In Part 1 of this article, the author addressed the need for retrofits of building enclosures, types of building enclosures that are promising candidates for a retrofit, and financing options for building owners and facility management to conduct a retrofit.
By Daniel Shields
Building envelope technology has come a long way as the variety of materials on the market has increased over time. There are numerous ways to retrofit a building enclosure, and the following describes several types of upgrades to increase energy efficiency when retrofitting a commercial building envelope.
Exterior Wall Systems
Exterior wall systems can be made of various materials including glass, stone, wood, metal, and fabric. Unfortunately, these building facades don’t always age gracefully. Over the years, cracks can appear in concrete, leaks can arise due to damaged silicone joints and glazing gaskets, metals rust, and building maintenance can become much more expensive due to rising operating costs and poor energy efficiency. Therefore, there are many reasons why a building façade may be retrofit by correcting issues with the original construction to creating a more energy efficient building.
Retrofit envelopes can provide new life to a building. In most cases, fixing the current façade is not an option because the systems are obsolete, beyond repair, or don’t meet the current code regulations. A reclad will fix these problems and allow the building to still be fully operational. With proper planning, the disruption to occupants is minimal. Façade retrofits allow for a wide range of materials and visual design to be incorporated into the new exterior enclosure. A dual façade may be required due to the fact that the old façade may need to remain in place during the installation of the new building’s skin. The unitized curtain wall installed during the reclad can often include infills in various finishes to completely change the look of the building.
Unitized curtain wall system panels for the reclad may include higher performance glazing, improved fire-rated glazing, spandrel, and shadowboxes in order to improve the performance while enhancing the appearance of the façade. Glazing units are typically shop-fabricated to control quality and expedite the installation time on site. The building should be reclad depending on the installation sequence required for the glazing assemblies.
The use of exterior insulation is an effective way to enhance the overall thermal resistance of wall construction. Additionally, exterior insulation has other advantages for commercial buildings, such as enhanced water management and increased air tightness of the building. For example, exterior insulation of 2″-8″ will be needed on existing masonry walls, while wood furring strips should be used on wood- framed walls.
Contractors add insulation to the exterior of existing buildings to achieve higher effective R-values. The R-value is important as it measures the thermal resistance of the insulation, indicating how quickly the insulation will lose heat. Another option is to use pre-insulated wall panels. The benefits of adding insulation go beyond the added thermal resistance by increasing the building’s durability and air tightness.
Windows provide the essential element of natural light, but in older commercial buildings they have very minimal insulation value. The two major components of a window system are the glass and the frame, both of which contribute to major energy loss. The glass installed in the window systems of 20 to 30 years ago would not meet current building codes today due to the stringency on the max U-value of the installed system. The U-value is the overall heat transfer coefficient that describes how well the element conducts heat of the rate of transfer of heat. A high U-value indicates poor thermal performance of the glass window systems.
Most common thermal problems in existing window systems range from air leakage and condensation to occupancy comfort and mold development. Correcting condensation problems can be costly, which is why proper window perimeter detailing is extremely important. Building professionals should recognize that window manufacturers develop their window systems based on general wall system designs. The retrofit design team must provide an integrated window system design to optimize thermal performance.
Insulated glass units (IGUs) improve the thermal performance in aging commercial buildings. Insulating the glass is one of the most effective ways to retrofit commercial building envelopes to reduce energy consumption and cost. Typical commercial spacers are composed of formed aluminum filled with desiccant to absorb any residual moisture inside the IGUs, reducing potential condensation. While aluminum is a structurally strong material, the aluminum-to-glass contact point is a very efficient thermal conductor and increases the potential for major temperature variances between the center and edge of the glass, which can cause condensation and reduce the unit’s overall U-value.
When IGUs are used in conjunction with low-E and/or reflective coatings, IGUs perform even better for conserving energy and complying with local codes. The most common configurations of IGUs in commercial buildings are a 6mm (1/4″) lite, 12mm (1/2″), or air space and a 6mm (1/4″) lite. Using two or more lites separated by a sealed air space enables the glass to meet two very different requirements of keeping heat in during cold weather and keeping heat out during warm weather.
Another major reason for updating or replacing glass systems is to reduce noise pollution. Noise pollution is a prevalent complaint among office workers as it results in decreased productivity. Upgrading the glass from a single pane to an IGU will reduce the sound transmission significantly. Varying the thickness of each lite of glass or using a laminated assembly in the IGU can help cancel out different frequencies, in turn improving the sound transmission class (STC) ratings.
Maximizing The Building Envelope Retrofit
A building enclosure retrofit is an efficient solution to improve energy performance and keep a building operational without the expenditures of complete demolition or reconstruction. It’s important to understand that the logistics and structural design are different from project to project. Additionally, an energy efficient retrofit can include an overhaul of the HVAC system and lighting system. Updating a building’s HVAC system with enhanced technology in addition to replacing traditional light bulbs with LED lights can also aid in the reduction of energy consumption. Coordination between the building owner, contractors, and architects is vital to finding the optimal retrofit solution.
Shields is the vice president of Planning & Development for IWR North America, formerly IWR Building Systems, and has approximately 20 years of industry experience. IWR-NA, headquartered in St. Louis, MO, is one of the longest standing specialty contractors in the United States that focuses on being a true building enclosure partner. IWR-NA is a subsidiary of MHS Legacy Group, a diversified national holding corporation also based in St. Louis with roots dating back to 1895. Shields can be reached at [email protected].