Designing hybrid insulated walls to combat climate change

December 16, 2018

by Rockford Boyer

All images courtesy Rockford Boyer[1]
All images courtesy Rockford Boyer

Canadians are used to cyclic weather patterns, and are becoming familiar with catastrophic weather events like flooding and high winds, thanks to their frequent occurrence. In the past decade, though, there has been an obvious increase in severe unpredicted weather events. Figure 1 indicates the increased cost to insurers due to weather-related damage. The damage arising from more frequent extreme weather conditions averaged $400 million a year between 1983 and 2008. This increased to $1 billion a year between 2009 and 2013. This article is not going to debate the reason for these increased weather events, but aims to provide guidance for reduction in carbon emissions in the insulation industry and increase the durability/resiliency of insulated building enclosures.

A recent article[2] in the Toronto Star suggested $1 out of every $2 provided to property insurance is set aside for moisture-related issues within buildings. Other studies[3] from the U.S. Department of Energy (DOE) and independent remediation experts claim 85 per cent of buildings will eventually leak and be responsible for 70 per cent of the construction litigation. With staggering statistics like these, there should be a greater requirement for water and moisture resiliency within the building’s design and operation.

In the author’s experience, the industry appears to believe fire-related disasters are more prevalent and costly than those associated with weather-related damage, especially after the fatal Grenfell Tower fire in the United Kingdom. However, building science professionals, remediation experts, and insurance companies are demonstrating moisture has a far greater potential for damage than building fires[4]. The author agrees fire safety is an important design consideration. Nevertheless, the trend in fire-related[5] building fatalities and damage is trending downwards (25 per cent in the last 10 years), while moisture- and wind-related[6] building damage is on a severe upward trend (2.5 times greater on average in the past 20 years).

Figure 1: Catastrophic weather-related loss trends in Canada from a 2016 presentation by Glenn McGillivray.[7]
Figure 1: Catastrophic weather-related loss trends in Canada from a 2016 presentation by Glenn McGillivray.

Resistant materials

There are several documents available currently to assist the industry with the design of flood-resistant buildings. One such document is the Federal Emergency Management Agency (FEMA) Technical Bulletin 2, Flood Damage–Resistant Material Requirements for Buildings Located in Special Flood Hazard Areas in accordance with the National Flood Insurance Program. To ensure durability and resiliency of building enclosures, it should be recommended or become code for all new buildings to comply with the flood-resistant material requirements specified in this document. The suggestion for all buildings to adhere to it is based on several factors such as:

Table 1 of the technical bulletin describes five classes of building materials according to their resistance to flooding. Table 2 of this document will be useful for designers as it provides generic material names and their applicability to the building enclosure as well as resistance to flooding, prolonged water exposure, and after recession of water. In general, the document states materials below grade and at a reasonable elevation above grade should be designed with completely water-resistant materials and insulated with only closed-cell foam products. Closed-cell foam is resistant to flood waters and can be adequately cleaned during a wetting event, whereas fibrous products can act as a filter and potentially trap hazardous pollutants.

Severe wind events are listed as the second largest driver[8] of property damage in the country, just behind water. The lighter the buildings (in terms of structural design) the more susceptible they are to damage from wind, especially during the construction phase. Figure 2 shows a structure in Southern Ontario that collapsed during the May 2018 windstorm, which caused more than $380 million in insurable damage claims.

Figure 2: Aftermath of the May 2018 windstorms in Ontario.[9]
Figure 2: Aftermath of the May 2018 windstorms in Ontario.


Moisture entering and staying in the building enclosure, while not having the ability to dry, has the largest impact on the durability of building enclosures. The majority of materials installed on the weather side of an enclosure have the potential to get wet and stay wet if draining/drying cannot occur. Water will eventually enter the building enclosure. Therefore, designers should always design for failure rather than for perfection. The practice of using materials or systems with no ability to absorb/hold water, allowing for drying in at least one direction (interior or exterior), and allowing easy installation with limited errors will ensure the prolonged success of the building enclosure. The intent of a durable wall enclosure is for the wall assembly to successfully withstand the damaging loads that have the ability to degrade or impact its performance.

Split structural insulation system

With energy codes becoming more stringent throughout North America, there is an opportunity to improve the resiliency/durability of building enclosures by designing a split insulation system. Structural rack and shear of wall enclosures can be increased up to 300 per cent by installing minimum 50-mm (2-in.) closed-cell sprayed polyurethane foam (ccSPF) insulation between the structural members of the enclosure. Installation of structural ccSPF with high R-value in the stud cavity increases the opportunity for using other outboard continuous insulation (ci) materials such as board foam (extruded polystyrene [XPS] and expanded polystyrene [EPS]), spray-applied polyurethane, and mineral wool to meet local energy requirements. When employing additional insulation types inboard of the ccSPF, a balanced hygrothermal performance shall be maintained.

In the author’s experience, the discussion around the use of hybrid insulated wall enclosures appears to occur in a horizontal plane (i.e. x axis). Hybrid insulated wall enclosures use various insulation types installed in a horizontal plane to control heat, air, vapour, and water. These types of insulated hybrid walls have been debated and designed accordingly for many years in Canada. However, hybrid insulated wall enclosure designed in the third dimension is generally overlooked. These hybrid enclosures can also occur in the vertical plane (i.e. y axis) to control more than heat, air, vapour, and water. They can also be designed to control flooding, wind, and potentially, fire.

Figure 3: Insulation product types that can be installed on the interior and/or exterior side of a building enclosure to increase the unpredictable weather resiliency and durability of the hybrid wall enclosures.[10]
Figure 3: Insulation product types that can be installed on the interior and/or exterior side of a building enclosure to increase the unpredictable weather resiliency and durability of the hybrid wall enclosures.

Insulations types used in horizontally and vertically integrated hybrid walls can be designed to meet various performance criteria such as structural, vapour permeability, added wind resilience, and fire performance (non-combustible cladding). Figure 3 provides a recommendation for application of various insulation product types that can be installed on the interior and/or exterior side of a building enclosure to increase the unpredicted weather resiliency and durability of the hybrid wall enclosures. The basis for these application recommendations is derived from the insulation types’ in-situ performance and characteristics when structural loading and resilience to water are required. Like other hybrid insulation enclosure designs, hygrothermal performance for the enclosures’ resilience should take precedence.


Frequency and severity of unpredicted weather events are only going to increase if factors affecting global warming do not change. Climate change is moving forward and will take many decades to slow down. Therefore, one must construct buildings to resist its consequences. Two of the most significant factors impacting a building’s resiliency and durability are water and wind. Water is the new fire; therefore, the industry should design building enclosures to not only resist water ingress from precipitation, but also to allow for resiliency after flooding. Wind inflicts huge amount of dynamic forces on buildings and using materials that can assist with structural durability is the key for success. Pop culture preaches one-stop shopping for ease and time savings. However, this is not true when designing buildings. Various insulation materials have different characteristics with the ability to significantly impact building performance. Horizontally and vertically integrated hybrid insulated walls are a great solution for meeting these strict requirements of building resiliency. Reducing carbon (carbon equivalent) is essential for slowing climate change.

When designers are reviewing products, there is a tendency to look specifically at the product’s performance and not the overall system performance. Understanding the system performance as well as its overall life cycle can help design professionals create sustainable spaces. To have a significant impact on climate change and reduction of carbon from construction materials, decisions should be completed systematically and not based on emotions or personal preference.

[11]Rockford Boyer is the technical manager, building enclosure at Elastochem Specialty Chemicals. He has a diploma in civil engineering, a degree in architecture (building science option), and a Master of Building Science degree. Boyer has more than 15 years of experience in the enclosure design field, including five years with AMEC, Earth and Environmental, 10 years with Roxul/Rockwool Insulation, and two years with Elastochem. He can be reached at[12].

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