Pros and cons of Grace Ice and Water compared to Tyvek Drainwrap
jamestimmerberg
| Posted in General Questions on
If applying a WRB under rigid foam insulation, what are the pros and cons of using Grace Ice and Water Shield compared to Tyvek Drainwrap, in terms of protecting the sheathing, serving as an air barrier, difficulty of installation, flashing details, and any other reason you might prefer one product over the other to serve as a WRB? Assuming that the Grace product is more expensive, do you believe that it is worth the additional cost on a 2,000 square foot home in Zone 5?
As always, any advice or opinions are greatly appreciated.
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These products aren't in the same category. I&WS is a roofing product, and it's hard to see any advantage to using it on walls. If there are particular areas of your project that might benefit from a self-adhering membrane, then I would look at Vycor, but it should only be on small areas of the wall that are still vulnerable with correctly overlapped layers of more usual materials.
I thought that they used Ice and Water Shield as a wrb in Persist and Remote wall systems. Do they use a different Grace product?
My minimal understanding is that those wall systems are for extremely cold climates, and that yes, you would possibly use a fully-adhered membrane. Is it cold enough where you are that people are building with those systems?
James,
The PERSIST wall system (as originally conceived) places all of the insulation on the exterior side of the wall sheathing. Stud bays stay empty. If you follow this approach, you can safely use a rubberized membrane like Grace Ice & Water Shield on the exterior side of the sheathing.
If you deviate from the PERSIST method by switching from R-20 or R-24 foam to just a thin layer of foam, or by adding insulation between your studs, then installing a rubberized membrane becomes risky.
In a wall with some insulation between the studs, and some insulation on the exterior side of the sheathing, you definitely want a vapor-permeable WRB rather than an impermeable barrier like Ice & Water Shield.
The PERSIST approach was developed in the 1960s before high-quality European tapes were available. The first approach to installing a PERSIST air barrier was to use torch-down membranes. After a few disastrous fires, PERSIST builders switched to rubberized asphalt.
Now that it's easy to buy European tapes designed to tape sheathing seams, builders have many more ways to create a good air barrier at the sheathing level than they did in the 1960s. I would advise you to tape your sheathing and use a conventional housewrap.
That said, if you are a PERSIST purist, and follow the PERSIST approach religiously, there is nothing wrong with the Ice & Water Shield approach.
P.S. to David Meiland: The PERSIST approach works in all climates, not just cold climates.
Martin,
Am I correct that, even if I use R-24 exterior foam, you would still recommend taping the plywood sheathing and using the Tyvek Drainwrap over the Grace product, and that you don't see any real benefit to using the Grace product if I am taping the sheathing seams?
James
James,
Every wall needs an air barrier and a WRB. Grace Ice & Water Shield can perform both functions, and can perform them well, as long as all (or almost all) of the wall's insulation is installed on the exterior side of the Ice & Water Shield.
But there are less expensive air barriers and WRBs. You should choose the products you prefer.
The proof is in the pudding. Many builders have achieved very low levels of air leakage (as verified by a blower-door test) with taped sheathing. You don't need Ice & Water Shield for a good blower door result.
Similarly, you can get good performance from Tyvek or Typar as a WRB, as long as the housewrap is installed carefully, with proper laps, and is well integrated with quality flashing.
There are lots of ways to build a wall. You should choose the products you are comfortable with -- the products you want to use.
Hard to see the need for I&WS over the sheathing, when you can much more easily tape the sheathing, you're installing foam over the sheathing, and you should probably tape the foam too. Isn't the foam enough of a vapor barrier?
I&WS is expensive, and placing it over the entire wall surface of a house, especially a two-story house, would be a major ordeal. You can't simply unroll it along the wall as you would a roll of felt (or better yet 9-foot housewrap) and you will need extra hands to peel the backing and keep it reasonably straight, while avoiding it stick to itself. And, it won't adhere agressively to the sheathing unless it's fairly warm, so the headache would be even worse in cold weather.
I chose to use a self-adhered membrane on my new house in zone 7 (eastern North Dakota). I didn't use a Grace product, rather an Owens-Corning product called Hydroseal 3000. Same concept, as far as I know. I got it on sale and did my whole house (approximately 2000 sq. ft.) for approximately $1000. So it only really cost me about $700 more than using a traditional WRB. My walls are OSB, then membrane, then 6" of EPS foam, then furring and cladding. With that much foam, the walls will need to dry to the inside, regardless of whether I have a vapor impermeable membrane or not. I opted for this method over taping OSB seams or taping foam seams simply because it seems like a more robust system in the long term. I'm planning to live in this home for many decades and I wanted to have as airtight construction as possible. The cost of going with Zip OSB and tape would have honestly been more than going this membrane route. There are a few caveats though: first is that it really is a bugger to install. If it's too cold, it doesn't stick well. If it's too hot, it just turns into a huge asphalt mess. I found that about 70 degrees was perfect weather for it. Also, if you do use a membrane, install your OSB with the smooth face OUT. Membrane sticks way better this way. I'm attaching a picture of my membrane job. I taped the top of the membrane with 3M 8067 tape and terminated the bottom with a high quality mastic.
Adam,
Did you use a primer? I've found peel and stick membranes are a lot easier to install if you do.
Malcolm, I did not. I also did not install the OSB with smooth side out, like I should have. Halfway through the project I thought about purchasing primer, but I opted not. Overall, it stuck well and once the foam and furring was attached (16"o.c.), the membrane was solid. Rolling with a laminate roller, especially on the overlapping seams is vital.
Adam,
Although it can be a pain to install, my experience with membranes is that the adhesion seems to get better over time. I have a small piece of peel and stick on my hammer-tacker than has been there for over twenty years. Neither god nor man could get it off now. I bet that if you removed some of your siding you'd find the same with your membrane.
Adam,
1. Did you do anything with the EPS joints, or did you simply leave them open?
2. Did you use any interior insulation?
3. Did you have any trouble attaching the furring through 6 inches of foam? I know that some builders routinely use thick foam. But other people have indicated that it would be challenging to hit the studs. Any thoughts?
James,
I used canned foam on the EPS seams anywhere there was a gap large enough to inject foam. I used two layers of 3" EPS. I didn't get too carried away, simply because the foam isn't my WRB. I did take care, however, to fill screw holes with foam. Since the screws were pretty expensive that I used for the second layer of foam and since they are a potential source of thermal bridge through the OSB, I removed them as I was installing my furring strips and filled all of those holes with spray foam.
I am going to install r-11 fiberglass in the upstairs walls, which are 2x4 and I found a ridiculously good deal on r-25 which I'm going to stuff into the 2x6's on my basement walls. Even with effective r-20 in the basement walls, I will wind up with about 55% of my wall insulation on the exterior, which I believe will keep my sheathing warm and dry. I am going to use the Airtight Drywall Approach to form an interior air barrier on my walls and ceiling.
Attaching the furring strips was difficult to get the hang of. 8" timber screws would have only penetrated my studs by about an inch so I chose to go with 10" timber screws. I make my measurements as accurate as possible on the exterior, but I did miss a few studs here and there. The problem when you miss is that it's often hard to tell if you missed left or right of the stud. I used approximately 850 screws total and maybe missed about 40 or so. Like anything, it takes time to get the hang of. I predrilled the screw holes in my 1x4's. I highly recommend also drilling a countersink so that no part of the screw will be proud of the furring. That way your siding install will be nice and flat.
James, here are a few pictures of my project. Let me know if you have any questions.
Thanks Adam.
When attaching fireing strips to 2" of foam, what size screw do you reccomend? Four inch? Or longer?
Joe,
Furring strip plus 2 inches of foam = 2.75 inches.
A 4" screw would penetrate the sheathing, and would be embedded 3/4" in the stud. That's not much.
What you want is a 4 1/2" or 5" screw.
Ideally the screws should penetrate the stud by at least 1.5", and given the moment-arm carrying the weight of the siding, cheating that by even 1/4" isn't a great idea. Go for the 5 inchers, and sleep well at night during major wind storms.
Adam thanks for posting the above pictures and to Martin and Dana for answering the length of screw question. I'm also interested in your view on the type and size of fastener attaching hardie vertical panel to the furring strips. I'm more interested in using screws than nails so I can remove the siding at will, if required. I was thinking about a 1 1/4" screw, something like this.
http://www.amazon.com/dp/B003IN9HWI/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=2O46K335XESSM&coliid=I29JB0CAOZLUV
Dean,
I've screwed relatively small areas of Hardi Plank successfully. Hardi panels are a bit more crumbly. Those screws will be fine but there will be a learning curve to sinking them flush without pull through.
Are you using Hardi trim over the panels? That's where the fun starts. Nailing through that much concrete-based material is difficult without pre-drilling and I'm not sure what screws would look like in the trim.
Hi Malcolm. Thanks for the feedback. My plan is to do an open joint rainscreen using vaproshield reveal shield as the waterproof membrane. I like how it's black and blends into the background. I also intend to paint the 1 x 4 vertical furring strips black as well. Seen here.
http://vaproshield.com/
I noticed the company in the link below use screws in their rainscreen application. They use a #8 woodscrew with hex head so that's another possibility.
http://blog.buildllc.com/2008/03/rainscreens/
From what I've read the risk with the hardie is if it gets wet at the back with nowhere to dry it's a goner after so many years. The good thing with the open joint system using screws is the vertical panels can easily be taken off and replaced if there is a problem. With nails it would probably all just crumble and fall apart. I plan to paint the back side of the hardie as well.
I asked a similar question of buildllc (last question on the blog link above) and they mentioned they attach the furring strips to the sheathing only and not the studs. I wasn't sure this approach would provide the holding power for the siding. Anyone know the building code on this?
Dean,
I hadn't heard that about the Hardi. My own unscientific test was to place pieces of both the siding and panels in a mud puddle next to a stream and left them half-submerged for a year. They emerged relatively undamaged.
Our code here in BC allows us to fasten the furring to the sheathing rather than the framing if the sheathing is:
a) 14.3mm lumber
b) 12.5mm plywood, or
c) 12.5mm OSB.
I like the idea of attaching your panels with gasketted screws. It would be an interesting part of the aesthetic, although you would have to be really careful with the placement.