English

Since 1970 measurements of air change rate have been carried out in about one thousand buildings by the Swedish Institute for Building Research (SIB). In this paper we present results from these measurements. The studied buildings are of various design and have ventilation systems of different types, natural as well as mechanical. The buildings include single family houses, row houses, and multi family residential buildings, erected between 1900 and 1982. The measurements have then been carried out using tracer gas (decay) techniques to determine the rate of air exchange.

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.

Air infiltration typically accounts for a third of the energy loss in a heated building. The driving forces for natural air infiltration are wind and temperature differences. For a given combination of weather conditions the amount of air infiltration is determined by the character of the building envelope, mainly its airtightness. A useful technique in characterizing this housing quality is to measure air leakage. An air leakage standard for new construction has been in effect in Sweden since 1975.

The air infiltration associated with ventilation in buildings is recognized in ASHRAE Standard 62-1981, Ventilation for Acceptable Indoor Air Quality. In the light of recent trends toward increasingly tight housing, which limits air infiltration for ventilation, dependence on this source of outside air is onepoint that must be carefully considered in the Revised Standard. Other points to be considered are ventilation efficiency, necessary dilution of particulates and other pollutants, and how changes in humidity, air temperature and local heating may alter pollution levels in buildings.

Eleven countries are cooperating to establish guidelines for minimum ventilation rates which are sufficiently large to meet the demand for outdoor air in buildings without unnecessarily wasting energy. The most important pollutants have been identified as: carbon dioxide, tobacco smoke, formaldehyde, radon, moisture, body odour, organic vapours and gases, combustion products and particulates. To a certain degree some of thesesubstances can be used as indicators for acceptable air quality to establish minimum ventilation rates.

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.

Reduction of fresh air ventilation is becoming the major means of energy conservation in office buildings. Simultaneously, health and comfort problems experienced by occupants are often suspected to be a direct result of reduced fresh air ventilation. However, there is little data available on health and comfort problems experienced by occupants of buildings operated under normal ventilation rates.

Ventilation standards in buildings are receiving increased attention because of energy conservation and indoor air quality. An important example of this is the current ASHRAE Standard 62-1981, "Ventilation for Acceptable Indoor Air Quality." This standard contains two distinct procedures that can be used to set ventilation rates. The first is a prescriptive specification that mandates ventilation rates for particular building types. The second is a performance specification that uses target concentrations of indoor contaminants as the basis for deciding the adequacy of ventilation rates.