Emissivity is defined as the fraction of energy being emitted relative to that emitted by a thermally black surface and is a measure of how efficiently and quickly a surface emits absorbed heat . Emissivity is defined on a decimal scale between 0 to 1. Emissivity of 1 represent a perfect emissive material that emit 100% of heat while emissivity of 0 represent a surface that absorb 100% of heat.

This article is aimed to provide typical values for roof emissivity based on type of the roof and roof construction material. Users can change roof emissivity value in cove.tool web app under baseline energy page. Roof emissivity is set to 0.9 by default. Users can change this value based on roof material of choice for their projects.

Following table provides typical values adopted from ASHRAE Handbook – Fundamentals version 2021 for roof emissivity value.

Roof Type

Roof Material

Emissivity

Sloped Frame Roofs

Metal roof, batt insulation, gyp board

0.462

Sloped Frame Roofs

Metal roof, batt insulation

0.462

Wood Deck

Membrane, sheathing, insulation board, wood deck

0.862

Metal Deck Roofs

Membrane, sheathing, insulation board, metal deck

0.462

Metal Deck Roofs

Membrane, sheathing, plus insulation boards, metal deck

0.462

Concrete Roofs

Membrane, sheathing, insulation board, 100mm LW concrete

0.920

Concrete Roofs

Membrane, sheathing, insulation board, 200mm LW concrete

0.920

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