# R 19 lnsulation in 2x4 wall. How? meet Code



## 56chevy

I am remodeling a house with 2x4 stud walls now that i opened them up i need to upgrade the insulation to 2009 building code standards R19. I was going to use 1" foam board R6 + R13= R19 but the building dept wont allow it even with 
1/2 drywall over it. Do i need to add 2" furring around the whole house or is
there a better way? Any money saving tips would be helpful here. Thanks


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## Clutchcargo

Typically R19 is for 2x6 walls. My local code grandfathers in insulation suited for 2x4 walls (R13-15). Check with your building inspector on what is required.


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## Hates my roof

furring strips at the least will needed. better yet is 1/2 of plywood over the foamboard, then drywall over that - use 5/8 drywall. SIP panels are another option but are pricier. Its usually better to place foamboard on the outside of the wall instead of the inside. Also be careful you dont create a double vapor barrier. The ISOboard used by roofers is a more vapor permeable foamboard than the dow blueboard or pinkboard commonly found at the homedepot. GBR WA is the expert on this kind of stuff - wall layup etc. if you are going to go this route, I suggest also sealing all stud to plywood junctions. Seal all the empty stud bays all around where the stud meets the sheathing before putting the fiberglass back in.


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## 56chevy

the building dept in my town will not allow foam insulation on the interior 
walls according to 2009 IRC ? im looking for other allternatives I guess I will have to give up on the foam board idea even though i have the board and think it is the way to go. Thanks


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## Hates my roof

how about if your were sprayfoaming? would the building dept allow that? If they allow sprayfoaming, but not foamboard would be strange. As clueless as some build depts. are, I wouldnt be suprised.


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## 56chevy

Good Point! Iam curious as to what the IRC has to say about it which is why I ordered the 2009 IRC code book. I may be fighting a losing battle
hear but due to the fact that is a lot of thermal bridging going on hear
and the amount of lumber in these walls. Thanks.


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## AllanJ

Adding furring strips will still be necessary. If you put in 1 inch (R-6) foam boards first, then when you squash the R-13 fiberglass batts back into the remaining space (2-1/2") the fiberglass R value drops to about R-9.


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## 56chevy

Please understand that the panels will be face nailed to the 2x4 studs with R 13 already in place I dont think the building dept will allow it I am looking for allternatives now im concidering a radiant barrier


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## Gary in WA

Welcome to the forums!

1. Where are you located?

2. Which Code reference did the Inspector site?

FYI- IRC 2000-2012, pick your poison; http://publicecodes.citation.com/icod/irc/index.htm

Gary


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## WillK

Well, ordinarily I believe that the 1" foam would be built on the exterior of the wall. Foam board is an air barrier but not a moisture barrier, so your wall wouldn't really be built correctly if you had the 1" foam on the interior side of the wall over R13 batts with the vapor barrier. To be correct, you'd need to use unfaced R13 batts and install vapor barrier over the 1" foam.

With that said, you'd also be loosing the structure for attachment of electrical boxes, heating ducts and anything else load bearing (pictures, TV, kitchen cabinets).


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## woodworkbykirk

in order to achieve the proper r-19 rating in a 2x4 wall you will have to do one of a few things.. a) use spray foam. spray foam will get you a rating of r-21

2) rip 2" peices of 2x from 2x6's and fur out the wall so you can use r-19 batts

3) insulate the cavitys with r-12 in the existing wall then install 2" foam over the studs then use 3" drywall screws to hang your drywall


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## 56chevy

Gary Thank you for the welcome to the forum. We are located in Chicago The inspector was citing the 2009 code they just adopted. Thanks for the site to pull it up. The interpritation is the key here
I didnt see the what if section ?


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## Gary in WA

Here is an index I use; http://www.everybodysbuildingcode.com/2.html

The sections are broken down in to sub-sections, very confusing, at first. Go to a subject, click on the main idea, then click on *"next section"* just below the info or bottom of page and 5 more might come up......

Foam board is acceptable; see section: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_3_sec016_par016.htm

On exterior of walls, it omits the interior vapor barrier if meeting minimum code: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_6_sec001_par004.htm

Also use it in an unvented roof assembly: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_8_sec006_par003.htm

And in attics: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_3_sec016_par007.htm

Protect from termites: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_3_sec016_par018.htm

Not on walls in “very heavy” termite zones: http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_3_sec018_par005.htm

More in detail on foam codes: http://www.greenbuildingadvisor.com...lating-minimum-thickness-rigid-foam-sheathing

So are you in a very heavy termite zone?

Gary


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## bill_3235

The issue is most likely fire related. Styrofoam gives off very toxic fumes when it burns. Deadly inside the house, no big deal outside.


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## joed

Post is 10 years old. I think its been resolved by now.


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