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Sealing In Energy Savings
Few people pay attention to the role of insulation in institutional and commercial facilities. In a typical construction project, insulation accounts for less than 1 percent of total construction costs. So it is not surprising that most specifiers pay more attention to finish colors than to the type and quantity of insulation installed in new construction and renovation projects.
Even though insulation so often goes unseen, it has a large impact on a facility’s energy use. And with rising concerns over energy costs, maintenance and engineering managers are paying more attention than ever to insulation and its role in controlling building energy use and costs.
Pressures to Change
This increasing interest in improving the thermal efficiency of buildings and their energy-using systems has prompted insulation manufacturers to develop new products and modify existing ones.
As a result of advances in insulation formulation, today’s products perform well over an extended period of time, often in traditionally difficult applications. This improved performance can help managers reduce energy loads while improving conditions within buildings.
Insulation used throughout buildings limits heat transfer and provides a vapor barrier against moisture. Its applications in structures include roofs, walls and foundations. Interior and exterior HVAC system ducts can feature interior or exterior insulation. Insulation also wraps hot- and chilled-water lines in HVAC systems, as well as steam and refrigerant lines, valves, fittings, and domestic hot-water system lines and components.
Roofing insulation plays several important roles. It limits heat transfer into and out of a building through its roof. This insulation also serves as a barrier to moisture and provides a smooth, clean surface to which installers can attach the roof membrane. Ideally, insulation materials limit condensation within roofing system components while resisting wind uplift forces.
Decisions on roof insulation go beyond initial construction, though. Most roofs require replacement every 15-25 years. At each replacement interval, managers have the option of replacing the entire roof or simply recovering it.
While recovering costs and disrupts operations less, it is not suitable for all applications. In cases where water has penetrated and saturated roof insulation, it is best to tear off and replace the existing roof.
The extent to which water saturates roof insulation often depends greatly on the type of insulation. Some types, such as fiberglass board, absorb water more easily than others, including all types of closed-cell insulation, which resists moisture.
Recently, extruded polystyrene has received increasing attention in roofing applications. Extruded polystyrene comes in rigid boards, resists moisture penetration and is suitable for use in recover and replacement applications.
Fiberglass batt has long been the most widely used insulation for exterior walls. While it is effective and costs relatively little, it is not the best alternative in certain applications.
For example, exposing fiberglass insulation to high moisture levels can significantly reduce its effectiveness. Fiberglass insulation also is not well suited for used in cavity walls with many obstructions that interfere with batt placement.
Expanded polystyrene — a rigid foam insulation that resists moisture penetration — offers an alternative to fiberglass applications in damp areas. It can be used both above and below grade. In above-ground applications, it can be used as sheathing, although it is considered non-structural.
Although expanded polystyrene insulation has been available for some time, manufacturers have improved it recently by adding different face materials to improve particular performance factors.
For applications where it is difficult to install fiberglass batts due to obstructions or unusual wall configurations, a new generation of spray-in-place insulation can be a good alternative. This insulation — more commonly called foam insulation — allows installers to tightly fill areas that would be difficult to fill with fiberglass batts.
Properly applied, this insulation provides excellent air-sealing qualities. Its closed-cell structure greatly restricts moisture penetration and provides an effective vapor barrier. Perhaps its biggest drawback is its cost — typically, two to three times the cost of fiberglass batt insulation.
A new generation of closed-cell polyurethane foam insulation uses a non-chlorine blowing agent, HFC-134a, which makes it an ozone-friendly alternative. It offers an R-value of about 6.5 per inch of thickness. Its biggest drawback is price — about three times more than other polyurethane installations.
Typically, manufacturers use sheet metal in fabricating HVAC-system ducts, along with either interior or exterior insulation. They typically use rigid fiberglass boards — not sheet metal — to manufacture low-pressure duct systems.
Growing concerns over indoor air quality have prompted manufacturers to move away from interior insulation because it can provide a base for the growth of mold and bacteria, which HVAC systems then distribute throughout buildings. For applications that require interior insulation, manufacturers have produced a new generation of closed-cell insulation because of its thermal and soundproofing properties.
A new type of fiberglass insulation also is well suited for interior duct applications. Traditional fiberglass duct insulation uses a short fiber that is prone to breaking. The new type of insulation incorporates a textile fiberglass fiber that is bonded with a thermosetting resin. The result is an encapsulated liner with superior strength.
This type of interior insulation also provides better sound attenuation, lower thermal conductivity, and higher moisture resistance. And with a smooth inner surface, the insulation does not tend to trap dirt the way that rough-surfaced fiberglass insulation does.
Properly installed pipe insulation is essential for the performance and long service life of piping systems.
For steam and hot-water piping, the primary role of insulation is reducing heat loss. For chilled-water piping, insulation reduces heat transfer from the surroundings to the piping, and it eliminates condensation formation on piping.
Condensation accelerates pipe deterioration, and if it forms within insulation, it reduces the insulation’s effectiveness.
Depending on the application, system designers and maintenance managers have had a range of insulation options. Traditionally, the most commonly used types of insulation have been rigid mineral, non-rigid mineral, and fiberglass.
Today, the options have expanded to include flexible and rigid closed-cell glass materials. These materials offer the advantage of blocking moisture that can condense in traditional fiberglass insulation. In applications where nearby activities can damage insulation, this insulation is available with a bonded-on limiting jacket.
One serious challenge that pipe insulation manufacturers have faced is preventing water penetration. Once wet, insulation loses most of its effectiveness.
One new system marketed for chilled-water pipes uses a wick wrapped around the piping. The wick absorbs any moisture that penetrates the insulation and condenses in it. The moisture then travels along the wick to the outside of the jacket, where it evaporates.
Underground piping systems also pose a severe challenge. In these applications, fill material and ground water can damage the insulation. Traditional underground pipe insulation is open-cell. As a result, it was not uncommon to find damage to vast portions of underground systems, due to water penetration of the protective jacket.
Today, a new generation of insulation for underground piping applications uses polyurethane foam. This foam typically consists of 92-98 percent closed cells, so it limits the impact of water penetration into the insulation, should the outer casing be damaged.
Finally, polyurethane foam also is an excellent insulator, making the installation energy efficient. The foam is suitable for applications where the liquid temperatures are 150 degrees centigrade or less.
James Piper is a national consultant based in Bowie, Md., with more than 25 years of experience in facilities maintenance and engineering issues.
Insulation, Beyond Installation
No matter the type of insulation that is installed, proper maintenance is essential for long-term performance and effectiveness.