Question? I’ve been reading alot lately about the trouble with walls harbouring moisture because of poor wall design and construction details.i.e poor air barrier, poor exterior insulation installations. If anyone with experience as to which combination of building materials would construct the most efficient wall.2×4 or 2×6 , r12or r20,Polystyrene or polyisocyanurate,tyvek or typar,tuck tape or no, please weigh in. This wall would be in a Michigan type climate and I’m looking for the most return(energy conservation) for my buck. I’d sure appreciate your responses.Thanks!
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Look at the Mooney Wall:
http://forums.taunton.com/tp-breaktime/messages?msg=65624.1
ICFs are great too & have other features in their favor (I am partial to concrete)
Some like SIPs too...
Best wishes.
The world's best wall in my experience is the REFORM wall. That stands for rigid external foam insulation over rubberized membrane.
Sheath the 2x4 wall with osb or plywood. Cover that with a peel n stick membrane, using the same membrane to form pan flashings and head flashings. Install 2" of polyisocyanurate foam panels outside that. There are various details for what comes next depending on your exterior facade. There is also a framing detail that extends the window rough frame to the outside face of the foam insulation so that your facade can return to it as usual.
If you are interested in this technique, I can walk you through the details.
This system works well in conjunction with an unvented sealed attic. I prefer to place my attic insulation in sheets on top of the roof frame but will spray foam in the rafters if it is a retrofit or a complicated roof design.
The idea is to get the entire frame inside the thermal and hygric envelope. This eliminates all moisture issues in the wall and roof structure and builds a much tighter and more efficient building.
More insulation can be used if desired but with this system, thermal bridging and air leakage is eliminated so the r-value does not have to be as high as you might imagine to achieve great performance. Cost is minimal, outside of a learning curve for the new technique. There are no new materials though and trades can pick it up pretty fast.
Ray, could you give some info on the peel and stick pans? I've made them, but they were clunky, and seemed marginally effective at best. "But to be honest some folks here have been pushing the envelope quite a bit with their unnecessary use if swear words. They just put a character in to replace a letter. But everyone knows what they're saying." Sancho
Check out these pictures. I have lots more but this should give the general idea.
There is only one planet earth. How many chances do you think we get with her?
Greetings Ray,
What an informative thread. Thanks.
Many viewers of Breaktime are on a dialup and cannot download real large files.
To assist the dialups with your photos, keeping the KB picture size to preferably 50 to 75 KBs or at least under 100KBs goes a long way.
It is overly time consuming for dialups to open large files if they can at all.
Cheers
Edited 1/23/2007 1:16 pm ET by rez
Where does the moisture go? In the reform wall system.
In a Reform wall, interior moisture never finds a cold surface to condense on because the sheathing stays at room temperature. There is no insulation in the stud cavity. Exterior moisture stays outside. In the winter, moisture levels can be higher than might be otherwise safe, needing only stay below the level where window condensation is a problem.
This creates a very airtight house so mechanical ventilation is required. The air in your home is now completely under your control. You bring in only the amount that is needed to maintain fresh indoor air and you bring it in through a filter to remove dust and pollen.
Energy efficiency is outstanding. My home is 3900 square feet of conditioned space and uses less than 1000 KWh per month on an annual average. We heat with a heat pump. We are located near Austin TX so air conditioning is our biggest energy consumer normally. We use propane for hot water and our cooktop. (11 gallons per month)
I am currently starting a 7000 square foot net zero home using this system.
There is only one planet earth. How many chances do you think we get with her?
Thanks Ray for answering my Question about the moisture, I'm hip about using rigid over the ext. sheathing to eliminate the dew point from forming on the surface of the sheathing , do you also use a barrier behind the interior wall surface, like over the studs behind the sheetrock? I don't know if my inspector up here will allow a house to go up without insulation in the walls.
I'm no expert, just a diyer with time for research.I just built my house sort-of reform...2x4 plus osb, the 1" polyiso, treated as the weather barrier, all seams were taped and the seams were offset from the osb. I flashed the windows to the exterior of the foil board.Inside I used unfaced r-15 fg batts, as I understand building science, my one and only vapor barrier is the foil board exterior.I am in Southern IL, considered a mixed humid climate.I really should have followed through with the insulated roof and conditioned attic, but things were to far along in the process, before that light finally came on.forgot to add.I haven't moved in yet, hanging rock now, so I have absolutely no idea if all this extra is worth the trouble or not, especially long term...;)
Edited 1/21/2007 5:10 pm by bigal4102
ray... we did some similars.....
one variation was 2" polyiso on the studs and 1/2 ply over that for a nail base
we used let-in T-brace for racking resistance...
next house, the BI pointed out that the T-brace wasn't rated so we put the ply back on the studs... blocked everything we needed for trim and windows/doors and used long nails for the siding
we stopped using polyiso when i went back to one of the houses to put in a new window.. we found the polyiso completely riddled with burrowing vermin
on another house we put the polyiso on the interior..
during a walk-thru with the owner, before we put up the blueboard, we heard a horrendous noise in one wall.. i cut the wall open and hundreds of carpenter ants came running out...
i advised the owner to get a pest control guy out
anyways... the only foam we use now is PERFORMGUARD, borate treated EPS
i assume your siding is something like a vinyl siding with long nails ?Mike Smith Rhode Island : Design / Build / Repair / Restore
I've considered using performguard below grade as a slab insulation but it provides a hidden path for termites and requires me to have infinite confidence in Termidor to keep them out.
We haven't had problems with pests in the foam but I've heard it can happen. We cap the bottom of the foam with treated lumber. (usually borate treated) Borate treated EPS is a good solution, though a little less r-value and a little higher cost.
We use commercial masonry anchors with long screws for masonry walls. We use treated furring strips with long screws for siding or stucco. We screen the vented cavity behind our siding.There is only one planet earth. How many chances do you think we get with her?
Thanks for the pictorial.We use a flashing system on brickmolded doors and windows, modified from a JLC article. Makes kind of bitithane fin.In your pics, are you adding another layer of rigid foam that will plane with the "sub" window frame?And, how do you turn up the pan on the inside of the window sill? We cut a narrow strip of bitchithane that sticks to the sill and turned up pan...but it is less than an elegant solution...and a real pain at door bottoms...We see door bottoms as the weakest link in most flashings...we live in mold central, so there's a lot of pressure washing...it doesn't take much to blow under a door sill...not that I see any moisture getting within 50' of your walls<G> "But to be honest some folks here have been pushing the envelope quite a bit with their unnecessary use if swear words. They just put a character in to replace a letter. But everyone knows what they're saying." Sancho
I was looking for some pictures that show the process further along but they aren't on this computer and the quicktime videos that I have of the process won't load onto this website. I'll go a little further now in my explanation.
First of all, in the pictures you see the window framing furred out past the foam because this building got hardi siding installed over treated furring strips. The furring strips came out flush to the back of the brick mold and the siding killed into the brick mold. The furring strips were treated 1x6 that was ripped to 1x3 in this case. It was attached through the foam into the studs with 4" screws.
As to the pans and window wrap: Notice the black strips installed below the window. These extend up into the membrane pan. They are made of a felt fabric that is designed as a protection course for waterproofing systems. This functions as a wicking strip to remove moisture from the pan in case of a leaking window. more on this later.
After the window is installed, strips of membrane are installed around the window to seal it into the membrane skin. Start at the bottom, sealing to the bottom of the window, over the wicking strips and down onto the wall. This strip would trap moisture in the pan, if not for the wicking strips. Continue up the sides of the window, sealing the brick mold into wall skin. Finish by sealing the strip that was left loose at the top to form a head flashing. The backing was left on this flap at the time of installation to allow for this.
Inside the window, turn the pan membrane up the backside of the window and staple to the bottom of the window frame This will later be hidden and secured by the window stool. Doors work the same way, but with the addition of a small shoe mold type trim that is usually installed anyway. There are small details at the corners where the strips are notched and stretched to overlap each other that I wish I could show you, but this should at least move the discussion forward.
Please note that this system should be installed with a focus on air tightness. It's primary function is as an air barrier system. The required wicking strip should be the only path for air leakage with this system. When used with brick molded windows, the weak link may be the connection between the window frame and the brickmold. Check out your window construction and add a flexible sealant at the joint from the back side if you deem it necessary.
No time for proof reading. Sorry if I missed any typos or gaffes.There is only one planet earth. How many chances do you think we get with her?
Thanks for the explanation. I would love to see some pics of the inside details, if you get a chance. The felt wicking strip makes good sense. Who supplies that?As far as the brickmold/jamb sealing, the JLC article is in January 2006, p.61. Extremly effective. "But to be honest some folks here have been pushing the envelope quite a bit with their unnecessary use if swear words. They just put a character in to replace a letter. But everyone knows what they're saying." Sancho
I'd read somewhere that polyiso was available in a borate
version, but I cannot google any up. I wonder if it's
only EPS.
Thanks for your insight. I've never heard of a reform wall in these parts.Some questions still linger though. What is the idea behind the membrane besides it being a rain sheild?Who would manufacture your product? Did you chose isocyanurate over styrene for a particular reason ? I/m interested because like you I to am searching for a reasonable costing wall system with performance results.And being earth concious at the same time.Have you had any feedback on your system? Thanks again to all your replys.
Polyiso gives a higher r-value per inch and costs the same per sheet. It also comes with a foil face which provides a radiant barrier when an airspace is used. The membrane provides a self sealing superior drainage plane but it's primary purpose is as the air barrier. In our humid climate, it also functions to reject exterior water vapor, which reduces latent load in our houses. This further reduces our air conditioning load.
I've used this system or a version of it on about a dozen homes so far, perhaps more. The 7000 foot home I'm starting now has 2200 square feet of glass area and still has been figured at only 8.3 tons of required cooling by our mechanical engineer due to the use of good glass and this wall and roof system. Proper orientation was also considered in siting the building. Our design criteria was for 100 degrees. We typically experience 30 or more days of 100+ weather and 108 happens more than it should.
Last week we were iced in for four days. Temps spent several days below freezing. Our heat pump ran about half the time and the electric backup strips have never activated. The home is always very comfortable.There is only one planet earth. How many chances do you think we get with her?
Ray
Two more questions in regards to the reform wall. In our building code we are required to have at least an R17 minimum insulation in exterior walls.Polysio 2" thick i'm guessing is about R12-14.Could traditional fibreglass be used in conjunction with reform or would that be counterproductive.Also we are required to install 6mil vapour barrier on inside surface of the wall. Is that also an issue with reform?The mindset of many builders is the higher the fibreglass r-value the better.I'm just beginning to try and understand the importance of air and moisture migration control.So much info for me to understand and so small a brain. Hope to hear your response.
Check out the DOE website and look for their whole wall R-value calculator. You will find that without thermal bridging the 2" of foam is equivalent to about r-19 of cavity fill and then the superior airtightness makes ir really outperform an r-19 cavity fill wall by a large margin. I have never had an inspector fail to see the light after a short discussion. The codes will slowly catch up, just as they have with unvented attics.
Fiberglass could be added to the interior at an added cost and the sheathing would then experience about half the temperature and moisture extremes as opposed to none. I see no problem with that. I would just prefer to spend that money on better equipment or the like. Really, if you try to justify the cost of both insulations to a client they will wonder why you use the foam if you already have fiberglass. The overall system cost goes up along with your difficulty in selling the superior system to your client.
Skip the fiberglass and the poly. Tell the inspector that the membrane is the vapor barrier and that it IS on the warm in winter side of the wall. (inside the insulation at least)
Come over to the dark side.There is only one planet earth. How many chances do you think we get with her?
Ray,I've read you past posts about your system and like it in principle. This past september's issue of Energy Design Update had an article about exterior styrofoam, (XPS) shrinking and leaving some significant gaps over the long hall. This causes a problem if its your only weather barrier, but if you flash the joints with peelnstick or cover the whole house like you do I imagine the gaps aren't a problem from a rain penetration point of view.However, given that you have no other insulation, won't any shrinkage in the foam panels provide thermal short-circuits and condensing surfaces?Does polyiso not have the same shrinkage problem as XPS?-Brian
Polyiso will not shrink. The gaps would cause heat loss but would not lead to condensation except possibly in the most extreme cold climates. The surface area exposed to cold from the exterior would be very small compared to the surface area exposed to the warmth from the interior. It would be hard to imagine the inside surface of the sheathing at these small lines becoming cold enough to build up condensation.
Love that publication but I'm not able to justify it's subscription cost. I'd like to see the article.
I think small gaps would be a small problem but only from a heat loss or gain standpoint. I think I'll set up an experiment to test the moisture collection issue. There is only one planet earth. How many chances do you think we get with her?
you are looking for SIPS
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