So I'm planning this siding project and I was just advised that I cannot insulate the wall to code with fiberglass if I do it from the outside. The reason is that it will place the facing on the outside instead of the inside. The only way to install it properly is to install it from the INSIDE, and I'll be damned if I'm going to rip my sheetrock and shiplap down.

The rub here is that per energy code I am not permitted to replace my siding without insulating the walls. How do I retrofit my walls from the outside? What about fully encapsulated fiberglass? The expense of spray foam is not really an option.

[This message has been edited by Ryan the Temp (edited 2/16/2011 9:55a).]

You mean the Kraft paper side of the insulation?

The actual Vapor barrier should go on the outside in south Texas. AKA Tyvec

Who is advising you? I think unfaced is the preferred method in South Texas with the Vapor barrier on the outside.



[This message has been edited by Maroon Argyle (edited 2/15/2011 3:11p).]

Yes, the kraft paper side. I was told the facing has to be on the "warm in the winter" side.

So unfaced should do the trick?

That is true, UNLESS you live in the extreme southern parts of the US...like Houston.

http://www.energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11810

You need to place the moisture barrier where it will do the most good. Moisture travels with the Warm air towards cooler air. In the North, that is USUALLY (most of the year) from inside to out. In the south, it is USUALLY (most of the year) From the outside to in.

You don't want both or it will get trapped in the insulation itself and condense.

You strip the exterior cladding down to the studs, stuff the insulation in with the kraft paper side facing the drywall (yes, this is correct) ... you don't have to attach the kraft facing to the studs.

Then your actual vapor barrier is on the outside -- tyvek housewrap or foam sealed with tape.

The inspector in Bryan said he didn't like when they did it this way, but I have yet to see a builder build a house with the kraft flaps over the studs to provide a contiguous semipermeable vapor barrier.

We do NOT use plastic vapor barrier down here on the inside like they do in the Great White North.

[This message has been edited by superspeck (edited 2/15/2011 4:39p).]

I might suggest you talk to another code enforcer. I don't see any problem with insulating from the outside, then putting tyvec before hanging the hardi-plank.
and the only advantage I know of with paper-faced batt insulation is that you don't have to physically touch much of the bare fiberglass. it isn't a vapor barrier because it isn't sealed to the studs..just stapled...in a few places to keep it in place until drywall goes up.

I worked on new home construction in houston from 96-99. Back then non had tyvek, all used blue foam on the outside, insulation was put with the kraft paper on the inside and stapled on the studs.

I'm going to insulate my garage and A/C it. Will have to see what they have under the siding from the inside. My garage is sheetrocked and I plan on tearing out the sheetrock and insulating.



[This message has been edited by BCOBQ98 (edited 2/16/2011 9:42a).]

Installing the insulation from the inside is not an option. It would require complete destruction of my sheetrock and full removal of 1 X 8 shiplap. I've been scouring Google for information on retrofitting walls, and none of what I've been able to find considers walls without sheathing. They all say to cut a hole in the sheathing and backfill the cavities with loose fill insulation.

With my house, once I pull the siding and felt off, I will have exposed framing and fully open cavities. There HAS to be an option for retrofitting this type of structure.

One thing Code Enforcement mentioned was consideration of unfaced fiberglass, but my question is this - if I am going to sheath the outside with foil-faced OSB and rigid foam, isn't the kraft facing moot on the outside? I would think it would be no different in function than unfaced, with the exception being that it can be fastened in place with staples. Well, that and Home Depot doesn't sell unfaced R-13.

quote:

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it isn't a vapor barrier because it isn't sealed to the studs..just stapled

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My understanding was the flaps have to be taped when doen as a new install on the inside.

All I could find was kraft faced. The only unfaced they have listed on the website is R-30.

Home Depot and Lowes both sell unfaced R-13 ... although the stock varies between stores. Smaller stores that don't supply construction trades may not have it.

I usually install it between bedrooms as I'm renovating for a little bit of sound absorption/privacy. Home Depot sells the pink stuff, Lowes sells J Mansfield, which I like better because of the formaldehyde-free composition.

The kraft face would go on the *inside* walls, not the *outside* walls. It really shouldn't be a problem to install it from the outside with the kraft face against the inside of the wall. It'll have the same exact effect as unfaced.

Bonus, though, the unfaced is cheaper.

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One thing you might have to take into consideration is if you run into any knob-and-tube wiring in the wall as you're demo-ing and removing things. If you do, then you need to remove it... code won't let it stay. And if you touch the circuit by re-running it with romex, and it's in a bedroom, you have to have an arc fault prevention device in place, which means if you've got a fuse box you have to pull the panel and put in one with circuit breakers and you can't hook knob and tube to it ... so, um, yeah.

Doing things right on old houses is such a pain in the butt.

Why not a blown cellulose product? My folks used it in their house when they built new. The outside was sheathed in OSB, and the installer stapled a nylon cloth over the studs, cut a small hole and blew the product in. It doesn't settle and is VERY dense. This stuff could be installed in your situation with ease.

My knob & tube is all gone and retrofitted with romex.

Kenneth -

You mean this?


This begs the question of how I have an insulation inspection done if I have to essentially sheath the walls to hold it in place. For this application, does it matter if I use a blower or simply break up and "fluff" the bale and pour it into the cavity? I suppose I could use clear plastic to hold it in place for the inspection, but I'm not sure how to maintain a 3" gap around receptacles when using this, though.

http://www.greenfiber.com/retrofitting_sidewalls_how_to_install.html

http://www.greenfiber.com/technical_documents_homeowners.html (See PDF: DIY sidewall insulation)

I don't know how you'd get an inspection on it besides leaving the plugs open, and I don't know how they consider the gaps. I'd call the inspector and ask... the ones in Bryan were more than happy to give me answers about stuff like that.

The kraft facing is a vapor barrier. If you are installing it from the outside, You might as well put the kraft facing on the outside and staple it to the studs as normal. Put a better vapor barrier over it.

As someone who makes a living selling insulation, use unfaced R-13. Lowes or Home depot can order it for you or (preferably) find an insulation or drywall supply house in the area and you'll save money.

Just use ceiling wire, run horizontally every 3-4 feet, to suspend it in the studs until you install the exterior sheathing or vapor barrier. Worst case is you have to stick-pin it.

I live in the southeast side of Houston and I used Rockwool insulation when we added a new laundry room addition to my 70 year old house. It's available at my local Home Depot and Lowes. I love it. It doesn't have any type of "facing". It just fits snuggly into the stud cavities is fire and water resistance and has a R-15 value which is pretty high for 2x4 walls. The rest of the house still has no insulation in the walls except for two walls on the back of the house where the siding was stripped off and Rockwool insulation was put in, new tar paper, and then new cedar shakes. Just google Rockwool and you'll get plenty of info.