Louver Design Recommendations

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To obtain optimal natural ventilation performance, a few design recommendations can be proposed. However, since the variables vary from location to location, thus these can be used as general design guidelines.

 

First and foremost, designing of the building’s openings (windows/louvers) to be perpendicular to wind speed (Department of Standards Malaysia, 2007; Walker, 2016). The rationale being, perpendicular wind speeds produce a higher volume flow rate. However, such a blanket statement can be insufficient because the presupposition is that higher volume flow rates are more desirable in an indoor region. On the contrary, better guidelines should propose the consideration by the designer of the purpose of the indoor region and the range of comfortable air velocities as denoted by ASHRAE 55 to be up to 0.8 m/s without local control of airspeed, and 1.2 m/s with local control of the airspeed (ASHRAE, 2017). These are guidelines that vary with a plethora of complex variables such as temperature, humidity, the turbulence of air, etc., and thus should be considered on a case-by-case basis.

 

Continuing on from the aforementioned author(s), low level openings should not be obstructed by furniture and interior partitions. Consider internal airflow through open internal doors of buildings or installation of high louvers at the top of the internal door suppose the former option is not available. As for consideration of room width, the upper limit of the width of a room/area that can apply natural ventilation is approximated at 14 meters.

 

For optimal results, every room where there exist inhabitants should each have their own supply air opening and exhaust air opening; where inlets at the windward size and outlets on the leeward side (Department of Standards Malaysia, 2007; Walker, 2016). Inlet and outlet windows should be positioned across the room (cross-ventilation) to increase the air mixture within the room. On top of that, obstructions to airflow within the room should be reduced as much as possible. If cross-ventilation is replaced with stack ventilation instead, place the exhaust location above the inlet to increase the efficacy of stack effect.

 

Window openings must be able to be manipulated by the inhabitants of the building and easily accessible. Avoid inlet and outlet openings directly across from each other in order to promote more air mixing and improve the effectiveness of the ventilation. Additionally, vertical louvers should be installed for east/west building façade, meanwhile horizontal louvers ought to be installed for south building façade (Datta, 2001; Palmero-Marrero & Oliveira, 2010).

 

Natural ventilation is not suitable in hot and humid areas. Natural ventilation could be used in these areas either as a night cooling system or in conjunction with a mechanical cooling system as a hybrid strategy (Emmerich et al., 2001, p.57). On the other hand, Walker (2016) suggests the consideration of the location and temperature of the building. An open-building approach is effective in warm and humid areas as the temperature does not change drastically throughout the day and night. In this case, daytime cross-ventilation is encouraged to maintain indoor temperatures close to outdoor temperatures. Good site planning, landscaping and plating strategies can be used to cool the incoming air (Department of Standards Malaysia, 2007).

 

Last but not least, it is imperative to take note that, best design practices must also include the awareness of the limitations of the application of louver technology in buildings; which include, its high reliance on outside climatic conditions and thus relevant study of the location of the site must be performed by the engineer (Atkinson J, Chartier Y, Pessoa-Silva CL, et al., 2009; Emmerich et al., 2001).

 

References

  1. ASHRAE. (2017). ANSI/ASHRAE Standard 55-2017: Thermal Environmental Conditions for Human Occupancy.
  2. Atkinson J, Chartier Y, Pessoa-Silva CL, et al., E. (2009). Natural Ventilation for Infection Control in Health-Care Settings. World Health Organization (WHO). https://www.ncbi.nlm.nih.gov/books/NBK143277/
  3. Datta, G. (2001). Effect of fixed horizontal louver shading devices on thermal perfomance of building by TRNSYS simulation. Renewable Energy, 23(3–4), 497–507. https://doi.org/10.1016/S0960-1481(00)00131-2
  4. Department of Standards Malaysia. (2007). MS 1525:2007 – Energy efficiency and use of renewable energy for non-residential buildings – Code of practice (FIRST REVISION). In Code of Practise On Energy Efficiency and Use of Renewable Energy for Non-Residential Buildings (pp. 1–46).
  5. Emmerich, S., Dols, W., & Axley, J. (2001). Natural ventilation review and plan for design and analysis tools. National Institute of Standards and Technology, NIS, 57. http://www.bfrl.nist.gov/IAQanalysis/docs/NISTIR_6781_NatVentTool.pdf
  6. Palmero-Marrero, A. I., & Oliveira, A. C. (2010). Effect of louver shading devices on building energy requirements. Applied Energy, 87(6), 2040–2049. https://doi.org/10.1016/j.apenergy.2009.11.020
  7. Walker, A. (2016). Natural Ventilation. National Renewable Energy Laboratory. https://www.wbdg.org/resources/natural-ventilation

 

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