chimney

An analysis has been made of draft failure with residential heating units operating at low rates of combustion during mild, calm weather. It has been shown that under these conditions the relation between chimney draft andhouse pressures becomes important in determining when venting failure will occur. A simple equation expressing this relation has been developed. It shows that draft failure will occur if the mean flue gas temperature in the chimney falls below a value that depends on the neutral zone level.

Several empirical models of house air infiltration, available from the literature, were reviewed and evaluated. Without exception, the limitations, inherent in these models, were found to stem from inadequate accounting of the interactive forces controlling air infiltration. In general, each of the available models was found to accurately reflect the specific real case used for verification, but extension of the model to other structures and situations was found to be totally inadequate.

Reports the results of an experimental assessment of the effect of a chimney on the air leakage characteristic of an unoccupied two-storey detached house heated by either gas or electric furnace. Measurements were taken of air tightness values and air infiltration rates with the chimney capped anduncapped.

Discusses five different models for predicting air infiltration. Presents a new model developed at the Institute of Gas Technology. The model is based on the results of tests to obtain the contribution of the existence of a chimney, and furnace operation, to house air infiltration. Reports verification of model by simulating results from 23 test homes. Concludes that model simulates with reasonable accuracy the measured values for a single-storey home equipped with an oil-fired central furnace.