NOCTI Pre-Engineering Practice Exam 2026 - Free Pre-Engineering Practice Questions and Study Guide

Fiberglass insulation reduces heat transfer by trapping air inside a network of fine glass fibers. Those tiny air pockets act as barriers to heat flow, so fiberglass has a high resistance to heat movement per inch and is easy to install in walls and attics. Brick and concrete are dense building materials that conduct heat much more readily and aren’t used primarily to block heat transfer; they typically need additional insulation to improve efficiency. Glass wool works similarly to fiberglass, since both rely on fibrous glass structures to create air-filled spaces, but fiberglass is the more common and widely used option in many construction practices. The effectiveness comes from pairing a material with many air pockets with low thermal conductivity, which slows heat transfer across the building envelope.