We decided to replace two old furnaces, and go with the highest energy efficient rated ones (Slant Fin). Northwood took a day to install each furnace, and continued working until the job was done, even until 9-10 p.m. at night. The worked they did looked neat, and they left the work areas clean. Several days later, a spark problem arose in one furnace, which shut down the heating in the whole house. Northwood came back, and hopefully the problem with the new furnace has been fixed. We believe Northwood did a professional installation, but the cautionary tale is to fully check out the new high efficiency furnaces prior to purchase. Our old furnaces were 20+ years old, and they never broke down. The new furnaces, while energy efficient, seem to be more complicated with more parts, so more opportunities for complications/problems.