Evaluating the Air Pressure Response of Multizonal Buildings

Abstract

Air flow in buildings is a complex flow and pressure distribution problem that makes quantification difficult. However, certain parameters have recently become easy to quantify – specifically the air pressure relationships within buildings. The measured building air pressure field can be used with network analysis to solve the building flow and leakage regime creating an analytical macro model of the building flow and leakage regime. The response of the analytical model can be further tuned by perturbing both the building air pressure field and the analytical model. Building analysis typically focuses on flows and requires that all flow paths into and out of a control volume be defined. The flow path resistances need to be characterized. Determining all air flow paths and determining the flow path resistances directly is difficult. As such, estimates of these flow path resistances are commonly used. These estimates are based on limited field data and laboratory measurements. The literature provides some component values that vary by orders of magnitude and their application is often unable to predict building flow fields (ASHRAE, 1997). Standard building analysis develops the building pressure field from the flow field. This paper argues that developing the flow field from the building pressure field is more powerful. Determining the characteristics of the building pressure field directly is considerably easier than determining flow path resistances. It allows closing of the gap between the mathematical sophistication of available multi-cell air flow models and the necessary input information defining the building boundary conditions. This approach allows the pressure response of the building to be used to ‘‘tune’’ the models extending the range of their applicability and accuracy.

Integrated Methodology for Evaluation of Energy Performance of the Building Enclosures — Part 1: Test Program Development

“…Only recently in Scandinavia and North America the focus shifted to frame walls and included effects of air flow. It was found that air flows carry more moisture than water vapor diffusion, and that air, in a manner similar to sound transmission, flowing across and along building partitions, may connect seemingly separate regions of the building (Lstiburek, 2000;Lstiburek et al, 2000 and2002). Furthermore, moisture carried by air is a major factor affecting durability of building materials.…”

Inter‐zonal airflow in multi‐unit residential buildings: A review of the magnitude and interaction of driving forces, measurement techniques and magnitudes, and its impact on building performance

“…Assuming that all pressure boundaries have the same n value, C values for each zone boundary can be determined using the BDT data. This technique has also been used to aid in calibration of airflow network models 176‐178 . More recently, Gray adapted the perturbation method to isolate exterior and interior air leakage rates at the suite‐level in MURBs 179 .…”

“…This technique has also been used to aid in calibration of airflow network models. [176][177][178] More recently, Gray adapted the perturbation method to isolate exterior and interior air leakage rates at the suite-level in MURBs. 179 Unfortunately, the changes in pressure induced by the perturbation were often lower than the wind-induced pressures and the results showed poor agreement with guarded BDT.…”

Is there an optimum range of airtightness for a building?

“…The effect of pathways created by external cavities and interconnected internal cavities communicating with HVAC systems on performance of building systems is often neglected (Figure 4). The significance of these elements has been illustrated in the few examples selected from case studies (Lstiburek, 1995, 2002, Lstiburek et al, 2000. Some other cases listed by Lstiburek (1998) are as follows: A facility located in a cold climate with inadequate provision for return air.…”