ID#2098 made on
EQp1 - Minimum IAQ performance
LEED BD+C: New Construction, LEED BD+C: Schools, LEED ID+C: Commercial Interiors, LEED BD+C: Core and Shell, LEED O+M: Existing Buildings
This project consists of 7 buildings in the United Arab Emirates, on the Persian Gulf. Each of the buildings has from 5-21 workshops for repair of boats, engines, transmissions, etc. There is no heati...
This project consists of 7 buildings in the United Arab Emirates, on the Persian Gulf. Each of the buildings has from 5-21 workshops for repair of boats, engines, transmissions, etc. There is no heating in the buildings and they are all cooled by natural ventilation. ASHRAE Std. 62.1-2004 paragraph 5.1.1, Location and Size of Openings states that "naturally ventilated spaces shall be within 25' of operable wall or roof openings to the outdoors, the openable area of which is a minimum of 4% of the net occupiable floor area." There is a louver in an overhead door in each of the workshops, plus one operable window. Because of the sandstorms in the area, the free unobstructed area through the opening of the louver does not meet the 4% requirement. Adding the area of the open window also does not meet that requirement. The area of the overhead door, when open however, more than meets the requirement. The standard mode of workshop operation in Dubai, where this project is located, is to leave the overhead doors open during normal working hours, except when there is a sandstorm. The other workshops in the area do not have roof ventilators, but rely strictly on the open overhead doors for ventilation. This project will have 2 wind-driven turbine roof exhaust fans located at the rear of each of the workshops on the far wall from the overhead door. Calculations show that, with an actual average wind speed in the area of 10.5 mph (the ASHRAE Fundamentals Handbook shows a max wind speed of 17 mph at 5%), the air change rate in the workshops will be from 6-9 air changes per hour, depending on the size of the workshop, i.e. the larger workshops will be closer to 6 and the smaller ones will be at 9. The exception in 62.1-2004 to paragraph 5.1 states that "An engineered natural ventilation system when approved by the authority having jurisdiction need not meet the requirements of 5.1.1 and 5.1.2". Paragraph 5.1.2 refers to control and accessibility of the operable openings, which this project meets. The authority having jurisdiction in Dubai will consider the calculations for the wind-driven turbine exhaust fans an engineered natural ventilation system. However, the likelihood of obtaining this approval in a timely fashion is questionable, as this project requires completion in less than 5 months; therefore we cannot wait for jurisdictional approval. As a result, we are writing this CIR and asking 2 questions: 1. Since the workshops have no interior walls and the roof exhausters are at the opposite end of the building, more than 25' from the overhead doors, and are also approximately 25' above the floor, will this be considered meeting the location of openings to the interior space? 2. Based on the different culture and customs of the country and the expectations of the workers relative to comfort conditions in naturally ventilated spaces, and based on these workshops having wind-driven exhaust fans providing 6-9 air changes per hour where other workshops have none, will this suffice for a natural ventilation system?
1) Assuming that there is one operable overhead door in each of the workshops, that the open area of the door is at least 4% of the floor area, and that the entire workshop area is within 25 feet of the operable door, then the workshop space will meet the requirements of ASHRAE 62.1-2004 Section 5.1.1 or equivalent. For those workshops whose entire floor area is not within 25 feet of operable area, an engineered natural ventilation as mentioned in Exception to 5.1 would meet standard 62.1-2004, provided it is approved by the authority having jurisdiction. 2) The system described falls under the description of an "engineered natural ventilation system". Applicable Internationally, UAE.
Related Addenda (Corrections & Interpretations)