Comments on: Be a Controlling Building Enclosure Control Freak with Control Layers

By: Cameron Taylor

Cameron Taylor — Sun, 30 Sep 2012 07:06:37 +0000

So if I know (or at least
So if I know (or at least study their writings) Joe Lstiburek and Frank Lloyd Wright, I'm set to make a great building? Yes! Art and Science as one. As Joe himself has said, when buildings are beautiful, people tend to take care of them.

Therefore make it durable, beautiful, and truly great shelter!

By: Skye Dunning

Skye Dunning — Thu, 06 Sep 2012 15:13:13 +0000

M. Johnson – The need for
M. Johnson – The need for protecting from bulk water entry may be well understood, but unfortunately you actually can’t see the water until much later (after the warranty period has expired). For this reason more than any other, builders consistently get it wrong. We do moisture diagnostics many times where there is plenty of blame to go around. I have a phrase I often use: “We could argue about whose fault this is, but I know whose fault it’s not, and unfortunately that’s who is going to pay to fix it.”

Kim Shanahan – I agree with Allison about enough exterior insulation (controlling temperature so you don’t have a condensing surface in the wall). Notice that he didn’t say how much that would be! Which illustrates the point that you could easily get that wrong. Like Allison, I’m from the SE so you should take this with a couple grains of salt, but I think you’ll have lot’s of vapor pressure from inside to out in the winter, & not much coming in during the summer months because it’s such a dry climate. So I would think a class 1 vapor retarder (we’re not supposed to say vapor barrier any more y’all!) would be a good idea. Regarding the air barrier (air retarder?), you have exterior layers that should be able to be sealed so that you don’t need one inside. But then you also have to top & bottom plates to think about. I find that these areas are rarely sealed well enough to trust. Also, you end up relying on caulk, glue, tape, etc., that is outside which I also don’t trust over time. For these reasons we always install an air barrier under any T&G; type material inside. We use Tyvek because it serves that purpose & has a sky-high perm rating (~50) so we’re not putting a tight vapor retarder on the inside in our climate.

By: Chuck Lohre

Chuck Lohre — Thu, 06 Sep 2012 04:27:09 +0000

Hi Allison, Janet and I live
Hi Allison, Janet and I live in the Frank Lloyd Wright Boulter House designed in 1954 and built in 1956. We've registered the home for LEED Certification and are currently working on the Integrated Design Charette for the improvements. The home is a passive solar design tucked into the hillside. The home inspired me to get involved with the Green Building movement and we Certified our offices LEED Platinum last year. Learn more at our Green Building Division www(dot)Green-Cincinnati(dot)com.

By: Corbett Lunsford

Corbett Lunsford — Thu, 06 Sep 2012 01:29:31 +0000

Allison, you are such a rock
Allison, you are such a rock star. Let's hang out at the conferences in the spring. Keep writing the good stuff!

By: Amanda Evans

Amanda Evans — Mon, 03 Sep 2012 05:35:36 +0000

Hey Allison, we're in New
Hey Allison, we're in New Mexico (Kim and me) and vapor barriers are not even in the code. Neither interior or exterior. Just like Joe Lstiburek recommends.

By: Allison Bailes

Allison Bailes — Mon, 03 Sep 2012 02:58:13 +0000

M. Johnson
M. Johnson: Yep, the hip bone's connected to the thigh bone.

Paul P.: Great questions. Yes, housewrap CAN be an air barrier but I wouldn't use it that way. I'd seal the sheathing. Yes, foil-faced foam board can control heat, air, liquid water, and water vapour. Not all peel-and-stick membranes are vapour barriers, though. Check their permeance. Also, I linked to my earlier article called Vapor Retarder? Vapor Barrier? Perms? What the Heck?! at the bottom of this article. If you click over, you'll find a link to an article by Joe Lstiburek that has a lot of different assemblies that work and it tells you what climates they work in.

Kim S.: If you've got enough exterior insulation, the vapor barrier inside should not be necessary. If humid air gets into the wall cavity and finds the sheathing, it should be warm enough not to cause problems. Martin Holladay wrote an article about how much foam board you need at greenbuildingadvisor.com. You should be able to find it easily with a quick search.

Cameron T.: Hadn't heard that story about the dripping yet. Thanks. Also, you may like this Venn diagram of those who know Joe and Frank.

Green Curmudgeon: Great point. Thanks for mentioning it here. I can't put everything in my articles for 2 reasons: (i) I don't always know everything, (ii) I like for smart, experienced readers like you to make the articles even more useful.

Debbie: Ah, yes...a perfect world! Until we get there, though, we need people like you to keep educating and doing the right things.

erika: Absolutely! Using the right materials and installing them properly is critical.

John P.: Good point. I don't know of any building scientists who are indifferent to resiliency. We all want buildings to last when we put a lot of resources into them, and we can certainly learn from the old buildings that managed to survive. I'm sure there were plenty of older buildings that weren't so resilient, though, and also, the conditions in our buildings now are much different with the high degree of conditioning we do in them. But resiliency is definitely a good thing.

Jeremiah E.: Well, house wrap MAY be an air barrier, if installed properly. See the article called 5 Reasons House Wrap Is Not an Air Barrier that I put in the Related Articles above.

By: Jeremiah Edwards

Jeremiah Edwards — Tue, 28 Aug 2012 23:36:22 +0000

@Kim Shanahan, <
@Kim Shanahan,

The nice thing is that you you already have the makings of an air barrier already and may already have one installed. What I mean is that the Tyvek building wrap is an air barrier already, but needs to be properly installed to be effective.

1. Every seam needs to be taped and properly lapped to shed water.

2. Every penetration (e.g. conduit, wire, pipe, dryer vent, HVAC penetration, etc.) has to be taped and sealed to the building wrap to seal the penetration.

Remember that air barrier have to go on all 6 sides of the building. Not have the ceiling or floor sealed for air infiltration greatly reduces the effectiveness of air sealing the walls.

Jeremiah

By: John Poole

John Poole — Tue, 28 Aug 2012 02:20:51 +0000

Allison,

Allison,

I totally agree with all you've said here, especially the part about controlling liquid water.

However, I'm eternally fascinated by how both workmanship, and what is (or what is though to be) the proper way to build control layers has evolved over time, and has almost invariably been driven by cost considerations, more so than anything else.

Consider that, in the distant past, exterior wood siding and trim in a reasonably well-built house was carefully scribed to fit tightly together, keeping both air and water out. There was no need for a secondary drainage plane -- the exterior was the drainage plane.

In time, of course, frames settled and boards shrank, and houses became drafty and prone to moisture infiltration. But that same draftiness usually (though not always) allowed a wet assembly to dry out quickly, and this observation is probably what led to trades persons of latter days cultivating the misconception that "buildings need to breath", when that actually was never intended by earlier builders.

Of course, all that measuring and cutting and fitting together of the weather shield required a great deal of skill and time, so in the interests of reducing costs, we eventually abandoned it all in favor of mass produced and easily installed exterior siding and trim, and this necessitated the need for a new, secondary layer (likewise cheaply produced and reasonably straight-forward to install) that now takes on the function of a true weather shield.

Now, an earlier comment here, posted by Erika, states (to the effect), what happens when foam panels shift in time? Or tapes open up? What then?

Well, it's interesting to note that the buildings of old that survived despite their leaky weather shields demonstrated a certain degree of "resiliency", but that resiliency was never actually intended, nor designed for. It just came about by chance (and then again, only in the buildings that survived moisture infiltration; not all did).

So, I think a key lesson from the past is that control layers are nothing new, and that we should design them in such a manner that they're not just effective when perfectly assembled, but also exhibit some degree of resilience or fault-tolerance, by intended design, in order to be considered ideal as control layers. Even if this means costlier production and installation.

Just as Wright was indifferent to water dripping in from his roofs, modern building scientists ought not be indifferent to resiliency as a fundamental design concept.

My $0.02, anyway :-)

~John

By: erika

erika — Tue, 28 Aug 2012 00:08:35 +0000
another important issue that
another important issue that was not discussed within any of your points is workmanship. a material or wall construction is only as good as the installer- and, for that matter, the logical long-term performance of the installation. for example, rigid board works great as a drainage plane as long as the joints are all taped/sealed and there is absolutely no relative movement of the boards. but what happens if those seals are not completely continuous? or if a slight amount of settlement of the boards occurs (it will)? better have a continuous backup to keep water out...

By: Debbie

Debbie — Mon, 27 Aug 2012 21:40:11 +0000
Hello..control freak here.
Hello..control freak here.

just a lowly energy rater here but I want to see felt over drip edge, all seams of foil/foam sheathing on exterior of walls taped, all penetrations sealed before cladding, ICAT can lights, air tight drywall

and calcs for hvac sizing,

duct sizing & design. and thats just the shor list.

In a perfect world architects would design with efficiency in mind. ducts in conditioned space, wide overhangs, etc.

tradespeople would know their jobs, seal their own holes and everyone would pass a blower door & duct leakage test.

until then..control freaks make good healthy houses.

imho.