[Greenbuilding] apples, oranges, and u values

[RT]

On Mon, 16 Apr 2012 11:46:27 -0400, John Straube <jfstraube at uwaterloo.ca>  
wrote:

> The Europeans DO measured U-value differently.
> They measure at an outdoor temperature of 32 F.  The result is slightly  
> higher R-value / lower U-values and slightly wider optimum air gaps.   
> They also design their hollow frames with larger voids as convection  
> does not set in as quickly.
> As a rule of thumb, I derate their R-values by 10% relative to NFRC,

Speaking of hollow voids, just to spread the slamming of window  
manufacturers from other countries around a bit ...

I have vague memories of a story that Stephen Thwaites (another enginoid  
whose alma mater is Univ of Waterloo, where WatJohn hangs his hat when  
he's in Canada) had told me about 12 or more years ago ( memory dim &  
noggin full of cobwebs so specifics may be a bit off).

I think the story was that Stephen was down at a window manufacturers'  
conference (trade show ?) somewhere in the US (SW ?) and one of the  
manufacturers who also supplied pull-truded fibreglass frame windows like  
Stephen's company Thermotec Windows  http://www.thermotechfiberglass.com/   
was puzzled as to why their windows weren't performing as well as they  
might (I don't remember the specifics but probably compared to  
Thermotech's) in cold climate applications.

To cut to the chase, it didn't occur to the US manufacturer to fill the  
hollow cores of the fibreglass lineals with insulation, like Thermotech  
did with theirs.  D'oh!

(Here's hoping Stephen sees this posting and sets the story straight where  
I may have "mis-remembered" some details.)


-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada

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