Intake and exhaust louvers contribute fresh, outdoor air to a building’s circulation while protecting the exhaust opening from water flow and other outdoor elements. They play a critical role in more sustainable and efficient HVAC systems, making them popular in modern times despite being originally invented in the Middle Ages.
Types of Louver
Traditional louvers were made of old wood barrels and often placed at the top of walls in large kitchens to increase ventilation while keeping out rain and snow. They eventually became more elaborate—constructed out of pottery in the shape of faces, where smoke from the kitchen would blow out the eyes and mouth.
As the popularity of louvers spread, so did their use, causing the term to mean a variety of things. Window shutters, for example, were traditionally referred to as louvers long before a pane of glass came to be placed in front. Intake louvers serve a similar purpose but have a more complicated system to meet the more demanding needs of a building HVAC system.
Understanding Various Intake and Exhaust Louvers
Like shutters, intake and exhaust louvers contain multiple blades that allow air flow while preventing other outside elements from entering. According to the Air Movement and Control Association (AMCA), traditional louvers were referred to as “Z” or “J” types and failed to keep out water. A “K” type was then introduced, which made promises about keeping water out but still failed to do so.
As a result, in 1999 the AMCA Standard 500-L test was introduced to ensure that HVAC-based louvers could withstand more severe weather. This brought a series of new innovations to the market, including adjustable blades, combination louver/dampers, vertical blades, and Y-blade and acoustical louvers.
Modern louvers are typically expected to meet criteria in these specific categories:
Pressure drop
Difference in pressure between two points of a flow system
Free area
Minimum area through which air can pass
Water penetration resistance
Amount of water that passes at various test conditions
If you are purchasing louvers, the categories above are worth considering before you buy—based on the current needs of your building, system, and regional climate.
Louver Features to Consider for Sustainability
Making the right considerations before you purchase a louver to assist your HVAC system can also lead to increased sustainability. Take these features into account.
Blade Profile
In an attempt to block unwanted elements, some blades might also restrict air flow. Blades with flat or fewer features tend to be more efficient. Chevron blades have a useful shape that contributes to natural air flow while restricting other elements, but are not as efficient as a straight blade.
Pressure Drop
A large pressure drop will require intake fans to work harder to pull air through the louver. To maximize efficiency, select a pressure drop that is exactly enough to prevent rain water from entering.
Free Area
An increased amount of free area will allow for a lower pressure drop. For the most efficient allowance of air flow, select a louver with maximized free area.
Increased optimization of HVAC-designed louvers has made them more popular, even in modern society, and the addition of tests ensures that the louvers can stand up to even more severe weather conditions. And taking sustainability features into consideration could mean an overall more efficient and cost-effective HVAC system.
Product Compliance and Suitability
The product statements contained in this guide are intended for general informational purposes only. Such product statements do not constitute a product recommendation or representation as to the appropriateness, accuracy, completeness, correctness or currentness of the information provided. Information provided in this guide does not replace the use by you of any manufacturer instructions, technical product manual, or other professional resource or adviser available to you. Always read, understand and follow all manufacturer instructions.