In another thread
http://forums.taunton.com/tp-breaktime/messages?msg=51427.48
piffin said 2×4 framing is better than 2×6. From most of what I’ve read on energy efficiency and affordable building, I’ve generally seen 2×6 @ 24″ OC recommended over 2×4 @ 16″ OC. Any dissenters care to hold forth?
Edited 12/16/2004 10:31 pm ET by tlambert
Replies
Won't that run the cost up a tad bit?
The ToolBear
"Never met a man who couldn't teach me something." Anon.
t.... 2x6 doesn't get rid of the thermal bridge at each stud
so in a typical wall instead of R-19.. you might really get R-15
there are a lot of better solutions for a really energy efficient wall that 2x6 , wether it's 16" or 24" oc
try a search on Mooney Wall
i think a 2x4 plain jane wall @ 16" oc with foam would give a better energy wall than a 2x6 wall with FG ( yuck ) or even dens -pak cellulose
our typical wall is 2x4 with dens-pak cells
our energy wall is a 2x4 Mooney Wall with cells
i'm going to figure the next job with foam walls and compare it to our dens-pak wall
Understood about the thermal bridging, Mooney Wall, foam vs FG and all that, but the original assertion was"Even with FG, 3.5" walls are the better framing choice."So 3.5" walls are not Mooney walls unless you've got 2x2 studs and 2x2 furring! BTW, I was pretty sold on SIPs, but after thinking about it all, I'm thinking of Mooney walls (though I had forgotten that name) ... or foam... or SIPs :-) At least I'm thinking about it."2x6 framing standard wastes too much wood."I think there's something to that. Especially in the not so uncommon case of people who think more is always better and go with 2x6 @ 16" on center, which is a waste on so many levels.
I don't know what a Mooney wall is .. Can someone give me a ref?
"try a search on Mooney Wall"BTW, I know it's called a Mooney Wall around here, but the idea goes back at least as far as Frank Lloyd Wright, who used what I suppose you would call a "Mooney Roof" (not to be confused with a moon roof) on the Usonian houses. Basically, he built a matrix of 2x4s and blew in cellulose.
frank loyd wright ain't got nuttin on Tim Mooney...
but thanks for the tidbit...Mike Smith Rhode Island : Design / Build / Repair / Restore
tlamber, thanks for the info. I'm still having problems finding Mooney Wall on the net with google. Can you (or anyone) give me some more info on this wall system? Thanks.
you need to search this site -
try these...37618.1 38760.1
"there's enough for everyone"
Hey Mike,
I'd be interested to know how the comparison comes out. I've been using dens pak cells for some time but I had a house insulated about 4 1/2 weeks ago and I'm still waiting on a few stud bays to dry. Way to much water. Drywall contractor was pizzed because I had to ask him to hang all lids upper and lower first then do only the walls with a low enough MC. Most drywall in the house is finished but 1 room remains unfinished because of those few stud bays. Insulation contractor says there were some problems with the blower on my job. That's an understatement. So let us know how it checks out.
Stay out d bushes
kcoyner
kay... sorry to hear about the wet pack..
have you tryed setting up a dehumidifier to speed it up ?... they really work good.. especially in one room
i'll see what i can do about the analysis..Mike Smith Rhode Island : Design / Build / Repair / Restore
As others have pointed out, there are alternatives to 5-1/2" batt insulation that yield sufficient R-value. Besides that, the majority of heat transfer tends to occur at the roofline and via air infiltration. Therefore, adding thicker walls is not really going to address the dominant part of the problem of heat loss.
To limit the discussion exclusively to walls, I prefer 2x4s at 16" centers because the sheathing and sheetrock are more amply supported. You can just feel the "springiness" when these type of sheet goods are put to a 24" span, and I don't like it.
Beyond that, I think having 2x6 walls leads to more wood being used unnecessarily at the plates and headers. When you throw in all the structural beams and whatnot, I think the newer houses waste a tremendous amount of wood. I'm not sure if this is directly related to the inception of the 2x6 wall, but there does seem to be a strong correlation. I work predominantly on houses built before 1929, and they're all 2x4 framed, have no plywood sheathing, and the headers and structural beams would never, ever pass today's code requirements. Yet, there they are, despite earthquakes, windstorms, and (in many cases) decades of neglect.
Anyway, my two cents says that the 2x6 framing standard wastes too much wood.
Les, why don't you use polyurethane SIPs instead? You solve the thermal bridging problem and yet don't need 9" walls to do it (6 7/16" panel would give you R-40)
In any case, if you offset the 2x4s (so effectively 12" OC) you still stop thermal bridging, but could have a much narrower wall... unless you're building a new warehouse for Santa.
Your offset 2x4 wall, that's with 2x6 plates and the 'inside' and 'outside' 2x4s 16"oc isn't it? With denspack or FG inside I guess? No bridging, and good support for drywall and siding. Downside is lots of wood and labour.
I don't know how else to avoid thermal bridging through the studs, other than the application of hard foam insulation panels to the outside sheating of a simple 2x4 wall with 2x4 plates as suggested by the previous poster.
In theory, yes, 2x4 studs on 2x6 plate. Like I said, for insulation, I would just do SIPs at that point and save a lot of timber and time. I actually got the idea from a friend who built luxury condos at a ski resort and they did something crazy like 2x8 studs on an 2x10 or 2x12 plate in order to stop sound transmission between units during the wild parties.
Wall options are numerous; 2x8s on 2x12 plates are new to me. Did that work sound-transmission wise? I am curious because there are cheaper ways of getting excellent predictable results, with much of the thinking going into not having floor and ceiling joists running perpendicular to (i.e. not crossing) the common wall, or at the very least, kerfing the subfloor. Masonry firewalls sure do help. ;)
SIPS are great - my sister has a post'n'beam with fat SIPS and a heat exchanger. Low energy costs combined with high indoor air quality.
Edited 12/17/2004 12:42 am ET by Pierre1
"2x8s on 2x12 plates are new to me. Did that work sound-transmission wise?"
Off-setting studs of any width decouples the two sides of the wall, so for sound to pass through, it must vibrate the wall on one side, be transferred to the air gap between the two and then cause the wall on the other side to vibrate and in turn to cause vibrations in the air in the other room.
2x8s offset on 2x12 plates should make very good sound barriers because the stiffer the wall, the less it can behave like a drum head, transferring acoustic vibrations to the air on the other side of it. Double drywall also helps by making the walls more massive, therefor requiring more sound energy to get them to vibrate. Of course, insulation further deadens the transfer of sound in the air gap from one surface to the other.
Any Canadians here using the Builder's Series of technical manuals from Canada Mortgage and Housing Corporation (CMHC)?
An excellent technical reference on sound transmission mitigation is their "Noise Control" booklet (code NHA 6012). $5.00 for laboratory and real life testing results, construction methods and options. Lots of stuff on STC (sound transmission class) ratings.
According to the booklet, details to pay attention to include:
- building walls and floors as 2 separate layers.
- use of dense, heavy, non-porous barrier materials.
- knowing about human perceptions of various sounds and sound levels.
- eliminating/reducing structural (i.e. solid) contacts between layers.
- greater cavity depth is better, without overfilling with insul. (that would be your buddie's 2x8 studs on 2x12 plates, Brucet999)
- cushioning footstep impacts.
- minimizing acoustical leaks at chases, pipes, wiring, etc. (with sealants).
- STC ratings for various const. materials and configurations for walls, floors and ceilings.
- controlling 'flanking sound' transmission.
- controlling plumbing noises.
- protection against outdoor noises.
- controlling appliance noise.
CMHC also publishes booklets on "Road and Rail Noise - Effects on Housing" and "New Housing and Airport Noise".
Fopam panels crossing the studs to break the thermal bridge belong on the inside,
Placed on the exterior side of studs, they form a VB omn the wrong side of the wall in a heating climate
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That is a good point - making sure a 'warm moist' cavity does not come into sudden contact with a cold surface.
Here, in Canada eh, it is common practice to have foam applied to the outside, over the ext. sheating AND to have a thick code-compliant VB on the inside. Elect. boxes and all VB perforations are sealed in and made good to the VB layer with caulk. All VB seams are caulked.
We've been building to airtight standards for some 25 years now....it will be interesting to see if these houses are still standing 100 years from now. Some folk are complaining of stale indoor air, so you see more and more air exchanger units installed.
Here's the way I like to do it: 2x4 studs 16 OC with R 13 unfaced fibreglas/ 1 inch R board 5/8 sheet rock inside/ 1/2 in plywood Typar outside. Works good!
fonzie -- how do you attach the drywall with the 1 inch sheet insulation on the interior. I have have had problems geting the rock to hang right when I cannot sung it agaisnt the 2 by?
As you know "R board" is solid so there's no "spring back" which pulls the screws through. We use 2 inch galvanized deck screws on the walls (and 2 1/2 ceiling). The screw adjustment is a precise one.
In my limited understanding of what happens with R board (INSTEAD OF VISQUEEN) on the interior of the studs: in the temperature/humidity exchange a INSTANT DROP of water is formed on the visqueen, but the heat and cold is DISPERSED on the R board. I haven't seen any mildew problems with the R board used as a vapor barrier - I have with the visqueen.
I have the screws pulling through the DW and I know the screw depth is critical -- I have been using R-max and the screws just do not snug the dry wall like I like it -- where I use the 1" board I also use the 2 and 2 1/2 screws but use the palster washers to snug things so it is really firm. I am surprised you can set the screw depth so precisley -- using a good screw gun but it pulls the screws through eventually. Dudley
Dudley, I think I was off on my screw length, sorry. I was thinking 2 inch screws for 3/4 in R Board.
We don't try to necessarily set the screws right at first on a piece of sheetrock. It seems to ask too much of the first few screws to do that so we let the sheet relax a little and go back and check all the screws.
Here's what I'm thinking for my addition. I think paying extra for spray foam is pretty much crazy if you don't also eliminate the thermal break through the studs. So I'm thinking 2x6 plates with staggered 2x4 studs on 12" centres (i.e. alternating 24" centres on the inside and outside. Then I'm planning to have icynene sprayed in. 2x6 framing around windows and doors to make trimming easy. Insulated headers. The foam fills out the entire cavity and gets trimmed back flush, so it should provide support between studs to take away some of the springy feeling on the drywall resulting from the 24" centres. I can add little strategic 2x2 horizontal blocking between studs in the right places for hanging cabs etc. without adding much thermal bridging. And it's only a small amount more wood than for the Mooney wall, with considerably fewer members to install. Any flaws in my logic?
The icynene guy wasn't worried about bowing the studs by having foam in behind the outer studs (should I be?).
Foam board on the outside means strapping for my insulation, and foam on the inside means either strapping or way more careful drywall installation than I'm interested in, as others here have pointed out.
Somebody should make a SIP-like sheathing (i.e. a layer of high density rigid foam fully bonded between two pieces of tempered hardboard) that would give a thermal break from the studs, provide adequate rack bracing strength so it can replace structural sheathing, and permit the installation of siding without needing strapping. Now THAT would be a useful product! I've seen foam sheathing used out there without any let-in bracing, but I don't know how they're getting away with it- and I wouldn't do it on my own house. I want a layer of sheathing on there to give the structure some strength.
Well, I have a couple of thoughts about what you're planning, and maybe they're worth what they cost. There are several angles to it.
One thing is the thought of running wires in the future. In fact, there is some consideration of foam all around the wires anyway (dissipating heat?). They probably have that all figured out. I've never sprayed the wall full like what you've described.
I like the plywood on the outside. It makes for a lot of triangulation as you know. It is at least one "hard surface" in the wall too. It also means you can deal with about any siding or brick easily. I don't like the straps personally.
But, you are talking about a real insulated wall there.
Wiring running in FG or running in spray foam- what's the dif? Wiring in exterior walls runs in insulation regardless.
All the pics I've seen of Icynene spray foam applications show the stud bays basically over-foamed so they have to trim some off afterwards. And unlike urethane, I think it goes on in one shot, rather than in 2" lifts. The guys who quoted me basically quoted to blow the stud bay full.
With wires and boxes exterior walls, I don't really have an alternative to spray foam that I'm confident will work. I couldn't find any installers who did densepack cellulose around here, so that wasn't a good sign as far as I was concerned.
I could be wrong, but I think the foam would be a lot more encapsuling than fibreglass. You may have the best idea there - I have never tried the full foam thing, so I'm totally ignorant of it.
(not trying to blindside you here either), but I do know I can run the fish tape through the fibreglass - filled cavity, usually putting a slight bend at the end to make it hug the wall, but I doubt if that's possible with solid foamed walls.
In my experience over even a 10 to 20 year period people want various wiring & convenience changes that I'm thinking will be handicapped with the full foamed wall. Just consider that. You might check with a electrician who has dealt with it - maybe it's not a problem.
Definitely an issue- re-work will be more troublesome than with FG. And a thinner layer of urethane foam would allow you an air space behind the drywall to fish new wiring. Then again, I certainly hope not to be re-working anything in exterior walls...
But that's another benefit of foam- though there'll be a vapour barrier installed, there won't really be one needed- and that means, if you do re-work, there's no vapour barrier to attempt to patch...
We've used R21 Fiberglass with 2x6 walls and got good results. A lot of homeowners seem to like the look of the thicker walls especially the added depth around the window openings.
tcochin, Be careful with such heresy on this thread! Some will get very very nasty with you. Your ignorance is showing to some. LOL.
R21 FG batts in 2x6 walls, poly VB on the interior and Tyvek air barrier on the exterior is pretty much standard wall construction up here in Toronto. Most of the higher end places have 1" of EPS foam on the exterior with polymer-modified stucco finish, which probably takes pretty good care of air leakage. But I hate stucco and can't afford it even if I wanted it.
My original wall plan was 2x6 studs 16" OC with mineral fibre batts and 1" of foam on the exterior- but then I found out that I'd have to put furring strips on before I put up my fibrecement siding. Then listening to these guys here, I was convinced that spray foam would do a much better job of both insulating and draft sealing without the exterior layer of foam and strapping to worry about. I can see that once you have the code-required electrical in your exterior walls, and all those drywall screws through there, the VB will probably be a leaky POS even if I try my best.
In my half-cathedral ceiling (i.e. shed roof), I'm not convinced that I need to spring for the extra cost of spray foam. I'm banking that I can't get away without venting under the sheathing for code/inspection reasons, so a good part of the benefit of spray foam in a cathedral ceiling is lost already. The only penetration in the ceiling will be my plumbing stack. So I'm planning to put spacers up, then 1/2" of foil-faced rigid foam as a radiant barrier and venting baffle, then 5.5" of mineral fibre batts, then poly VB and 2" of rigid foam on the underside of the rafters, then finish with T&G which I think I can manage to do without furring. Sounds like a lot of work, but I absolutely want a thermal break in my ceiling- no point in paying all that money for foam when half the heat will travel through the rafters anyway...
Not all heat goes into the ceiling. thermal breaks need to be put between the bottom plate and the stud wall, and eps (blueboard is what we call it here) under the foundation. A good VB in the crawl space as well. The problem that alot of these discussions is that there is an assumption that heat rises. NO, warm moist air rises. heat, radiate, and conducts. The convection comes from dynamics of the gases or particles that are heated through these means. Air infilration into your ceiling and rafters is important, but do not forget to worry about the holes and issues at the bottom part of your house. Warm air is more likely to escape throught the top if there is an inlet for cold air in the bottom.
Don't worry- mine will have a full basement with foam under the slab, basement walls cast in ICFs, rim joist space insulated/sealed with spray foam, and a gasket between the sill plate and the wall and between the sole plate and the subfloor platform. The bottom of my addition will be at least as well insulated and leak sealed as the upper floors. Unfortunately the existing house leaks enough to ventilate the addition so I won't need HRV...
Actually a HRV is still a good idea. It will allow you to take the pressure off of those inlets and control at a poit that you specify. The bonus is the you also get to recoup the energy.
I still remember the momnet the little light came on in my head about that one
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Owens Corning is based in Toledo OH. I have family there and was in the TOledo Airport this week.
OC has a display in the airport and I saw something that caught my eye, but I can't find any info on their website.
The had wall cutaway showing some metal brackets that looked like they'd come from simpson, not OC. They used three of them on an stud to hold a 2x2 to a 2x4, parallel and inline. The were there, I suppose, to stop thermal bridging.
I will keep looking, thought you'd find interesting though.
PS - have you ever run into concerns of leaving sprayed foam uncovered in a crawl?
No copncerns there specifically. There was only one time I had a HO querstion foam when they could afford iot. That was a concern over off-gassing in fire. The reply that carpet and other products in the hosue would be off-gassing long before any fire got to the foam didn't phase them and I don't argue with strongly helf beliefs of customers.
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I have a question for you about the "Mooney Wall" system.
Does the strapping go across the foam and leave an airgap between the foam and the gyp; or does the strapping go across the studs and the foam is cut to snug fit between the straps and then it is all taped or poly'd.
If it is the former, how long of jamb extensions do you spec?
Just curious . . .
Actually, mike Smith is the mooney wall afficianado. As I understand it, the Mooney wall has no foam but has 2x4 furring perpendicular to the studs, a comntainment fabric over that, and blown cellulose in the cavity. That way. there is less thermal bridging - it happens only at points of contact between stud and furring strap.I use foam over the studs to break the thermal bridge and add R-value, and then run strapping over that. Which way the strapping runs is of little importance to me - both ways are fine according to some other potential issues, i.e. whether I will be doing wainscoting and chairail...We always make out own extension jambs.
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Thanks for the reply. I understand now.
Can anyone identify and comment on the green strip of foam shown in this photo? Just in case I'm unable to upload the photo, here is a description : The photo shows some rolls of a green strip product lying at the carpenter's feet. Nearby, the product is shown installed running atop the floor joists. My guess is that it is some sort of foam. Like a sill sealer except just 1 1/2" wide, made to staple to 2x studs. I'm guessing that in this photo, the strip is being installed as a sound break between the subfloor and the floor joists. I was wondering if this product would be useful to staple to the exterior surface of my wall studs instead of investing in full-coverage rigid foam boards. I'm just looking to break the thermal bridging between the exterior sheathing and the wall studs. Before I saw this photo, I was imagining getting some 1/2" polyiso board and cutting it into 1 1/2" strips and attaching them to the studs. Time not a problem, cuz I'm an owner-builder and will not be paying someone else to do this tedious task. I'm in a hot/dry climate zone (California, in the hot central valley), so I don't need any external insulation. I do have to sheath the entire house in plywood because the house will be fully covered with Hardieshingle. Anyway, bottom line is I'm looking for a foam tape like in the photo to use as an exterior thermal break. Thanks to all who respond.
IMO its too thin for a thermal break. I think that its meant to keep floor squeaks to a minimum.
How would sub-floor glue work with that?
I can see the issue of remodeling work. I wonder what percetage of homeowners want more outlets after say ten years? Not that it is a measure of anything, but never have. Although, they never put enough outdoor outlets in and I have added a few over the years.
Not that this solves all problems, but I like to run a PVC pipe here and there for future pulled wires. Not an original idea either.
Like every system, no insulation scheme is perfect. The best laid plans of mice and men . . .
I'd just frame a 2x6 wall with 2x6 studs on 16" centers and then let the icynene guy go to town. If, as I have been told, the icynene gives a 2x4 wall r-19, then a 2x6 wall with icynene should be in the high 20's, r-factor wise. The icynene gives you better air seal, too. Cuts way down on drafts.
I just read your last post in this thread about spraying the attic. My climate is much milder than yours, I'm sure.(You are in Quebec, you said?) My icynene guy puts 4" of icynene in the attic, then adds blow-in fiberglass to give a total of r-44. I have done some research on the icynene, enough that I had it installed on my home I'm presently building. (Not enough to be an expert, though) My experience to this point has been positive. I think it will be very popular in the next few years. I also think it is far superior to present forms of insulation, for a variety of reasons. I don't know about pay-back over a period of years, but I'm sold on the fact that my new house is going to be toasty warm and the comfort level is going to exceed the house I'm presently in, which has 2x6 walls with blow-in-batt insulation.
I inch R Board under teh sheetrock?
What is R board? And does putting foam type boards under sheetrock make nails or screws more likely to pop, Does it cost more to hang the rock (longer screws?)?
I got mixed up on my screw length. We use 2 1/2 screws with 1 inch R Board.
The product here called R Board is a pretty HARD foam with a fibreglas reinforced skin. It's not reflective - it's dull gray in color.
Yeah it costs more to hang the sheetrock, but the difference in the insulating result is amazing.
Fonzie,
Thanks for the reply. I have never seen anyone use it or any sheet foam for that matter under sheetrock. I ahve read about, jsut don't see it.
Sure sounds like a pain with the screws and going back to double check etc..
We run strapping over the Foam board and under the SR to solve all that, miostly because it is hard to hit the studs with SR screws thru long setbacks. It can be done without by a hanger with patience.Ever seen a SR hanger with patience?;)
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And do you need to add some kind of nailing strips around the windows so moldings can be firmly attached?
Yes, there are problems like that. We have done that. We have even use the "splice boards" on the ceiling butt joints above the "R board" and it worked great.
That's the best way I know of for the money. You get a wall that figures to be R21 or so. Newer dens FG batts gets you r-15 plus the R-7 of the foam panel breaking that thermal bridge and end up with R - 22 plus an R-1 for the sheathing and siding and SR for a total of R23to spend more money I like sprayed in foam to do better on controling vapour and infiltrationinstead of batts the infiltration is also better controlled with denspack cells or BIBBs
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Like you, I have read where critics say the 2 ft module is a more efficient use of lumber and the 2X6 allows more room for insulation and therefore a higher R-value.
No doubt if you compare the strength of a 2X4 against the strength of a 2X6 the 2x6 comes out being the stronger of the two...like-wise, a 2X6 will accept more insul than a 2X4 stud....but to say 2X6 framing is more affordable isn't so.
EXAMPLE....framing a length of wall, say 16 FT long X 8FT tall...composed of a single bottom plate and a doubled top plate will require 3 plates and 9 studs using the 2X6 framing module. The actual material cost of these components amount to approx. $78.00 ( 2X6 cost in my area is 65 cents per LF)
Using 2X4s on 16 inch centers, this same wall will require 3 plates and 13 studs. The approx cost for this wall amounts to $45.60 ( 2X4 cost is presently 30 cents per LF).
This cost difference between the two systems is substantial. a person could raise up approx 27-1/2 LF of wall using 2X4s for the same money to raise 16LF using 2X6s.
Although a 2X6 is inherently stronger than a 2X4, I personally believe that a 16 inch OC framing system is superior to a 24 inch OC system . I believe this is due mostly in part on my assumption that a stud wall gains most, if not all, of its inherent stiffness after being sheathed. The sheathing keeps the wall straight and prevents racking tendencies. Sheathing nailed off on 16 inch centers allows for a closer nailing pattern and thus a stiffer wall than that using a 24 inch center pattern.
A 2X6 wall costs more to insulate as well simply from the fact that more insulation is being installed in said cavity. Will the initial higher cost offset itself by giving back lower heating bills in return? It very well should. How long to realize this return? I honestly don't know...but I'm sure there are experts who can give numbers to this equation.
Bottom line, I think the framing choice (2X4 vs 2X6) one chooses is determined by many factors. The design of the home must be considered. The availability and cost of the lumber and insulative choices must come into play. The geographic location is a definate factor...and so is the amount one has budgeted for a project.
I'm not going to say a 2X4 wall is superior to a 2X6 framed wall...or visa versa. Both have their merits, and their faults. Strictly from a materials cost point of view, 2X6 wall cost more. From a remodelers point of view (mine), I prefer 16 inch studs inside walls that require me to hang cabinetry or shelving....simply because a l;ot of pre-made shelving and cabinetry is set up to be supported (fastened to) studs that are 16 inches OC. You cant' hit a stud at each end of a 32 or 36 inch long shelf, now, can you?
That's why hollow wall anchors were invented in the first place...to ease the frustrations and loud cursing of the poor home remodeler who has to hang that handrail, or shelf, or wall fixture, or whatever, and unfortunately can't find enough solid studs to mount it to .
Davo
The claim wasn't that it was cheapest first cost. It was affordable housing in cold regions and the calculation concerned extra cost as a monthly amount on your mortgage versus savings on utilities bills which gave you actual monthly cost to the owner.
"the calculation concerned extra cost as a monthly amount on your mortgage......"
Right. So in this article you read, how many months ( or years) of energy savings did it take the homeowner to acquire before they "broke even" on the material cost differential?
If it takes 20 heating / cooling seasons to pay back the b higher costs of 2X6 framing/insulation, and the homeowner's goal was to build the house, live there 10 years or so, then upgrade to a bigger, new home...then the 2x6 framing was a detriment .....
So, what figures were calculated?
Curious to know.
Davo
Edited 12/17/2004 12:57 am ET by Davo
I can't find the article, but you're missing the point a bit. The idea was not to calculate payback time, it was to calculate monthly costs from day 1.I don't remember the numbers, but this is the principle:Let's say that the energy efficient changes made (not just wall thickness), cost $5000 and the savings are $62/month. Assuming you get 5% on your $5000, that's about 15 years to break even, right?But, in fact, the $5000 on a 30 year mortgage at 5% only adds $28/month to your mortgage, so you actually reduce your overall monthly costs - mortgage + costs to run the house - by $34/month. Obviously, I chose numbers that are too optimistic. The idea though was to find strategies (more insulation, more efficient heater) that would increase the mortgage by less than the amount you would save in energy, so it would bring your expense down right from the start. The analysis was for very cold climates like Montanna or something.
Edited 12/17/2004 4:17 am ET by tlambert
davo... we started building energy efficient / solar homes in '74 and we had to calculate pay-pack.. after a couple of years it became obvious that someone either wants an energy efficient house or they don't..
we don't calculate payback anymore..
i can tell you this... we've built three of our own houses.. each one more energy efficient than the previous..
if i build another one for ourselves, it will exceed the one we're living in..
this one has a double wall exterior.. (2x4 @ 16" oc outside... a one inch airspace...
and 2x3 @ 16" inside....
the full basement is insulated on the walls and has 2" of foam under the slab
the attic has 18" of cellulose
if we build again.. the walls will either be Mooney wall or foamed.. the attic will have 24" of cells
any slab will have foam under it
what's the payback ?... don't know .. could care less
our design criteria is 6000 degree days.. so we have a 5 month heating season
and a lot of people use air conditioning which is probably a two or three month seasonMike Smith Rhode Island : Design / Build / Repair / Restore
>if i build another one for ourselves, it will exceed the one we're living in..I didn't know you were thinking about my stuff!?!! Cool. You know where to reach me! Ha ha ha.Be round...
cloud.. sans doubt !
i was thinking Arts & Crafts maybe ?
can you tweak oneayur domes into an A&C ?Mike Smith Rhode Island : Design / Build / Repair / Restore
For a price!:)
Google returns nothing useful on Mooney walls so what gives?
dave... here's a link to the Mooney Wall discussion
http://forums.taunton.com/tp-breaktime/messages?msg=37618.1Mike Smith Rhode Island : Design / Build / Repair / Restore
Davo,
you got that right. I think people who say they don't care about the payback or internal rate of return on any investment, and insulation is an investment, are irrational or insane. I mean would you walk into a car lot and pay 25,000 for a 20,000 car and say "I don't care"? Same thing.
To say that is to say I will spend $5,000 more to insulate my house to save $10 each year. That is just plain sill to say the least. Perhaps a different S word would be more appropriate.
Obviously to sane people there is some cost benefit thinking going on. Sure some people are not going to dig in to every detail, but they are generally interested in the economics. And some are not going to ask too many questions if you are talking the difference between $1,000 and $1,200. Ok, spend the $1,200, then let's move on.
One, thing in favor of over spending on insulation if you plan to stay in a home for a very long period is that it is pretty darn likely that energy costs will rise over time making the return on investment rise over time. So "over" paying today, if not too much, could pay off.
I agree that the cost of improved energy efficiency and the payback period is something to consider. But I think you're forgetting about the other factor which is comfort. It is probably worth it to many people to pay a higher amount in order to ensure that the house that does not have cold spots and drafts
to ensure that the house that does not have cold spots and drafts
Which is more tied to the air-tightness rather than the depth of the walls. If you can isolate the temperature differences, the comfort leve usually is percieved to increase. Not leaking outside (un-conditioned) air inside is probably worth am inch of insulation.
Of course, that's the "trick" of the thing, controlling airflow while still allowing operable openings.Occupational hazard of my occupation not being around (sorry Bubba)
Quick question? If thermal bridging is a big concern on a 2x6 wall why not just have a saw kerf put into the studs at the mill =x=. A 1/4 to 3/8 web could be left thus lowering the thermal bridging by aprox 80%. Another benefit would be since this would probably qualify as a machining operation the studs could come from Canada minus the tariff.
I am really interested in this idea. Be interesting to see what comes of it here on in the forum.
It would seem to be a quick and easy way to limit the thermal bridging without overly complicating the framing operation with special allowances.
Jim, Don't you just hate it when there are five hundred ways to solve a problem all with different levels of sucess? As for the releaf cut idea. I am sure it would work, but unless it were widely practiced the cost would be hugh. don't you suppose?
And if you did that on a 2x4 you likely would greatly reduce the strutural strength.
People talk about this draft and this leak. Well, I live in the norhtwest and lived years in Minnesota, in houses built in the 50's 60's and 70's. I have NEVER been bothered with a draft. Never. NOw on a zero degree day, if I were to put my hand six inches from a window, I could feel the cold. But how much TV watching do I do with my hands six inches from a windo?
Just my take.
"I mean would you walk into a car lot and pay 25,000 for a 20,000 car and say "I don't care"? Same thing."Not exactly. It's more like walking into a car lot and saying "I'll pay an extra $25,000 for a fuel-cell vehicle and some solar panels to run it off, even though it will never live to see payback." People do that sort of thing for the same reasons that people pay more for automatic transmission or for solar panels on their house - because they want to and the added expense is worth it. Unless you're so far out that it will cost a fortune to run power to your house, building a house off the grid will not ever pay for itself unless prices of energy skyrocket.The bigger problem is that people often don't do a total cost analysis on either a monetary *or* environmental basis. For example, twenty years ago, the embodied energy in solar panels was greater than the energy they could be expected to produce. A thinking person might still have justified the action based on stimulating research, but there was no payback on that exact item in either dollars or pollution caused.It can be the same thing with straw bale. Very low embodied energy, and can be built very efficiently. However, there have been cases (according to an article from a straw-bale magazine posted at our local building department) where people decide to put the whole thing on a full-basement foundation as wide as the bales. There's so much embodied energy in that concrete, that the lifetime savings from the straw bale construction is fully negated.For many of us, it's a cost/benefit analysis that looks at where we will spend our "extra" cash to do the most for the environment. Sometimes insulation is a stupid way to spend that. If I live in a mild climate, I'm way better off to spend that money on appliances than R-50 roofs.... a bit of ramble. sorry.
tlambert, I like you fuel cell analogy. perfect.
One of my several points is that people have money to burn and they do it. They don't use any rational sense to see if it makes any sense. Ok, more power to them. I still think it is stupid. I will be fully retired (as a posed to semi retired at 45) long after they are still trying to figure out why they don't have a pot to p . . . in. Which again is a to each there own. If people love to spend money and love to work, who can argue. I just like fishing and hunting better.
jack... you sure do have a way with words , don't you?
when i said i don't care.. i should have added that i don't care to calculate the payback..i certainly do care.. and personal experience has taught me that it was all well spent
every house we've built , the energy features were always paid for by inflation..
if i were a tract builder on spec.. i wouldn't care either.. because the average consumer will not pay for those features unless they're required by code..
my customers, and myself , are very interested in energy conservation and comfort..
as les pointed out.. energy walls create rooms that are more comfortable to sit in and live in..
when you start down the road to building energy efficient homes, it doesn't take long to find out that some things have a greater return than others.. hopefully our package provides the comfort and low cost of heating /cooling that our customers demand..
but guess what.. they won't be your customers.. cause you don't talk the talk, and walk the walk..... Mike Smith Rhode Island : Design / Build / Repair / Restore
You "don't care to calculate the payback", but insist that "the energy features were always paid for by inflation".
Ok, what ever you say. You don't measure before you cut, but you are sure it ain't short. Ok, typical.
What are you hoping to accomplish with the sarcasm that couldn't have been accomplished without it?
No sarcasm. Some one says he does not care about flushing money down the Kamod. Ok, his choice. It's a free country, I think. Call it insane, call it stupid. Not that I would say that, but you or someone else might.
He said he did not measure the payback of an investment but is sure it is good. You nod your head up and down in agreement to that? Ok, what did W. C. Fields or was that P. T. Barnum say, "there is a suc. . . ".
Don't tell me what I nod my head in agreement to. I don't even do frame. I put my money--for myself and my clients--into an entirely different kind of structure. And even though I believe what I do has superior energy usage, superior strength, superior sound properties to anything else available today, I won't call all you frame builders/owners stupid or insane or accuse you of flushing your money. That's just common decency. Y'all may have different priorities. You may look at different elements on the cost or benefit side. Sheesh, just because YOU don't understand why someone makes the choices they do doesn't make THEM wrong.Now let's get the focus back on building methods and quit casting aspersions on people.
My, my, my! The point is, I am not the one to say. "I don't measure, I don't care". The tenor of your post, ie give a nod, was to support such think. I just graciously disagree. So, take a stress pill. Life is too short.
you sure got all the answers , don't you ?
after calculating payback for the first 5 years of our solar homes.. it became obvious that it was an exercise in futility.. the payback always came earlier than the projections
what were you doing in '75? did you turn your thermostat down ? did you wait in any gas lines ?
c'mon , mouth, tell me more.... what is your standard wall ? what is your design degree day ? what is your strategy for reducing heat loss and cooling gain?
have you got one ? let us in on it ...
me... i'm looking for the most practical methods of solving problems... and i haven't heard any solutions from youMike Smith Rhode Island : Design / Build / Repair / Restore
Mouth already told us his best solution is to do what his daddy did by using FG batts and plastic overalls, and stay away from the windows with his hands. Worked for his daddy so it must be good for the rest fo the world, regardless of what everyone has learned since then that he doesn't want to know about.
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Well, piffin untill you recently started using a poody-mouth I expected more from you. And I certianly can lump you with a not so elite crowd if you can defend, "well I don't mesure paybacks, but they always come in less". If you think that is brilliant, more power to you. As for me it tells me all I need to know about you and a few fellow posters. Good Luck.
.
there is absolutely nothing gracious about the way you disagree.
You came into this arguing in behalf of using FG with VB although you made it obvious that you had absolutely no idea what its shortcomings were. You have any idea how ignorant that makes you sound?
then, with no experience of your own using foams, you attack the grounded years of experience of others with plenty of good experiences. You have any idea how insane that makes you sound?
Then, you call others insane and stupid. you wanna know how phychotically elitist that makes you sound? You must have a wad of FG stuck tight in your ears. if you want to argue your poiint, do it from facts instead of assumptions. Speaking of assumptions...
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Well, if you insist on name calling, what an angry old fart.
First off, I never argued in favor of FG. Apparantly another of your numerous shortcomings is an inability to read.
Secondly, I was asking questions about foam expecting to dig deep to understand the pluses and minuses as well as teh science of the entire issue. Never once claiming command of the issues. Clearly your sensitivity in the matter proves your lack of confidence in the facts, and a shame of your arogance in light of it. Try humility. One of the pluses and minuses are teh economic issues, which brings me to the third point.
Thrid, some moron's response to the economics question was, "don't measure, don't care".
If you are so weak in your convictions as to be bothered by a question, I just can't help you. If you support the, don't measure, don't care concept, then there is no point in discussing economics either.
Very kindly, I have no intention of arguing with you. Your words say it all, you don't have to measure. You said it. If you not realize how that makes you sound, think about and live with it. Really, I have know idea why anyone would be upset by there own words. To others it may sound silly or worse or even arrogant, but to be upset with yourself?
I don't think you are talking about sane vs insane. That just makes you an azhole with words puking out of your mouth. You are talking about "percieved value" whether measured or and carefully calculated or done instinctively. But it is good to be educated about it
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Did you see the comment made about a kerf in the studs to limit the thermal bridging?
I am interested in your (and others) thoughts on this.
Maybe someone with some of that fancy FEA modeling software can tell us if it would matter.
Also, your comment about the foam on the outside - talk about having an A-HA! moment. I originally disliked the wall design that only ply'd or osb'd the corners and covered the rest with angle bracing and foam because it just seemed less "secure" than covering the whole place in sheathing - now I know that it also puts the (a) VB on the wrong side of the wall. THanks for that comment.
Many of the places I see with that wall design are probably getting batts and poly on the interior, too. Do you think that re-opening those walls in a few years will show some very wet and moldy insulation?
I am in southern WI, by the way. Heating Climate, VB on the inside.
Edited 12/18/2004 9:43 am ET by Jim
That comment about kerfing was probably meant well, but failed to take in to account the structural deficiencies it would introduce. It also would do nothing to eliminate thermal bridging at top and bottom of stud and at plates.Trying to hand nail to such a kerfed studd would be hard with the slice bouncing all over on you
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A 2X6 wall costs more to insulate as well
That's likely the only "quibble" point--at a certain percentage of wall opening, the "loss" from having openings (doors & windows) is "made up" with the deeper wall. But only up to a point (which varies by exposure & climate and everything else it can vary by . . . )
We modeled up some walls scheduled by the opening percentage, solar gain, exposure and what not. The problem was that some of the walls wound up wanting to be 2x12 framed for the insulation "make up." That was a non-starter then and now (and, partially, an "artifact" of the software--no depth of wall really makes up for a patio slider and two side lights, facing North, at 44º N lattitude when the opening is over 68% of the wall).
A real problem, in my book, is that there is no realy good residential modeler. There's versions of the long-form ashrae calcualtions, and some of the other calculation models, true enough. But nothing that really can map the difference between, say, thermally-broken windows versus solid vinyl; or 1" rigid foam added on, or that sort of thing.
The "devil in the details" of it being the structure and application of the calculus--do you just sum all of the R values in the "average" wall section, and treat the wall as a uniform mass? Or, do you try to factor in the transmissivity and thermal lag?
Occupational hazard of my occupation not being around (sorry Bubba)
"thermally-broken windows versus solid vinyl; "You model the thermally-broken windows with a hunk of rock <G>"The "devil in the details" of it being the structure and application of the calculus--do you just sum all of the R values in the "average" wall section, and treat the wall as a uniform mass? Or, do you try to factor in the transmissivity and thermal lag?"In googling in the past I have seen some alternate calcuations of "effective" R values for high mass walls. And some codes allow for a smaller "sum of the parts" R value for high mass walls.That same googling showed some test that had been run and large gains in the effectiveness of high mass walls in climates with large daily temp swings such as in AZ. If I remember correctly in the area of 30-50%. While places like Mineapolis and Miami where close to zero and places like Nashville 5-10% improvement.
That same googling showed some test that had been run and large gains
There's the rub of it--which modeling software was used, and was it run to get a result? While in grad school, I found that there were several places that made good test subjects (Wichita Falls, TX; and Wichita, KS) because they have near similar hdd & cdd, and enough latitude separation to be able to factor out solar gain model differences. I was flat out told that using those sort of sensible considerations was ineffective, and there was never enough "dramatic" difference to "sell" a particular model. And this without addressing the deficiencies in using a commercial building modeler to model a residential structure.
But what point is there in even presuming that anyone would be daft enough to try and make a structure suitable for Phoenix, AZ "work" in Portland (OR or ME)?
Back to the thread topic--a person could make a case for 2x8 dimensioned walls, here at 29º N., using two separated 2x4-framed walls. With about 250 cdd versus 40-50 hdd, a model of a "refrigerator under an umbrella (sun shade)" makes a certain sort of sense--until you start ciphering the costs out.Occupational hazard of my occupation not being around (sorry Bubba)
Les,
There was a guy here in town that built a house like that (it was a funded study of some kind). I went to the open house and saw it partially completed. The building inspector moved into it.
It had two separate walls separated by a space, el boxes caulked, etc, over this and over that. It turned out too tight. He tried a heat exchanger but I think I was hearing in the lumberyard that problems continued to develop.
Just read all the posts on this thread and thought I would add a little info on my project. We are currently building a vacation home 2500 sq. ft. We have a limited budget so do not want to spend any money needlessly but we plan on retiring to this home in approx. 5 years. We are building in the mountains on a lake at a higher elevation (that equals cold winters) at this point we have an income and enough funds to build this home but when we retire we will be on a limited income hence we are willing to go overboard on the insulation component now so our operating costs are lower when we retire.
We are framing the exterior wall with 2 x 4 plates and 2 x 4 studs at 16" insulated with blown in cellulose than 1" foam on the interior and than another 2 x 3 wall framed against the foam on the interior for all wiring and plumbing than drywall. The only reason for using 2 x 4 for the exterior wall is we have our own bandsaw mill and want to use the smaller trees for the mill so we can leave a lot of the larger doug firs standing. Just thought I would share one reason why some people don't worry about the payback.
We have discussed this whole thing a half dozen times before. Try the archives - advanced search for terms like R-value and Mooney wall, or Thermax
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