Let's not over value archaic vents. Full opinion mode on. Vents do next to nothing for egress in a sprinklered building, or more so with an ESFR system. Let's note the second letter in the acronym ESFR. If it's suppressed there is no reason to leave never mind debating the means of how to get out. Even with more conventional sprinklers the smoke is significantly cooler than in an unsprinklered building thus the vents even if open don't allow much smoke to leave due to the reduction in buoyancy.
Should the sprinklers fail there is still a cooling effect so again vents are a marginal improvement. Should the valve be completely off think of the volume for the upper layer to develop in. These building are usually very tall and at 500' there's a whole lot of sq.ft. to spread the smoke. It's going to take a VERY long time to affect the few that populate these buildings. Sure I'm making a few assumptions but bottom line is the correlation to value of vent and anything is weak IMHO. Especially when taking about the gravity kind. Even the mechanical kind are tied to the expected gravity volumes. Unless the code changed we don't design vents assuming a failed sprinkler system. I know the performance standard at least at one time expected PBD to assume some failures. Sorry haven't kept up on all the details since I became a lowly sprinkler contractor (that will be soon unemployed and perhaps no longer a contractor). And finally 200', 250', 500' or whatever are code numbers there is no technical merit in those numbers either. Chris Cahill, P.E. Fire Protection Engineer Sentry Fire Protection, Inc. 763-658-4483 763-658-4921 fax Email: [email protected] Mail: P.O. Box 69 Waverly, MN 55390 Location: 4439 Hwy 12 SW Waverly, MN 55390 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Brad Sent: Wednesday, June 23, 2010 1:09 PM To: [email protected]; [email protected]; 'George Church' Subject: RE: IBC egress distances >250' George-- Can I have your autograph? This is the old unresolved controversy of sprinkler/vent interaction. I think what you ended up with is best, and it still will be (ESFR-no vents) But it never was intended to allow the additional 150' without vents because vents improve visibility (therefore egress speed). The reason the increase is no longer allowed is because the vents do not work (mainly due to sprinkler water in the ceiling jet cooling the vent element). Here is a piece of the code talk: Group F-1 and S-1 occupancies protected by a sprinkler system and provided with smoke and heat (roof) vents. At present, the IBC permits travel distance to be increased from 200 feet to 250 feet in Group F-1 and S-1 occupancies when sprinkler protection is provided. Section 1016.2 allows an additional 150 feet of travel distance in Group F-1 and S-1 occupancies above and beyond that permitted when sprinkler protection is provided when smoke and heat (roof) vents are also provided. While smoke and heat (roof) vents by themselves will automatically vent smoke and heat generated by a fire in an unsprinklered one story building, there is serious doubt whether or not smoke and heat (roof) vents actually perform their intended function in buildings protected throughout by a sprinkler system. ------------then a lot about different tests------then------------ Given the above, it can be concluded that smoke and heat (roof) vents do not actually operate as expected in buildings protected by a sprinkler system. Based upon this, it can be concluded that there is no technical basis for permitting an increase in travel distance of 150 feet beyond the travel distance permitted for Group F-1 and S-1 occupancies protected by a sprinkler system when smoke and heat (roof) vents are provided. -----Original Message----- From: Brad [mailto:[email protected]] Sent: Wednesday, June 23, 2010 8:34 AM To: 'George Church'; [email protected] Subject: RE: IBC egress distances >250' George, I guess now the ONLY methodology is smoke modeling and timed egress analysis (which is no guarantee- you have to do the work, hit calc, and keep your fingers crossed). Is this what you did in the past to "...gain variances..."? You should still be able to install mass quantities of ESFR though because even with auto vents the dist cannot be increased. One of the code gurus here is going to find out the reasoning for no increase with auto vents now. -----Original Message----- From: George Church [mailto:[email protected]] Sent: Tuesday, June 22, 2010 6:02 PM To: [email protected]; [email protected] Subject: RE: IBC egress distances >250' Let me re-phrase the question, now that we in PA have adopted the 2009 I-codes. In 2006 edition we could extend egress distances from 250' to 400' by using vents. That section isn't in the 2009 edition, so we've lost the ability to efficiently build big boxes wherein I'd like to install mass quantities of ESFR sprinklers. Has anyone seen a methodology within the 2009 edition of the IBC to replace the Vent exception? That's my question. I'm aware the 2006 edition's vent exception, and have gained variances using the approach I explained in the first post. But that's not what I'm asking now, I'd solved that problem, now we have a new playbook and I can't find the one marked "extended egress". Thom, the tunnel would work if a) the building was up and that was only quick way to get occupancy b) they figure how to do that under a floor capable of supporting rack storage. I can ses it now, a mini-London Underground below the warehouse, Tube stops. Mind the gap! glc -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Brad Sent: Tuesday, June 22, 2010 1:26 PM To: [email protected]; [email protected] Subject: RE: IBC egress distances >250' I should re-phrase-----how were we successful in maintaining increased dist? -----Original Message----- From: Brad [mailto:[email protected]] Sent: Tuesday, June 22, 2010 12:00 PM To: [email protected] Subject: RE: IBC egress distances >250' No- Section 104 allows alternate methods and materials- such as smoke modeling with timed egress analysis-- horizontal exits at 250' max would work. (btw- the previous code allowed deleting auto vents, but the travel dist. Could not be increased too) -----Original Message----- From: George Church [mailto:[email protected]] Sent: Tuesday, June 22, 2010 11:51 AM To: [email protected] Subject: IBC egress distances >250' Back under the 2006 IBC, we could go thru the motions of providing roof vents, get the egress increase under 1016.2 Roof Vent Increases, and then install ESFR and loose the vents, and we'd been successful in maintaining the increased egress distances (to 400'). However, while we're pretty fond of the IRC part of our new code, the 2009 IBC has totally removed the 1016.2 increase for a S1 occupancy. Now that the occasional big-box distribution center comes out for bid after the economic mess, is there another means to erect an S1 building wider than 500'? glc _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
