R21 Insulation - Commercial Construction - Contractor Talk

R21 Insulation

 
Thread Tools Search this Thread Display Modes
Old 08-25-2019, 08:52 AM   #1
Thread Reading Aficionado
 
Builders Inc.'s Avatar
 
Trade: Certified Building Contractor
Join Date: Feb 2015
Location: Florida
Posts: 1,785
Rewards Points: 1,426

R21 Insulation


At what scenario, in walls, is R21 high density fiberglass insulation used over R19?


Sent from my iPhone using Tapatalk
Builders Inc. is offline  

Warning: The topics covered on this site include activities in which there exists the potential for serious injury or death. ContractorTalk.com DOES NOT guarantee the accuracy or completeness of any information contained on this site. Always use proper safety precaution and reference reliable outside sources before attempting any construction or remodeling task!

   

Advertisement

 

Old 08-25-2019, 09:25 AM   #2
Fire up the BBQ
 
griz's Avatar
 
Trade: GC
Join Date: Nov 2009
Location: CA
Posts: 22,065
Rewards Points: 3,058

Re: R21 Insulation


when you want a higher r value.

or when the energy calcs call for it.

Advertisement

__________________
SOME JOBS JUST AREN'T WORTH DOING:
griz is online now  
Old 08-25-2019, 10:32 AM   #3
Pro
 
Randy Bush's Avatar
 
Trade: Exterior Remodeling
Join Date: Mar 2011
Location: Great Falls, MT
Posts: 5,505
Rewards Points: 1,436

Re: R21 Insulation


I would use the R-21 regardless.
Randy Bush is offline  
The Following User Says Thank You to Randy Bush For This Useful Post:
ScipioAfricanus (08-25-2019)
Sponsored Links
Advertisement
 
Old 08-25-2019, 12:35 PM   #4
Thread Reading Aficionado
 
Builders Inc.'s Avatar
 
Trade: Certified Building Contractor
Join Date: Feb 2015
Location: Florida
Posts: 1,785
Rewards Points: 1,426

Re: R21 Insulation


Well here’s the scenario. We work off of a consultant xactimate scope, bid it sight unseen and what was there was R19 and the consultant wrote R21. I bought R19. R19 is 6.25”. The walls are metal stud 2x8 on first floor and 2x6 from there up. The R21 insulation is spec’d for light gauge metal studs 5.5” the consultant wrote it wrong from being like kind material. We now have to do a deductive change order since the consultant spec’d the wrong pre existing material. From a municipal stand point for cost effectiveness and why would an architect would spec using R21 when there wouldn’t be a need for the “high density” feature of R21. From a comfort aspect I seriously doubt you could feel a difference in R21 vs R19 in a finished space other than your wallet or budget. I screwed up ordering R19 and just glanced at the 6” line item in the scope but the estimator screwed up in adding R21 to the scope instead of looking and seeing it actually had R19.... either way the customer is ok with us using R19=what is there previously.


Sent from my iPhone using Tapatalk
Builders Inc. is offline  
The Following User Says Thank You to Builders Inc. For This Useful Post:
hdavis (08-26-2019)
Old 08-25-2019, 11:27 PM   #5
Pro
 
Fouthgeneration's Avatar
 
Trade: Masonry
Join Date: Jan 2014
Location: Middle
Posts: 2,434
Rewards Points: 8,713

Re: R21 Insulation


With metal studs bridging the space between your sheathing and Dry wall your wall averages about R8.6 with 24 C to C studs and R19 glass,,, R9.0 with R21 glass

Install a layer of 0.5" ANYTHING on the outside and you are a Genius.... And no silly tear outs.
__________________
I might be an Idiot, but I know things that You don't: Please wait till after you get my know-how to insult me....
Fouthgeneration is offline  
Old 08-26-2019, 06:13 AM   #6
General Contractor
 
greg24k's Avatar
 
Trade: New Home Construction-Additions-Remodeling
Join Date: May 2007
Location: NJ
Posts: 7,588
Rewards Points: 8,314

Re: R21 Insulation


If you using high-density insulation... R-21 id for a 2x6 wall.

If you want to achieve R-21 in a 2x4 wall you have to use Polyurethane Rigid foam insulation which comes anywhere from R-18 to R-28 and it's 3 1/2" thick or use spray foam insulation.
__________________
I never lost a cent on the jobs I didn't get!
greg24k is online now  
Old 08-26-2019, 04:30 PM   #7
Pro
 
Fouthgeneration's Avatar
 
Trade: Masonry
Join Date: Jan 2014
Location: Middle
Posts: 2,434
Rewards Points: 8,713

Re: R21 Insulation


Greg24K: You can't achieve R-24 with a 2 x 4 steel stud framed wall with the "steel" short circuiting the heat flow between the dry wall / exterior product.

Two inches of foam mounted across the studs on the exterior, and some fiber glass for sound control?

R-15 fiber glassed metal studs = ~7.8 R value for the whole panel....24" spacing, 6.4 R value for 16" C to C studing.
__________________
I might be an Idiot, but I know things that You don't: Please wait till after you get my know-how to insult me....
Fouthgeneration is offline  
The Following User Says Thank You to Fouthgeneration For This Useful Post:
greg24k (08-27-2019)
Old 08-27-2019, 05:41 AM   #8
General Contractor
 
greg24k's Avatar
 
Trade: New Home Construction-Additions-Remodeling
Join Date: May 2007
Location: NJ
Posts: 7,588
Rewards Points: 8,314

Re: R21 Insulation


Quote:
Originally Posted by Fouthgeneration View Post
Greg24K: You can't achieve R-24 with a 2 x 4 steel stud framed wall with the "steel" short circuiting the heat flow between the dry wall / exterior product.

Two inches of foam mounted across the studs on the exterior, and some fiber glass for sound control?

R-15 fiber glassed metal studs = ~7.8 R value for the whole panel....24" spacing, 6.4 R value for 16" C to C studing.
I was referring to wood studs before he made a follow-up post (I just saw it) where he mentioned metal studs.
I never use metal studs and the only time I used them is when I was doing a commercial job (25 years ago) and we didn't use insulation (it was between 2 stores) so I'm not really familiar with insulation methods when it comes to metal framing.

Advertisement

__________________
I never lost a cent on the jobs I didn't get!
greg24k is online now  
The Following User Says Thank You to greg24k For This Useful Post:
Fouthgeneration (08-27-2019)


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Join Now... It's Fast and FREE!

I am a professional contractor
I am a DIY Homeowner
Drywall Talk is for
PROFESSIONAL CONTRACTORS ONLY!

At DrywallTalk.com we cater exlusivly to professional contractors who make their living as a contractor. Knowing that many homeowners and DIYers are looking for a community to call home, we've created www.DIYChatroom.com DIY Chatroom is full of helpful advices and perfect for DIY homeowners.

Redirecing in 10 seconds
No Thanks
terms of service

Already Have an Account?