modelling

Uses wind tunnel model studies of houses to determine how best to reduce the surface pressure variations from wind and the associated air infiltration emphasizing the correct placement of suitably modelled coniferous trees. Finds that tree crowns convert the directed kinetic energy of approaching wind into random turbulent energy, which reduces pressure gradients on the windward walls, a prime region for air infiltration.

Presents a review of the main methods used for the study of air movement. Includes sections on physical modelling (wind tunnel modelling etc), analogue (water and electrical) models of air movement, mathematical models and digital computer analogues, and full scale investigations including pressurization andtracer gas techniques.

A model that relates fan pressurization results to infiltration values during the heating season is the basis for infiltration estimates in several different audit programs. Describes the model and presents validation results. Uses the model in 3 different audit strategies. The first is an energy audit to determine economically optimal retrofits for residential buildings, based on actual, on-site measurements of key indices of the house. Analyses measurements on a micro-processor and determines retrofit combinations compatible with minimum life-cycle cost and occupant preferences.

Discusses principle that the position of supply air devices has a considerable influence on the ventilation efficiency that can be achieved. Considers factors affecting ventilation efficiency and different ventilation models. Illustrates different air supply systems.

Compares measured hourly data on indoor humidity with data obtained by calculative values for NBS Houston test houses and for the high mass test building in an environmental chamber. Measured values are usually very different from the calculated values if no considerations are given to moisture absorption and desorption phenomena that take place at the interior surfaces. Introduces the Tsuchiya model that permits the evaluation of room surface moisture absorption capability.

Uses a two-zone model to describe the concept of and to define the effectiveness of ventilation. Deals with multiroom aspects and procedures for measuring ventilation effectiveness. The simple two-zone model predicts generally high effectiveness for ventilating systems using the displacement principle, taking advantage of stratification. Reviews tests using thisprinciple in an office room for 1-3 people (28 sq.m., 2.8m ceiling height).

Investigates the reliability of the single-room infiltration model used in the computer program ENCORE. Compares calculated air change rates with tracer gas (N2O) measurements in 25 identical one and a half storey detached houses. Describes the infiltration model, the parameters and some results. Thecomparison shows good correlation at low wind speeds (< 3m/sec) but the model's values at higher wind speeds are too high.

Studies the predictive accuracies of infiltration-pressurization correlation models by subjecting a group of identical homes in Freehold NJ to both pressurization and tracer gas measurements of infiltration. Compares infiltration and pressurization test results. Uses four air infiltration models to predict the infiltration rates in the houses, and compares these predictions with the measured rates. Makes predictions using several different values of the inputs required for the models, and studies the effects of varying these inputs.

Long-term efforts in Belgian research has led to the development of computer models for energy consumption predictions. Describes some simplified methodologies to be used for quick analysis of situations, especially in 2 cases:< 1. The analysis of the impact of certain design options on the thermal and energy balance of a house.< 2.

Measures houses with energy efficient designs in Eugene, Oregon and Rochester (NY) for effective leakage area using blower door fan pressurization. Determines air change rates by tracer gas decay analysis. Makes fan pressurization measurements on 13 new houses in the San Francisco Bay area that have been partially sealed with polymeric foam sealant. Measures a similar group of 13 unsealed houses as a control. Uses the results of thesemeasurements in conjunction with an infiltration model developed at LBL to predict average annual and heating season infiltration rates.