Building airtightness

Building airtightness (also known as airtightness envelope) can be defined as the resistance to inward or outward air leakage through a leakage point or areas in the building envelope. This air leakage is driven by the differential pressure of the stack. Airtightness is the fundamental building property that impacts infiltration and exfiltration (the uncontrolled inward and outward leakage of outdoor air through cracks, interstices or other unintentional openings of a building, caused by pressure effects of the wind and / or stack effect). An airtight building has several positive impacts when combined with an appropriate ventilation system (whether natural, mechanical, or hybrid): good building airtightness Conversely, poor airtightness may prevent achieving the desired indoor temperature conditions. From an energy point of view, it is almost always desirable to increase air tightness. However, it is often unclear how effective this dilution is and causes it to be uncontrolled and potentially poorly ventilated rooms may be sufficient. This adverse effect has been confirmed by simulated simulations in which it has been shown that typical mechanical ventilation systems are better. Air leaking across the envelope from the relatively warm & humid side to the cold & dry side of the air.

Leakage is a characteristic of the following locations.

The airtightness of a building is usually expressed in the airflow rate by the building envelope (usually 50 pascal) divided by the: For all of these metrics, the lower the ‘airtightness’ value is for a given building, the airtight building the envelope is.

The relation between pressure and leakage is defined by the power envelope as follows: q L = CL Δpn where:

Building airtightness levels can be measured by using a fan, installed in the building envelope (a blower door) to pressurize the building. Air flow through the fan creates an internal, uniform, static pressure within the building. The aim of this type of measurement is to relate the pressure to the environment. Generally, the higher the flow rate required to produce a difference, the less airtight the building. The fan pressurization technique is also described in many standard test methods, such as ASTM E779-10, ASTM E1827-11, CAN / CGSB-149.10-M86, CAN / CGSB-149.15-96, ISO 9972: 2006 (now superseded), & EN 13829 which is now ‘withdrawn’ due to the updated ISO 9972: 2015.

Most European countries include in their regulations or require minimum airtightness levels with or without mandatory testing. There are several countries (eg, United Kingdom, France, Portugal, Denmark, Ireland) where, by regulation, airtightness testing is mandatory for certain building types or in the case of specific programs. In the US, the IECC of 2012, the requirements of the United States, including mandatory testing. In addition, in May, 2012, USACE issued a new Engineering and Construction Bulletin in collaboration with the Air Barrier Association of America, outlining Army requirements for building airtightness and building air leakage testing for new and renovation construction projects. Washington was the first State to institute air barrier requirements and maximum permeability rates. There are several voluntary programs that require minimum ventilation (Passivhaus, Minergie-P, Effinergie etc.). Historically, the standard passivhaus, originated in 1988, was the cornerstone of the airspace envelope. ). Historically, the standard passivhaus, originated in 1988, was the cornerstone of the airspace envelope. ). Historically, the standard passivhaus, originated in 1988, was the cornerstone of the airspace envelope.