Matching Design Aesthetic with Performance

Louvers as a decorative element to achieve thermal performance

Andrew A. Hunt

Louvers play a critical role in commercial construction, offering a multitude of benefits. In addition to providing intake and exhaust ventilation, louvers have evolved to become architectural features that seamlessly blend design aesthetics with performance qualities. This article explores the benefits and advantages of incorporating louvers into commercial construction, highlighting their ability to enhance the overall building design while optimizing energy efficiency, indoor comfort, and air ventilation. Moreover, it delves into the significance of incorporating "blank-offs" into the design as well as the importance of rigorous testing to ensure the effectiveness of these systems.

GETTING TO KNOW LOUVERS

Louvers are horizontal or vertical arrangements of blades or slats that are used to control airflow, water penetration, and even light penetration. By altering the configuration of the blades and varying the free area, louvers achieve certain functions that architects desire for their projects. Installed on the exterior in an opening seamlessly integrated into a building’s facade, louvers can provide a wide range of benefits, including improved airflow and ventilation, privacy, and water protection for sensitive equipment, and offer a creative and unique aesthetic.

There are different types of louvers that architects can specify: non-drainable units; drainable options; storm-resistant products that resist wind-driven rain; extreme weather louvers that can withstand tornados, tropical storms, and hurricanes; acoustical versions that are engineered to minimize noise and sound leaving the building; and blast-resistant louvers that are designed and manufactured to withstand the shockwave from an explosion and not break apart and become a projectile.

The number, size, spacing, and design of the blades provide varying degrees of protection as each blade type has a distinct configuration, allowing for different degrees of air and water to pass through. Generally speaking, the Louver profiles get more complicated as the performance requirements go up. Architects and engineers will need to determine the type of ventilation and water protection they need in order to determine the number, size, and design of the louver panels.

THE CASE FOR LOUVERS

Louvers have many uses and benefits for engineers and architects. Their primary purpose in commercial buildings is to screen air intakes and vents from unwanted elements and facilitate beneficial air movement in and out of essential equipment, but louvers make buildings energy efficient and comfortable as well. They also offer an opportunity for architects and designers to enhance the visual appeal of their buildings.

To better appreciate how louvers can help improve energy efficiency, sustainability, and health and wellness, it helps to understand their intended function. When combined with other ventilation accessories, louvers help supply additional fresh air to HVAC systems. Outside air is brought into the building, filtered, then picked up by the air handler and cycled through the ductwork. The louvers help push out the hot, stale air, and keep buildings cooler throughout the summer months.

This air-regulating property has an added benefit. Appropriately sized louvers can enhance the energy efficiency of a com-mercial space because areas using outside air ventilation require less reliance on mechanical HVAC systems. The adequate ventilation allows fresh air to circulate throughout the building, creating a more comfortable indoor environment and maintaining optimal temperature and humidity levels throughout the year. The additional ventilation also reduces the likelihood of mold in buildings by reducing the amount of moisture vapor in the circulated air.

Choosing the right louver can also help support sustainable building practices, reduce the carbon footprint of a project and contribute to the overall environmentally responsible goals of a project. When properly incorporated into a design, louvers can qualify for Leadership in Energy and Environmental Design (LEED) credits.

One of the big benefits to louvers is that they help improve indoor air quality by enabling a steady flow of fresh air and exhaust of used air, which reduces the buildup of pollutants, allergens, and odors. Adjustable louvers allow building control systems to manage over airflow, ensuring personalized comfort and improved productivity. By strategically orienting louvers and utilizing advanced materials with high solar reflectance, buildings can minimize energy consumption, resulting in reduced carbon emissions and long-term cost savings.

LOUVER TYPES

In order to select the right louver, an architect must look at each unit’s performance criteria and decide what is needed. Manufacturers likely have their products categorized by depth, free area, pressure drop, wind-driven rain, and extreme-weather defense, including impact rating, giving an indication of the capabilities.

For example, an architect would look at the rain defense to see how successful it is at keeping water from entering through a louver. Rain defense performance is measured by several test methods. Wind-driven rain rejection tests by BSRIA (Building Services Research and Information Association)and AMCA (Air Movement and Control Association) measure a louver's effectiveness under simulated rainfall, air intake, and wind speed. Louvers are organized from the most effective rain defense louver to the least.

Another performance category that architects can check is the louver's Free Area, the minimum area through which air can pass. The free area is determined by calculating the percentage of the total opening that is unobstructed by blades and frame. Such louvers are organized from the highest to the lowest free area. A high percentage of free area allows for more air to enter via a smaller opening, reducing the expenses involved due to less total louvered area required for the same airflow rate. The free areas usually range from 35% to 60% of a louvered opening depending on model and opening size. An important note about free area is that free area and rain defense are inversely correlated, meaning the more free air flow a louver allows, the greater the opportunity for water to move through the louver along with that enhanced airflow. While this is generally true across all louver types, it can be mitigated somewhat with sophisticated blade profiles.

Architects also should specify a louver with a Pressure Drop performance, which is the measurement of the pressure differential from one side of a louver to the opposite side. Pressure drop is used to measure the resistance to airflow across an open louver and is important in the sizing and performance of louvers. It is usually expressed in inches of water at a specified velocity and is always the result of a physical test of units.

An important thing that architects must consider is the depth of a louver or the measurement of the depth of a frame. Depths of louvers vary due to one or a combination of the following criteria: air performance, water protection, sound transmission, installation/site requirements, and aesthetics. When evaluating frame depth, louvers are organized from the widest to the narrowest depth, independent of model type.

The more weather protection a louver system must provide, the more its configuration will have an impact on airflow and acoustics. In order to achieve a successful installation, architects will have to be very clear in their designs and be clear with engineers about the louvers’ “free areas,” keeping in mind that louvers generally perform at about 35% to 60% of free area. As a result, best practices suggest that if an engineer gives you a free area in square footage, you generally need twice as much louvered area to achieve desired performance after installation.

Because louvers are primarily located on the outside of buildings, it’s important that they blend seamlessly with the aesthetics of a building or at least support the project’s overall design. Fortunately, manufacturers produce a wide range of options so architects may specify systems in different sizes, standard and custom widths, different textures, and unique shapes. It’s also possible to intersperse different blade depths within one louver unit or combine performance louvers with various aesthetic scrim elements to blend in perforated sheets, panels, bar grating, mesh, or other design styles.

Louvers typically can be oriented horizontally or vertically and can be finished in numerous colors and textures. Manufacturers offer louvers in a variety of materials such as fiberglass, composite, and wood, but most louvers in commercial applications are made of aluminum although occasionally galvanized steel or stainless steel is available. {{question1}}

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BLANK-OFFS EXPLAINED

When it comes to louver design, one thing architects should know is something called a blank-off. It essentially refers to an accessory added to a louver system that does not have perforations or openings. A blank-off is a metal sheet or a system that consists of insulating material encompassed between two sheets, rendering the louver inactive.

Sean Carver, Senior Business Manager for Construction Specialties has a long tenure in working with architects and engineers to incorporate louvers into projects and believes blank-offs have a very unique and important role in a building design. It closes off unused areas of louvers, so if you have 100 square feet of louvers but only 50 are required for mechanical purposes, the quickest solution is to simply take the blank-off and block off the unused 50 square feet of louver.”

While louvers provide ventilation, incorporating blank-offs in the design can offer additional benefits. Blank-offs enhance privacy by restricting views from outside, ensuring confidentiality of more sensitive areas. They also act as a visual break, adding texture and depth to the building facade while complementing the perforated louvers.

There are two types of situations where the temporary application of blank-offs offer exceptional value and performance. One is for data centers that, by design, must provide exceptional security and protection for delicate equipment within. Blank-off panels are oftentimes used to close in a building and prevent some of the construction dirt and debris from coming through so that the servers and high tech equipment can be installed and protected.

Another situation for a blank-off is when a developer has an empty retail space that likely will be occupied at some point in the future. In such cases, an architect may specify a blank-off panel and then when the tenant comes in, they can take off the blank-off panels and use them just like a normal louver. This situation is temporary, but it could be utilized for a longer duration, as compared to the short-term needs of a data center. For the retail space, the blank-off, (when the unused louver area is closed off) is designed to remain in the fixed position indefinitely, until such a time that it can be removed to allow for an update to the building.

There are two methods for the application of blank-offs. Under a standard method, a simple compression gasket is installed on the back side of the louver framing and held in place with fasteners. In many cases, the fasteners penetrate through the gaskets or other wet areas of the louvers, which is particularly problematic. This is what’s known as an “80/20 principle” of blank-offs. In other words, the application will stop most of the water that it faces, but it absolutely will not stop all the water. If such an installation is problematic for a design, specifiers will need to have a backup plan to prevent any water that has penetrated the blank-off system from getting into the building or collecting behind the installation.

But there is another way to attach and seal blank-off panels–one that is not an 80/20 solution like gaskets. Rather, it’s almost 100 percent waterproof. It is called an enhanced method that uses a true weather silicone sealant. The method uses a butyl tape and silicone that’s applied around the edge. The result is a complete unbroken system that almost hermetically seals the louvers.

For the enhanced method to be effective, the sealant has to be tooled. It will not be enough to simply apply silicone sealant in a conventional way. The manufacturer will have to tool it into the joints appropriately or the effort is almost worthless. For the weather seal method to be truly effective and achieve a proper level of water resistance, the manufacturer has to be experienced and highly skilled. {{question4}}

SPECIFYING LOUVERS

The type of louvers architects specify varies from building to building and project need. A parking garage, for example, might require good airflow but not need protection from rain. On the other hand, a data center or mechanical room that contains sensitive electrical equipment may require louvers with strong protection from storms and high-performance airflow specs to ensure that the hardware is effectively cooled. When specifying a louver system, it’s essential that architects and designers have a clear understanding of the project requirements and which louver characteristics will meet those needs.

A common approach to specifying louvers is to have the performance needs dictate or drive the facade and envelope design. By first understanding the performance requirements of the project, the architect can then narrow down the available options in louver design. Paramount to this process is to understand the performance criteria for louvers, then consider security, airflow intake, and exhaust, then expected weather or storm durability, as tested and certified by a third party like AMCA. After the needs of the building and safety of the occupants have been determined, specification sheets from the manufacturer or supplier can be utilized to further narrow down louver options. Depth, free area, static pressure, rain defense, and hurricane preparedness should all be included in manufacturers’ documentation on their louver products.

One thing that is important for architects to remember is how louver size affects airflow. The size of louvers directly affects the amount of airflow they allow. Essentially, larger louvers allow more air to flow into the building, facilitating better ventilation.

Choosing the right size louvers will result in an installation that is much more effective, enabling a steady flow of fresh air and reducing the buildup of pollutants; enhancing the energy efficiency of spaces; and maintaining optimal temperature and humidity levels throughout the year.

But there are other things to consider in relation to louver size. For example, it’s important to be familiar with local building codes and regulations, as some areas have specific requirements for minimum ventilation rates, which must be adhered to for safety and compliance. Architects should know the purpose of the commercial space and the number of people occupying it—for example, high-occupancy areas, such as healthcare facilities, where indoor air quality is critical. Also data centers that need a consistent indoor temperature to protect equipment may require larger louvers to accommodate higher airflow demands.

The physical nature of the site confers other important and related considerations for louver specification, like environmental factors and building orientation. Where the building is located plays a significant role in determining the ideal louver size because areas with extreme weather conditions, such as hot summers or cold winters, may require larger louvers to facilitate efficient heating, ventilation, and HVAC systems. These considerations are especially important in modern society where air changes per hour and general fresh air transfer rates are considered in relation to COVID transmission.

Similarly, how the building sits on the site is an important factor. The orientation of a commercial building, window placement, and other factors can impact the amount of sunlight and airflow throughout the day. Properly sized louvers can help regulate solar heat gain, reducing the need for artificial cooling and optimizing energy consumption.

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LOUVER STANDARDS

When architects or engineers are deciding on a louver, one of the first things they are likely to do is review a product’s specifications and product performance details. But how do they know if the performance numbers are accurate? That’s an important question because an essential part of selecting louvers for a project is the confidence that the potential product or system meets appropriate performance standards. Knowing how a louver is expected to perform is critical to ensuring that it will stand up to real-life conditions on the job.

The Air Movement and Control Association (AMCA) and other industry standards provide guidelines for testing louvers. Specific tests include static pressure water penetration, wind-driven rain resistance, sand resistance, and acoustical performance. By adhering to these standards, architects and builders can have confidence in the performance and reliability of the chosen louver systems.

AMCA conducts the tests at one of their accredited laboratories where a manufacturer has its louvers tested. With the results of these lab tests, the manufacturer is allowed to post the results on its louver submittal page, along with an image of the AMCA Certified Ratings Program, or CRP, seal. Some louvers can be certified for multiple performance factors and may display the appropriate seals accordingly. These seals help architects identify tested products and then can obtain technical data sheets from the manufacturer.

ANSI/AMCA Standard 500-L helps specifiers understand what testing in accordance with this AMCA standard proves and does not prove about the louvers they are considering for a project.

AMCA publishes test standards that are universally accepted in the industry, and it provides third-party testing to confirm the accuracy of manufacturer data. AMCA’s members—companies that manufacture air movement and control products such as louvers—must agree to accurately represent the performance of their products according to AMCA guidelines set forth in a variety of AMCA publications and abide by a stringent code of ethics.

Once a project is awarded, the architect or specifier must review a louver’s submittal sheet, which reveals technical information that describes the louver’s performance. These submittal sheets help engineers assess if the louver selected for the project has the right performance attributes for their project’s requirements.

It is important to emphasize that neither AMCA nor manufacturers test or certify equipment in the field after installation to verify performance. Installation practices, location, and specific building orientation can all impact the performance of louver. However, manufacturers can perform tests of other specific or unique performance criteria, like storm resistance, in accordance with AMCA protocol. This type of performance testing is done on the manufacturer’s own equipment, and is very useful to validate the performance criteria of louvers that may have screens or unique design elements.

Still, the first step when specifying louvers to meet or exceed specific performance expectations is to understand the testing protocols of the AMCA. Louvers are designed to protect air intake and exhaust openings from the infiltration of unwanted water or particles while allowing airflow into the space, and different louver models offer varying levels of performance. In many cases, an architect or engineer chooses a certain louver system because it satisfies a specific performance requirement, so these AMCA standards are extremely important. AMCA Standard 500-L covers five testing protocols: {{question6}}

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Pressure Drop

This test determines a louver’s resistance to airflow. Because some equipment needs air to operate effectively, airflow is an important factor. If an architect is considering a louver for a space containing this type of equipment, its pressure drop test results should be one of the first things to look at.

The pressure drop test requires air measurements for a number of intake/exhaust velocities and the resulting pressure drops. ANSI/AMCA Standard 500-L specifies that, for pressure drop, a 1219 mm × 1219 mm (48-inch-by-48-inch) louver sample shall be tested. The information on the louver’s submittal page reflects the results of the test.

Air Leakage

The air leakage test determines the relationship between the airflow leakage rate and the static pressure for a louver mounted in a test chamber. The test can help architects properly select an operable louver in its closed position for a building’s needs after considering airflow, the need for energy savings, and the importance of having a sealed building envelope.

Similar to the pressure drop test, there are five or more determinations that are taken at equal increments of pressure differential that cover a desired range during equilibrium conditions.

Water Penetration

The water penetration test is designed to determine the intake air velocity at which water begins to penetrate the louver. A common misconception is that the test reports how much water penetrates the louver during service conditions, but this is not the case. This test is meant to show how the louver will perform under what are considered typical conditions rather than heavy rains or windy conditions. It is important to understand that there is no wind at the face of the louver during this test, and the only airflow is being pulled through the louver from an intake source.

During the test, technicians release water droplets in front of the louver to mimic light rainfall at a minimum rate of .1 inches per hour as well as simulating water coming down and exterior wall at a rate of 3.28 L/m per linear meter (0.25 gpm per linear foot). At the back of the testing chamber behind the louver, an intake fan pulls air through the louver at a variety of intake speeds until water begins to come through the louver. This is a key test and an important one for AMCA because the space behind the louver needs to be kept dry, particularly when adequate drainage does not exist.

Wind-Driven Rain

During this test, a louver is set up in the testing chamber, a high-powered fan is set up in front of it to simulate 12.96 m/s (29 mph) winds or 22.35 m/s (50 mph) winds. Nozzles will spray water at the louver, simulating an external rainfall of 5.08 cm/hr (3 in./hr) when the fan is running at 12.96 m/s (29 mph) and at 20.32 cm/hr (8 in./hr) when the fan is running at 22.35 m/s (50 mph).

The test observes the water supply rate, the water penetration rate, and the airflow rate through the louver. Once the test is completed, a louver’s performance is marked by the quantity of water that penetrated the system during the test compared to the amount of water that would have passed through the test wall opening if the louver was not present. This comparison is what is referred to as the Efficiency. For the architect and specifier, the important information is the assigned class rating efficiency: Class A – 99% to 100% effective, Class B – 95% to 98.9% effective, Class C – 80% to 94.9% effective, and Class D – Anything below 80% effective.

The results of this test show efficiencies of the louver’s ability to reject wind-driven rain at up to 11 test points ranging from 0.0 m/s to 5.0 m/s. Most manufacturers also relay these test data points in terms of the intake velocity or intake Free Area Velocity. These intake velocities differ slightly from one louver to another; however, the value remains constant or all louver models and manufacturers in order to allow the specifier to compare apples to apples in design performance and expectations.

Wind-Driven Sand

The latest addition to the ANSI/AMCA Standard 500-L is the testing protocol for wind-driven sand. It measures a louver’s ability to resist intrusive sand. When air systems that lie behind the louver are exposed to sand particles, it can clog up air filters prematurely.

Adopted in December of 2015, this test introduces airborne dry sand particles at different airflow rates to the louver under test. The louver is mounted and sealed within the sand injection chamber, so all sand ingress measured has come through the louver’s blades only.

The size for the louver in this test is 1220 mm × 1220 mm (48.03 in. × 48.03 in.). The test is carried out with dry sand that is uniformly distributed through a blower while the pressure drop is documented. During the testing, the free area velocity is observed and recorded. Once the measured weight of the sand has been entirely injected into the test duct, the exhaust fan and sand injector blower will continue to run for two minutes. The sand that is prevented from passing the louver is collected by a vacuum cleaner, and the difference between the sand blown at the louver and the sand that is rejected by the louver is then documented. {{question8}}

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DESIGNING WITH LOUVERS

As stated earlier, louvers have many functional benefits, but they provide architects with an opportunity to enhance the architectural interest of a building. That’s because louvers have transcended their utilitarian origins to become an integral part of the architectural language.

Whether it's a sleek, minimalist look or an intricate and decorative pattern, lovers allow architects to enhance the aesthetics of a commercial structure. While not typically considered an obviously sexy design feature, the right louvers can add an economical design element to the facade, adding contrast to a facade or blending with it.

After architects have determined their needs, the design options are wide open–from color, texture, size, and design. Some manufacturers offer louvers in standard colors or up to 500 resin-based and metallic finishes, while other suppliers offer color-matching and wood-grain patterns. Architects may also specify intricate custom shapes.

More than simply squares and rectangles, louvers can be specified in almost anything an architect needs, allowing units to fit the design of the building and not the building to the louver limitation. But architects must remember that changes in louver shape will alter its performance.

AMCA's standardized test methods only apply to louvers as they are intentionally designed, but do not account for louvers that have decorative screens placed on them as an after-market option. Decorative screens change the air flow and performance of the louvers, which can create an issue for the project when trying to meet both performance and aesthetic goals.

The critical requirement for the designer or engineer is to ensure the manufacturer will provide a complete system, as specified, to the end user and be able to test the product to AMCA standards. This will allow for the inclusion of decorative elements, like screens in front of the louver that also meet or exceed the performance expectations. Not all manufacturers are capable and willing to provide this next level of assurance, which makes specifying a product that has full support of the manufacturer especially important.

For example, if a louver with an AMCA seal rating for air performance, the seal will not apply to the louver if a decorative perforated panel is added to the front of the louver. One thing to note is that wind-driven rain and extreme-weather defense louvers are not available with custom-shape options other than square or rectangular. Because they are designed for heavy rain and severe winds, their design cannot be modified.

Specifiers and architects typically must decide how they want the louvers to be used in a project, as there are many options. Specifiers may choose recessed- or hidden-mullion options, which can remove the visible divisions between louvers, creating a continuous line for panels that are linked together. Hidden mullions are completely concealed behind the blades, but the application may affect the louver's wind load capabilities, as the blade supports will not have the same structural integrity of a standard frame louver. As a result, the application will be affected by high winds. Architects should consider where such an application will be installed before deciding. Architects use louvers in a variety of project types and in ways to solve problems creatively.

LOUVERS IN THE REAL WORLD

One example of adding louvers into a project to blend classic charm with contemporary performance expectations is Rose Hill, in New York City. Owned by the Rockefeller Group, Rose Hill is a new, 46-story, thin residential building in Manhattan that has the unique design attribute of a dedicated mechanical floor at both the top, and bottom of the building. To facilitate air to flow in a circular manner to both mechanical spaces, thus keeping the building and its occupants healthy, louvers were specified to be installed at entry-level near the occupant entrance.

While the louvers would supply ample fresh air required for the building, the challenge was finding a way to incorporate the equipment into the ground-level facade in a tasteful way to match the desired Rockefeller Center stylized theme.

The solution was to employ custom cut metal screen covers placed over the louvers, to blend in with the rest of the facade and still be manufacturer tested for Pressure Drop and Wind-Driven Rain. CetraRuddy, lead architectural firm on the project, were led by Senior Associate Project Designer Charles Thompson, LEED AP, and leveraged the chevron as a common design element for the project. The facade at the base of the building, railing, as well as the custom metal covers on the louvers all carried the chevron pattern, creating a uniform and consistent visual aesthetic.

Another project that benefited from the flexibility and resilience of louvers was the Children’s Hospital of Philadelphia. The Children’s Hospital of Philadelphia (CHOP) is the nation’s first hospital devoted exclusively to the care of children, and since 1855 has had many notable firsts in pediatric medicine.

When an update to the facade was commissioned, architectural firms Ballinger Architects and Kohn Pedersen Fox were faced with two challenges. With the increase in frequency and severity of extreme weather events, especially the harsh storms that occur on the East Coast, the louvers specified had to be up to the task of enduring extreme weather conditions. Also, the louvers needed to blend seamlessly with the design of the building. The solution was a hearty storm-resistant rated system that wrapped completely around the building’s facade. Seven-inch louvers were specified to allow for ample flow of free air for circulation, and the depth allowed for an imperceptible visual transition to the active and insulated louvers.

Another inspired example of what can be achieved by customization of louvers is the air traffic control tower at San Francisco International Airport. The owner wanted something unique—a form that did not resemble the typical lollipop-shaped tower that one finds at many major airports around the world.

Completed in 2015, the $80-million, 221-foot-tall air-traffic control tower replaced the existing tower atop Terminal 2 when it opened in 2016. The 5,652-square-foot structure was the tallest vertical self-centering post-tension concrete structure in the United States when it opened. The building ascends in a graceful arc, topped by a cab that is offset from the central column. A ribbon of glass runs the vertical length of the tower, reflecting sunlight during the day and illuminated by interior lighting at night.

The louver manufacturer’s ability to form special shapes and configurations was essential on this project. Using this capability, designers devised a spiral form resembling the double helix of DNA. The louver manufacturer came up with a unique compound curving concept providing the tower with a distinctive look. Complementing the curving louvers, the west face of the tower features an LED backlit glass element resembling a waterfall that reaches 147 feet in the air.

With the appearance of a trumpet standing on its end, the building curves inward at the middle and then flares out again at the top. And then on the outside, the skin is made up of metal panels and louvers that spiral up the outside of the building in a complex geometry. Essentially, the challenge for the designers and manufacturer was figuring out a way to take a louver that has a rigid, fixed profile and make it move up the building like a flexible element. The result is something that is extremely unique and fulfills the client's desire for a design that had never been done. {{question10}}

CONCLUSION

Louvers can play an important role in commercial construction. As shown in the case studies, incorporating louvers is a simple but effective way to architecturally break up the mass and scale of a building as well as to create exterior design interest. With skillful design intent and the assistance of a good manufacturer, a louver installation can elevate a project's overall design.

Fortunately, architects, designers, and developers also reap the additional benefits that louvers provide. Specified correctly, they block rain and severe weather and promote energy efficiency.

The evolution of louvers means architects and designs can do more with a versatile system that can adapt to many situations and needs and look good while doing it.

Andrew A. Hunt is Vice President of Confluence Communications and utilizes over twenty years professional writing experience in residential and commercial building science to produce marketing, training, educational and multi-media material. www.confluencec.com