Metal construction businesses share a common challenge with the entire commercial building industry: the need to design and build energy-efficient structures and do it at a competitive cost, while creating an end product that’s practical, aesthetically pleasing and performs well over time. The critical path to success always includes a carefully designed building exterior, which avoids energy loss, maximizes technology advances in materials and controls cost. One of the most advantageous systems currently gaining popularity in metal construction for maximizing a structure’s thermal performance is continuous insulation.
Continuous insulation
Continuous insulation by definition is insulation with two primary characteristics. It runs continuously over structural members and is free from significant thermal bridging. The only exceptions can be the particular fastening systems used to anchor the insulation wall systems.
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Building science has proven that continuous insulation is the most effective way to insulate a building for energy efficiency. But there are questions about relative cost and practicality in some designs. Many of these questions are dispelled when the practical aspects of continuous insulation are considered in the overall project execution and building performance results.
Extruded polystyrene (XPS) has been one of the most common materials used in continuous insulation. Polyisocyanurate (polyiso) rigid board products are becoming more frequently specified for continuous insulation because they’re also easy to work with, versatile and have exceptional R-value.
Metal construction advantages
Key to the entire process is how the continuous insulation usage reduces the possibilities of thermal bridging. This is especially critical for metal construction because of the increased opportunity for energy loss through the studs. Steel has many advantages over wood for commercial structures, but it conducts heat hundreds of times faster. The layer of continuous insulation prevents hot and cold air from passing through the studs from the inside or outside of the building. Fastened directly to the outside of the studs, only a minimal amount of energy passes through the fasteners.
Multiple functions
There are some practical advantages in the application of polyiso as continuous insulation, which are economical for designs and also efficient for contractors. Polyiso board used as continuous insulation can be easily configured to perform a variety of functions in the wall assembly and be used with multiple assembly types.
Rigid polyiso board installed as continuous insulation can be used alone as a sheathing or combined with gypsum on the exterior and attached over it. Properly installed continuous insulation can also perform as an air barrier.
Joints in continuous insulation can be sealed with proper tapes and adhesives. Flashing of wall penetrations forms a drainage plane. If water passes through the cladding, this drainage plane can prevent potentially damaging moisture from getting into the wall assembly.
Multiple claddings and assemblies
Continuous insulation, performing the afore-mentioned functions, works well in a variety of assemblies. It doesn’t limit your crews to being able to work with particular assemblies. It actually provides you with opportunities to work on a wider variety of projects, since it delivers superior performance with many types of installations and systems.
When continuous insulation is installed behind uninsulated metal panels, but over steel studs, it enhances building envelope performance by reducing or eliminating conductivity between the two steels, with the exception of the small amount of bridging which remains via the fasteners and girts. For continuous insulation designs there are often concerns about fastener length requirements according to code and the ability to attach certain claddings. Contacting the cladding or fastener manufacturer is a great way to gain a better understanding of these details and what’s possible in a particular application.
Efficiency and quality
Commercial crews working with continuous insulation are doing more than simply working to the print. They’re installing systems that will ultimately serve to deliver long-term energy performance and prepare structures for the future. There are also cost savings built into each project. These savings are the result of installation efficiencies and the multiple functions continuous insulation can serve on the structure.
Since using continuous insulation often eliminates the necessity of applying additional materials to achieve air and moisture barrier requirements, this reduces material and labor costs. Design-build teams can use this advantage in competitive situations to both reduce costs and control construction schedules. While joints must be properly taped and sealed, and rough openings flashed, these tasks can be completed in a single pass.
Energy-efficient structures
Continuous insulation is a single component that contributes extensively to energy-efficient structures. It’s a way to add significant R-value to the outboard side of the building envelope. Rigid polyiso is a leading choice for energy efficiency in continuous insulation because of its high R-value, which means a thinner wall assembly.
There are additional safety issuesthat give polyiso continuous insulation an advantage. For example, it doesn’t melt in ASTM E84 fire testing. Polyiso chars, but won’t melt or drip down when burned. Continuous insulation helps buildings to last longer without need for repair and upgrade. Ultimately this also contributes less waste to landfills and requires fewer replacement materials.
All things considered, the most remarkable aspect in wrapping a building in thermal insulation is the ongoing reduction in energy use. When building with continuous insulation, most structures will yield consistent, significant energy savings over time. Alec Minné, a LEED Green Associate, recently joined Atlanta-based Atlas Roofing Corp. as director of its marketing commercial division. To learn more, go to www.atlasroofing.com.
