WSS, WRB, AB, & VP - Oh My!

After my last post, many of you are probably left wondering: "Has he done ANYTHING on his design yet?"

The truth is I have; not all my time over the last 4 or so years I have been ‘working’ on this project has been wasted.  Although I do not have any hard blueprints or floor-plans yet, I have continued to flesh out ideas for different components of the build by continuing to invest considerable time into research, seminars, technical courses, and discussions with colleagues.

One of the components I have invested the most time into (I would estimate at over 200 hours to date), is what will be best practice for my water shedding surface (WSS), water resistant barrier (WRB), air barrier (AB), and vapour barrier (VB).  There are probably as many opinions in this field as there are blades of grass in my front yard.  And it has taken me over five years to come to some conclusions of my own in this area (was interested in this subject long before I started this latest design journey) but even now, I am running lab tests to prove or disprove whether my decisions are wise enough to proceed on the real thing.

One of the key factors in deciding on a WRB, is first deciding on an AB strategy.  The most common strategy this (in my region) is an attempt to seal the vapour-barrier-poly on the inside surface of the wall (beneath the drywall) to also serve as the air barrier.  As a home inspector who has been in hundreds of attics, crawlspaces, and basements, I can honestly say I have yet to see a poly-vapour-barrier adequately detailed to form an effective air barrier.  It is next to impossible to form a lasting air-tight seal using poly and tape around penetrations like wiring, floor joists, knee walls, etc.  In most homes I have looked at, there hasn’t been a serious attempt to install this so important barrier.  The reason?  It is hard, takes a long time to do right, and is therefore expensive.  So it tends to just get a half hearted effort so that the contractors can tick off the requirement as they move forward in the build.

Let’s back up a moment: "Isn’t making a house more air tight why we are having so many problems with moisture issues and mould in North America?"  I am quite confident a large number of people reading this right now agree with this statement.  "After all, we did not start to have these problems until we started to make our building stock more ‘energy efficient’ – Right?"

The truth is, it is the process of adding additional insulation, and not ‘attempting’ to make our assembly’s air tight (I state attempting because we have actually done a really poor job in this field to date), that has led to the increased risk for our wall and roof assemblies.  I talked about this last March in my ‘New Education’ posting. You see, in the old days our houses were very inefficient but somewhat durable.  Sure the huge volume of air that flowed through our assemblies helped to keep some components dry, but it was the heat escaping through our poorly or un-insulated walls and ceilings that was doing most of the work.  This heat acted to ‘cook’ out any moisture in the wall and roof sheathing.  Once we started to increase insulation levels, we started to cool these surfaces down and eventually we cooled them down enough to reach the dew-point potential of our standard interior air (which for the Pacific Northwest at 21°C and 50-55% RH is around 10°C).  As we can reach this temperature for most of the fall through early summer in my region, the risk is actually very high and I see the outcome often, especially in attic cavities, in my inspection practice where a great number of homes I have looked at over the last four years that have had ‘modern levels’ of insulation in the attics, have also had moisture problems and mould in the attics.

As we have added more insulation to our dwellings to make them more comfortable and energy efficient, the air barrier, which has been the most ignored barrier to date in our building codes in my view, needs to become the star of the show.  In truth, it should have always been the star of the show, because reducing the air exchange through the assemblies automatically makes the home more comfortable and energy efficient without adding a stitch of insulation (read about my personal experience back on my January ‘We own a House’ entry).

To emphasize the importance of the air barrier, let me provide this graphic from Building Science Corporation in their paper RR-0412: Insulations, Sheathings and Vapour Retarders.  This provides a dramatic visual of how much vapour movement can occur through the smallest of holes in the air barrier compared to a large hole in the vapour barrier.

Fig 1: Over one heating season in a cold climate, 30 quarts of water can flow through a 1” x 1” hole in an air barrier by means of air movement, but only 1/3 quart of water can flow through a 4’x8’ hole in a vapour barrier by means of vapour diffusion.

As you can see, the air barrier is very important in keeping our walls dry.  Even small holes (imagine trying to prevent these holes with tape and poly) can lead to large amount of moisture, in vapour form, entering our wall cavities where it can then condense on the surfaces we have cooled down by adding more insulation.  This is because air movement is smart.  It moves in a three dimensional way from one hole to the next.  It can enter the wall cavity in one location and find its way out of the cavity to the outdoors on a completely opposite side of the house.  As a result, an air barrier has to be continuous (details are important), durable for the life of the assembly, and most importantly – buildable.  A designer or architect should be able to take a pen and draw the complete air barrier on the design without ever taking the pen off the paper.  If they can’t – its time to find a new one, because if they cannot draw it, how do you expect the contractors to build it!

One convenient fact about the air barrier, unlike the vapour barrier that must go on the high pressure side, is that it can be placed anywhere in the assembly.  There is no rule that states that the AB and VB have to be combined, and there are much easier ways to detail the air barrier than trying to seal the poly.  What IS important to pay attention to is the vapour permeability of the air barrier, and ensuring it is appropriate for the location installed.  In a heating climate with the vapour barrier to the inside, you want to ensure all components installed outboard of that barrier are as vapour-permeable as possible, to allow the assembly to breath to the outside.  So if you are creating an exterior air barrier, it is very important that the barrier has high vapour-permeability. 

When choosing your products make, sure you get independent data to support the manufacture’s claims of permeability.  We recently tested several sheet style sheathing wraps for vapour permeance at a Building Envelope Lab course at BCIT.  There was no surprise that our control wrapped in Poly was still soaking wet after 10 weeks, but what was a surprise was how long it took some of the sheathing membranes - Typar and Vapro Shield specifically - to dry out.  Both of these developed considerable mould on the samples because they had not dried out fast enough.  Even 2 layers of 60 minute building paper outperformed them and exhibited only a few tiny spots of mould.

Some options for creating an Air Barrier are as follows:
    •    Air Tight Drywall Approach
    •    Sealed Poly Approach (Combining with Vapour Barrier)
    •    Sealed Exterior Sheathing Approach
    •    Sealed Exterior Insulation Approach
    •    Sealed Exterior Sheathing Wrap Approach (cannot use building paper for an air barrier)
    •    Sealed Interior Sheathing Approach (Used a lot in the PassivHaus circles)
    •    Combinations of all or some of the above

Many in the scientific community advocate an external air barrier approach.  The benefits of an exterior air barrier approach are as follows:
    •    Can be detailed and tested early in the construction process to ensure you are on the right track and address if you are not.
    •    Is easily reparable during the build, up to the time the cladding or exterior insulation is installed.
    •    Is usually easier to make the barrier much more durable if the barrier is sandwiched between components.
    •    My favourite - Opens up the possibility of using a liquid applied barrier.
    •    But probably the most important - There are far fewer penetrations on the exterior of a wall assembly and most of those penetrations have square sides and are therefore easier to detail.

Because of these benefits, and my research to date, I have elected to implement an exterior air barrier approach on my build, and I'm currently testing a liquid-applied barrier from Prosoco called R-Guard Cat5.  This would act as both the Air Barrier and Water-Resistant Barrier.  If all goes well in testing, and I proceed with this approach, I will be applying the product to the exterior sheathing prior to installing my outboard continuous insulation.  I will discuss this a lot more in future postings but for now I have started to video diary my product tests on a mock-up which I have uploaded to You Tube.


I would welcome any comments or words of warning you may have.  Next month we will talk about the Water Resistant Barrier.   Thanks for reading!

SENWiEco takes a shot at applying R-Guard Fast Flash from Prosoco

The second in a series of videos providing a demonstration in the application of the R-Guard product line.

SENWiEco applies R-Guard Joint & Seam from Prosoco

The first in a series of videos demonstration the application of the R-Guard system.

My Ingredients for an Owner Built Home

Sorry for the delay in this posting.  The truth is, it is time for a confession - I am stuck!  I am also sorry in advance - this is a long one!

I have been in a hole I do not seem to be able to dig myself out of for many months now – 300 days to be exact.  You see, this was the day that I found out that the Municipality I lived in (District of North Vancouver - DNV) was not as ‘green’ as I had anticipated/hoped, and I was going to have a FSR (floor space ratio) issue with my fatter-better-insulated-walls.

But more on that in next month’s posting, I want to talk now about the ingredients I think are needed for an owner built home – some of which may surprise you (they did me). The basic ingredient list for your owner-build recipe might be something like:

•           Money

•           Skills or willingness/ability to learn

•           Component knowledge or willingness/ability to research

•           Health

Money – Obviously you are going to need a sizable quantity of cash or credit.  In my region this can be anywhere from $75/ft² at the extreme low end, $130-$150 as an average value, and $200-$300/ft² and up for a highly custom home with high end finishings.  These are the costs to have the home built 100% by others, any sweat equity that you put into the process can allow you to lower your costs or increase the quality of your finishings.  It is important to define a budget right at the beginning, as this will allow you to make decisions throughout the process as to how to best meet the budget and goals of your build and see, quite clearly, where it makes sense to put the money. We have an initial budget of $300K-$350K.

Skills – Sure, you have built a greenhouse or garden shed – but do you really have the skills needed to build your own house, including installing/constructing each of the components that make up a finished dwelling?  It is important to realize your limitations early in the process so that you can focus on what you do well at, pay others for what you really are poor at, and practice on what you probably know how to do but are not great at.  This will also allow you to get some training and practice in those areas to hone and polish your skills in these areas before you get to the ‘big tent’.

Knowledge – Skills are great, but if you do not know what you need to do, it really does not matter that you have the ability to do it. Knowledge can be gained in many ways and often at very little to no cost.  There is a vast array of free knowledge on the internet.  Building forums, manufacturers websites, and consumer review sites are just some of the resources available to you, at no or very little cost, on the net. There is then the local technical school courses available on most of the systems and components found within a home. These are often just a few hundred dollars for 6 or 12 weeks of instruction. They will give you a fundamental in the system of interest and show quickly areas where your knowledge may be weak.  One of my favourite sources of knowledge is to attend industry sponsored seminars.  The BC Building Envelope Council, Thermal Environmental Comfort Association, Home Protection Office, and the Electrical Inspectors Association of BC are my personal four favourite seminar sources.  You hear directly from industry experts what are the current challenges and solutions available in the marketplace.

Knowledge and skills are probably interchangeable as to which is more important in this list.  You really need both to proceed.  I personally listed skills as more important for me as this is probably the area I am weaker on and is harder to improve. You can of course have natural skills, but most skills are learned by watching others.  You usually need to physically see someone else doing it right to understand the steps to doing it right yourself. This, of course, is the fundamental element of ALL apprentice, articling, or residency type programs out there.  You Learn by Watching and then Practicing and Applying.

Knowledge can be read or researched.  It can be studied and reviewed.  This is for me fundamentally easier and more available than honing my skills. You can research on the internet, read books, take courses and, go to seminars. All of these will help you gain knowledge, but how do you gain skills?

I have found a few ways to do so. Courses that include hands on components are an excellent start.  The BCIT Building Envelope Lab is a great example of this type of course and has been invaluable to me. In it we have been physically practising the application and detailing of rain barriers, air barriers, flashing, window detailing, etc. It has reinforced that having knowledge alone without skills is not good enough. I was horrified when the window I thought I had so carefully detailed --- leaked! Another way to practice your skill is to volunteer at an organization like Habitat for Humanity. You can work on an actual site and be guided by pros in the various construction fields. I have also found that helping with neighbourhood projects has been a great benefit. You can learn from others or if you are at the top of the knowledge pole, can practice doing it right before tacking something much larger or more expensive.

Health – Obviously you need to be able to physically do the work.  While this is taken for granted for many, the requirement has delayed our build for years now.  We have had plans to ‘start’ at least 4 times over the last 6 years. Two lengthy illnesses (thyroid and back), each a year or more in duration, each 100% debilitating to the point that all normal life activities stopped during both, managed to derail all previous attempts to start. The back issue in particular, I had two bulged and torn discs, can haunt a person.  Is it going to hold out? Or will it fail part way through? I do not know the answer and instead will take a leap of faith and do everything I can to protect it during the build and strengthen it prior to the build. I have discussed this with my wife, who has a lot less confidence than I, and said, “I need to try and do this, if it fails we will just have to hire someone to finish the build”. This for me is probably the biggest wild card in the plans, and we just have to make an assumption that I will remain healthy or this project dies before it ever begins.

The above four ingredients were the ones I was expecting going into this process.  The next items were ones I did not anticipate needing in such large quantities:

            •           Organization

            •           Optimism

            •           Support

            •           Resolve

Organization – this has turned into the most needed skill of all. As I do not normally work in the construction industry, I needed to find ways to catalogue the huge volume of information I am amassing because I would not otherwise retain the information.  Whether it was a tip I saw on a TV show, an article I read, a product I saw on the way home one day, or an insight I gained at a seminar or class, this all needed to be stored in a way that was easily retrievable and in a format that was flexible for the different types of information I needed to store. I have gone through at least 6 iterations of this ‘knowledge database’.  I started with an Excel spreadsheet but that soon became unwieldy. I then transitioned to a Word document, but it became too difficult to navigate and add information. I started to build an Access database and realized quickly that it would be too rigid.

I was then exploring a new laptop I bought for my wife one day and came across a program from Microsoft called OneNote. My search was finally over!  This was a program that acted like a database, was searchable, infinitely flexible, had tabs along the top that I could use for all my major components groups (like plumbing, electrical, exterior, interior, …) and then each tab had ‘pages’ and ‘sub-pages’ down the side that would let me break up each major component into as many sub groups as I wanted. So for instance, I could take Exterior and break it up into Cladding (and break that up into main and feature sub-pages), Windows and Doors, Roof, Flashing, Water Resistant Barrier, Sealants, etc… Each page then allowed you to store pretty much anything you wanted in any format.  There was no structure, I could just click on any part of the page and start typing. I could embed videos, pictures, sketches, and hyperlinks - and of course text as well. I have been using it for over 6 months now and have not found a shortcoming for the type of data storage I need on this project.

Optimism – When everyone around you is telling you that “you are nuts”, you need to have a healthy dose of optimism to proceed down this path.  Most people I know are interested in the process and some of my professional colleagues actually support me. But those who know me the best doubt my ability to build this by myself.  I do plan on getting some extra hands at key stages where one set of hands just will not be able to lift something or hold it in place and secure it at the same time.  But for the vast majority of the build, I plan on performing the labour myself.  I will fully admit, many have tried and failed, but many have also tried and succeeded. So I need a very healthy helping of optimism to take me through this.

Support – This comes in many flavours.  Emotional support is something I crave and probably have the least amount of (and probably will not be able to increase as I do not have any one around who has the same ‘dream’ as I). As I stated above, most people in my close circle just think I am nuts. Technical support is also very important and an ingredient I feel I am blessed with. I have developed some great technical support relationships in the construction field, and feel well covered in terms of building envelope, building code, electrical, HVAC, general design, roofing, tile and brick, and interior layout. Many of my technical support networks could also most likely lead me to trades people should I ever get stuck (this allows me to have optimism that I have a chance of doing it myself).

Resolve – The last ingredient is probably the most important, and one I have not totally mastered yet. Because I have never attempted anything like this before, I do not have a good blue-print on how to proceed.  What needs to be done? When does it need to be done? How does it need to be done? How does one item tie into another? This list is endless and unless I break it down into one small chunk at a time, it is all-consuming and totally overwhelming! I need to figure this all out as I go, but the problem is, I am not one to jump into the deep end. I like to know where I am going before I start. I am known for endlessly researching a topic. I am having the most difficulty with this ingredient, and am stalled on making decisions and moving forward. I am always wanting to research just a little more, or consider one more alternative. Some of this is healthy and even required, but I guess I am so scared of screwing up, I am unable to start.

So I blame various setbacks (like the meeting I had with the district back in Sept 2011) on the delays in the design and engineering. I make excuses that the delay is actually a good thing because the codes are changing and I would have had to re-design the plans if I was already done at this stage. 

However, I think the real reason I find myself deep in a hole right now is because I am just too chicken to stick my head out and get moving!