Submitted by Maria.Kapsalaki on Tue, 03/22/2016 - 11:04
In determining ventilation rates, it is often necessary to combine naturally-driven ventilation, such as infiltration, with mechanical systems. Modern calculation methods are sufficiently powerful that this can be done from first principles with time varying flows, but for some purposes simplified methods of combining the mechanical and natural ventilation are required—we call this “superposition”. An example of superposition would be ventilation standards that may pre-calculate some quantities within the body of the standard.
A simple model is developed for the estimation of annual rates in single-family houses using indicators for both house tightness (air changes at 50 Pa) and site climate (the leakage-infiltration ratio). This technique is best suited to low-accuracy, large data set problems where detailed data are not available. The method is similar to the method attributed to Kronvall and Persily (ie, the K-P method), but is derived from a physical model, the LBL infiltration model.
Fan pressurization techniques are being employed by an increasingly large number of contractors and auditors to determine the leakage characteristics of structures. In this study, a large data base of flow exponents and flow coefficients are compiled to determine the degree of correlation that exists between flow parameters. The resulting empirical relationships are then used to determine the feasibility of predicting these flow parameters directly from a single pressure difference test. On the basis of these correlations, a new pressure independent tightness parameter is proposed.
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
Outlines the foundations for calculating and designing natural ventilation: conditions for the building unit: technological prerequisites: components: sound insulation: calculation methods: fields of application: combination of mechanical and natural ventilation: and models for optimization of new buildings and for reconstructing factories.
The investigation was divided into several parts: 1, measurements of a mechanical ventilation system, 2, calculation model for this system, 3, measurements of the air leakage of the facades of a flat and 4, calculation model for this flat.
Reviews air infiltration measurement methods, prediction models, and flow through components of buildings. Attempts to construct a device capable of measuring air flow through a building component under a given pressure difference and to investigate the existence of a coefficient which, when multiplied by the pressure difference, raised to an exponent, will yield the air flow through that component. Components were tested under differing pressure differences and the testing device was calibrated by a tracer gas technique.
A comparison of various ventilation strategies and their effect on air infiltration using a pair of experimental single family size houses. Discusses natural ventilation with and without ventilation grilles in the windows, centralized and decentralized mechanical ventilation. Concludes that mechanical ventilation is not economic at present energy prices.