Why do we continue to drill holes into our buildings?

I was recently driving by yet another building with vapour ‘diffusion’ ports (VDP’s) and it got me thinking:

Why do we continue to let our buildings be drilled full of holes?

I have always believed that the ports did not work based on previous information I had reviewed, and they are certainly not a recommendation made in the Best Practices Guide published by the Home Protection Office (HPO) in collaboration with some of the best engineering firms in the North America, firms like RDH, RJC, and Morrison Hershfield.

So why do a limited number of buildings still incorporate these ports in their designs?

First of all, we need to try and understand the intent of vapour diffusion ports. As I understand it, the intent is to help walls ‘dry out’ by allowing the wall assembly to ‘breathe’ more easily.  The ports are intended to increase the breathability of the assembly by means of diffusion, over a solid sheathing base line. By ‘breathing’, we are referring to the wall’s ability to ‘lose’ moisture in a vapour form, by allowing that moisture to go ‘through’ a wall’s materials and evaporate into the outside air (low vapour pressure side). We say walls can ‘breathe’ if all of the materials on the low vapour pressure side (which can change direction depending on conditions) are vapour-open, or that they have a high permeability.  In simple terms, this means that the pores of the material are large enough to allow a water molecule in vapour form to pass through the material.  The mechanism of passing through the assembly is usually termed ‘diffusion’, but a review of Chapter 8 of Building Science for Building Enclosures by Straube/Burnett details that the actual mechanisms involved with moisture movement through a porous material are extremely complex and can involve surface diffusion, capillary action, evaporation, convection, absorbed moisture transport, etc.  Even today, the flow of moisture through materials is not fully quantifiable by scientists or fully predictable. What is a provable fact is that in order for vapour diffusion to take place there needs to be a difference in vapour pressure across the two sides of the material (or assemblies) in question.

So are these ports working as intended?   How wide a range does each port have? Are there other mechanisms at work?  Is this an effective drying strategy?

In researching this topic I came across two related studies performed in the late 1990’s after the leaky condo crisis.  The first study titled The Envelope Drying Rates Analysis Study looked at the abilities of various wall assemblies to dry out (in lab conditions) while changing up components like sheathing materials, capillary break depth, and sheathing membrane materials.  What I found most surprising was that none of the panels were dry to safe levels (below 20%) even at the end of the 2000 hour study.

The second study titled Evaluation of Vapour Diffusion Ports on Drying of Wood-Frame Walls Under Controlled Conditions utilized the same panels, but drilled out vapour diffusion ports on some of the panels and then re-ran parts of the experiment to look at the effectiveness of the vapour diffusion ports specifically.  What was again remarkable was that, although the VDP’s did provide a minor increase in the initial drying rate of the OSB panels (no change in the rate of drying in the plywood panels which was already higher than OSB with or without the VDP’s ), all of the panels (OSB & Plywood) again contained areas with dangerous levels of wood moisture at the end of the study (which repeated the first studies results).

After reviewing these studies and Building Science for Building Enclosures,  I now have a better grasp on the true mechanisms at work with vapour ‘diffusion’ ports, and only a little of the process actually involves diffusion.  Where the ports have been effective to any measurable level, some form of convection must take place in conjunction with lots of capillary movement. Let’s look at these mechanisms in a bit more detail.

Convection (or air movement) can occur because of air leakage through an assembly from the high to low pressure side.  It can also occur by means of the convective currents that can develop within each stud bay if a low density batt and fill insulation (i.e. fibreglass) is used.  Neither of these mechanisms is desirable from an enclosure performance standpoint. Convection forces within the wall assembly can deliver moisture-rich air derived from the ‘wettest’ parts of the wall assembly (studs, plates, & insulation) and deposit that moisture onto the back side of the sheathing (which can allow a generalized increased drying rate from the sheathing by means of diffusion to the outside air). Where that moisture is close enough to a port, there can also be a localized marginal increase in permeability over the base-line sheathing.  This can help dry an assembly if no additional moisture is introduced through the convection mechanism, but air leakage through an assembly can often bring with it high levels of moisture into the assembly from the interior of the dwelling.  And once in the assembly, that moisture can then condense on any of the wall elements with surface temperatures that are below the dew point of the leaking air. (See my July/2012 and March/2012 blog entries for more info on dew points and moisture in wall assemblies).  Stud bay convective currents often create ‘air pumps’ that can lead to cold interior walls and thermal bridging, causing additional heat loss (you are bypassing the insulation by delivering heat to the outside sheathing and taking it from the inside wall board).

Now lets look at capillary and diffusion forces in connection with these ports - as areas close to the ports dry out via diffusion through the holes in the sheathing (which have a higher permeability because the moisture has to only diffuse through the sheathing membrane and not though the membrane AND the sheathing), or by air leakage through the holes (because the sheathing membrane has been damaged or is not sealed as an air control layer), that moisture is replaced by wetter neighbouring regions.  The process continues until, over time, the moisture levels within the assembly equalize.  The assembly as a whole is also trying to equalize with its lower vapour pressure neighbours (so in this geographical region, usually to the outside).  The entire process continues until all regions have the same vapour pressure (something that in practice rarely occurs as there is always changing interior and exterior humidity and temperatures which lead to changing vapour pressures).

The problem however, with relying on the diffusion and capillary forces alone is that, although capillary forces are faster than diffusion, both forces will not dry a wall assembly out fast enough to be an effective deterrent to decay and fungal growth.   This was confirmed in both studies, where portions of every test panel still had wood moisture levels in the danger zone for promoting (not just maintaining) rot, even after close to three months, regardless if VDP’s were installed or not!  These studies only had one wetting period - What happens when you have repeated introductions of moisture (interior air leakage, exterior leaks, or plumbing leaks)?

What does all of this mean? Are these results important?

Let’s look at where moisture can originate and how effective VDP’s are at addressing that moisture source.  There are five causes that come to mind:

• Initial wood moisture elevated during construction due to the rain forest we are building in, 
• Bulk water entry (after construction) from the exterior around poorly detailed penetrations and even through vapour diffusion ports, 
• Bulk water entry from water pipe and drain leaks within the assembly,
• Air leakage through the assembly causing condensation,
• Vapour diffusion into the assembly (usually caused by excessive RH% levels in the dwelling’s interior and/or inadequate vapour control layer)

The easiest way to address the first cause is to leave the drywall, poly, and insulation off the interior of the structure until the assembly dries out.  The problem is that construction schedules are so tight; we typically do not allow adequate drying time.  If we are unable to allow sufficient time for a wall to naturally dry out before boarding, then we need accelerate the process by adding heat and air movement to the mix (and in some extreme cases, de-humidification). If we rely on the VDP’s alone to allow the wall to diffuse the moisture out and close up the assembly in a wet state, we could be waiting many months for safe moisture levels within the assembly to occur, and by that time a healthy crop of fungi would most likely have already taken root leaving us with a sick wall assembly. 

VDP’s Score: F

The second and third mechanism only has one solution – stop the bulk water entry!  There is no effective strategy to manage bulk water entry once it has occurred. Even BC’s Rain-Screen requirements will not solve repeated bulk water entry into a wall

assembly.  You must stop it at the source. 

VDP’s Score: F

The fourth mechanism of moisture entry is also somewhat simple to address. Stop the air flow through the assembly by means of an effective air control layer.  Unless you stop the air flow and the resulting condensation, the rate of moisture input will again often overwhelm the slow drying rate of a wall assembly by means of diffusion only, with or without VDP’s.

VDP’s Score: C- down to F (depending on the incoming moisture levels and type of sheathing installed). 

The final mechanism also has an easy solution in most dwellings.  Control the interior humidity by means of mechanical ventilation and/or install an effective vapour control layer in the assembly.

VDP’s Score: C down to F (depending on incoming moisture levels and type of sheathing installed).

Let’s summarize this information.  If a VDP is sealed against airflow, we are generally relying on diffusion and capillary forces and possibly stud bay convection currents to help dry out a wall assembly.   However these processes are slow, and the VDP’s only account for a limited improvement of drying potential over base lines.  As a result the assembly would typically not dry out in time to prevent decay regardless of the presence of the VDP’s.  If we allow air movement to occur through the ports, the air movement that would occur through the assembly can often bring with it levels of moisture that are easily able to overcome the limited additional drying capabilities represented by the VPD’s.

Are there downsides to including VDP’s “just in case”?

Well, it turns out these holes are usually conveniently placed just below windows and other enclosure penetrations where any incorrectly detailed flashing or membrane (like the holes drilled through all the water-resistant layers in the photo - below left) could direct water along the surface of the sheathing and into the wall assembly through these strategically placed inward water highways!  Is this really a wise practice?

We need to stop this insanity.  I put a challenge out to all of the engineering firms that know better.  Please stop allowing your buildings to be drilled full of holes. Start taking the architects, building officials, and contractors to task to stop this poor building practice. Start educating the teams you work with and let’s start building smarter!

WHAT WERE THEY THINKING?

Figure 1 Vapour ‘Diffusion’ ports (holes in sheathing that act as inward water highways) on buildings under construction in North Vancouver, BC

 

Fall 2012 Energy Efficiency Public Review

BC has been pursuing energy conservation and greenhouse gas reduction goals in buildings for more than five years. In September 2008, the Province adopted new energy and water efficiency objectives and requirements for all buildings in the British Columbia Building Code. Since that time, staff have been working on the next steps to improve energy efficiency in buildings consistent with the goals in the Clean Energy Act (2010).

We invite your feedback on a set of proposals to adopt updated energy efficiency requirements in the British Columbia Building Code, including:
 
Large Residential, Industrial, Commercial and Institutional (Part 3) Buildings: A proposal to reference both the 2011 National Energy Code for Buildings (NECB) and ASHRAE 90.1 – 2010 as two possible compliance options in the BC Building Code.

Housing and Small Buildings (Part 9): A proposal to adopt the package of new revisions to the National Building Code relating to energy efficiency for housing and small buildings.

Ventilation (Part 9): A proposal to adopt new ventilation requirements for Part 9 housing to maintain occupant health and safety.

The proposed changes would have an impact on Part 10 in the BC Building Code. If these proposals are adopted, Part 10 would look like this.

Alfie Lives

Well Alfie did not exactly get the life of leisure I promised him.  I immediately put him to work on my 'rock pile' in the back yard that was hidden under years of blackberry growth.

Start of job - find the rocks and dirt through the mountain of blackberries and ivy!

 A lot of rocks to screen.  This is excess soil and fill that accumulated from previous projects around the yard like the perimeter drainage, garden sprinklers, and the start of a waterfall, pond and stream.

Not exactly Kutny's Soils scale, but it worked wonderfully.

The finished screened pile (about 20 cubic yards worth) - I have a lot of stone work in my future.  Plan on a stone wall fence, stone wall raised garden beds, stone herb gardens, and a selection of stone and gravel stream bed.

But just before getting to the above finished stage, poor Alfie had to have a rest.  He had been leaking fluids before I liberated him, but the vendor had thought they had addressed the issue by flushing and cleaning the radiator.  Well the problem was a bit more terminal than that and poor Alfie required bed rest for the last 3-4 weeks while we searched for a suitable heart donor.   A suitable replacement water pump was located last Friday and Alfie went under the knife last Monday.  After 4 hours of anticipation and worry, wondering if he would or would not make it, Alfie woke up and jumped out of bed and started digging.  

After looking at the pump that was removed, we are amazed that it was still in one piece with the cracks radiating around the entire perimeter.  We are thrilled with his recovery to date but he is not out of the woods yet.  He still gets flushed after a few hours work and needs to take a break to cool down.  We will work together to get through this season and then he will go see a specialist.  We are all routing for him here at SENWI.

Alfie the Excavator joins the SENWI Team!

When I was younger, I always wanted a fancy tractor to play in the sand box.  Well 40 years later I got one.

We would like to welcome Alfie the Mini-Excavator to the SENWI team.  Alfie spent most of his life up in the Whistler, BC area where he worked on the rock gang and was often left out in winter's cold cold harsh weather.  We at SENWI wanted to rescue Alfie and let him live out his senior years in the relative comfort of the lower mainland.

Alfie has an impressive 10ft digging depth and due to his rigorous exercise schedule is able to fit through a 5'3" opening.  So he is great for those small back yard projects you have been putting off.  He loves to dig and is quite skilled at digging a small trench for a perimeter drainage system.  For fun he likes to knock out stumps, small trees, and brush and has even been know to transplant the odd bush or two.  His thumb makes it child's play for him to move around rocks or slabs in the various landscaping projects he will be helping us with.

We decided to ask Alfie to join our team, as I anticipated having a large volume of landscaping to be done on our build.  Having a help like Alfie on site during the build itself will also be invaluable.  He has already provide some ideas on how to create a small deck on his boom to help me lift materials up to the second floor and claims he is up to the task of removing our structure and concrete slab when we tear down our existing dwelling.  He also can't wait to show his brawn and lift in all the heavy beams I will have on the first floor ceiling.

A friend of Alfie costs $3200 a month to rent.  If we only rented when we really needed a helper like this, then we would not have one around for all the small jobs that Alfie will be great at.  At a minimum, we would need one of Alfie's friends for a period of 6 months at a minimum cost of $19,200 + Tax.  At a purchase price that was less than this, Alfie just makes financial sense.

His arrival has also sparked up interest in the neighbourhood and he has already been asked to play at two yards nearby which of course helps reduce his purchase costs.  For longer trips, he has made friends with Butch the tow truck during his trip down from Whistler, so that he can get out and play in other yards on occasion.

Finally Re-Started

I can proudly say, as of yesterday, I have finally restarted the design process for the floor layout with an effort this time to maximize the sun’s exposure for living areas (align living areas along the south side and utilities along the north) and minimize the floor area in general in order to lower costs and also fit within the District of North Vancouver’s floor space ratios (even with my thicker walls).  In a jet-lag-induced-stupor, I broke out AutoCAD (which I use for prototyping), blew away all the walls on my previous designs and started the process over. I have done this probably a dozen times over the last 10 -12 years and it always surprises me that the ‘next’ design is often substantially different than the last design.  As my priorities and goals change, so does the layout of our home.

For instance, when I intended for this to be a retirement home, I did not worry about what would make the design ‘marketable’, but only on what we as a couple needed and wanted.  This resulted in a 2-bedroom house with lots of extras like a gym, second laundry, office & study, theatre room, etc.  Then about 5 years ago, I came to a realization (my wife also to a lesser extent) during an annual stay at a vacation rental house on Chesterman Beach in Tofino, that I really did not want to live in North Vancouver for the rest of my life.  When I moved here 13 years ago, it was a drastically different place, and I intended to ride out the remainder of my life here.  But, in my view, the North Shore has deteriorated substantially since then.  Traffic is my number one concern.  Because the Upper Levels Highway has reached capacity, a lot of traffic now spills onto Marine Drive and through residential areas.  In my neighbourhood (which has not seen ANY increase in the density of homes), the flow of traffic at a nearby intersection has gone from 2400 vehicles a day in 2008 to over 5000 vehicles a day last March (this increase is generally vehicles cutting through the neighbourhood between the Upper Levels Highway and Marine Drive).  Marine Drive has now become choked for a large portion of the day and it can often take 15+ minutes to get to a nearby mall during the day (10 blocks) when the same trip at night only takes three minutes.  And now the District is supporting heavily increased densities along Marine Drive without any meaningful plan to address the traffic.  Until and unless the North Shore Communities demand that the Province upgrades the highway and bridges, the problem will only get worse.

But I digress. That is a conversation for a totally different blog.  The point is, I do not see that this will be a pleasant place to live for decades (if ever), and so the emphasis of my design will now be marketability as opposed to personalization.  In this region that means bedrooms, the more bedrooms the better.  It does not really matter on what size the bedrooms are and many are filled up with a queen sized bed.  If I were truly building to market demands, I would also add more bathrooms.  Many homes in my neighbourhood have a bathroom attached to each bedroom.  But in my books, this is just nuts.  My generation and my parent’s generation managed just fine with only one bathroom in the house.  Yes that’s right one bathroom!  Can you imagine?

Although I will be building with marketability in mind, I still believe that builders should be providing a legacy in the structures that they provide and not a liability.  So I will be trying to provide the ‘features’ that the current buying public want, but not at the expense of the building envelope and compactness of the home.  I will talk about this and my design process more in future posts.

For now though, I would like to leave you with some thoughts I have as a resident of the North Shore on my return from a holiday to Chicago, Scotland, and London.  I feel I am further up the curve of what I consider a sustainable path through life, just by the programs in place where I live when viewed in contrast to these recently visited regions.

Let me start with Chicago.  This is a LARGE city by Canadian standards (approximately 4-5 times bigger than Greater Vancouver) and there was a lot of waste produced and a lot of traffic.  What was not visible were recycling efforts or car pool/transit lanes.  

When I talked with our drivers, they did not think anything of the traffic, and felt it was acceptable to commute through communities in order to miss the back-up on the highways.  Really???  The City is looking at adding ‘green-wash items’ like bike lanes in the core, but what about the gridlock?  Why not reward drivers who carpool and take transit by allowing those drivers/passengers an expedited path through the gridlock.  This will help solve many of your problems including road capacity (encourages denser passenger ratios), pollution (less stop and go traffic), and less cars means less damage to road structure.

As a resident of Greater Vancouver, I was also shocked at the lack of recycling generally available in the City.  For any city in any part of the world, recycling just makes common sense.  Yes there is an expense to do so, but let’s consider the savings.  The pickup costs are largely offset by the reduction in garbage pickup volume.  Reduced garbage volume means less pressure on the landfills.  Much of what is normally recycled are often items that do not readily break down in landfills and can often leach all kinds of nasties into the surrounding soil and groundwater.  By recycling them we can reclaim many of the materials in the products we throw out.  This reduces costs to remediate dumps, reduces manufacturing costs (recycled material is by its nature pre-processed and so often easier to incorporate into a manufacturing process than raw material and usually much cheaper to purchase as well), and of course recapturing raw materials puts a lot less strain on the diminishing natural resources on this planet and reduces our need for their exploitation.

Scotland also lacked any visible recycling program, and I felt horrible, throwing away plastic, paper, and glass while there.  With a total population of just over 5 million (less than Chicago) and a land mass of 30K square miles compared to Chicago’s 1487 square miles, their logistics challenges for collection is understandable.  But I am sure that the Country could come up with some innovative methods if they put their heads to it.  For me, it felt almost barbaric,  like living with an attitude that stated - Not a problem – we have LOTS of room to just dump it.

The other surprising point for me in Scotland was the food.  It was generally heavy (meat and potatoes or seafood and potatoes), and often lacked the addition of fresh vegetables.  Salads were never a standard part of the meal in most locations we visited.  One server just could not understand that we wanted vegetables with our dinner and not chips. Near the end of our trip, I remarked on this to a Chef at an Inn in Gairlock, and the son of one of our neighbour’s.  He advised that the growing season in Scotland just does not support the production of produce.  Indeed in my travels, I did not drive by even one farm, lots of fields of grazing sheep, but no crops of any nature.  He advised that the vast majority of the Countries’ food is imported from the nearby European neighbours.  They apparently do not even eat a lot of lamb and instead export that product because it is generally too expensive for the ‘locals’.  Fortunately, he followed up our conversation with a large salad course to our meal that was a welcomed addition. 

This, however, got me thinking about the sustainability of that type of culture, and the need for innovative solutions.  If we can grow tomatoes in a greenhouse in the Vancouver region, why can’t others?  It made me realize that a lot of the things I take for granted back home are really very innovative and environmentally responsible, compared to the practices in many other parts of the world:

• We generally have car pool and transit lanes on many arterial routes into and out of the cities (still LOTS of room for improvement).  We provide special parking for small cars, electric cars, and co-op cars.
• We recycle a lot of our trash (the percentage is growing all the time – the District of North Vancouver recently introduced a food waste recycling program) and if our Municipalities are unable to provide recycling pick up or drop off, there are companies like Pacific Mobile that provide drop-off service for many non-compostable products that we as a society would otherwise throw out. 
• We have available to us locally grown and raised produce.  I can even go to a major chain and buy vegetables and fruit grown locally in BC (far less often as we should be able to, but it is a start).  And if I am willing to split my shopping trip up, I can buy fresh and often organic meat and vegetables from smaller stores or directly from the producers.
• We in BC enjoy one of the cleanest electricity grids in North America if not the world. 
• We in BC have much better building standards for insulation, soon to be air tightness, and requirements to keep water out compared with much of the world.

I leave you with this thought:  

WIKI describes “produce” as a description that is often implying that the products are fresh and generally (being made available) in the same (region) where they were harvested.  

Think about this the next time you pick up a bag of grapes, melons, or even snap peas at the local supermarket.  Look at the labels for where the ‘produce’ was grown.  I think you will be shocked.   

Now, think of all the actions required to get the product from where it is grown to the shelf that is now in front of you.  Think of the fuel burned in trucks, boats and planes to move that product. Think of what chemicals and pollutants the ‘produce’ may have been exposed to back in the growing country.

Ask yourself. “Are these sustainable practices?”  I know my answer!