Acoustics
Energy efficiency
Sustainability
Fire safety
Sound absorption

Continuous Exterior Insulation: The Path to Greater Home Energy Efficiency

1 January 1

Building or remodeling? This insulation strategy provides benefits to the home and homeowner, from greater efficiency & safety to increased comfort & durability.

Whether building or remodelling, achieving an energy efficient home is an objective that is more top of mind than ever

As homeowners, we are increasingly conscious of the rising costs of fuel and maintenance, as well as the environmental impact of our dwelling and its carbon footprint.

The installation of continuous exterior insulation is a highly effective and affordable path to efficiency, reducing reliance on a home’s mechanical systems and lowering energy demand. In addition to providing better thermal performance, quieter spaces and greater occupant comfort, homeowners can also reap considerable savings on annual heating and cooling costs.  

The value of insulation has long been recognized in all types of buildings and across a wide range of climate zones, but to reach today’s stricter energy code requirements, we must think beyond traditional cavity insulation. Continuous exterior insulation is a requirement within the building code in a growing number of regions, and it’s quickly becoming standard practice as code drives us toward a more energy-efficient built environment. As such, wall systems have moved toward a split insulation assembly that includes continuous insulation on the exterior of the home, in addition to standard cavity insulation within the interior stud bay.

What is continuous exterior insulation?

Continuous insulation, is defined in the standard ANSI/ASHRAE/IES Standard 90.1 - Energy Standard for Buildings Except Low-Rise Residential Buildings from the American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE 90.1), as: 

“Insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior, exterior, or is integral to any opaque surface of the building envelope.

Continuous exterior insulation comes in a variety of types, sizes and compositions.  As a non-structural exterior sheathing board, continuous insulation is significantly more dense and rigid than common batt insulation. It affixes over a home’s exterior sheathing and weather-resistive barrier (WRB) to create, as the name implies, a continuous and uninterrupted blanket of insulation around the outside of the dwelling. Often likened to a warm sweater or jacket, the exterior insulation helps achieve a higher performance building envelope and contribute to protect the structure, making it more durable.

 

 

 

Installing continuous exterior insulation

Installing continuous exterior insulation offers significant benefits. It does, however, require careful attention to detailing in order optimize performance. Fenestrations and transitions are the most common areas where detailing errors tend to occur and where adherence to installation best practices is critical to ensure long-term durability of the structure. Properly sealing connections—whether these are below grade to above grade, window or doors to wall, wall to roof, or penetrations—can help prevent the lion’s share of potential building envelope failures. In a split insulation assembly, for example, special considerations must be taken to maintain:

  • air barrier continuity,
  • water resistant barrier (moisture barrier) continuity,
  • thermal continuity (minimizing thermal bridges, cladding attachment and focus on detailing, and
  • adequate drainage and ventilation of the wall cavity

Proper installation of all components and the detailing of the air, water and vapor control layers, including careful sealing and taping, is key to avoiding moisture issues in the future.

Questions surrounding window detailing with continuous insulation are very common among builders and contractors in residential construction. ROCKWOOL has developed some resources, including the Comfortboard 80 Installation Guide as well as a video how-to guide, illustrating in detail, the step-by-step install of continuous exterior insulation on a typical wood framed and sheathed wall with a non-flanged window.

Why use continuous insulation?

Buildings account for approximately 40 percent of the total energy demand and 38 percent of total carbon dioxide emissions in the United States—more energy use than the entire transportation industry. As such, buildings also represent the greatest opportunity for targeted energy reduction, especially through retrofit and renovations.

Continuous exterior insulation is effective in reducing thermal bridging, a significant source of heat loss in the built environment. Thermal bridges are penetrations in a building’s insulation layer that allow heat (energy) to escape during winter. Studies, including one by RDH Building Science1, have found that thermal bridging through framing components reduces insulation performance by as much as 30 – 50 percent. That’s a lot of wasted energy that can impact your heating/cooling costs and your level of comfort in your home.

In addition to reducing thermal bridging and improving efficiency, continuous exterior insulation can contribute to a more durable structure. How? By keeping the temperature of the sheathing above the dew point and reducing the risk for condensation or other moisture related issues, which can create durability problems and reduce the indoor air quality by promoting the growth of mold. Opting for a vapour permeable insulation, like stone wool, can increase the drying potential of the building enclosure, by allowing moisture to dry inside or the outside of the wall assembly. That will help maintain the integrity of the wall system and result in more reliable thermal performance and durability. Choosing non-combustible stone wool for your continuous exterior insulation can also substantially improve a home’s fire safety, providing valuable passive fire protection to the building envelope. This can be particularly beneficial in areas with increased fire risk such as wildland urban interface (WUI) zones where the exterior wall assembly is part of the first layer of defense.

Further, continuous exterior insulation can help create a quieter home, reducing noise transmission from outside to inside for an overall better experience in your space. The key is to select an exterior insulation with excellent acoustical propertie



Why you should discuss your insulation strategy with your builder, architect or contractor?

When building or renovating, it’s beneficial to speak with your builder, architect or contractor about adding continuous insulation to the exterior or your home. From the homeowner perspective, it makes a lot of sense, resulting in a higher quality build, better efficiency, safety, durability, sound and moisture control, higher efficiency, lower energy costs, and greater levels of comfort. Equally important, it can help future-proof your property, ensuring it reflects existing energy code and potentially tighter code requirements to come. That can help protect your property’s value, as buyers are often more likely keen to purchase homes that are up to date with current code standards. A good building professional also understands that climates change means our homes need to be built to stand up to harsher conditions, with more extreme weather events. Planning to make continuous exterior insulation a key part of your building envelope will help it stand the test of time and conditions for decades to come.

Planning to make continuous exterior insulation a key part of your building envelope will help it stand the test of time and conditions for decades to come. Your architect or builder can also connect with our building science or technical services team for support in maximizing the performance of your home/building: 1-855-876-3755

Why stone wool for your continuous insulation application?

Thermal Performance – Reduces thermal bridging through wood framing, leading to a higher-performing building envelope. 

Moisture Management – Vapor permeable enabling superior drying potential within the wall system, minimizing the risk water accumulation and moisture related issues

Fire Safety – Non-combustible, stone wool can withstand temperatures of approximately 2,150°F (1177°C). 

Sound absorption – Stone wool provides excellent sound absorption and reduces sound transmission from outside to inside, as well as from room to room or floor to floor. That helps contributes to quieter, more productive environments.

Comfort, health and wellbeing – With excellent thermal performance, sound attenuation, and resistance to mold and mildew (protecting air quality), stone wool insulation contributes to greater occupant comfort in buildings, better wellbeing and better productivity.

Certified, Tested, Transparent – Transparency is an important part of ROCKWOOL’s commitment to people and the planet. ROCKWOOL labelling and information practices ensure that homeowners, builders, contractors, architects and designers feel confident in selecting, installing and using ROCKWOOL products—informing individuals on product composition, production processes and benefits to health, wellbeing and the environment. ROCKWOOL products are tested and certified by third-party laboratories in a wide variety of applications, verifying characteristics, performance and lifecycle information.

Sustainable and Circular – Since buildings account for a major share of energy demand and carbon emissions, ROCKWOOL believes the building sector must play a major role in helping communities adapt to and mitigate climate change impacts.  As such, it is committed to sustainability and circularity. ROCKWOOL stone wool insulation products are made from natural, abundant and recycled raw materials, which can be recycled again and again to make new stone wool insulation.  ROCKWOOL is a net carbon negative company, in that over the lifetime of its use, the building insulation ROCKWOOL sold in 2020 will save 100 times the carbon emitted in its production. ROCKWOOL products are also exceptionally durable, maintaining their properties and performance more than 55 years after their initial installation. This durability contributes to resource efficiency in the building sector and in manufacturing. At ROCKWOOL, sustainability and accountability go hand in hand.  The company has set measurable and achievable sustainability goals, including cutting factory absolute greenhouse gas emissions by 38 percent by 2034.  ROCKWOOL’s sustainability efforts also support 10 out of 17 United Nations sustainability goals (SDGs) that endeavor to improve quality of life and wellbeing of people, while protecting the planet.

Properties:

  • Easy to install - Can be easily cut with a bread knife
  • Non-combustible with a melting point of approximately 1177°C  (2150°F)
  • Excellent sound absorbency
  • Vapor permeable
  • Does not rot or promote the growth of fungi or mildew 
  • Low moisture sorption
  • Chemically inert; non-corrosive
  • Water-repellent
  • CFC- and HCFC-free product and process
  • Made from natural & recycled materials
  • ROCKWOOL® can contribute to earning LEED® points

Effective Insulation Systems

Effective insulated assemblies slow the flow of heat and deal with the movement of moisture. To do this, they have the following:

  • An air barrier, which prevents the movement of interior or exterior air through the system.
  • Carefully filled cavities, which leave no gaps in or around the insulation and which do not compress the insulation.
  • A minimum of thermal bridges. These are parts of the wall that, with a lower R-value, extend from the warm side to the cold side of the insulation, giving heat an easy escape. The structural members in the wall will often be thermal bridges. As a best practice, continuous exterior insulation helps reducing thermal bridging, increases the overall R-value of the wall system, and improves building comfort, safety and durability.
  • A vapour control layer, which control the flow of water vapor though the assembly. This control must be defined in accordance with the type of assembly, the type of building and the location of the building.
  • Drying potential, which is the ability of the insulated assembly to release any moisture that gets into the system.

1 Straube, J. & Simonji, J. & Schumacher, C., RDH Building Science (2019). 2019 Buildings XIV International Conference. © ASHRAE (2019). Thermal resistance measurements of two-and three-D thermal bridges using an ASTM C177-based apparatus