Paul Fazio

The influence of turbulent wind on air change rates—a modelling approach

Abstract Turbulence in wind-induced pressures on a building envelope causes fluctuating air infiltration. The resultant airflows are influenced both by building characteristics, the resistance of the openings to flow, the inertia of the air mass in the openings and the compressibility of room air, and by frequency characteristics of wind pressures, their power spectra and the correlation among them. A new approach using the spectrum analysis technique is proposed to model the pulsating flows through openings of a building. The governing equations for fluctuating airflow behaviour are obtained from the pressure/force balance between the turbulence pressure differences across openings and the forces required to overcome the flow resistance and inertia of air. The proposed approach is applied to a single-zone enclosure with a single opening and with two openings, and can be easily extended to multi-zone buildings.

Development of an energy rating system for existing houses

This paper presents the development of a new energy rating system for existing houses, combining the information from utility bills with on-site measurements and computer simulation. The proposed system was tested on a sample of 45 houses in Montreal, with the following main objectives: (i) to evaluate the quality of results given by the system (e.g., energy performance of houses, thermal resistance of exterior envelope, air infiltration rate), and (ii) to evaluate the methods of measurement and simulation (e.g., time required on site to collect data, time for computer simulation, accuracy of measurements and simulation).

Modelling of indoor air humidity : the dynamic behaviour within an enclosure

Abstract Indoor air humidity behaviour within an enclosure has been mathematically modelled. A linear differential equation is used to describe the response of indoor air humidity to different moisture transport processes within the space. The modelled processes include: moisture absorption/desorption, surface condensation, air movement across enclosure boundaries, indoor evaporation, and indoor moisture generation. By using a discrete time step, nonlinear processes, such as surface condensation, can be assumed linear within the time interval. The differential equation is solved as part of a comprehensive numerical formulation through which the behaviour of moisture transport process and its contribution to indoor humidity dynamics are modelled. A theoretical study of indoor air humidity response to different moisture transport processes has revealed the importance of the involved processes in determining indoor air humidity behaviour. The relative influence of a particular process depends on its time constant, its interaction with other processes, and the continuity of the process. In addition, the impact of a given moisture transport process will also depend on the building physical and functional characteristics, as well as the prevailing outdoor environmental conditions.

Comparative Review of Existing Certification Programs and Performance Assessment Tools for Residential Buildings

Several existing certification programs and assessment tools that evaluate housing performance are presented in this paper, showing that there is global trend in defining and evaluating the overall building performance. Some programs are focusing on selected aspects only, such as energy efficiency and quality of materials and workmanship, with only PASS and FAIL categories of assessment. Others evaluate environmental impact of the building by introducing weights to the achieved scores, and by that, they reflect priorities among the parameters. This comparative review presents the state of the art in this field, helps identify the knowledge gaps and research needs, and, finally, serves as a starting point in the development of Canadas evaluation protocol and performance assessment tool for light-frame building envelopes used in residential buildings.

Thermal performance of a hollow core concrete floor system for passive cooling

Abstract A preliminary technical study of the thermal performance of a hollow core concrete floor system for passive cooling is presented. Numerical techniques have been used to solve the one- and two-dimensional models of the transient heat transfer through the building components. Computer simulations for a warm and sunny day in Montreal show that, during occupancy, the hollow core floor system provides thermal comfort without mechanical cooling.

A quantitative study for the measurement of driving rain exposure in the montréal region

Abstract Thirty years of climatological data for the Montreal region have been analysed. The driving rain exposure of a vertical surface of a building has been quantified. This index is useful in the design of building envelopes since it provides the exposure conditions of a vertical wall to rain precipitation as well as rain intensity.

Dynamic modelling of moisture absorption and desorption in buildings

Abstract Moisture absorption and desorption by building materials in the hygroscopic range have been theoretically modelled. The Biot number which can be defined as the ratio between the material moisture resistance to the convective mass transfer resistance has a significant meaning in relating where the greater resistance to moisture transfer occurs. Using Biot number, the dynamic moisture behaviour of building materials within the indoor environment has been classified into three main categories. At high Biot number ( Bi → ∞), the material surface attains instantaneous moisture equilibrium with the surroundings. At low Biot number ( Bi → 0), the material moisture behaviour can be described through a lumped-parameter modelling. For most materials in buildings, moisture interaction with the surroundings occurs through a thin layer of material surface, and the amount of moisture absorption or desorption is mainly determined by the material surface moisture conditions. In order to evaluate material surface moisture conditions, the governing moisture transfer equation is solved via an approximate analytic technique (i.e. the moment method) in conjunction with numerical formulation. Both the dynamic and the alternating nature of the absorption/desorption processes can be modelled by this proposed analytic-numeric method. Comparison with experimental results and numerical solutions shows satisfactory agreement with the proposed model. Using this model the dynamic effect of moisture absorption and desorption by interior materials on indoor air humidity can be modelled.

Mapping of Air Leakage in Exterior Wall Assemblies

A full-scale wood frame test hut with nine wall specimens, typical of low-rise residential construction in the province of Quebec, was built inside an environmental chamber. This test hut was subjected to 66 days of simulated winter and 47 days of late spring climatic conditions to verify the feasibility of different methods of mapping and representing graphically air exfiltration. Through a better understanding of the movement of air through the envelope, the risks related to moisture condensation within the envelope for different wall compositions can be better ascertained. The air leakage pattern characterization methods implemented were two-dimensional grid moisture content monitoring and three-dimensional grid temperature monitoring. The moisture content and temperature data were presented in a graphic form, using isohygrons and isotherms. Temperatures without the impact of air leakage were also calculated using a three-dimensional conductive heat transfer model. The air leakage pattern characterization methods and the resulting moisture and temperature maps are presented and discussed herein.

A procedure for calculating the weight-matrix of a neural network for resource leveling

Abstract In this paper, a new approach for the computation of the weight-matrix of a neural network (NN) for resource leveling (RL) is introduced. The proposed method achieves significantly improved efficiency over the conventional technique of employing the functional expressions of the weights, by exploiting the structural properties of the matrices arising in the formulation of the RL problem as a quadratic zero-one optimization. These structural properties are identified, and stated in terms of template-matrix contributions of the cost and constraint functions of the quadratic optimization, to the weight-matrix of the NN. It is shown that by using these templates, the weight-matrix can be filled-in directly, based on the early start schedule of a project.

Quantitative driving rain exposure on a vertical wall at various Canadian cities

Abstract The quantitative driving rain exposure for 15 important Canadian cities is derived by making use of the climatological data recorded at local meteorological stations. The driving rain parameters, namely, precipitation, intensity, impact frequency and impact duration, provide both long term and short term characteristics of local driving rain exposure on a vertical surface. These driving rain parameters are useful to designers in designing tight building envelopes against rain penetration. A realistic driving rain exposure test environment can be simulated by making use of these quantitative results for evaluating the performance of the building envelope.