C.I. bypass

[rbcameron1]

Are there any instances where I can get away without having to use cont. insul. on my exterior walls? I have a mixed use building with commercial on the first floor and residential apartments (wd const.) w/ R19 batt in the walls. I'm in category 5 (Nebraska) as far as IECC 2009 is concerned. I can probably get away with it by passing COMcheck right?

 

[Frank]

You can also use the annual energy cost budget method in ASHRAE 90.1. Walmart uses this method to avoid CI

 

[Mech]

I can probably get away with it by passing COMcheck right?

I will say yes, as long as your state accepts COMcheck.

 

[David Eller]

I think yes.

 

[Keystone]

Not to steal the tread, who here accepts R19 on a Res or Com-Check if placed in a 2by6 wall cavity? Our office policy is the Res or Com-Check must be revised to indicate R18. This is based from manufactures testing showing the effective R Value of R19 when installed and compressed into a 2by6 cavity.

 

[mtlogcabin]

Just require R-21 since there is no compressed value loss according to Owens Corning

http://www2.owenscorning.com/litera...ul Compressed R-Value Chart Tech Bulletin.pdf

 

[Jmb]

If the U-Factor Alterative, IECC 2009: 502.1.2, is used then Table 502.1.2 is applicable. This table never mentions CI insulation.
In speaking with an ICC instructor at a seminar, this could be a complaint method.

 

[ICE]

The chart that

Just require R-21 since there is no compressed value loss according to Owens Corning

http://www2.owenscorning.com/literature/pdfs/10017857 Building Insul Compressed R-Value Chart Tech Bulletin.pdf

The chart lists R-38 and R-38C. What does the C stand for.

Thanks

 

[rogerpa]

502.1.2 U-factor alternative. An assembly with a U-factor,
C-factor, or F-factor equal or less than that specified in
Table 502.1.2 shall be permitted as an alternative to the
R-value in Table 502.2(1). Commercial buildings or portions
of commercial buildings enclosing Group R* occupancies
shall use the U-factor, C-factor, or F-factor from the
“Group R” column of Table 502.1.2. Commercial buildings
or portions of commercial buildings enclosing occupancies
other than Group R shall use the U-factor**, C-factor or F-factor
from the “All other” column of Table 502.1.2.

Zone 5
*Residential portion = U-0.051 (19.61)

**Commercial portion = U-0.064 (R-15.62)

 

[mtlogcabin]

. What does the C stand for.

Thanks

C-FACTOR (THERMAL CONDUCTANCE). The coefficient of heat transmission (surface to surface) through a building component or assembly, equal to the time rate of heat flow per unit area and the unit temperature difference between the warm side and cold side surfaces (Btu/h ft2 × °F) [W/(m2 × K)].

 

[ICE]

Oh that....Ya I use that all the time....R-38C has better performance numbers than plain old R-38.

 

[jwilly3879]

R-38C is for use in cathedral ceiling with 2x12 framing and leaves room for the air space above.