McGough on WCC Elevator Smoke-Control

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0 McGough Jive Generalions Building, Confidence the requirements of incidental uses.The doors are all 1-3/4 inch solid-core doors and they will be provided with smoke gaskets. 1-3/4 inch doors have traditionally been considered more or less equivalent to 20-minute rated doors and it was pointed out during the meeting that the 2003 IBC has"corrected"the language regarding elevator lobbies by changing the wall requirement from a"fire barrier"wall to a"fire partition"wall. Thus,when the adoption of the 2003 IBC is complete, only a 20-minute door will be required for elevator lobbies regardless of the number of stories. Thus we seek your approval to just construct the described elevator lobby on the lowest level and recognize that the upper two levels,open to each other in this area,can not be effectively separated. Elevator B: Elevator B is the elevator in the new addition that travels from the sub-basement through the ground floor to the 15`floor. The travel is more than 25 feet so an elevator vent has been provided. It was acknowledged that the intent of the smoke-and draft- control provisions for elevators was not necessarily to prevent smoke from entering the elevator shaft but,rather,to prevent smoke from migrating to other floors from the level of development. Therefore, it should be possible to either provide a positive or negative pressure within the elevator shaft to control the movement of smoke. A positive pressure within the shaft could prevent the smoke from entering the shaft and a negative pressure might be utilized in conjunction with an exhaust fan, in lieu of the elevator vent,to send smoke within the shaft out through the top of the shaft to the exterior. Dave and Gerry indicated their concurrence, in principle,of this approach but also noted that it would be up to the AHJ to determine if this was appropriate and what other considerations would be necessary. After consultation with our Mechanical, it was decided that pressurizing the elevator shaft would be the most effective method. If you consider this an acceptable option,the design team will put together a fmal design for your approval. The system will be designed to only operate when one of the local smoke detectors in the adjacent draft curtain detects smoke. It will then pressurize the shaft with a fan sufficient to keep smoke from migrating into the enclosure. The fan will draw outside air for this purpose and the opening into the shaft will be protected by a combination damper. There will be a keyed control for the fire department. If you agree that we may take the approaches noted,we will work with Miller Dunwiddie to put a final design package together as soon as possible. I have copied Dave and Gerry with this memo so they can let you know if I have not correctly interpreted their comments. Thanks much for your assistance in this matter. We look forward to your response. 2737 I•AIRVII W AVENUE NOR t S C. i'AUI.... MINNI:::SO'FA 55113-1372 PIIONF:: (651) 633-5050 I AX: (651) 633-5673