Lobster time (at Boutiliers Point)

Stopped in to visit our friends from Amos Wood at their new digs on Agricola Street in Halifax. All we can say is WOW. What a great space and great products. We are big fans of Amos Wood - they are true professionals and have an amazing array of wood products. 

If you haven’t stopped in to see Jeff be sure to do so. He is a pleasure to deal with and can certainly help you with most anything you might need. You can’t find this level of service or quality of products at the big box stores. 

Above is a nice mix of soft maple flooring (natural colour) and stained pine. The outside decking is a great product out of New Brunswick called ThermalWood - check it out. 

Great job on this build MRB Contracting

Looking for an invisible fastening system for Cembrit Panels on wood strapping? Tweha LijmTec is your solution and Keel AP can help.

Are We Sealing the Right Walls in Buildings?

This is a very interesting article by Joseph Lstiburek of Building Science Corporation that we stumbled upon in Durability + Design. It touches on two of our core strengths here at Keel AP, building envelope and fire protection. To be honest we never put these two in the same category unless trying to create fire separations at each floor in the ventilated facade cavity. This is an entirely “new” and interesting way to look at the building as a whole. Looks like we might be talking about Vaproshield and STI Firestop in the some conversation.

* I shamelessly paraphrased the title of a paper Mark Lawton wrote 20 years ago: “Are We Sealing the Wrong Walls in Apartments?” Royal Architectural Institute of Canada Advanced Building Newsletter, Vol. 1, No. 4, July 1994. The Lawton paper was based on G.O. Hand-gord’s work that he didn’t get around to publishing until 2001. Gus was on to this very early; he just didn’t always write things down and get them published and peer reviewed in a timely fashion. He finally wrote it all down in 2001.

I first heard it from him when I took his class at the University of Toronto in 1982, and he was talking about it much earlier than that. I was sold and began pushing compartmentalization when I first started working in the United States in the mid-1980s. I still smile when I remember the arguments with the Chicago high-rise boys during the early years. See Handegord, G.O. “A New Approach to Ventilation of High Rise Apartments,” Proceedings of the Eighth Conference on Building Science and Technology, Ontario Building Envelope Council, Toronto, Ontario, February 2001.

The term “air barrier” has gone from obscurity to buzz word in less than a decade, and everyone is running around sealing the outside of buildings. But if you look at the physics, we are sealing the wrong walls. If we really want to improve the building performance of multi-story buildings, we should be air-sealing the interior demising walls and isolating floors from one another.

On the exterior of the building, the water-control layer and air-control layer have pretty much merged into a single material or product, typically called the “air barrier.” It is pretty obvious that the water-control function “air barriers” handle is significantly more important than their air-control function. We probably should have had WABAA, the Water and Air Barrier Association of America, rather than ABAA, the Air Barrier Association of America. Owners rarely get a call at 2 in the morning saying their building is leaking air … but the calls regarding water leakage happen 24/7.

The good news for ABAA and “air barriers” is that “air barriers” have turned out to be magnificent water-control layers. That by itself “wins” the value proposition; water control is why most owners buy “air barriers,” and water control is why most architects specify “air barriers.” Assemblies leaking rain just don’t fly, any more than water-leakage liability does. But in terms of overall building performance, the “real action” is on the inside. That’s where the energy penalties lie, that’s where the indoor air-quality penalties lie, and that’s where the smoke- and fire-control penalties lie.

Most folks in the air barrier business think that the “air barrier” is the primary air enclosure boundary that separates indoor (conditioned) and outdoor (unconditioned) air. Most folks forget that in high-rise buildings and in multi-unit apartment construction, the air barrier system is also supposed to separate the conditioned air between floors and from any given unit and adjacent units. Even more importantly, the air barrier is also the fire barrier and smoke barrier in these inter-unit separations. This inter-unit separation must meet specific fire-resistance ratings. There is a huge untapped business opportunity here, more surfaces that need to be air barriers (hint, hint, nudge, nudge).

Creating 10 One-Story Buildings

The key to this argument is understanding the stack effect.

The stack effect gets its name from the same phenomenon that causes hot combustion gases to rise in a chimney or chimney stack. A heated building can be considered a giant chimney that we live and work in. The taller the building, the greater the stack effect. The colder the temperature, the greater the stack effect. In heated buildings, the air tends to flow out of the top of the building, while inducing air to flow in at the bottom. A real smart old guy wrote about this in 1926.

 No, I never met Professor Emswiler. Not even I am that old. Check out the reference at the end of this article. University of Michigan lad. Go Wolverines. Professor Emswiler also wrote a classic text on thermodynamics amazingly enough called “Thermodynamics.”

Stack effect-driven airflows in tall buildings compromise smoke control and fire safety, adversely affect indoor air quality and comfort, and increase operating costs for space-conditioning energy. The air in lower floors ends up in the upper floors (figures 1 and 2). I guess that is why folks in the upper floors pay more for the privilege.

Fig. 1: Stack Effect in a Tall Building — Interior airflows in tall buildings compromise smoke control, fire safety, indoor air quality, comfort and energy use.

Fig. 2: More Stack Effect in a Tall Building — The air in lower units ends up in the upper units. I guess that is why folks in the upper units pay more for the privilege.

By isolating the floors and units from each other and from corridors, shafts, elevators and stairwells, we can control stack effect-driven interior airflows (figure 3). Today we call this compartmentalization. The most elegant argument for compartmentalization of tall buildings came from Handegord (2001).

Fig. 3: Compartmentalization — Basically, you turn a 10-story building into 10 one-story buildings that are stacked on top of one another. By isolating the units from each other and from corridors, you can control shafts, elevators and stairwells stack effect-driven interior airflows.

Basically, you turn a 10-story building into 10 one-story buildings that are stacked on top of one another. So why do it?

Well, now the air-pressure differences are much lower. Rather than a 10-story stack effect acting across your building, you have 10 one-story stack effects. Neat, eh?

With one-story stack effects, you can have operable windows in tall buildings. Check outphotograph 1. Clearly not a North American building. If you proposed this to your mechanical engineer, his or her head would explode. You might want to mention this to them for the entertainment value alone … but wear a raincoat and goggles to handle the gray matter and bone fragments.

Photograph 1: Operable Windows in a Commercial Office Building — somewhere in a European country that is known for pasta.

The irony is that we pioneered this concept in North America in the 1930s. North America is where tall buildings were first built, and we built them with operable windows (photograph 2). We were able to do this because we compartmentalized and we didn’t move air between floors for conditioning and ventilation. Ducts and shafts running between floors defeat compartmentalization. Elevator lobbies needed to be in vestibules, and they were.

Photograph 2: Old School — magnificent Depression-era building with operable windows. Not bad for a bunch of geezers, eh?

I don’t know any architect who would argue against having operable windows in a tall building. I don’t know any occupant or tenant or employee who would argue against having operable windows. Only engineers do. But they didn’t in the past. The reason engineers argue against operable windows is that you need distributed mechanical systems that are limited to serving a floor or a unit or a “compartment.” You can move chilled water and hot water across compartments and across floors, but not air in ducts. This means more fans, and apparently that drives some engineers insane.

The architect’s argument against compartmentalization and distributed mechanical systems is that they don’t like the “holes” and “penetrations” in their nice facades. Come on folks, make them look good. You want operable windows, you are going to have to live with more holes. You want that LEED “compartmentalization” credit, you are going to have to live with more holes. Running exhaust ventilation ducts up to the roof is not going to fly in a truly high-performance building.

Achieving compartmentalization is not easy. You have to think three-dimensionally and treat your interior walls like exterior walls (figure 4). Back in the day, some of us guessed at what unit air tightness should be. I proposed a minimum resistance or air permeance of 2.00 liters per square meter at 75 pascals (Lstiburek, 2005). It seems to be working. This level of unit air tightness is necessary to control stack effect air pressures and to limit airflow from adjacent units and cross-contamination.

Fig. 4: More Compartmentalization — You have to think three-dimensionally and treat your interior walls like exterior walls. A minimum resistance or air permeance of 2.00 liters per square meter at 75 pascals of unit air tightness is necessary to control stack effect air pressures and to limit airflow from adjacent units and cross-contamination. Individual units are air-sealed and tested by pressurization or depressurization for compliance.

If this number sounds familiar, it should be. It is the same resistance or air permeance that most groups recommend for the entire building enclosure.

Rethinking What We Think We Know

How do you meet this level of compartment “tightness”? Be anal regarding the fire code and smoke-control practices. For once, the smoke and fire guys are on the right page. Run the compartment demising walls to the underside of the floor above and seal them airtight. It should be happening already (photograph 3).

Photograph 3: Compartmentalization Air Sealing — gypsum board is run up to the underside of the floor sheathing above and sealed with joint compound.

The bottoms of the walls are typically sealed with gypcrete (photograph 4). Electrical boxes are sealed with “putty pads,” and joint compound is used to complete the seal between the box and the cut opening in the gypsum board (photograph 5). Compartment doors are weather-stripped (photograph 6).

Photograph 4: More Compartmentalization Air Sealing — bottom of walls are sealed fabulously well when gypcrete floors are used.

Photograph 5: Weather-Stripped Door — a beautiful thing if you are worried about fires.

Photograph 6: Airtight Electrical Box — putty pads are used to seal electrical boxes airtight. Joint compound is used to complete the seal between the electrical box lip and the cut opening in the gypsum board.

Let’s say you achieve compartmentalization. You are not done. Now the mechanical engineer can screw it all up by running ducts and shafts vertically. No central systems. You can’t make that work. You need to keep the ducts within each compartment and vent directly to the exterior (figure 5). No complaints from you architects about penetrations being ugly. Just deal with it (photograph 7).

Fig. 5: Unit Ventilation — Do not run ducts and shafts vertically. No central systems. You can’t make that work. You need to keep the ducts within each compartment and vent directly to the exterior. No complaints from you architects about penetrations being ugly. Just deal with it.

Photograph 7: Penetrations in Exterior Walls — yes, there need to be more of them.

You need to deal with the vertical communication that elevators cause. The elevators now have to go into vestibules (photograph 8).

Photograph 8: Elevator Lobby — enclosed in a vestibule, or “air lock,” that isolates the vertical communication from the horizontal communication.

The compartmentalization principle also needs to be extended to heating, cooling and domestic hot water. Individual mechanical systems located in each unit provide unit space heating and cooling and hot water (figure 6).

Fig. 6: Space Conditioning and Hot Water — The compartmentalization principle can also be extended to heating, cooling and domestic hot water. Individual mechanical systems located in each unit provide unit space heating and cooling and hot water.

The principles behind all of this are pretty straightforward. The approaches are pretty straightforward. The need to do this is pretty straightforward. Execution is anything but.

Execution involves architectural rethinking, engineering rethinking, contractor and trade rethinking and owner rethinking. The good news is that we did it almost a century ago when we first started to go big and tall. I think it is time again. Think of the possibilities that new materials and new systems can bring to the table.

About the Author

Joseph Lstiburek is a principal of Building Science Corp. (buildingscience.com). Lstiburek has been a licensed professional engineer in the province of Ontario since 1982 and is an ASHRAE Fellow. He is also an adjunct professor of building science at the University of Toronto. He has more than 30 years of experience in design, construction, investigation and building science research. He is a building science pioneer, particularly in the areas of air barriers, vapor barriers and vented and unvented assemblies, and he has had a lasting impact on building codes and practices throughout the world.


  • Emswiler  J.E.  “The Neutral Zone in Ventilation,”  ASHVE Journal,  Vol. 32, 1926.
  • Handegord  G.O.  “A New Approach to Ventilation of High Rise Apartments”Proceedings of the Eighth Conference on Building Science and Technology,Ontario Building Envelope Council, Toronto, Ontario, February 2001.
  • Lawton  M.  “Are We Sealing the Wrong Walls in Apartments?” Royal Architectural Institute of Canada  Advanced Building Newsletter,  Vol. 1, No. 4, July 1994.
  • Lstiburek  J.W.  “The Pressure Response of Buildings” Thermal VII, ASHRAE/DOE/BTECC, December 1998.
  • Lstiburek  J.W.  “Understanding Air Barriers,”  ASHRAE Journal,  July 2005.
  • Lstiburek  J.W.  “Multifamily Buildings,”  ASHRAE Journal,  December 2005.

Keel AP is often asked how our Cembrit High Density Fibre Cement panels differ from the conventional medium density panels that are common here in Canada and the USA. Our friend M. Steven Doggett, Ph.D. LEED AP at Built Environments has published his recent findings. Key points from their findings:

  • Increased density imparts greater strength, stiffness, and moisture resistance for much improved in-service performance.
  • Fiber cement resiliency under normal weathering demands critical re-examination.  Absent of other major agents, moisture and freeze-thaw cycling remain the primary determinants of durability.
  • Reduced service lives of 10 years or less are common.  In many of these instances, installed conditions are substantially compliant with manufacturers’ requirements.  Examples of such risks include materials prone to back-splashing, snow coverage, or inadequate drying (e.g. lack of rainscreens).
  • Service lives in excess of 20 years demand very robust assembly designs as well as construction practices that exceed manufacturers’ requirements.
  • Expectations of durability also demand better understanding of the material’s inherent vulnerabilities so that assemblies may retain resiliency despite shortfalls in cladding performance.

Click link above for their full report. 


Chad Jamieson Halifax, Nova Scotia


Stefan Bolduc Keel Architectural Products 


MRB CONTRACTING Halifax, Nova Scotia 902-455-3202


  • WRAPSHIELD® Water Resistive Vapor Permeable Air Barrier Membrane
  • VaproLiqui-Flash™ Vapor Permeable Liquid Applied Flashing VaproFlashing


Approximately 3,000 sq. ft. (278.71 M²) of WRAPSHIELD® Water Resistive Vapor Permeable Air Barrier Membrane was installed on this modern city home located in Halifax, Nova Scotia.

Environmentally friendly WRAPSHIELD® Air Barrier produces zero VOC’s and can maximize energy efficiency. WRAPSHIELD®’s sustainable air barrier design can reduce a residence’s energy consumption by as much as 40% per year over the life of the home. This not only conserves energy but can save the homeowner money year by year.

WRAPSHIELD® Air Barrier also offers excellent perm ratios of 50. A high perm rating allows moisture vapor to escape the residence’s building envelope. This can help to prevent the formation of mold, mildew, rot and unhealthy indoor air environments.

The Leadenhall Building. London. UK

Design and engineering

The structure’s distinct asymmetrical shape – a response to planning requirements to maintain views of St Paul’s Cathedral – meant settlement both in the foundations and through compression of its elements would be irregular. The solution was to design the building to be erected slightly off the vertical so that it would settle in its correct form. This made the construction process exceptionally challenging. Working with tall building expert, Bill Baker of Skidmore, Owings & Merrill, Laing O’Rourke came up with an innovative alternative. Now, when the building reaches the 19th floor, steel along the sloping face will be tensioned to pull the structure back to the vertical. This process will be repeated every seven storeys.


An iconic building

The development’s tapering shape, which when viewed from the west will appear to ‘lean away’ from St Paul’s Cathedral, delivers varied sizes of floor plates, all offering spectacular views over London. Practical completion of the shell and core is scheduled for mid-2014. The geometry of the 52-storey skyscraper makes it theoretically unstable. Exceptional engineering skills were necessary therefore, to develop a construction methodology that enabled the building to stay upright – with tolerances of plus or minus 20mm required on all but five of its floors.

Using multidimensional Building Information Modelling (BIM) technology, Laing O’Rourke devised an innovative delivery strategy that harnesses the benefits of offsite manufacturing. This ‘virtual construction’ approach allowed the client to visualise our solution in intricate detail. Critically, by integrating data from the architects and structural engineers, the team was able to achieve the early design coordination needed to meet such a challenging programme. The model also combines information from key trades to ensure the compatibility of the different packages.


- See more at: http://www.laingorourke.com/our-work/all-projects/the-leadenhall-building.aspx#sthash.5I4rlcYg.dpuf

Moisture Entrapment Behind Self-Adhered FlashingSelf-adhered flashings (SAFs) and peel-and-stick membranes are used extensively in moisture control strategies for building enclosures.  When properly integrated with flashed components and weather-resistive barriers, this approach is seen as a time-saving, cost-effective solution to moisture-related failures.   However, an unintended problem occurs when moisture accumulates between the flashing and sheathing due to moisture leaks or as a result of exfiltration from poorly-sealed rough openings.  The problem is worse in cold climate construction as a result of low-permeability interior vapor retarders that restricted inward drying.

Moisture Entrapment Behind Self-Adhered Flashing

Moisture Penetration
The figure below illustrates what happens when moisture is introduced at surfaces adjacent to those covered by self-adhered flashing.  Moisture migrates from the source by means of surface diffusion, vapor diffusion, and capillary conduction.  In certain materials, such as OSB, we know that moisture diffusivity within the panel increases exponentially with increasing relative humidity but movement through the panel is less efficient.  In other words, moisture moves more freely within the panel than it does through the panel.  Some moisture will move inward into the cavity, but interior vapor retarders restrict inward drying.  Likewise, the impermeable self-adhered flashing prevents outward drying.  Moisture must now traverse the space that is contained by the self-adhered flashing on the corresponding exterior sheathing surface.  The likelihood of moisture-induced failures increases as the rate of drying is diminished.

Moisture Entrapment Behind Self-Adhered Flashing

Moisture Exfiltration
A similar problem occurs when moisture is allowed to migrate from interior spaces into the assembly cavity.  For example, the schematic below illustrates a window rough opening where self-adhered flashing is applied over the nailing flange as is typical for window installation in residential and light commercial construction.  Exfiltration occurs through poorly sealed interfaces on the interior side of the window, wall framing, and interior finishes.  Again, the impermeable self-adhered flashing restricts outward drying.  In winter conditions, when prevailing vapor drive is from interior to exterior, moisture sorption often exceeds drying rates at interior and exterior faces of the affected sheathing.  Like the prior example, this results in moisture accumulation and a higher likelihood of premature degradation.  A cautionary note: In cold-climate construction, do not assume that sheathing temperatures are too cold for mold growth.  The minimum threshold recommended by ASHRAE 160 is 41°F for a 30-day running average.  Several fungal species grow well at 34-36°F.

Moisture Entrapment Behind Self-Adhered Flashing

We see the issue worsening.

Reason #1: “If some is good, then more is better”.
There is a growing reliance on SAFs in a wide range of flashing applications, from base of wall detailing and window flashing to below-grade waterproofing and roofs.  Self-adhered flashings are also spanning larger areas.  For example, in a 10’x10’ a brick-clad wall containing a single window, we might see SAF at base of walls, sills, and windows.  Using current practices, we could see as much as 26% of sheathed surfaces covered by impermeable self-adhered flashing.    As these materials enjoy greater use, while also spanning greater surface areas, the risks of associated failures become more apparent.

Reason #2: Most assemblies do not accommodate normal moisture loading.
Moisture, whether in vapor or bulk form, will come in contact with sheathing materials.  When it does, moisture moves in the x, y, and z planes at varying rates and efficiencies.  Assumptions that self-adhered flashing serves as an impenetrable moisture barrier to moisture penetration must also account for its effects on moisture impedance and drying for the greater assembly.

Reason #3: Component interfaces at assembly penetrations often lack robust seals.
Building code requirements for sealing interior air and vapor barriers are not necessarily detected by traditional code enforcement practices or routine QA/QC protocols.  We find these recurring problems:

 a) Reliance on air-sealing approaches such as batt insulation chinking doesn’t prevent vapor transport to the cold sheathing.  Surprisingly, we see this approach still used.   Not surprisingly, we still see major problems.

b) Spray foam applications are imperfect.  Some products, when used without a sealed interior air barrier, will enable unacceptable amounts of moisture transport to cold sheathing.  This problem is compounded by wetted sheathing or highly permeable sheathing materials that allow moisture to move further outward to colder surfaces where the rate of drying will be much reduced.

c) Poorly applied interior sealants are readily exploited.  Interior caulk joints are often viewed as an unnecessary precaution to an already ‘sealed’ and ‘insulated’ rough opening.   If sealant is used, haphazard applications or poor joint sizing can seriously undermine the intended purpose.


The intended purpose and benefits of self-adhered flashing are duly noted.  These materials provide effective workable solutions to many of the industry’s pervasive problems. But the potential for moisture entrapment warrants careful design considerations, especially in cold climates and interior environments subject to high humidity.


Ofori-Amanfo, C. and M.J. Spink. 2008. Condensation damage behind self-adhering membrane flashing and interior furnishings on exterior residential walls.  Journal of ASTM International.

This is a great hotel project that was built for the Sochi 2014 Olympics called Russian Seasons featuring Cembrit Zenit High Density Fibre Cement cladding on aluminum sub framing.

Like most of Europe, the substrate is generally block and concrete whereas here in North America we tend to build with heavy gauge steel studs. These aluminum subframes can easily be adapted to our construction methods and Keel AP is a big proponent of manufacturers such as Tweha from the Netherlands. Why chose an aluminum subframe over the conventional galvanized  z-girt and hat channel? 

  • Aluminum will not rust.
  • Aluminum subframes are completely adjustable whereas conventional z-girts and hat channels must be shimmed.
  • Aluminum subframe systems are thermally broken, if connected directly to steel studs a thermoplastic isolator is provided.
  • Highly adaptable, can be used for ACM, Fibre Cement, HPL, Metal, Wood, Terracotta and more. 
  • Many manufactures are able to offer slab-to-slab solutions with would virtually eliminate thermal bridging and allow for a much faster installation. 

Feel free to contact us should you have any questions about sub framing or cladding, we’d be glad to offer advice. 

This is a great blog entry by our at Built Environments in Minnesota. 

"The principles and practices of green building have had a transforming effect on the way we build, work, and live. By ‘green’ I refer to a collective of high-performing objectives in sustainability, energy-efficiency, healthy building, and resiliency.  Inherent to its mission are claims of improved building performance – that is, perceived betterments in resource use, energy efficiency, and building service life.  Directives further brim with expectations for improved health, comfort, and productivity.   And, according to some, the payback to society knows no bounds.  The natural leap in logic, or at least perception, is that green buildings are better performing buildings, or just better buildings.  But are they?  Below I illustrate the tenuous nature of how green design can fall short of expectations. (more)

This is a project we followed closely - wow, they did a fantastic job!

We are firm believers in learning from our clients and the more time spent in the field the better for us and our future clients. 

This is our first VaproShield project with the good folks at ColeBuilt. After a few initial meetings and discussions with the architect they decided to work with VaproShield and Ventgrid for this project and expect to use it on all future projects. Today we learned a GREAT trick from them for windows - use a small flap of VaproFlashingSA (self-adhered) at all corners for extra protection. Thanks ColeBuilt, looking forward to working with you on this great project.