[Greenbuilding] NumberNoidal stuff (was Re: using roxul-confessions of an old foamer)

[Rob Tom]

some Murrican sparky-hoser wrote:

> To put this in perspective, what would be a typical range for PSF under
> a slab on a typical house?
>
>  Us Erlectrical injuneers ... are allergic to any units that aren't  
> metric

>> FWIW, Roxul also makes a higher compression resistance board insulation:
>> "RXL 80"  compression resistance = 27.1 kPa  ( or 3.9 psi in Murrican) @
>> 10% deformation
>> For the sake of comparison,compression resistance (CR) of Expanded  
>> Polystyrene(EPS) = ~ 10 psi @10% deformation
>> and CR of XPS (Extruded Polystyrene) (ie Dow-Corning's "SM") = 30 psi  
>> (at 10%)

In an attempt to prevent unnecessary sneezing-fits:

In SI Units:

Concrete density =  ~2400 kg/m^3

non-loadbearing residential floor slab thickness typically = 75 - 150 mm  
thick
(ie not of the loadbearing, thickened-edge variety)

Specified live load for residential floors (for the purposes of Code  
required minimums (ie the cheesiest that the law will allow) typically =   
1.9 kPa or less
			=== * ===

Or for non-allergenic Murrican non-sparkies ( metrically-challenged sorts):

For concrete density 150 lbs/cu ft,
Unfactored slab dead load:   - 3" slab thickness = ~38 psf  (6" = ~76 psf)
Unfactored Code-minimum specified live load: 40 psf

So stresses from *unfactored* residential slab live + dead load not likely  
to exceed 5.5 kPa  (or 0.8 psi in Murrican).

Recall that compression resistance of Roxul's "Drainboard" product = 17  
kPa ( or 2.5 psi)

But enginoids would never design anything using unfactored, specified  
loads as the design criteria. (ie For (Canadian) Limit States Design,  
specified live loads are in most cases, multiplied by a factor of 1.5 ...  
and dead loads by a factor of 1.25)  And no one who aspires to make good  
buildings would use Code minimums as a target to aim for. Eh ?

Whoa! That last remark must have ticked SomeOne off because there's  
thunder a-boomin' ominously outside and Nosey (a mutt) is looking for a  
hiding place. Better shut this box down before it gets fried.

-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at   C h a f f Y a h o o  dot  C a  >
(winnow the chaff from my edress in your reply)