Pre-cut insulation within a membrane is usually referred to as what?

Pre-cut insulation that is typically found within a membrane is known as blanket insulation. This type of insulation is designed to fit snugly between structural elements, such as studs, joists, and rafters, which helps to reduce thermal transfer and improve energy efficiency in a building. Blanket insulation is characterized by its uniform thickness and the fact that it can be purchased in pre-cut sections, making it easier to install in specific areas.

In the context of the options provided, blanket insulation can refer to fiberglass batts or mineral wool, which are commonly used in residential and commercial applications. This option emphasizes the insulation's practicality and effectiveness in achieving desired thermal performance.

While the other types of insulation mentioned have their specific uses, they do not align with the description of pre-cut insulation within a membrane. For instance, loose-fill insulation is typically used to fill cavities and is not pre-cut, reflective insulation is designed to reflect radiant heat rather than fitting precisely between structural elements, and spray foam insulation is applied in a liquid form and expands to fill gaps rather than being pre-cut. Understanding these differences can help clarify why blanket insulation is the correct choice for this question.