Holes Keep Walls Dry – Fact or Fiction?

It seems counter-intuitive to add holes to a wall to keep the building envelope dry, but it is a necessity in rainscreen building envelopes. In preparing for a presentation we will be doing at the Sealant, Waterproofing & Restoration Institute 2010 Fall Technical Meeting this October, I came across an excellent article by Brett Newkirk entitled, “Creating Holes to Stop Leaks” in the August issue of The Construction Specifier. If you have any reservations about the necessity of drainage in rainscreen walls, I encourage you to read this article.

In summary, Newkirk posits, “Holes or weeps are needed in buildings constructed using water-managed cladding systems…because it is anticipated that water will penetrate the veneer and drain down the underlayment and exit to the exterior.” We need to provide a drainage plane and weeps (holes) at the lowest point in the wall to make this possible! According to Newkirk, “The only type of wall not requiring holes is a ‘barrier’ system…and that is an extremely difficult system to successfully achieve 100% of the time.”

So what’s the quick take? In MTI’s opinion, and it is an opinion based on testing and research, if you are building with a rainscreen building envelope, you need to provide a drainage plane and weeps (holes). The drainage plane needs to be a predictable void behind the veneer; it also needs to be a predictable pressure equalization plane. The weeps are an integral part of this drainage plane system, and they need to be placed frequently and at the lowest point of the wall.

Newkirk goes into great detail about the why and where of “holes”. The article is available online, and I encourage you to read it. Those are my thoughts, as always, I welcome yours!

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Trying to Do the Right Thing Sometimes Creates Unintended Negatives

I was doing some online research yesterday and ran across several interesting articles/URLs discussing the unintended consequences of tightening buildings to save energy. One thing they all had in common was that creating a tight building envelope more often than not leads to SBS. Building envelopes that can’t drain or breathe lead to entrapped moisture issues. It doesn’t take a great deal of effort to find information related to this issue, and I encourage you to do so. It is this very idea that has lead to the tremendous interest in the rainscreen or curtain wall method of building.

MTI has done a great deal of study on this issue as have many of the recognized building envelope moisture management authorities including Lstiburek, Burnett, Straube, Karagiozis and Williams. ASHRAE commissioned a study of air movement in walls recently, and the report is well worth reading. MTI has a report on Sure Cavity Moisture Testing that specifically addresses how little entrapped moisture it takes to create serious SBS problems. I also would encourage you to take a look at our short Course 1 in Drainage Plane University found on our Education page.

It’s important to build for energy efficiency! However, we need to plan and build to counter the entrapped moisture issues that come with it. Those our my thoughts, I welcome yours!

I don’t know what the summer has been like for each of you reading this post, but the summer of 2010 in the Upper Midwest has been extremely wet and hot! As I write this posting, it is just beginning to clear off after some morning showers and the heat index is supposed to be near 100 this afternoon. And this scenario has been repeated quite often lately. This is the kind of weather that makes one very thankful for air conditioning! It also makes me revisit the reason Masonry Technology Inc. began business nearly a quarter of a century ago.

Moisture issues are one of the leading causes of building envelope failures. Find a study on building envelope failure causation, and you will probably find moisture issues at or near the top of the list. Masonry Technology Inc. was started because of a noticeable increase of moisture problems in the building envelope that began to occur shortly after the first energy crisis of the 1970s. As energy costs began to escalate, more and more designers and builders began to institute materials and methods that “tightened” the building envelope. While the tightening process was a logical reaction to increased energy costs and diminishing energy resources, the resulting moisture-related problems were unexpected and often dramatic. Materials that used to last for decades in the building envelope often showed signs of major degradation in just a few years (sometimes even months). Even though building envelopes were tighter and air movement into and through walls was nearly zero, moisture was still able to find a way in through storm-driven rain, condensation and other means. And with no built in system to get the moisture out, it stayed and percolated leading to a rash of rot, mold and pest problems.

The 21st Century has not seen an end to these building envelope moisture problems. In fact, in some cases they are even worse. Over the last thirty years the impetus to control heating and cooling costs and the desire to find new materials and methods to create more sustainable buildings has lead to new moisture problems in the building envelope. Some of these new materials have created unintended vapor barriers while other new materials have actually acted as sponges, pulling in and trapping more moisture in the building envelope. I even saw an article recently that suggested that certain “Green Building” practices actually amplified some of the problems they were designed to overcome.

So what’s my point? I am not saying that we should abandon “Green Building” practices, and I am not saying we should abandon the effort to tighten buildings to save energy. However, I do believe we need to rethink the process. We need to move away from simply “throwing a new material” or a “new process” at a problem in the misguided belief that it won’t impact other parts of the finished product. We need to work holistically with all parties involved in the design-build process to plan for unexpected outcomes. We also need to realize that if we are truly committed to healthy, sustainable buildings, we must include the correct rainscreen moisture management systems to deal with the entrapped moisture problems that will result when we tighten and employ certain new materials. Finally, in this time of worldwide economic slowdown, it is “penny-wise and pound-foolish” to omit the best rainscreen drainage plane systems available in the fallacious belief that we will save a buck! We may save a buck, but what is the cost to our reputation?

Those are my thoughts, I welcome yours!

Sarah Leaves MTI for Grad School

MTI is sad that our Media Technologies Specialist, Sarah, has left us.  However, she is off to a new and exciting venture at grad school, and we know she will do well.  Sarah has created all of our social media sites, and they all have been top notch!  It will be difficult, if not impossible, to match her writing and research ability, but we do intend to keep on with our Dry Facts blog and most of our other sites including Facebook, Twitter, LinkedIn, etc.  So if you are currently connected to us via any of these sites, don’t give up on us while we sort things out!

Mark A. Johnson

Media Technologies Mgr.

MTI