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Lots of discussions about energy efficient walls, but not sure I’ve seen this answered. Seems like a no-brainer if you’re using brick veneer — you’d put the RFBI on the outside, right? But what about if using vinyl siding? Was glancing through a book today (and old book) and they showed the RFBI attached to the studs with the sheathing on the outside. Can you DO that? Seems that your siding would lie flatter. Even if you nail your siding to the studs as recommended, it’s got to be hard to get it to lie flat putting it against RFBI. And it seems you’d get a better thermal break at the studs. Of course you’d have a stiffness problem, but could you “let in” 1×4’s on the diagonal to overcome this?
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Crusty. I've posted extensively on wood let-in corner bracing--it doesn't work, even with metal braces. Search the archives.
Bdtter way to do it is to install 4'x 8'sheets of 1/2-inch plywood or OSB vertically in each corner of the exterior wall. Cover this with 1/2-inch rigid foam board insulation (RFBI)and then install the 1-inch thick sheets of RFIB on the rest of the studs. However, additional bracing must be installed every 25 feet. Tape seal all all joints and bnutts in RFBI. GeneL.
*With the above, do you put sheathing over the RFBI? Years ago they did that around here with what's called "black board" and then later foam board -- with vinyl siding it's called a "walk-through" wall because you just about could if you wanted to. I will probably use full sheathing though; just wondered if it's ever put over the RFBI (except at the corners where bracing is needed).Along these lines, I read an article in JLC which discussed the importance of "house wrap" in keeping the walls dry when using siding. The idea was basically that properly lapped, and installed around windows and doors, it will keep rainwater out of your walls and insulation. But if you don't need it as an air block (say you have foil-faced RFBI with the seams taped), is it justified just for the waterproofing?
*Crust...( i still can't remember what RFBI stands for).. if yur gonna use sheathing..put it where it belongs.. on the outside.. then no matter what kind of siding u use now or in the future, u'll have a good nail base...the racking resistance of plywood is only fully realized if the plywood is in contact with the studs and top plate and bottom shoe..Gene managed to convince me that the let-in bracing was questionable.. so much so that i rethought our energy wall that i've been using for ten years..here's the layers of our old wall:(out>1/2 inch ply>1 inch poly iso foil faced>2x4 stud @16 oc with Simpson let-in brace at the corners> with densepak cellulose or high density fiberglass and 1/2 blueboard/skimcoat..) this required a lot of one inch blocking for soffits , corners, plywood edges (to prevent crushing), and a nail base for windows and doors. We were also using let-in brace (steel) to regain some of the racking strenght we had lost because the ply was one inch off the studs..our new wall will be the same nailbase plywood and studs, but now the iso will be replaced with one inch EPS on the INSIDE and horizontal furring @16" oc , then te blueboard/skimcoat..the benefit of this is there is no blocking needed on the exterior for nailing trim or windows or doors...and all of our electrical devices will be in 4 inch square boxes with one & one half inch plaster collars so i can get a good seal around them and almost 3 inches of cellulose BEHIND the box... and with the one inch EPS my cost per sheet goes from about $13 to $3.. the Rvalue goes from 7 to 4.. but we definetly get the thermal break at the studs i want and it facilitates the insulator blowing the walls from the inside BEFORE the bluboard/ drywall..another benefit is that i don't like the ISO anymore.. too many instance of vermin and insect infestation..until the ISO industry takes care of that problem, i won't be using any in my foundations and walls..... the EPS we'll be using will be Performguard, which is Borate treated so it will not support termites and carpenter ants....my wall goes from a nominal R20 to a nominal R17..but the performance is enhanced at the electic device locations...Gene gets around the elec device problem by using surface mounted elec....but my customers don't want that look...
*Really F*#@ing Big InsulationI learned that over at JLC.Hey, you know, those guys aren't half as bad as Crusty says they are. *ps, I deleted the above post because I had hit the wrong reply button.*
*Hey Luka, who'd I say was "bad" ??I gathered that RFBI was "rigid foam board insulation" -- was I wrong? I assumed it's sort of a generic designation. What is ISO & EPS?GeneL recommended to me that I use 1" foil-faced RFBI on the outside and tape the seams. I live in Arkansas where our climate is moderate, but humidity levels are high year round and hover between 85-95% in the summer, and that's on a nice hot, dry day. Again, it's that "regional" thing.What about the housewrap??
*LOLDon't worry about it, Crusty. My job here is to rabble-rouse.Just doing my job.: )I've never been to the JLC site. (They would undoubtedly waste no time kicking my butt out of there. LOL) 'Till yesterday I didn't even know what JLC stood for.
*In answer to the question:"I gathered that RFBI was "rigid foam board insulation" -- was I wrong? I assumed it's sort of a generic designation. What is ISO & EPS? "ISO = Poly-isocyanurateEPS = Expanded Polystyrene, not to be confused wtih Extruded Polystyrene (XPS)ISO examples are Thermax, R-max, ENERGy, Tuff-REPS examples are AFM affiliates, many small manufacturers...XPS examples are Styrofoam, Amofoam, FoamulaR, Diversifoam.Now, were you guys meaning "XPS" when you said "EPS"? Because I think I remember learning somewhere that the Expanded stuff is like coffee cups, not real tough - lots of little round balls of white styrofoam result from cutting it. The Extruded Polystyrene is, I think I remember, much tougher and more generally used in construction.Someone please tell me if this is correct or not!By the way, the above information was gathered from the following website (I found in the archives here):www.eduild.com/Archives/Features/Insulation/table2.gif
*Mike. Not all of my customers allowed me to install Electrostrip surface mounted wiring (SMW).The structurally correct way to install RFBI and plywood or OSB sheathing is to install the wood sheathing directly to the studs. Now install the RFBI over the sheathing.Because corner bracing, metal or wood, does not work and one wants the RFBI directly on the studs, use 4'x8' of plywood or OSB sheets vertically on each side of the corner. Now install 1/2-inch RFBI to the plywood and install 1-inch RFBI on the rest of the studs. However, you must install additional bracing every 25 feet. The codes allow that the interior gypsum wall board (GWB) adds some structural stability to the wall.But some engineers claim it is not enough. Nporm Kerr. Beadboard is not Styrofoam. Styrofoam is a registered trademark of DOW Chemical.GeneL.
*Norm... gene has recently posted some threads that changed my thinking on EPS (bead board) some of the duration testing they are doing is showing no signs of water absorption, after three years submerged... also the AFM afiliates are mfrg in different densities for different applications.. and i am VERY concerned about vermin infestation...so.....i used to be a big fan of XPS under concrete slabs...and ISO on my walls and cathedral ceilings..now i will be using AFM EPS until further developments....Gene.. what are u goin to do.. ? those pesky people who pay the bills don't always want to go along with the program , do they?..i still don't like the ISO on the wall under anything besides Vinyl siding... and we don't do vinyl siding so my nail base will be 1/2 inch CDX until Advantec gets their price below plywood.. this is a window , and trim installation problem with me.. i have too many problems with crushing the foam when we're trying to install windows and trim....which meant tons of one inch blocking all over the place..which means , until further developments... my one inch foam will go on the inside of our 2x4 walls...