Attic guide

Attic floor or roofline: what are you insulating?

Define the enclosure before deciding where the foam belongs.

In this guide

Two different approaches
Review the existing conditions
Prepare a useful request

Two different approaches

Insulation at the attic floor leaves the attic outside the conditioned enclosure. An insulation strategy at the roofline can put the attic inside that enclosure. These approaches affect ventilation, air sealing and equipment differently; they are not interchangeable upgrades.

Review the existing conditions

Describe roof leaks, ductwork, exhaust outlets, lighting and access. Have defects assessed before covering surfaces. Discuss how air sealing and ventilation will work together with the proposed assembly. Do not block existing vents as an isolated change.

Prepare a useful request

Include attic dimensions if known, photographs, the location of heating or cooling equipment and whether existing insulation needs evaluation. Ask which surfaces are included and what preparation or inspections are required.

Technical background: PNNL — Attic air sealing, insulation and ventilation. Sources checked October 20, 2026. General planning information; the project professional must verify product instructions and applicable local requirements.