With the wide selection available today, choosing the proper louver for your application may appear to be a difficult task. By considering the requirements of the application and understanding what models are available, louver selection can be relatively straightforward. In this article we will examine the factors that affect louver selection and some of the more common louver styles available.
Selection generally starts with a desired airflow. Practically any louver style will handle any amount of airflow if it is large enough. However, system designers usually have to deal with size constraints. The task then becomes finding a louver that will handle the desired volume while providing adequate rain resistance and airflow characteristics. Here are some considerations:
- Rain Resistance: Rain penetration through louvers is undesirable. When louvers are close to water-sensitive surfaces, rain can be extremely harmful. If rain penetration can be managed or it is not harmful, a standard louver may be suitable. If the application cannot accept rain penetration, wind-driven rain resistant louvers should be selected.
- Pressure Drop: How much pressure drop is acceptable? This may be the deciding factor in louver selection. Most standard louvers are designed to give good air performance within their intended airflow ranges. It is good to remember that published Air Movement and Control Association (AMCA) certified pressure drop performance figures do not include the effects of a bird or insect screen. This can add from 10 to 15 per cent additional pressure drop depending on the screen type.
- Airflow Shutoff: For applications that require airflow only at certain times, operable or combination louvers that completely close the opening are available. These are good choices for emergency-generator or warehouse applications.
- Appearance: Is a particular louver design or appearance desired? Does the louver need to blend in with or match other building elements? For architectural louver applications, appearance sometimes is the most important feature. The appearance of louvers can be changed to suite almost any application. Other considerations in selection are security, sound, and structural integrity.
Now that we outlined some of the considerations for louver selection, let us review some common louver styles.
Standard Louvers are the standard horizontal blade models that have been available for many years. Typically they are 4 to 6 inches deep and are tested to AMCA Still Air standard. These basic louvers provide good free area; however, in our
climate they are less effective at rain protection. The blades do not collect water; therefore, rainwater cascades from blade to blade. In our climate louver blades of drainable-blade louvers feature small gutter in their profiles that collect water and drain them to downspouts in the jamb frames. They have better rain resistance than non-drainable but are not effective in storm conditions.
Sight-proof louvers most often utilize a chevron or inverted “Y” shaped blade to prevent see through. This prevents passage of objects through the louver wall. Free area is smaller and pressure drop is usually worse requiring larger louver area for the same airflow.
Thinline louvers are 1 to 2.5 inches deep. They generally air used for curtain wall applications and are a very good choice for small openings.
Wind-driven rain resistant louvers have been developed over the past decade and utilize new technology to minimize rain penetration. The louver depths range from 4 to 8 inches. The blades may be horizontal or vertical and generally feature complex profiles. Blade spacing is closer and unlike standard louvres these are tested in AMCA’s Wind-Driven Rain Penetration test, which simulates severe storm conditions. Many models can provide water penetration efficiency of 99 per cent. These louvers can be as much as two or three times the cost of standard louvers, but in many cases can be half the size.
Acoustical louvers feature blades filled with sound-deadening material, typically mineral wool or fibreglass. They are usually fairly deep, as much as 12 inches. The free area is usually less than standard louvers; these models can provide as much as 10-12db noise reduction in free field conditions.
The louver styles described in this article make up the majority of louvers available, but there are other specialized louver products available. Even though there are many louver products to choose from, selection can be easier with a clear understanding of the design needs. You local louver representative can be of great assistance.
