AIVC - Air Infiltration and Ventilation Centre

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mathematical modelling

Interstitial condensation. Assessment of risk.

Sets out the mathematical techniques for determining 1 the most likely position of the condensation plane, 2 the limiting humidity at a given room temperature, below which condensation will not accumulate within the structure, 3 the rate at which condensate is likely to accumulate at the plane if the relative humidity within the structure persistently exceeds the limiting humidity. The technique is a graphical one and assumes that the conditions chosen for the purpose of the analysis remain constant indefinitely, a condition known as "steady state".

Tightness of pre-fabricated outer walls and its influence on heat demand in apartment dwellings.

Uses air leakage measurements in laboratory and site studies in Poland to define a power law relationship between pressure acting across the opening and flow rate, and explains the effects on heat loss calculations. Results of indoor climate measurements over a two year period are given. Describes use of a computer model to calculate heat demand of different ventilation systems. Real heat requirement is about 40% larger than the calculated values.

Indoor air quality environmental information handbook: combustion sources.

This environmental information handbook was prepared to assist both the non-technical reader and technical persons, such as researchers, policy analysts, and builders/designers, understand the current state of knowledge regarding combustion so

Air infiltration - modelling and practical results.

A steady state multi-cell calculation model has been developed in order to predict the interconnection between airtightness and ventilation rates. The model has been tested with measured leakage data of a detached house. 

Steady-state one-dimensional water vapor movement by diffusion and convection in a multilayered wall.

Current moisture analysis methods for walls ignore air leakage effects or are not directly applicable to multilayered walls. Mathematical equations were developed for water vapour flow, vapour pressures, and moisture accumulation under steady state conditions with homogeneous one dimensional air flow through a multilayered wall.

Personal exposure to respirable particles: a case study in Waterbury, Vermont.

A study to assess personal exposure to respirable particles was conducted during January to March 1982 in Waterbury, Vermont. 48 non-smoking volunteers carried Harvard/EPRI personal samplers every other day for two weeks. 

Effects of residential wood combustion on indoor air quality: a case study in Waterbury, Vermont.

An indoor/outdoor monitoring study was conducted during January to March 1982 in Waterbury, Vermont. Respirable particle measurements were made inside and outside 24 homes (all occupants were nonsmokers), 19 with wood-burning appliances and 5 without. Data were also obtained on seasonal air exchange rate, heating fuel consumption, and relevant home characteristics. Findings indicate that indoor particle levels are consistently higher than outdoor values regardless of heating fuel type.

Infiltration models for multicellular structures - a literature review.

Infiltration models are used to simulate the rates of incoming and outgoing air flows for a building with known leakage under given weather and shielding conditions. 

Air movements in buildings

The indoor air quality depends on several different factors. One is the air flow or air movements within the building and through its external walls. These flows are governed by the type of leakage openings and the pressure differences across the walls and the air terminal devices. The pressure differences are caused by wind, thermal and fan forces. Mathematical models can be used to calculate the different air flow rates. A simple example is used to demonstrate magnitude and consequences of this air leakage for two different ventilation systems.

Ventilation measurement using spot sampling of sulphur hexafluoride on a solid absorbent

Describes the technique employed, including the mathematical model as well as results from a validation test using an experimental chamber. The model assumes an exponential decay of the tracer gas concentration. The precision of the analytical procedure is estimated at better than 9%, while the error of the measured ventilation rate of the test chamber was 5%.