Total Construction Duration to date

Monday, 31 August 2015

Insulating a Durisol ICF Foundation

Hey folks, sorry for the time span since the last post.  I have been concentrating on keeping my building journal up to date.

As I recently have had some free time due to yet another set of medical setbacks, I recently finished editing and uploading a video showing my process of adhering the Roxul ComfortBoardIS mineral wool insulation to my ICF foundation.

The Soprema Colphene Torch'N Stick membrane would typically be used on a site formed concrete foundation, but because I am using a ICF product from Durisol (made from mineralized wood fibre and cement slurry), I too could use this torch on membrane (a process that would destroy conventional EPS foam ICF forms).  The 'tacking' of the insulation to the membrane is only a light mechanical bond and is only suitable for a temporary support of the insulation (or dimple board and other protection sheets) until the backfill takes place.  You would not be able to use the method for a permanent attachment in an above grade assembly.

Once the insulation was attached, I then fastened dimple sheet to the insulation, installed a granular drainage plain, geotextile, and then compacted backfill.  You can read about these steps on my "coming out of the hole" journal entry.

The overall foundation assembly will have multiple layers of safety and will be very durable, but the installation is costly and very time consuming. I can understand why many of these steps are not incorporated into most residential construction. But then, most residential below grade basements are wet to some degree. As my friend Murray Frank often says "You never hear a comment 'It smells as good as a basement'".

Thanks for visiting folks. I will hopefully post a review of all the products I have used to create my foundation walls within the next few weeks. A majority of the products get a thumbs up from a technical standpoint, but one in particular is a two thumbs down with extreme prejudice.  I encourage you to subscribe if you want to be notified of when this review is posted.

Friday, 29 May 2015

Air Leakage of Old House - Does it matter?

*** Update - Upon further reflection of this topic, I do feel there is one additional reason to perform energy upgrades and discuss it in my project journal ***
This blog entry will analyze the air leakage of a 1954 house and relate that to the energy use and durability of the house.

Before I started tearing down my 1954 single storey 1500 sq ft bungalow to make way for, I decided to have the house tested for air leakage by Michael and Deborah from H&H small home solutions inc (hhsss at shaw dot ca).  H&H typically perform leakage testing to determine the EnerGuide rating for new construction, so this was going to be a new experience for them (and their blower door).

They came by in late March of 2014 after I had moved out but before I had completely emptied the house and before any deconstruction had been performed. The house was prepped by sealing the wood burning fireplace insert, range hood, and the through-wall mailbox before setting up the blower door.

We first ran the door in a B configuration and were unable to get up to the final test pressure of -50 Pa. But even in this configuration we got some scary results.  I had not really made any great attempts to air seal this house over the years.  There was weather stripping on 1 of the 3 doors, and the cedar siding had each coarse sealed to the next and the siding sealed to most of the window and door frames. But no attempts had been made to seal the interior interface with the attic plane and 1 of the doors had a cat door in it and the main door itself had very large gaps around it.

Prior to starting the test I had predicted an air leakage around 8-10 ACH (Air Changes per hour) @ -50 Pa, but early in the test we could tell it was going to be well above this. Deborah could tell just from the sound the fan was making (there previous worst house they tested was 11 ACH @ -50 Pa which was scary as it was new construction).

Right off the bat we reached 28 air exchanges at only -15 Pa!  To give you an idea, 15 Pa relates to a wind speed of only 11 MPH.  In the fall, I regularly recorded winds speeds on the property at this speed or higher so during those events all of that CONDITIONED air in the house was potentially changing over 28 times every hour. That is a lot of extra load on the heating plant and also explained the drafts my wife typically was feeling.

Over the next hour or so we tested at various configurations until we ran the fan at full open configuration (no restrictor plates). Only then could we get enough air volume to allow us to reach the target test pressure of -50 Pa.  AT the full test pressure we recorded an air leakage of 21.74 ACH -50Pa.

Now wait, some of you may have noticed that that is less air leakage than what we observed at only -15 Pa.  How is this possible you say?

Well, it is actually quite common.  As more and more negative pressure is placed on a dwelling, the two surfaces on each side of an air path (leak) can start to come together.  Eventually they can close up tight and stop that leak.  This why I have a bit of an issue (actually quite a bit), of testing dwellings at -50 Pa.  This relates to a wind speed of 20 Mph which is much higher than some locations would experience on a regular basis and much lower than other locations average wind speeds.  As such, it is my opinion that their should be a standard test pressure PER geographical region.  This could be a table much like the climate zone charts, but would be based on the average yearly mean wind speeds for a specific area.  Homes in higher wind speed regions should be tested at higher pressures than homes in lower wind speed regions.

(Side bar - the reason the wind speed is important is that it is this force that will effect the pressures on a dwelling.  Yes a house can depressurize under mechanical ventilation, but these are usually infrequent where wind depressurization or pressurization of the dwelling could occur for months at a time in windy locations).

So - these tests showed that the house was VERY leaky.  What does that mean in terms of heating bills, comfort, and building durability.

Heating Bills

The truth is, this air leakage did not really make a huge difference in energy costs.  My heating bills (for space and domestic hot water) were typically well under $2000 a year (We are under $2000 for both gas AND electrical use).  As I am a heavy bath user, it is safe to say aprox 40% of this was domestic hot water use.  This leaves an estimated $1000 in annual space heating costs.  That works out to less than $100 a month, or well less than the cost of a weekend dinner out.

We typically had the heat set for 72-73F in the wintertime and basically did not tough the thermostat all year.  It was not uncommon for the heat to come on during cold late spring and early fall evenings.  We did however use a programmable thermostat that was set to come on at 7 AM, step down to about 65F at 8:30 AM, come back to temp at 4 PM, and step back down to about 68F at 11:30 PM.  This was only partially for energy savings.  The night time set backs were used because we had hydronic heating through large built-in wall registers (1-2 per room) via a 1980's gas boiler.  The pipes went through and rubbed on the wood sub-floor assembly, so if the heat came on during the night the 'clicking' would wake me up.  So we partially closed the bedroom door (so cats could still get in and out and not cause another source of nighttime wake-ups) and used an electric oil heater to maintain a comfortable temp in the bedroom.

While air tightness is important, it will not make a huge difference to your pocket book unless you have a very large and leaky house.


The air leakage did however make a big difference in occupant comfort and should, in my opinion, be the biggest (and probably only) reason to upgrade an older home.  The house was uncomfortable to sit in near any exterior wall in the winter months due to the drafts present.  I was quite surprised when I saw how leaky the fixed, but home made, windows in the living room were.  The builder had just placed the single pane of window glass against a wood surface and clamped it with a second wood component.  At -15Pa, the wind just whistled through these locations.  There is no question, that making the house more air tight would have made the house more comfortable.


Normally when one discusses the reasons for making a dwelling air tight, it is in the context of a 'modern' home with current levels of code required insulation.  With modern levels of insulation, it is critical to ensure that air leakage does not occur, in order to prevent interior air leaking into the wall or roof assembly and condensing on cold sheathing.  Left unchecked, this will often lead to mold and rot within the assembly.

The key here is the qty and location of the insulation.  As soon as enough insulation is placed inside of the sheathing to allow the sheathing to cool down below the dew point of the interior air, you now have an assembly with a very high liability should any appreciable amount of air leak into that assembly from the conditioned interior. This is because air currents are the #1 mover of moisture next to bulk water leaks caused by plumbing leaks or incorrectly detailed cladding or roofs that permit bulk rain water entry into the assembly.

But in older houses like the one I took down (which had ZERO insulation in the walls), there is not enough insulation present to block the heat loss from the house enough to allow the sheathing to get to the dangerous dew point conditions.  If you never reach the dew point, you can have huge amounts of moisture moving into the wall via air leakage and never have to worry about it because it stays in vapour form and just moves on through either to the outside of the dwelling or back into the inside. There is never liquid water that results from this air leakage. This is the reason why older homes have performed so well over many decades without the presence of air barriers, vapour barriers, or even effective water shedding surfaces.  The heat loss has always been enough to 'cook' any accumulated moisture out of the assembly.


We have identified in this article that there is not a huge financial penalty for a leaky house.  In my case, the costs per month for space heating were under $100/month in what is considered a cold-heating-dominated climate.  This $1200 annual investment would not get very far in paying for a deep energy retrofit which typically would cost 10's of thousands of dollars.  Lets say you could reduce the heating load even as much as 75% (purely speculative and most likely could not meet), this would represent $900 annual contribution to renovation costs.

A REALLY cheap stud level renovation for my home (including new windows and doors) would have been at least $60K (going to need to rip out parts of bathrooms and kitchens so most likely will totally renovate those rooms - my budget of $60 assumes very low end cabinets for these rooms).

A very intensive attic floor plane sealing regime would have been at least $15K (not going to do this process without bringing attic up to current insulation levels when done).

At a highly inflated $900 annual savings, these two projects would have a 66 and 17 year payback respectively. The attic plane sealing payback would most likely be much longer as only sealing this plane would probably represent only 50-70% of all air leakage present and therefore there would be reduced energy savings.

And my house did not represent an unusual annual energy bill. This US Energy Summary shows that for the West, the average annual winter heating bill per household varies between $1300 and $800 depending on year.

In the end, due to our really low energy costs, and the likely hood that they will not appreciably escalate for many decades due to Government interference, it makes very little sense to upgrade an existing homes energy performance for personal financial savings.  Therefore the type of renovation needed to reduce air leakage or increase thermal performance, only makes sense if the home is being renovated anyway for cosmetic or occupant comfort reasons.

On a separate track - this logic also holds true when analyzing extreme new construction programs like Passive House.  The costs to reach passive house levels of energy reduction will not be paid back over the lifespan of the dwelling in most cases. The added detriment of these programs is that the embodied energy of the insulation products built into these dwellings also do not have a pay back within the lifespan of the dwelling.  Instead for new construction, it makes more sense to build a "Pretty Good House" (coined by Joe Lstiburek) and then use the excess capital available to either contribute to distributed or on-site energy generation.

It is however critical that air leakage be reduced down to a minimum (experts do not agree how little is adequate - but the number is somewhere between 1ACH+/-50 and 3ACH+/-50) for new construction or energy retrofits IF, you have built an assembly with enough insulation inboard of the sheathing to cause the sheathing to cool down to the dew point potential of any leaking interior air.   If you build a safer assembly with the insulation outboard of the sheathing (or enough outboard to maintain the sheathing above the dew point potential), then while air leakage is still important to address from an energy loss standpoint (the costs to get it right during construction are minimal and will be paid back by reduced energy usage), it usually will not cause a durability concern for the assembly.  This of course is all from the perspective of a heating dominated climate.  The direction of flow and order of layers for the assembly are different in a cooling dominated or mixed climate.

Sunday, 5 April 2015

Foundation Rebar Installation Primer

Wow - cannot believe it was last November when I last posted to this blog!  I promise to start writing more technical posting (as opposed to the daily journal entries found at my building web site).

I posted this on my journal as well, but felt it was important enough to also post here.

I received some feedback to my journal posting yesterday that was suggesting I should look at the 'other' ICF manufacturers if I wanted to know how Rebar was 'supposed' to be placed.  I did and the result sure is scary.  Because you are allowed to install ICF walls without ANY engineering assistance (as long as you meet the building codes requirements including max unsupported wall height) and therefore engineering inspection, there is a plethora of miss-information out there regarding the requirements for rebar reinforcing of an ICF wall.

At least the BC Building code makes it pretty clear on the requirements, but I suspect that because the Municipal inspector is not present at time of pour, these requirements may not be adhered to - at least that is what is evidenced by one of the discussion forums I visited last night.

So - lets first look at the BC Building Code requirements.

The Horizontal rods are to be installed every 2 ft vertically and are to have 1-3/16" inside minimum cover (30mm) meaning that the rod is to be held off the outboard surface of the inside ICF panel to allow 1-3/16" of concrete to be present on the inside face of the bar.

The Vertical rods are to be installed per tables BCBC A to C depending on core thickness and height of wall.  The first options calls for vertical rod placed every 16" horizontally with again 1-3/16" inside cover (30mm) minimum.

Obviously both vertical and horizontal bars are unable to occupy the same plane off the inside face of the foundation, so the code also specifies a max cover by stating the bars are to be "located located in the inside half of the wall section".

My requirements were much more stringent because of the height of the wall.  The engineer specified vertical bars every 12" horizontally and horizontal bars every 2' vertically.  I was not given a range for the vertical bar - it required 1.5" of inside cover.  When I asked if 2" or even 2.5" would be OK, I was informed that they would have to rerun all of the calculations and that they suspected there would be problems.  So, I did by best to ensure 1.5" cover.

My drawings also specified 1.5" cover for the horizontal bars, but I failed to abide by that when placing the bars.  Because I drew up the structural drawings (with the instructions received from the engineer), and had drawn the horizontal in the centre of the core, and because I am more of a visual person instead of word person - I placed the horizontal bar down the middle of the blocks during installation.  Fortunately, my blunder was forgiven.  When doing the calculations for the wall, the engineer had generally only used the vertical bars in the strength calculations and the horizontal bars were more present for crack control. I was very relieved (and thank-full to Tacoma for providing very fast responses to all of my rebar questions), as by the time I had discovered the blunder, all of the horizontal bar had already been placed.  While waiting for the reply to come the following morning, I tossed and turned all night worrying I was going to have to disassemble the wall or pay for a fibre additive to add to the concrete for strength, like the Helix fibre (you may remember from an earlier posting, I was looking at this but had ruled it out as being too costly considering it could not replace ALL of the vertical rods).

The most important point of this primer is that you MUST pay attention to the cover stated for each bar installation.  A bar placed without the appropriate cover almost becomes a bar that no longer contributes to the strength of the wall. For instance, if the bar was placed on the outside half of the core, you may as well not even have it there.  This brings me to the next part of my primer.

Rebar chair is used to hold rod at a precise cover off the inside face of the forms.
Why is rebar installed in concrete anyway? 

Concrete has awesome compression strength but is quite poor in tension. Because the weight of the back-filled soil is pressing on the foundation, it wants to  'bow' inward under the pressure.  This would place the outside half of the core into compression but would place the inside half under tension (just like a floor joist but in a vertical plane).  The inside half of the concrete core is trying to stretch to accommodate the bow.  As concrete is not good when pulled on, the stretching would eventually cause the concrete to fracture.  By placing rebar into the concrete, it prevents the concrete from stretching too far and fracturing.  The closer the bar is to the inside face of the concrete core, the more tension forces it will encounter.  Another way to look at this is the distance it would take to run or drive around the outside of a track compared to the inside lane of a track.  The further outboard you get, the farther you run or the longer the circuit is.

So, if your wall is designed with 1.5" inside cover, that means the engineer has calculated the stresses of the wall at that 1.5" plane and ensured to call out a rebar pattern that can accommodate those stresses. If there is not enough cover, then there will not be enough concrete to properly capture the bar and keep it in place, but if there is too much cover the rebar will not be able to remove enough of the load from the 'stretch' of the wall and the concrete will fracture. If the rebar was placed in the outside half of the core, it would no longer be subjected to ANY tension and in fact would be being squeezed by the surrounding concrete that is under compression forces.

While researching this last night I came across the installation instructions for a very popular rigid foam based ICF (and the manufacturer that was reportedly sued in the West Vancouver failure).  They instruct the installer to "Place plastic sleeves (1½" [38mm] conduit) over stub steel for later placement of vertical steel" meaning to slip chunks of plastic conduit over the dowels placed in the footing to later capture the bottom end of the vertical rod.  But as the dowels are placed typically down the centre of the footing, this would place the vertical rods down the neutral plane of the foundation wall, or a spot it will do very little good to resist the tensions of the foundation wall.

I also came across this forum on discussing the placement of the steel and it was very clear a majority of the contributors did not truly 'get it'. Lets quickly correct some of the miss-information.  
  • Why do we tie off rebar under some circumstances?
Simply to hold the bar in the RIGHT position until the concrete has been poured and can hold the bar for us.  It provides NO structural strength whatsoever. 

So why is the tying off of the rebar inspected before pouring by the engineers? Why is it important that the tie-off securely fastens the bars together?  Because as we have discussed above, it is critical that the bar is placed in the right position to ensure it can bare the intended load.  As the tie wire is quite brittle, if the bars can move slightly because of not being tied-off tightly, there is a chance the sudden shock of the movement could break the wire which would now allow for the bar to move substantially out of position.
  • Is it important that the horizontal bars are tied to the vertical bars (something that cannot be done in ICF construction)? 
No - full stop.  Each orientation of the bar is typically handling separately calculated loads and not considered an 'assembly' (In some extreme cases I do believe it is a 'grid' that is designed, but in these cases sophisticated FEA software is used and the bar must be welded together not tied).
  • Is staggering the horizontal bars to capture the vertical bar the required solution?
No - this is only appropriate for above grade ICF installations.  In order to ensure the vertical bar was placed inboard enough on the core, the inside horizontal bar would not have enough cover.
  • Why is it important to tie-off splices?
You need to ensure that the bars are fully encased in concrete.  If the bars were not tied tight to each other, they would allow small pockets to form between the bars that were too small for the flow of concrete.  This would provide a weak point because the bar would now not be in communication with the concrete and therefore unable to bare the intended load.  This is why bars in close proximity, and in the same plane, need to be tightly bundled or held apart a minimum distance by means of chairs or other securing.
  • Why do the vertical bars not need to be tied-off or otherwise captured to the footing dowels?
Footing dowels or any other dowels have nothing to do with the tension stresses a concrete  assembly is under.  Their sole purpose is to tie the concrete on each side of a cold seam (concrete poured at two different occasions) together.  SO in the case of a footing dowel, the purpose is to ensure the foundation wall cannot 'slip off (shear)' of the footing.  This is why most codes also allow the formation of a key in the footing, instead of the dowels, to capture the bottom side of the foundation.

Hope this has been of some assistance. Should there be something that you disagree with, then please provide documented background for your disagreement and I will reconsider.

Thanks for visiting.

Wednesday, 12 November 2014

Choosing Materials

The green building movement makes a big deal about choosing the right materials to ensure a product can be reused or returned to the raw material market at the end of the life-cycle.  The end goal is of course to reduce the embodied energy of the project.

While this is a lofty ideal and worth pursuing, a reality check often shows that while a material is technically recyclable, there often (usually) not programs in place to actually process the used material.  During the deconstruction of my house, I ran into two good examples.

My kitchen floor was pure linoleum tiles (essentially linseed oil).  This is a product that can be composted or used as fuel for large scale heating boilers.  But in my region, there was no program set up to process the product and I ended up taking it to the landfill (I did not have the facilities to grind up and compost myself).

The second product I failed to recycle was all of the plastic pipe I salvaged from below grade.  This included PVC drainage pipe, PVC irrigation pipe, and ABS sewer pipe.  For this commodity, there was a program in place to recycle the material, but only if it was VERY clean (think like new).  The process available could not handle pipe with any dirt or other sediment on it.  SO in the end, it too had to go to the landfill.

Misc Pipe and Plastic that was not accepted at recycling facility.

While we should endeavour to reduce our footprint on the planet and choose materials with lower embodied energy, we should also ensure that the materials we do choose are the most suited to the application.

I see too many 'green' building designs that choose a 'green' product due to a promised carbon footprint as the primary focus, without ensuring the product will be durable long term in service. This often will result in the need to replace the product after a very short life cycles.  Even if the product can be returned back to the raw material supply chain, this still represents an increased burden on the planet compared to a competitive product that while being less 'green', is more durable in service.  And if the 'green' product cannot be returned to the supply chain, you are just that much further behind.

Instead, my focus is to start at the most durable end of the spectrum and then try to pick products with lower embodied energy characteristics from the high performance candidates, AND install the products per best practices to ensure they are as useful and durable as possible.

My long term hope is that the cost of new materials becomes so high that even the main stream players in the market see recycling as a no-brainer.  This would address the fact that right now, recycling often does not make sense from strictly a financial platform.  However part of the problem is also the technical challenges in recycling a product.

Fortunately, there is some visionaries that have been working for many years to solve some of these hurdles. Mike Biddle has been working on a system that can separate bulk shredded plastics into the different colours and materials solving one of the biggest stumbling blocks to mass recycling of plastics (read PopSci article for full storey).  The beauty of his system is that this is all done in N.A., saving the need to ship offshore, via an automated process (no high labour costs). By keeping the product on our shores, we reduce the pollution our society is creating within poorer countries.

Lets hope others are working on the myriad of other materials we as a society currently just discard.

Mike Biddle has developed an automated (IE cheap - labour free) method of allowing plastic materials to be ground up on mass and then separated into the individual colour and materials making up that mass.

Wednesday, 15 October 2014

Does PassiveHaus make sense?

Just a short update to showcase an article at Green Building Adviser that perfectly sums up the conclusions I made about the Passive House program and why I cancelled my plans to build to that standard.

The author of the article, found at, tracked the actual energy use of several homes in Massachusetts and has determined that even a modest investment in insulation and air tightness (termed a pretty good house by Joe Lstiburek) is more than enough to reduce the heating and cooling loads to the point where it makes more sense to concentrate on plug and domestic hot water loads as is shown in the below graphic.

Extracted from

The real world data monitoring has also shown that the assumptions made in the PHPP (the modelling system for PassiveHaus) are often wrong.  The author states, “PHPP assumes 6.6 gallons [25 liters] of hot water a day per person, but that’s not enough for normal Americans.”

I jumped on board the PassiveHaus train for about a year in the early design stages of my upcoming build.  It was easy to be swept up in the well polished program and fall in love with the projected savings.  But as I became better and better educated on building science, source energy, and embodied energy, I felt their were huge holes in the program.  The underlying principles of air tightness and thermal bridge free construction were sound, but in my view the chase for heating and cooling reductions bypassed the sweet spot where it made much more sense, from an embodied energy and a cost point of view, to look at on site production than further reduction. The biggest stumbling block was the claimed 10-15% added build cost to reach PH when in reality it is much closer to 200% on average when comparing to a code min house (which after all is what the majority of homes in North America are built to).

In the end I decided to build a "pretty good house" and will monitor energy loads once occupied and then model whether or not I reached the sweet spot between reduction and production.

Thanks for visiting.  For the current status of the build please visit

PS: For an excellent article on why  more insulation is not always better, read

Sunday, 31 August 2014

Sub Slab Insulation - EPS vs XPS

As some of my regular readers know, I tested samples of EPS and XPS in an underground wet environment to see which over time absorbed more moisture.

I described the experiment design in my blog posting of Aug 22, 2013 and describe the start of the experiment in my posting of October 6, 2013.

Fig 1: Samples at beginning of experiment.  These were buried below aprox 4 ft of dirt in a wet environment subjected to regular/constant ground water.
 I dug up the samples March 25, 2014 and the results do not look good for EPS.

Table 1: Weight of buried samples at end of 9 months.
As you can see in table 1, over the same period of time and in the same conditions, EPS absorbed an average of 258% of its original mass in additional water compared to only 31% for XPS.

Once I finished my on-site testing of the samples, I then took them all down to Fitsum Tariku, an instructor at BCIT and Director of Building Science Centre of Excellence (to name just some of his many accomplishments and titles). Fitsum offered to have some of his Masters students in the Master of Engineering in Building Science program run some experiments to determine the total moisture take-up potential of both products as well as the thermal resistance once saturated.

Unfortunately they were unable to use my buried samples because they were too damaged (I should have bed them in a thicker layer of sand both below and above to protect the integrity of the samples - however it was still a very revealing test based on my results in table 1 above).  Instead they used samples I had submerged in a tub of water and others I had on a shelf during the experiment.

In the following tables, you can see that EPS also does poorly from a R-Value retention point of view when saturated compared to XPS.

Table 2: Dry weight of samples measured by BCIT
Table 3: Measured R-Value (using Hot Box) of both dry and wet samples
Table 4: Difference in R-Value between two insulation types both when dry and wet.
Table 5: Loss of thermal resistance when saturated.

The last graphic tells it all - EPS looses 15.7% of its thermal resistance when in a wet environment and saturated compared to only 3% for XPS.

So why is EPS used in many 'green' projects.  This stems from the EPS industries claims that it represents a lower Global Warming Potential vs XPS due to its use of Pentane as a blowing agent compared to the traditional HCFC agent used by the XPS industry.  But XPS manufacturers like Owens Corning have already replaced their blowing agent with a Zero Ozone Depleting formula.

Finally, one positive recorded result is that both products met or exceeded their published thermal resistance per inch of R4.27 for EPS and R5 for XPS (as shown in table 3 - dry state). 

The outcome in our view is pretty clear cut - over the extended period representing the lifespan of a dwelling (50+ Years), the lower initial thermal resistance, and then the significant deteriorating of R value if EPS gets wet and stays wet, far out-way any environmental benefits claimed for EPS.  The obvious choice for below slab insulation applications is clearly XPS when all factors are taken into consideration.

Sample Specifications:
XPS - Owens Corning Foamular C-300 (30 psi) 
EPS - Plasti-Fab PlastiSpan 30 (30 psi) 

Sunday, 10 August 2014

SENWiEco concludes testing of DURISOL ICF Block

When choosing a foundation your options are typically a site formed and poured concrete wall or some form of insulated concrete form (ICF) wall.  Early on in the process I gravitated to an ICF wall because it would eliminate the need to hire forming crews and rent and fabricate forms.

When looking at ICF, the traditional product is made from some form of EPS foam which has a very high embodied energy, lots of off-gassing, and is made from non-renewable components. The foam industry (EPS and XPS) will try to 'green-wash' this by stating the foam, as an insulation, reduces heat loss and reduces carbon output over the lifespan of the dwelling.  Yes this is true for ANY insulation, so choosing an insulation with a starting lower embodied energy will put you that much further ahead on your reduction goals. So again, early in the process I looked for a product that on the surface was friendlier to the planet.

One of the benefits of all ICF walls is that they typically require a smaller concrete core than a standard foundation.  The code allows for a 5.5" core on ICF walls where a standard site formed wall generally start at 8".  The reason for this escapes me because the ICF product itself is not considered structural so why would all walls not be allowed to be only 5.5" regardless of forming method.  If someone knows the answer to this please post a comment.  The smaller core of the ICF significantly reduces the concrete needed and therefore the cost and embodied energy of the overall wall.

One of the other downsides to a typical ICF forming material (foam), is that you end up with too much insulation on the inboard face of the core.  This decouples the core from the interior environment and can lead to condensation in some isolated cases, but more importantly it limits the walls ability to be a moderating force to the homes inside environment. An exposed concrete wall can buffer the temperatures by acting as a thermal mass.

The further downside to foam style ICF blocks is that just about everyone loves them from rats to ants.  They burrow and nest in the product creating holes in your thermal blanket.  They are also quite fragile and can be easily damaged during construction and require significant blocking during pouring to prevent blow-out.

My quest for the perfect block led me to the Durisol product.  It is made with virgin but scrap wood (manufacturing waste and tree tops).  This wood is chipped and then through a patented process, the organics are removed to create a mineralized wood fibre (think petrified wood).  This is then added to a cement slurry and formed into the ICF block.  This process and product would help meet my goals to dramatically reduce the embodied energy of the foundation.

There is another similar product made by Faswall, but my research indicated that this product utilized non-virgin wood sources like used pallets and had a lot more dimensional tolerance issues with the block itself.  I also was informed that Faswall was initially going to be a licensee of Durisol but ended up swiping the formulation and heading out n their own.  This did not sound like the right fit for me so I focused on Durisol even though it meant I would have to freight them from back east.

Once I decided to seriously consider Durisol, I then wanted to ensure it was suitable for the task. My immediate concern was that the blocks would rot.  But the product has been used for decades as sound abatement walls on highways (where some of the wall is always buried) and I received a letter from the Ontario Ministry of Transport advising that they have never had to repair a wall due to decay (just traffic accident damage).

My next concern was how would this wall act from the point of view of air and moisture movement.  It was made clear from the beginning, that I would need a independent air barrier as this product was air permeable (it has webs that penetrate through the concrete core so the core is not continuous).   So this was a negative against the product when compared to foam, but as I wanted a bullet proof building enclosure, I had always planned on an robust WRB (water resistant barrier) on the exterior of the foundation.  I think the idea of 'damp-proofing' a foundation wall in a rain forest climate is ludicrous and had always planned on Water Proofing my wall.  And a waterproof membrane is almost always also an air barrier.

My next concern was how the blocks would act if subjected to regular wetting.  The manufacturer claimed the product was unable to support capillary action and had some university testing to support.  But I was not satisfied and so set out to torture test the product over 16 months.  I started the experiment in Jan of 2013 (Begin experiment).  At the eight month mark I posted the status) Status at 8 months) and then altered the block to also contain the concrete core.  The experiment concluded on June 1, 2014.

All off my testing supported the manufactures claims.  This was a free draining assembly that did not support moisture movement from the outboard to inboard face.   I will also be preventing moisture movement through the footings via a FastFoot mebrane and also using a touch-on or self-adhered AB/WRB mebrane on the outside face of the foundation and so will have a very durable and forgiving assembly.  I now felt confident using this product on my project and have now received the product on site.  Once the excavation is complete, I will post some videos on the installation of the product (visit my project journal for the tribulations in getting these goods to site).

As I have time (may be at end of construction, I will also try to post some cost comparisons between the various options and the embodied energy numbers).

Thanks for visiting.