Several builders in our area are looking for an inexpensive - effective way to improve the R-value for an exterior wall. Advanced framing offers a small improvement as there is less wood & more insulation. Due to wind and earthquake issues we need to maintain good lateral stregnth so replacing OSB or plywood is really not an option. ANY SUGGESTIONS??
First, let me state that while there are many worthwhile points to parts of the system like the ladders & the THREE stud corner you should be careful. I would evaluate carefully what some of those changes will do with the rest of the building system. Using clips for drywall can cause some major issues, just like using a hanger instead of a jack & king stud can cause not only problems with the trim out, but later on down the line with strength & racking issues. http://blog.sls-construction.com/2010/building-green-homes-the-buil...
Onto the sheathing issue - I can't recall the name of the product, but someone is making an insulated sheathing product that supposedly combines the best of OSB/Ply with insulation - as for it's cost & performance, I haven't used it so I don't know. I think the best way to add to the walls insulation value, while still meeting your seismic & wind concerns is to wrap a 1.5 to 2" thick layer of foam on the exterior. So from the interior out - drywall, framing, OSB/Ply, Tyvek/Typar/Felt, Foam, (if you want to create a rain screen detail, add some furring strips) exterior finish
I wish I had done that with the house listed above, but I came about the info a little to late.
STYROFOAM SIS™ Brand Structural Insulated Sheathing
|Nominal Board Thickness(1), in||R-Value(2)||Board Size, ft||Edge Treatment||Min Compressive Strength(3), psi|
|0.5||3.0||4 x 8 / 4 x 9 / 4 x 10||Square Edge||20|
|1.0||5.5||4 x 8 / 4 x 9 / 4 x 10||Square Edge||20|
What I like to do to afford a better wall is make the home smaller. So now there is money to do the wall much better. I draw plans so I have some control here. I also frame the home too. I could be a wise guy and say elimilate the granite counter tops and put the money into the walls. Builders are just going to have to make a mental shift to allow enough money for a better wall system. I think of it like this; A home is an investment way into the future and if you save lots of energy then this is the cheapest home in the long run. I like the fact that you are trying to be efficient with the budget for walls. I think you can look to a smaller, more efficient design and it will have benifits way beyond walls. So educating homeowners and builders is a must. And hopefully they will make good choices.I have built 2x4 walls, 2x6 walls, double 2x walls of 10", 12", 16", ICF walls of 6" and 8" of concrete, Sips walls of 6" and 8", and straw bale wall systems. Oh, I forgot about the log dog stuff. Some log home walls too. My current idea, is to frame a 2 foot on center wall using 2x10's and using a R 38 ceiling fiberglass batt, then 5/8 plywood sheathing housewrap and then some rigid foam, maybe 1 1/2" of polyiso. I have found the double stud walls to be quite labor intensive and it feels like I have built two houses, framing all these walls has been great fun and a lot of work!
Terry first off very great points & thanks for popping in & telling us about your challenges in Montana and what has worked for you - it is very much appreciated.
Now if I may on your latest idea, but you may wish to ditch the 2x10's and consider using I-Joists instead. I would also recommend going with a sprayed in cellulose or FG product instead of batts. I know GBA & BSC both have had a ton of good info on these systems, Larson trusses, etc... recently
I would be interested to hear about the pros and cons as you see it for all those different wall systems you have done - major bonus points if you have gone back & seen them / have data on performance
Hi ya, Sean.
Thanks for the appreciation! I know about using I-joists for studs. I'm trying to lower my walls' construction costs. 9.5" I joists cost $1.28 per lineal foot, where a 2x10 #2 costs me $0.76 /lf. The dense packed cellulose insulation cost around $2.09 / LF installed at 9.5", and the recycled content R 38 fiberglass cost me about $1.00 per square foot. I then install the fiberglass with myself and my crew. The crew is very carefull to install it right, and while my crew have trouble working for other contractors because they look slow, I know they will do a stellar job. I am saving the profit from the insulation sub here. The recycled glass doesn't itch nearly as bad as the older fiberglass did, and it smells like burnt toast, for some reason.
I'm using the dimensional lumber not only to save on costs, but I build these walls in a unique way to make the task of labor easier.
I glue gaskit down the base plate and then stand the 2x10's up one by one, toenailing them to the plate. Then I jump up on my 10' rolling pipe scaffolding and nail the top plate down. this saves the back, big time. I cannot toenail the I joist sucessfully, so I would have to frame these walls platform style, on the sub floor deck and use my wall jacks to raise them. OOOFFDA!
What do think the compressed R 38 high density batt will be in R, when compressed down from 10.25" to 9.5" ? I am loosing energy through the 2x too, so I will wrap the walls in rigid foam.
I have no performance data on these walls yet, but I have data on a log cabin looking home that I call walden passivhause.
The home is a double stud 22" wall with a double parallel mono roof truss of 22", 7.5" underslab foam and tripane windows, solar thermal combi system ( space and domestic hot water heat) and a laim 70% only ERV. An ach 50 of 0.49, 1400 square feet , 7700 hdd65, yearly heat bill of $120.00 at .05 cents per KWH. Insulation works! It doesn't look sexy, though. No shiney solar collectors, or rorter blades spinning. It just sits there, doing its job.
Thank you Sean for letting me share this info and keep up the good work! You can see a picture of the Walden house on my website www.naturalhousebuilder.net It's the smaller log dog house with the solar thermal collectors on the roof.
Great for cold climates, provides continuous insulation without thermal breaks, may be used with 2x4 framing and eliminates the need for an interior wall vapor barrier.
Not necessarily cheap though and somewhat labor intensive. I'm using it on my own home with 4" EPS exterior and R11 batt between studs. Tyvek drainwrap under the foam. 3/4" treated ply furring strips hold the foam to the studs with Timberlok screws and support the finish siding and provide, essentially, a rain screen/ventilation behind the siding.
May be worth a look.
I think your wall system will work really well. I'm thinking the treated 3/4" plywood strips will bend into the foam when screwed with the Timberloks. Maybe you could use 1x4's. How wide are your strips? I've had challenges compresing the foam using 2x4's. Keep up the good job!
Strips are 3.5" thick. I've had to countersink (not planned and time consuming) holes for the timberloks.
Just enough to get them a start. Otherwise, like you say, they will definitely compress the foam and still not countersink.
My reason for using was just the fact that they were treated and cheap-- I can get a lot of strips from a sheet.