Complex sentence: Modern building techniques have created tightly sealed homes, forcing many pellet stove manufacturers to recommend their stoves be installed with outside air intake to ensure the stoves will run efficiently and prevent potential negative pressure within the home.
Split into simpler sentences: Modern building techniques have created tighter sealed homes, forcing many pellet stove manufacturers to recommend their stoves be installed with outside air intake. This ensures their stoves will run efficiently, and prevents potential negative pressure within the home.