{"id":1361,"date":"2020-11-18T12:00:42","date_gmt":"2020-11-18T17:00:42","guid":{"rendered":"https:\/\/info.glass.com\/?p=1361"},"modified":"2022-04-04T11:41:13","modified_gmt":"2022-04-04T15:41:13","slug":"what-is-r-value-u-value-glass","status":"publish","type":"post","link":"https:\/\/www.glass.com\/info\/what-is-r-value-u-value-glass\/","title":{"rendered":"What is the Difference Between “R Value” vs. “U Value” of Glass"},"content":{"rendered":"

Question: What is the “R-Value” of Glass?<\/strong><\/h2>\n

Glass Detective,<\/em><\/p>\n

Can you tell me how to calculate the \u201cR-Value\u201d of glass based on its \u201cU-Value\u201d? I have an issue with a building inspector in my town based on energy codes, and my wall area must achieve a certain overall \u201cR-Value\u201d for me to get a certificate of occupancy permit. I have \u201cR-Values\u201d for everything but the glass. The glass company that put the glass in can only tell me the \u201cU-Value\u201d which they said is 0.29. According to the label on the glass when it was installed, the glass is an insulated unit of Solarban 60 with Low-E. Does any of this make sense to you, and if so, how do I get an \u201cR-Value\u201d for this glass?<\/em><\/p>\n

Thank you,<\/em><\/p>\n

Dave R.<\/em><\/p>\n

\"r-value-window\"<\/p>\n

Answer:\u00a0<\/strong><\/h2>\n

Dave,<\/p>\n

This whole \u201cU-Value\u201d vs. \u201cR-Value\u201d thing can be a little confusing. For many years now, most glass manufacturers have provided \u201cU-Values\u201d only. However, the conversion, or glass “R-Value” calculator if you will, is pretty simple. You see, \u201cU-Values\u201d and \u201cR-Values\u201d are the reciprocals of each other. Remember those old high school math classes? We were taught that to get any number\u2019s reciprocal, you simply divide 1 by that number. So the reciprocal of your glass unit\u2019s \u201cU-Value of 0.29 can be determined by dividing the number 1 by 0.29 which would give us 3.4482 or roughly 3.5 and that would be the \u201cR-Value\u201d for your glass. If you had a product\u2019s \u201cR-Value\u201d and wanted to know its \u201cU-Value\u201d the process would get reversed \u2026 divide the number 1 by its \u201cR-Value\u201d and you would have its \u201cU-Value.\u201d I really hope this helps and thank you for reaching out!<\/p>\n

-Glass Detective<\/p>\n

 <\/p>\n

It\u2019s a question regularly asked of us at Glass.com. What is the difference between R-Value and U-Value? Which one is more important when dealing with glass installations? The answer is that they both are actually dealing with the same issue but doing so differently. Before we go any further with this, let\u2019s get a basic understanding of what these values are and how they differ.<\/p>\n

\"thermal-efficiency\"R-values are calculations based on a formula that measures the amount of heat flow that a given material (insulation, for example) allows. The \u201cR\u201d represents \u201cresistance\u201d to heat transfer. Thus, the higher the R-Value rating, the better that material or assembly resists heat transfer. If you were buying an insulating material to be used in a wall or attic, for instance, the higher the R-value, the better that material will be at keeping you warm in the winter and cooler in the summer.<\/p>\n

Similarly, U-Values measure the transfer of heat through a material. The formula for this approach does not directly provide a resistance factor or resistance value<\/em> but merely a rate of heat transfer based on a formula that provides an actual amount of transfer (stated in BTUs). So in the U-Value approach, the lower the number, the better.<\/p>\n

Now one might ask why there are two approaches for the same thing. Why can\u2019t everything be measured or rated the same way? The simple answer might be that it could be done this way. From an engineering perspective dealing with BTUs is necessary for determining heating and cooling requirements for a building. For instance, furnaces and air conditioning equipment are engineered to provide the output levels required to deal with the anticipated levels of heat or cold anticipated in a given climate zone. Merely knowing the resistance rating of a material is good but precise measures are needed to determine what equipment will be required. This explanation is somewhat simplistic but stay with us for just a bit longer.<\/p>\n

\"energy-star-glass\"In doing a little research for this report, building code requirements were reviewed for a given part of the country. Code reviewed referenced what is known as \u201cEnergy Star\u201d standards. The Energy Star program is administered by the federal government\u2019s Environmental Protection Agency (EPA) with energy evaluations and recommendations being provided for everything from refrigerators to windows and other building products. \u00a0In this Energy Star report, the following requirements were discovered:<\/p>\n