How Duct Leaks Can Affect House Pressures




Depressurized house

1 Supply ducts leak air outside living space
 2 Return takes more air from house than leaky supply ducts replace
 3 House is depressurized
 4 Air leaks in through holes in house air barrier

Pressurized house

1 Return duct leaks take air from basement instead of house
 2 Supply ducts add more air to the house than leaky return ducts remove
 3 House is pressurized
 4 Air leaks out through holes in house air barrier

Excerpted from No-Regrets Remodeling by Home Energy (1997)