ventilation needs

Ventilation is a key factor in low energy housing and in temperate maritime climates such as Britain's moisture is a major factor in determining ventilation needs. Outlines necessary levels of humidity for both people and buildings. Summarises sources of moisture. Discusses control of humidity by either mechanical ventilation or heat pump dehumidification.

Increasing use is made of open front or cold confinement buildings for fattening beef cattle. Reports model study of an open front beef confinement building a) to evaluate the effects of ridge vent design on airflow characteristics and temperature and b) to determine prediction equations forthe relationship between wind velocity and outlet velocity. Reviews literature on the subject. Compares results with previous studies. Discusses relationships between outlet velocity, wind speed and temperature difference. Recommends open and baffled ridge vents.

Uses Turk's equation to obtain CO concentration v time curves in an office and a one-family house. Compares results with similar studies, current threshold limit values and ambient air quality standards for CO. Finds model is apparently valid for CO and probably for other gaseous contaminants not affected by absorption or deposition. Concludes that commercial environments should have at least 5 cfm fresh air per occupant and that a value of 50 cfmfresh air appears to be adequate for a one-family dwelling.

Reports first report from committee, "Preliminary proposals for measures against radiation risks in dwellings". Notes that prime source of radiation, alum-based lightweight concrete, has been banned in new buildings in Sweden, but is still present in 10%of pre-1975 houses. Provisional limits for gamma radiation for undeveloped sites: 30-100 micro.r/h (site should only be built on subject to other conditions), more than 100 micro.r/h (building inadvisable). suggests that geological radiation maps be charted. Notes reduction in radon content through house ventilation.

Presents mathematical model for predicting the heat transfer and moisture- transfer processes in residential attic spaces. Uses model to predict attic ventilation rates required for preventing condensation or frost accumulation on the underside of roof sheathing. Gives attic ventilation charts covering a wide range of outdoor temperatures, ceiling thermal resistances and ceiling air penetration rates. Finds that the addition of a ceiling vapour barrier reduced the required attic ventilation rate by36%, but the effectiveness of a vapour barrier was reduced by air leakage into the attic.

Radon is a radioactive gas which diffuses naturally from all mineral based building materials. States for most homes, concentration of radon is approximately inversely proportional to the ventilation, although this is not valid for very low or very high air change rates. Gives brief results of measurements of concentration of radon in dwellings. Outlines health risks from radon and daughters. Reviews norms laid down in some countries for specific situations. Discusses ways of reducing radon concentrations.

A supply of fresh air is necessary in any dwelling to ensure a comfortable, safe and hygienic environment, but the heat loss to this air, during the heating season, may represent a substantial proportion of the total heat loss. This points to the need forgreater control of domestic ventilation, either by using a mechanical system or by better design for natural ventilation. This paper touches upon both of these possibilities. Gives simple method for assessing approximately the possible reduction in heat loss achieved by the use of a mechanical ventilation system.

Gives state-of-the-art review of ventilation needed to control carbon dioxide, odours, cigarette smoke and moisture mentioning main results. Gives sketch graphs illustrating these results. Outlines the effect of opening windows on air -change-rates andgives tables showing average window opening, the moisture generation from various activities and the solar radiation falling on vertical surfaces.

States that the need for fresh air to dilute cigarette smoke is the dominant criterion for ventilation design. Reviews the literature of the subject and concludes that the three main health factors are carbon monoxide, acrolein and particulate matter. Finds very wide differences in sensitivity between people. compares IHVE guide of 1970 with the british standard draft code of practice CP3 concludes that cigarette smoke shouldbe treated as a contaminant and not linked with body odour dilution.

Discusses fresh air requirements and tolerable levels of contamination from various sources within a space. Explains the calculation of dilution rates. States that in summer the rates required will generally be higher than those derived from theinformation given because of the need to reduce temperatures in non-air-conditioned buildings and gives method for calculation of ventilation rate required.