Wm2/K?
James_Mustillo
| Posted in General Questions on
Hello,
I am doing some energy analysis for a Swedish colleague. I generally use Imperial units when talking about window U-values (Btu/hrft2F) but the window he supplied me specifies a “U-value” in Wm2/K–not W/m2K like would normally be seen in an SI U-value. I have scoured the companies spec sheets and I can’t find anything in W/m2K,. Can someone explain what Wm2/k is? Is it possible to convert this to U-value?
Thanks
James
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Replies
Multiply the Imperial unit by 5.678 to convert to the equivalent SI unit.
While double checking the unit of measure, I noticed that Wikipedia cites our own Martin Holliday’s post on the subject at this link: https://www.greenbuildingadvisor.com/question/metric-and-imperial
The unit itself is the watts that move through a square meter of material multiplied by degrees kelvin. Similar to the imperial unit that is BTUs that move through a square foot of material multiplied by degrees Fahrenheit. Both represent the amount of thermal energy lost or gained through a given area of a material at a specific temperature differential. Same thing being measured in each case, just different units of measurement to express the result.
Bill
Looks like it may just be a typo, W/ m2 K is the unit. The opposite would be the inverse, whether your talking resistance or conductance.
Do a search for "engineering power tools" and download or go to engineering toolbox. It has a great conversion chart as well as other features. There are others sites out there too.
Bill and Tom gave you good advice.
As an aside, in my experience with several engineering organizations, the engineers and designers that actually developed the product are not deeply involved in creating the marketing literature and whatever gets published on the companies website. Not catching a typo would be pretty minor, and if that's all that gets mixed up in translation to marketing speak, that'd be good.
To be fair, a lot of engineers (can't write so good), so a team is usually required to market and sell whatever has been designed.
>”To be fair, a lot of engineers (can't write so good), so a team is usually required to market and sell whatever has been designed.”
I R an inganeeer? :-)
Good technical writers get paid pretty well because engineers are not known for their communications skills and someone has to translate.
I agree it’s probably just a typo in the unit. Putting the slash in the wrong place makes a big difference mathematically, but you can figure out where it should go based on the context of what you’re trying to do.
Anytime you have a “this” with a “per unit that”, your formula will look something like “this/that=something”. It would be read “this over that” (normal math notation would have the first “this” literally above the second “that”), and in our case here it would be “this” many things divided by “that” big of an area to give the “this” per “that” relationship.
Hopefully that makes sense. Math ‘splaining is white board stuff for sure :-)
Bill