Electrical and mechanical systems that connect between a garage and a living area must be designed to keep fumes and exhaust from entering the house. There are many types of doors for garages. The sectional overhead door is the most common. It has rollers at each section fitted into a track up each side of the door and along the ceiling. It also has a counterbalance spring to ease the operation of the door. These doors are usually fitted with automatic openers. CARPORTS Carport roofs are usually supported by posts located on top of concrete piers. Piers should be at least 190 × 190 mm (8 × 8 in.). Cylindrical piers are often used for this purpose. The base of the pier should be sufficiently large to ensure that the safe bearing pressure for the soil is not exceeded and far enough below grade to prevent frost heaving. Where wood posts are used, the concrete piers should extend at least 150 mm (6 in.) above the ground to protect the posts from ground moisture. Anchor posts securely to both piers and roof framing to resist wind uplift. SUSTAINABLE HOUSING INSIGHT Healthy Indoor Environment Attached garages are required to have an airtight barrier and weather-stripped, self-closing doors between them and living spaces. Carbon monoxide (CO) detectors are required for adjacent bedrooms.