Rigid Boardstock Insulation Moisture Management Issues

Rigid Boardstock Insulation: Friend or Foe?

“When the message is absolutely critical, and not heeding the message increases the likelihood that a disastrous outcome will occur, then repeating the message is (or should be) a professional imperative! This has never been more true than with the issue of specifying and installing rigid boardstock insulation exterior of WRB’s and exterior sheathing on the exterior building envelope.”

The preceding paragraph is from the introduction to John Koester’s new white paper on potential moisture management issues architects, contractors and building owners face when they choose to use rigid boardstock insulation directly behind the exterior veneer of the building envelope (see image below). Normally, we release these articles after they have been published in industry-related magazines; however, this one addresses a topic that is so timely, we are going to release it immediately via our electronic newsletter, our website www.MTIdry.com and our social media sites. There is absolutely no charge nor are there any other conditions to access this article. It is immediately available as a PDF document via the link at the end of this article.

The following are some highlights from the “Exterior Rigid Boardstock Insulation Moisture Management Issues” article.

  • Most boardstock rigid insulation has some moisture-resistant characteristics.
  • When layered against a weather-resistant barrier (WRB) on exterior sheathing, an undrained cavity/void will be created that may entrap moisture.
  • Installing a thickness of rigid boardstock insulation over WRBs and exterior sheathing may have an impact on the fastening patterns and/or structural requirements to secure thin veneers (stucco, adhered thin stone and thin brick and various other siding systems).
  • Rigid boardstock insulation may have dynamics of its own.
  • Installing a thickness of rigid boardstock insulation over WRBs and exterior sheathing will impact exterior building envelope rough openings…

The article goes far beyond simply pointing out problems. Through the use of text and numerous detailed drawings (17) it shows how to solve or avoid the problems. We hope you find this information helpful, as well as timely. MTI believes that too much time is spent on the energy-saving side of the building envelope detail while often ignoring the moisture management side of the equation.

Building envelope moisture management must be equally involved in the building envelope detail if sustainability and energy efficiency are the goal!

Download the Rigid Boardstock White Paper



Frank Lloyd Wright Architecture – Sustainable or Not?

A 21st Century building project will probably not get off the ground if it isn’t tied to sustainable design, and most of us would agree, “That’s a good thing!”  But building and architecture during the late 19th and most of the 20th Century were not driven by any national push to be sustainable and environmentally friendly.  So did Frank Lloyd Wright, one of that time period’s most influential architects, build sustainability into his buildings?  It really depends on how you interpret his designs.

Wright was a major proponent of organic architecture.  This school of thought believes that architecture should reflect nature, and that organic design should put humans, and the buildings they inhabit, into a harmonious coexistence with nature.  Wright’s love for nature came, at least in part, from growing up in rural Wisconsin.  His designs sought to incorporate nearby, natural materials when possible, and to use them in a way that allowed their natural beauty to show through.  Wood wasn’t covered with paint; stone shouldn’t be plastered over; let buildings appear to be emerging from the land where they are situated.  Many of his projects, including his own home, Taliesin, used local material.  Taliesin, located on a hill overlooking the Wisconsin River, features locally quarried limestone and plaster made with sand from the banks of that river.  By using natural material obtained nearby, transportation costs and fuel use were greatly reduced.  By limiting what was painted, fewer chemicals entered the living space. both of these are sustainable practices.

Another sustainable idea Wright incorporated into many of his buildings was thermal mass walls.  This practice aims at reducing heating and cooling costs because a large volume of masonry material has the capacity to store thermal energy for extended periods of time.  Wright also used a lot of glass for natural lighting.  He combined this use of glass with a large overhang on the roof.  This large overhang did two things that align with sustainability.  First, they shaded the windows so that the building would stay cooler in the summer, and they moved moisture (in the form of rain) out and away from the windows and walls so that there was less external moisture penetration of the building envelope.

Not everything Wright designed turned out to be a study in sustainable perfection.  Often the windows designed to let in and utilize natural light, also let in the wind, cold and rain.  This happened because the union between the wall and the window was not taken into account by Wright’s design nor by his instruction and supervision; it just wasn’t that important to him.  Projects like his Freeman House, where concrete block was manufactured on site, often turned into disasters of cost overruns and product failures; good sustainable design, but poor sustainability from a supervision and implementation standpoint.  Even his architectural gem, Fallingwater, literally fell apart because of poor material and bad engineering of the cantilevered decks.

So what can we conclude about sustainability from a study of Frank Lloyd Wright?  In my opinion, he was a true architectural genius, and many of his ideas were and are good, environmentally sound, sustainable practices.  Where he failed in the realm of sustainability was in his lack of supervision and follow-through.  I get the impression that at a certain point his mind became bored with the mundane world of follow-through and follow-up.  His genius was racing on toward the next great design.  We can all take away something from this that too often rears its ugly head, even today.  All parties involved in a building project need to be involved at all stages of a project.  Everyone’s input is necessary and important, and we can’t walk away from the building process just because we are done with the design.  Does the design translate from the conceptual to the practical?  Are we on the project looking to see that our design works and is it being followed correctly?  Is the supervision on the jobsite ever-present and effective?  Are the materials we’ve specified working together properly and doing what they were marketed to do; and if not, are we making the necessary changes?  These nuts-and-bolt, mundane issues are as important to sustainability as the design itself.


Frank Lloyd Wright:  His Philosophy of Architecture

Building Envelope Design Guide – Masonry Wall Systems

Wrights Taliesin Showcases “Organic” Architecture

USA Home and Garden:  Fallingwater

Frank Lloyd Wright overhang above many windows.

Creating Sustainable Rainscreen Building Envelopes: It’s Like Motorcycles and Rain Suits!

Sustainable building isn’t possible without moisture management.  And for those forced to live or work in a building without moisture management, life becomes a health and safety nightmare.  Bold statements, but totally supportable.

According to the HUD’s Path Project, “Moisture, in all of its physical forms, is commonly regarded as the single greatest threat to durability and the long-term performance of the housing stock.  Excessive exposure to moisture is not only a common cause of significant damage to many types of building components and materials, it also can lead to unhealthy indoor living environments.  A long list of serious adverse effects can result from moisture problems in houses.  There is wide agreement that successful management of moisture in its various forms is essential for houses (buildings) to be durable, safe and energy efficient.”  In its 2004 report, the Path Projected listed the following outcomes of uncontrolled moisture in the building envelope:

  • Decay of wood and corrosion of metals
  • Infestation by termites and other destructive insects
  • Negative impacts on indoor air quality
  • Growth of mold, mildew and other biological contaminants
  • Reduced building material strength
  • Expansion/contraction damage to materials
  • Reduced thermal resistance of wet insulation
  • Premature failures of paints and coatings
  • Damage to building contents
  • Negative effects on building aesthetics

Enter the key phrase sustainable rainscreen building envelope into Google and you will get more than 18,000 results, including MTI’s “Drainable is Sustainable” presentation delivered at last fall’s technical meeting of the Sealant Waterproofing and Restoration Institute.  A key point of the presentation is that a moisture management solution for the rainscreen building envelope requires a systemic/holistic approach.  There is no single magic bullet; it takes a well-thought-out, coordinated system of products and processes designed and implemented by a team of professionals working collaboratively at every stage of the project to reach a successful outcome.

To illustrate the importance of a coordinated system in moisture management, I used the analogy of a motorcyclist riding towards an approaching storm in that presentation.

“It’s a nice sunny day, so I decide to go for a motorcycle ride.  Being an experienced motorcyclist, I always have raingear in my saddlebags because it’s summer and anything is possible!  As I move through the countryside, I notice that the sky is darkening and a storm is imminent so I pull over and put on my rain suit.

In a matter of minutes, the rain starts.  It’s light at first but soon becomes heavy, and it’s coupled with a driving wind.  Rain is forced around my windshield and into my eyes greatly limiting my ability to see the road.  Water cascades off my helmet and runs down the back of my neck soaking my shirt.  The water on the highway flies upward leaking into my boots through the seams and around the tongue.  To make matters even worse, it’s a hot, humid day so beads of condensation start to form on the inside of my rain suit making for an increasingly miserable ride!  Obviously, even though I thought I was prepared for rain, I hadn’t looked at all possibilities.”

Even though I had a collection of items designed to keep me dry, I hadn’t thought out the outcome fully, and I hadn’t properly combined the items into a functioning system.  If I had used goggles or a helmet with a visor, I could have seen the road better.  If I had used the hood on my jacket and worn it under the helmet, I wouldn’t have gotten rain down my back.  If I had used a rain jacket with vents, air could have moved around inside the system and reduced the condensation. Finally, had I worn rain boots with my rain pants lapped over the top of the boots and fastened snugly, I wouldn’t have got wet from the water spraying up from the road.

So what can be learned from this analogy about the importance of a system in solving the building envelope moisture management problem?  It takes many products, put on in the right order and at the right time, to create a positive result. We need to look at how many factors are in play and then employ several moisture management solutions as part of a system to solve the problem.

This same idea of a coordinated, multi-component solution can be applied to the people designing, specifying and constructing a building.  Gone are the days when designers, specifiers and contractors could successfully do their jobs in a vacuum.  There are just too many new products, processes and complex codes for the “Lone Ranger” approach to work.  Everyone must collaborate and communicate if a sustainable, healthy building is the goal.

Those are my thoughts; I welcome yours!

HD Big Twin

The Green “Blowback” Effect

A recent study initiated by the EPA and conducted by the Institute of Medicine indicated that unintended and potentially serious health risks could be the result of too much “weatherization.”  The report stated, “Even with the best intentions, indoor environmental quality issues may emerge with interventions that have not been sufficiently well screened for their effects on occupant safety and health.”

MTI has made this point many times in presentations that we have done, and our AIA/CES courses, “Breaking the Mold…” (MTI409) and “Don’t Waster Your Energy…” (MTI509), detail the sustainability and health risks that careless weatherization can cause.  Don’t get me wrong, we are not against saving energy through tightening buildings, but like the report from the IOM, we feel that planning and coordination of efforts need to take place first.

For too long, building has been done in a compartmentalized fashion.  All the parties involved tended to “do their own thing” rather than working as a team.  With a plethora of new materials and methods in the construction world, holistic building is a must!  Architects, specifiers, engineers, contractors, and manufacturers of building materials need to be on the same page.

For example, entrapped moisture in the building envelope has skyrocketed over the last 25-30 years (a time period following the first energy crisis of the 1970s).  Why, because better windows, more and better insulation materials, more sealants, more unintended vapor barriers, etc. were being used without much thought to unplanned consequences.  When you seal the building envelope too tight, you get moisture issues.  You also get a building that has less fresh air injected into the living environment.  The IOM report states, “By making buildings more airtight, building owners could increase indoor-air contaminant concentrations and indoor-air humidity.”  This could lead to mold and rot issues and poor indoor air quality.

When you tighten the building envelope, you must know how all the materials and techniques are going to work or not work together, and then include materials and methods to counteract any negative outcomes such as entrapped moisture.  In most cases you need to include effective building envelope moisture management systems.  You also need to work with the manufacturer of these systems to make sure you have the right products and design for your specific details.  That’s why the architects, specifiers, contractors, and building owners need to be on the same page.

Those our my thoughts, I welcome yours!

*I have added some pictures from a house built in the 1960s that show how buildings used to be able to breathe.  Notice how clean and dry the wood looks after the old siding was torn off.  There is no rot or water-staining, not even next to the window, and the window is a bathroom window.  Air was able to get behind the siding and into the building envelope to keep it dried out.

Of Parapets and Peril

MTI has put together a series of articles on “special moisture management problem areas.”  The first of these articles was the Window Rough Opening piece we blogged about last time.  This month we are making available “Moisture Management of Parapet Walls.”  The following text is an excerpt from that article.  The entire piece can be downloaded at http://www.mtidry.com/news/ParapetWallArticle.pdf.  You can also find links to this article and the previous “Moisture Management in Window Rough Openings” on our News an Views page at http://www.mtidry.com/news/index.php.

Parapet walls – what are they good for?  Parapet walls perform a number of important functions:

  • They can be designed in various shapes to create a desired façade
  • They can be designed to hide roof top equipment (AC units, etc.)
  • They help prevent roof edge blow off by diverting air flow up, over and away from the roof edge.
  • They can be a stable termination point, for roof edges and flashings.

However, even though parapet walls perform a number of important functions, they are moisture management headaches!

The phrase ‘Out of sight out of mind” is, unfortunately, the rule of the day with construction details that are not easily accessible.  Parapet walls fall into this category.   The required timely maintenance is neglected because of this and regrettably, the need for maintenance becomes apparent only as a result of a failure such as a leak.  On top of this, parapet walls have a rather rough life since they are subjected to wind, dramatic temperature changes, moisture from three sides and roof system stresses.  The result is a construction detail that is both neglected and abused.

The answer to the question “Why do parapet walls fail?” seems obvious.  The solution is just as obvious – design them to be better and maintain them properly.

The most fundamental rules of moisture management “Keep moisture away from, off of and out of a construction detail” and “Move moisture away as quickly as possible” always apply.  However, two additional practices should be employed.  First, use good moisture management design and identify and isolate the moisture risk zones in such a way as to separate high risk from lesser risk.

Like all structures a parapet wall suffers the fate of its roof – the coping.  Failure of the coping is closely followed by wall and interior failure.  Use the link above to access the entire article with proposed solutions to the parapet moisture management dilemma.Adobe House with Parapet

Leaky Windows — Are We Blaming the Wrong Thing?

One area of the building envelope that catches a lot of grief for being a “leak” problem is the window.  However, most quality windows of the 21st Century are extremely well built and probably aren’t the cause of window area water and air leaks.  If windows are properly installed, the majority of the leaks blamed on windows will probably disappear.  We need to focus on the window rough opening to solve the problem.

MTI recently wrote an article on this issue.  Here are some of the highlights:

  • Exterior building envelope construction systems (roofs and walls) often fail in the detailing of openings, projections and transitions.
  • The need for holistic building is imperative.  Each party involved needs to know how their task, and materials used to complete that task, impact the final result.
  • When a potential problem isn’t addressed in one area, it often leads to failure in another.  A poorly prepared rough opening develops leaks that then get blamed on the window.
  • The bottom of the Window RO needs to be covered with waterproofing material that runs a minimum of 8″ up the sides; there needs to be a back dam; and the sill needs slope-to-drain to the outside.
  • There needs to be a drainage plane at the bottom of the window RO.
  • There needs to be a moisture diverter above the window RO that moves moisture away from the RO into the building envelope drainage plane.

MTI is not the only entity to have made these points recently.  Brett Newkirk, P.E. has authored an article in the Winter 2010 issue of Applicator magazine entitled “Forestall Sill-Flashing Failure.  His premise is that many of the techniques we are currently using to protect against moisture failure in and around the Window RO are actually causing the problems we are trying to avoid.

Below are some MTI drawings of the procedure for properly protecting the Window RO.  If you would like a copy of the MTI article by our CEO, John Koester, you can download it at http://www.mtidry.com/news/windowRO.pdf.

Drainage Planes, Weeps and Motorcycles

I love to ride my Harley!  It’s a great stress reliever to role through the countryside; on a bike you can truly feel the world.  You can actually smell, feel and hear nature, not just see it through the car window.

That leads me to a revelation that I had while riding in the rain last August.  Riding a motorcycle in the rain is a lot like moisture management in the building envelope.  Consider the following scenario:

It’s a nice sunny day, so I decide to go for a motorcycle ride.  Being an experienced motorcyclist, I always have raingear in my saddlebags because it’s summer and anything is possible!  As I move through the countryside, I notice that the sky is darkening, and a storm is imminent so I pull over and put on my rain suit.

In a matter of minutes, the rain starts.  It’s light at first but soon becomes heavy, and it’s coupled with a driving wind.  Rain is forced around my windshield and into my eyes greatly limiting my ability to see the road.  Water cascades off my helmet and runs down the back of my neck soaking my shirt.  The water on the highway flies upward leaking into my boots through the seams and around the tongue.  To make matters even worse, it’s a hot, humid day so beads of condensation start to form on the inside of my rain suit making for an increasingly miserable ride!  Obviously, even though I thought I was prepared for rain, I hadn’t looked at all possibilities.  So what did I learn?

In analyzing the situation I realized I had only looked at a part of the rain vs. rider problem, and in doing so, had left several other points of water penetration unprotected.   I realized there were several single solutions that had to be used in concert to solve the “hole/whole” problem.

  • Wearing a rain jacket with a hood under my helmet would keep the water from running down my back.
  • Wearing goggles would keep driving rain from limiting my visibility.
  • Using waterproof over boots would keep my feet dry.
  • Finally, the condensation problem could be solved by purchasing a rain suit with vents that allow for air movement under the suit.

Handling moisture problems in the building envelope is much the same.  It takes a holistic/systemic approach to solve the problem.  There isn’t a single fix in most cases, especially if the moisture issues are multiplied or take place over an extended period of time.  The more protective elements you incorporate into the moisture management system, the more likely you are to prevent permanent building envelope failure.

We need to get all parties on the same team.  Architects, specifiers, contractors and owners need to work together, and they need to work with moisture management experts to create the right solution for their specific building.  Don’t just trust a sales force to give you the right fix.  Work with companies that are willing to give you individual attention and actually take your project’s unique details into account.

Those are my thoughts, I welcome yours!