: a measure of resistance to the flow of heat through a given thickness of a material (such as insulation) with higher numbers indicating better insulating properties compare u-value

Examples of R-value in a Sentence

Recent Examples on the Web For kids, aim for an R-value of at least 2, which should keep them comfortable down to 30-degree Fahrenheit temperatures at night. Mandy Harris, Travel + Leisure, 18 Oct. 2023 Made of several layers of materials and fabric, they are designed to provide thermal resistance (known as R-value) and prevent thermal transmittance conductivity (known as U-value). Heidi Wachter, Treehugger, 14 July 2023 In isolation, R-values tell you very little, even the standardized ones. WIRED, 18 June 2023

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'R-value.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History


probably from thermal resistance

First Known Use

1948, in the meaning defined above

Time Traveler
The first known use of R-value was in 1948

Dictionary Entries Near R-value

Cite this Entry

“R-value.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/R-value. Accessed 2 Dec. 2023.

Last Updated: - Updated example sentences
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