Building airtightness

The content presented comes from the paper under review “Quantitative correlation between buildings air permeability indicators: statistical analyses of about 500,000 measurements” (Moujalled, 2023a).

AIVC's Ventilation Information Paper #45.9 summarizes current knowledge on trends in building and ductwork airtightness in Japan.

AIVC's Ventilation Information Paper #47 gives guidance to perform a pressurization test in high-rise buildings and suggests new criteria to replace standard requirements when they cannot be met.

Many simplified models have been developed and are used around the world to estimate the infiltration rate for Energy Performance (EP) calculations, with different levels of accuracy, as described below. For example, the wind velocity can be estimated hourly, monthly or annually; based on the local climate or fixed estimated values; with or without taking into account shielding factors; etc.

AIVC's Ventilation Information Paper #46 aims to explain these simplified models and give some examples of methodologies applied in various countries.

Cracks in building fabric lead to air infiltration due to wind and buoyancy driven forces. In the heating season, the cold air entering the building needs to be heated up to room temperature, thus leading to an energy demand. Conventionally, the measured infiltration rate at 50 Pa (expressed as n50 or q50) is recalculated into an average infiltration flow rate (yearly based) using leak infiltration ratio’s (LIR) ranging from 0.033 to 0.1, the origin of these values being sometimes unclear.

The fan pressurization method that is widely used to measure the airtightness of buildings is known to have quite large measurement error. It is made up of random measurement error (precision) and systematic measurement error (bias).