Jim from Green Guild explains how contractors determine which insulation to use based on the type of attic. For example, for a big attic with sufficient ventilation, the obvious choice is open cellulose insulation. From Jim’s experience, he has installed open cellulose in a 2000-square-feet attic in just 2.5 hours. For attics that have a low roof pitch, no ventilation, and heating equipment, spray foam insulation is used. This will insulate the roof assembly and bring the heating equipment inside the thermal barrier. On rare occasions, Jim has also encountered a house that is fully insulated.