| Why is Building Pressure Important |
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Building pressures are an important factor in the overall performance of both commercial and residential buildings. Pressure evaluation should be at the top of the list for energy audits, building commissioning, moisture management and indoor air quality investigations. Understanding pressure within a building requires an experienced investigator. It would seem that pressure measurement should be a fairly simple procedure. However, very few building professionals really understand air movement in a building and often, critical measurements are overlooked. There are hidden risks associated with building pressurization and if the pressure relationship to the outside environment and / or relationship between interior spaces is not correctly established and maintained, indoor air quality problems can develop.
The movement of air through the building determines the pressure relationships inside the building, and between the inside of the building and the outside. These pressure differences determine the amount of air leakage into the building, which can cause comfort problems and energy waste. In some buildings, such as hospitals and laboratories, these pressure relationships are also important for safety. When the pressure differential is not correctly maintained or worse yet not properly designed the building develops indoor air quality related problems.
Building design often fails to pay adequate attention to these issues, resulting in air intake that does not satisfy ventilation standards. You can save energy, avoid health problems, and make your home or building more comfortable by making a few improvements. One group of design activities avoids unnecessary or excessive intake of outside air by better arrangements of intake fans, relief fans, exhaust fans, and dampers. Pressure may also fluctuate considerably in a building based on temperature, operation of fans, air handlers, exhausts, etc. There is also changes associated with “Stack Effect” which can create a wide variation of pressure across a building envelope. The pressures are negative below what is called the neutral pressure plane and varying degrees of positive pressure above the neutral pressure plane. Large buildings create unique problems when measuring pressures. Isolating sections of the building and measuring it separately is one method. Whether to use the mechanical systems or specialized equipment to pressurize and/or de-pressurize the building is another consideration. In order for any of these to work, the ability to isolate areas of the building is important and this is not always as simple as it sounds. |
The first thing to understand in measuring building pressures is that there are numerous zones in buildings and varying conditions which affect building pressures. These conditions include temperature, humidity levels, wind conditions, building pathways and interconnectivity of those pathways and mechanical system operation. The pressures within these areas and zones can change frequently based on other systems or any of the parameters previously mentioned. The ability to understand how the building and systems communicate is a critically important and often overlooked. There are numerous issues in buildings which can be traced to building pressures including comfort complaints, indoor air quality, moisture related issues and building degradation. Some of the conditions created by pressure imbalances can be serious safety concerns. For example, if the building is de-pressurized and the negative pressure is causing spillage of combustion gases into the building. Some other issues may seem minor (e.g. difficulty opening ground level doors) but can be an indication of more serious problems. In other cases, the problems caused by pressure imbalances may go unnoticed for years until a significant amount of damage has occurred. In larger buildings monitoring and understanding pressure can get far more complicated.
