Selecting the Right Insulation Thickness
10/08/2021
Selecting the right thickness of mechanical insulation is a question that many ask, hoping for a quick and simple answer to a bit of a complex matter. Mechanical insulation is used for five key reasons. These key reasons are energy savings, condensation control, process control, personnel protection and acoustical control. Each application requires an assessment of the desired end result and the surrounding conditions impacting that result. The efficiency of the insulation material to be used is a primary consideration in all these uses. A less efficient material, indicated by the thermal conductivity of the product, will require a greater thickness of material to achieve the goal, while a more efficient product, like fiberglass, will require less thickness to achieve the goal.
Saving Energy with Insulation Thickness
Insulation thickness can be and is normally a part of an economic calculation that considers the typical factors associated with a facilities investing decision. How much the investment return, or what will the ROI of an investment in mechanical insulation be? Mechanical insulation has an excellent ROI term, typically less than 12 months. The insulation thickness calculation will impact the ROI, since as thickness changes, so does cost of materials and installation. Along with the change in cost, the amount of energy savings will change and impact the ROI. Some information to have at hand when considering energy savings and economic thickness is the operating temperature(s), ambient environmental temperatures, cost of installed insulation systems, cost of energy on a unitary basis, and internal financial benchmarks like cost of capital. All these factors and more enter a sound investment-in-insulation decision. An economic thickness calculation that considers these factors can be conducted using industry software to make the calculation and thickness selection faster and easier.
Controlling Condensation
The thickness of insulation is selected for the insulation system’s ability to reduce the amount of time and the severity of condensation formation on the outer surface of the insulated assembly. Data to be collected and included when deciding the correct thickness includes operating temperature of the system, ambient temperature of the surrounding environment, relative humidity in the surrounding environment, any air velocity that might be expected like wind for outdoor systems, and final protective finishes that might be used. The most severe conditions anticipated should be used to achieve the most satisfactory results. Commonly, it is thought that the hottest part of the day is the most severe condition for condensation formation. This is not always so. In the cool mornings, the relative humidity is usually the highest, creating a much higher possibility that the surface temperature of the system will achieve the dew point temperature than in the hot afternoon, when the relative humidity is lower, when the dew point temperature is harder to achieve. When selecting the correct thickness of insulation for condensation control, check the thickness required for morning conditions and afternoon conditions. The thickness required in the cool, humid morning may be thicker than the thickness required in the drier, hot afternoon.
Selecting Insulation Thickness for Process Control
Process control requirements for insulation thickness selections are widely varied. Typically, the process or the product, resulting from a process, is desired to be held at a temperature or within a specified temperature range that avoids negative impacts to a process or finished product. Again, key data required for a correct thickness selection would include surrounding ambient conditions, process temperatures, and a specific set of conditions that is desired for the process or the product. In an application where controlling the heating or cooling of a product is the key goal, the specific heat value of the product is required. Kinds of desired outcomes for a process control application might be to avoid solidification of a liquid, avoid condensation of a gas, limiting the loss of temperature to a specific value, maintenance of a specific temperature over a given distance, slowed heating or cooling of a process or product. All of this relates to heat loss or heat gain, with a specified amount that is dependent on the needs of the process. The specified loss or gain can be controlled by the thickness of insulation selected.
Protecting Personnel with a Thermal Barrier
Personnel protection applications for pipe and equipment insulation are safety-in-the-workplace applications for insulation. When referring to personnel protection, this means that insulation is used to keep the surface temperature of the system either low enough in hot operations or warm enough in extreme cold systems to avoid contact injuries due to burns or frostbite. A more recent recognition of a personnel protection application is insulation applied to an environment that allows a certain level of comfort to avoid heat-related stresses like heat exhaustion or heat stroke, and hypothermia in the case of extreme cold environments. There are industry standards for this kind of personnel protection and these standards should be consulted in making a decision on the end goal desired. The insulation system thickness requirement and selection will be heavily dependent on the final goal desired.
Acoustic Applications
In acoustical control applications, insulation controls the flow of sound energy instead of heat energy. Much like thermal insulation, sound insulation efficiency and effectiveness is heavily a result of the thickness of the material, not the mass of the material. The thickness of a sound insulation will impact the ability to reduce sound transmission far faster that selecting a denser or heavier insulation of the same type. Typical reasons for using mechanical insulation to control sound is to absorb noise or stop noise transmission in pipe and duct systems in high-occupancy or critical-occupancy buildings like offices, recording studios, theater and performance venues, medical offices, confidential business venues. These are all types of facilities that can be less suitable for use if the acoustical quality of the space and the systems serving it are not properly insulated against sound transfer, be it by transmission or reflection. High noise levels in the industrial environment is growing in concern. It is well recognized that high noise levels impact the long-term hearing ability of workers. Containing that noise and reducing the level in the industrial or work environment is another application. The correct insulation thickness selections for acoustical control can positively impact the acoustical quality of the systems serving the occupied space in all kinds of environments.
3-E Plus Calculator
Once the desired end result has been established and the correct data gathered, the fastest way to do an insulation thickness calculation for energy savings, condensation control, personnel protection, and process control is to employ a software application that uses calculations based on information detailed in ASTM C680. There are manufacturer-specific applications that use this practice. There is an industry-wide application, 3-E Plus, that is supplied as a free download from Knauf Insulation. Anyone can use the formulas provided in ASTM C680 to build their own calculator, if desired. As for acoustical control, it is best to consult the Knauf Insulation technical team or acoustical designer to help determine the appropriate thickness needed to provide the end goal.
Knauf Insulation North America manufactures a range of highly-sustainable, high-quality fiberglass insulation materials that are efficient and effective for all the needs described above, in thicknesses to meet most needs that arise on a day-to-day basis. There are times when unique needs arise, and the solution may not be so apparent. In either case consult with the Knauf Sales and Technical team to help provide the right selection of insulation thickness.