ummmm, explain what?

depends on what kind of glazing is used in the curtain wall.

1" insulated low-e glass

well it'll probably be the r-value of the glass

Well...you'd need to calculate it for the entire assembly, not just the glazing (but in a curtain wall, obviously, you've got mostly glass). Double, clear low-e coated glass has an R-value of around 3.2, but I wouldn't take that number to court. It depends on the glazing you've specified.

good info....just one thing though. what is it? what does it represent? the power of the sun apon the wall? I don't get what R-Value is measuring. Does "R" stand for something?

Thx

Get the performance data from a glass manufacturer you intend to specify. You will also want the shading coefficient and U-valcue.

Check the internet & glass mfgr. websites for good explanations of R & U values.

Get the performance data from a glass manufacturer you intend to specify. You will also want the shading coefficient and U-value.

Check the internet & glass mfgr. websites for good explanations of R & U values.

R value is the reciprocal of the U value which represents a degreee of resistance to heat transfer calculated according to the conductivity of the material and its thickness. Like folks have already said, you need to look at the manufacturers specs to get the exact conductivity value for the glass you're interested in. And to get an accurate reading for a curtain wall you should probably calculate the values for the steel as well.

R value stands for resistance value, and it is the ability of a material to retard heat flow (insulation). The U value measures heat transfer rate, in other words, how fast the heat will pass through the building. This is found by adding all of the R values together and taking the inverse of that number. 1/sum(R)=U. Technically the U value stands for the number of BTUs trasferred through 1 square foot of your bulding in 1 hour . It also depends on the difference in temperature between the inside and outside of the building. With these values, you can calculate that amount of heat loss or gain that a building with endure in any given situation. The U value multiplied by the number of hours you are accounting for, times the square footage of the building, times the degree difference (Farenheit) between the inside and outside of the building, will tell you how many BTU's you will lose in that given time.

Hope that helps

Find a curtain wall product (Kawneer, Efco, etc.) that approximates what you want. The product specs should list a U-value for the assembly with some assumptions for the glazing.

Thank you all!