5 to 4.5 years. All the houses were timber framed ones, equipped with mechanical ventilation systems. Only two houses out of the 15 tested showed clear changes in air tightness. Thus the air tightness behaviour of the houses seems to be fairly constant.

In Finland there are not yet any regulations or standards concerning the airtightness of buildings. Drafts have caused discussion about whether controlled airtightness would increase the building costs too much, and improved airtightness worsen the indoor air quality. In modern Finnish buildings a good or satisfactory airtightness can be achieved with normal careful workmanship. To secure good indoor air quality, a functioning ventilation system is also necessary. There seems to be no return to traditional 'breathing' structures and natural ventilation.