This well constructed, superbly engineered chimney damper eliminates 90% of the winter heat and summer cooling loss that leaks past your current damper. It also eliminates downdrafts and keeps moisture and animals out of your chimney and home. Moisture in your chimney causes unwelcome odors and leads to deterioration of bricks and mortar. The Lyemance Top-Sealing Damper works year round to protect your chimney.