Airtightness and Resistance Effects Most of the hazardous particulates enter the home from outdoors. The airtightness of a home is the most important factor to minimize airborne particles, known as PM2.5, in indoor air. PM2.5 means particles of less than 2.5 microns...

Masonry air leaks Masonry materials must be airtight and have airtight joints between the building assemblies to function as air barriers. Masonry roofs, walls, and floors may or may not be airtight. For example, concrete block isn’t itself airtight. Joints between...