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Heat Recovery in Building Envelopes

Infiltration has traditionally been assumed to contribute to the energy load of a building by an amount equal to the product of the infiltration flow rate and the enthalpy difference between inside and outside. Application of such a simple formula may produce an unreasonably high contribution because of heat recovery within the building envelope. Previous laboratory and simulation research has indicated that such heat transfer between the infiltrating air and walls may be substantial.

The use of blower door data.

The role of ventilation in the housing stock is to provide fresh air and to dilute internally-generated pollutants in order to assure adequate indoor air quality. Blower doors are used to measure the air tightness and air leakage of building envelopes. As existing dwellings in the United States are ventilated primarily through leaks in the building shell (i.e., infiltration) rather than by whole-house mechanical ventilation systems, accurate understanding of the uses of blowerdoor data is critical. Blower doors can be used to answer the following questions:.

Heat recovery in building envelopes

Infiltration has traditionally been assumed to contribute to the energy load of a building by an amount equal to the product of the infiltration flow rate and the enthalpy difference between inside and outside. Some studies have indicated that application of such a simple formula may produce an unreasonably high contribution because of heat recovery within the building envelope. The major objective of this study was to provide an improved prediction of the energy load due to infiltration by introducing a correction factor that multiplies the expression for the conventional load.

Using forced ventilation to mitigate mold growth in existing multi-family housing

Increasing emphasis on energy-efficiency has many jurisdictions enacting stricter energy codes. Yet, these same green building codes typically do not adequately address ventilation when a building envelope is designed to both minimize infiltration/exfiltration and maximize thermal efficiency. Our company investigated an apartment complex in Southern California, U.S.A. that was designed 25% more thermally efficient than required by State Code. Within months of occupancy, the first complaints of biological growth at windows and closets occurred.

Simulation of air infiltration through revolving doors

Air infiltration through revolving doors may have significant impact on the heating load of commercial and institutional spaces, and may create discomfort to people. This paper modifies a 40-year old model by Schutrum et al. (1961), composed of two components:
(1) estimation of air exchange between one segment of the revolving door and the indoor/outdoor,
(2) estimation of net air infiltration rate.

Computer simulation of thermal impact of air infiltration through multilayered exterior walls

Convective air circulation occurring through wall layers is frequently observed in building envelopes. Significant thermal coupling can take place between the incoming cold/warm air and the wall structure, thereby modifying the thermal performances of the envelope. This paper presents an unsteady threedimensional numerical heat and air transfer model, which was developed to

Thermal balance of a building as a tool for evaluating infiltration rate

Theoretically if the thermal properties of a building envelope and the power of the HVAC systems are known, then air infiltration becomes the only one unknown component of the thermal balance of a building and could be defined from it. In reality, all data are approximate. Modern measurements and data processing techniques allow one to evade this obstacle.

Calculations and Notes on the Quadratic and Power Law Equations for Modelling Infiltration

Calculations using CFD are presented for adventitious openings in which the flow is not fully developed. It is shown that the quadratic equation performs significantly better than the power law i.e. a recent claim that the power law equation is preferable to the quadratic equation under such circumstances is not supported. Other recent claims that have been made to support the power law in preference to the quadratic are also examined and reasons are given as to why they are unfounded for conditions of typical, naturally driven air infiltration.

Field measurement results of the airtightness of 64 French dwellings.

This work presents a field measurement study, investigating the airtightness of 64 French dwellings less than ten year old. Buildings have been classified according to the type of construction (masonry or timber frame) and of occupancy mode (multi- or single- family). Using a fan-depressurization technique, we assessed the air leakage rate of each dwelling, based on a theoretical flow model that relates the infiltration airflow rate to the differential pressure .

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