Protect Dome Using Deluge Sprinkler System?

8/8/2022

We have a church project with a 22'-0 wide dome in the ceiling (all steel w/sheetrock finish), the dome itself is 13'-0 tall.

The consulting engineer is saying the dome doesn't need sprinklers in it - they just did one in a different state and they put sprinklers around the base of the dome to protect it, but nothing in it or at the top.

The dome is on the second level ceiling/roof - so if you stand on the first floor you can look all the way up to the dome.

They originally did not want us to sprinkler it. We ended up putting 4 pipes symmetrically with a sprinkler at the end of each one, keeping spacing correct, etc. They didn't hide it behind the sheetrock as originally intended and they don't want to build soffits around the pipe, so they are back to wanting me to remove them. I explained it is my interpretation that this is a ceiling pocket by definition and there is nothing in NFPA 13 allowing me to exempt sprinkler coverage from the floor space below this dome.

The fire marshal and the engineer conversed and they suggested putting an open head deluge system in this area with 4 evenly spaced open sidewalls in the soffit at the bottom of the dome spraying toward the center with a single or double electric deluge system.

I wouldn't want to do it with a single device personally, I would suggest a heat and smoke, both needing activation for the solenoid to open. I think the sidewalls would get the spray over the hazard (covering the floor area), but I'm concerned they won't activate properly.

What is your take on this?

Is detection using heat or smoke at the high point of the dome for activation with open-head deluge sidewall sprinklers code compliant?

New to me, thanks in advance!

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14 Comments

chad

8/8/2022 08:10:27 am

Deluge seems a bit aggressive and potentially problematic. Of course you are right about it being a ceiling pocket.

Do they need to sprinkle it for insurance purposes to call it "fully sprinkled"?

I would be in favor of omitting the sprinklers in there as the AHJ, if this is a historical building, provided that you add beam smokes accounting for stratification throughout below and a spot head in it. Add some side walls around the opening for a feel good measure? I know we are talking performance based esque stuff here but it just my gut reaction to it.

Putting two devices near the top that will be never really tested and serviced and potentially cause false alarms connected to a deluge does not seem ideal

Peter

8/8/2022 08:58:07 am

Aggressive is an understatement. This may make everyone feel warm and fuzzy for the installation, but this is going to be an ITM nightmare. NFPA 25 requires deluge systems to be flowed annually. While I won't speak specifically about this church, I have been in enough of them to know that discharging water inside one would be challenging at best. In reality, the deluge system will never be properly tested. Testing heat and/or smoke detectors located at +/- 43' inside the dome will also be an ongoing ITM nightmare.

Glenn Berger

8/8/2022 08:14:42 am

1) Sprinklers would be required in this space to consider the facility fully sprinklered.

2) I do not recommend a deluge system for this application.

3) Need to check the construction details on whether piping can be installed out of sight.

This is a why coordination is required during design to ensure a code compliant design is the outcome. Since this has become a retro-fix case, recommend beam detectors be placed below the dome level of the second floor, if possible to get the alarms going and fire department response.

Dan Wilder

8/8/2022 08:35:50 am

Have you reviewed NFPA 914 for Historic Buildings?

I've done similar deluge systems but only to half the total height of the protected space (ceiling was at 110') open head deluge (sidewalls) tripped by UV/IR was around the 60' mark (Las Vegas).

If there is an engineering report detailing out the alternate and the AHJ had bought off, feel free to write in your recommendations but at that point you are an installing contractor and not the EOR, just document everything and follow the installation criteria. Yes the pocket would need protection to comply with "fully sprinklered".

https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=914

Jesse

8/8/2022 09:35:15 am

It does need to be sprinklered, and I agree that an open head deluge system is a bad idea. The ITM requirements alone make we want to forget this idea entirely.

8/8/2022 10:15:41 am

- This is not a historic buiding, actually new construction.
- It does need sprinkler protection to be fully sprinklered
We coordinated way ahead, we ran four wet sprinklers with our piping up tight to the four steel beams from base to high center, the contractor did not buildout the ceiling to conceal the pipe as they were supposed too. Now they want us to remove it and not protect it or find another way.
We could find no other way to protect it reasonably or per code and the fire marshal suggested the open head deluge. I doubt they will do it due to price, but I couldn't think of any other way to provide coverage. My thought was to build the ceiling out and leave the four sprinklers there...
An engineer they brought in wanted us to provide pendent sprinklers around the base as they have done in another facility in another state - I explained this was a ceiling pocket, not a vertical opening and being 22-0 wide presents another issue for coverage, not to mention heat collection at the sprinklers...

8/8/2022 10:21:51 am

Its new construction?!?!--- don't back down, you are in the right. make them change it if they don't want soffits or to see the pipe, you warmed them. Sheesh.

Albert

8/16/2022 09:36:39 pm

Make the fire marshall change? That’s a good way to make a new friend.

Tim De Witt

8/10/2022 01:24:20 am

There is a paper published that indicates sprinklers will have significant delay in response or even not operate at all with such extremely high ceilings or soffits. Available methods of calculation will proof that. I will consider engineered smoke control design with aspirated early warning detection which will satisfy life safety. Non-combustible building materials with fire proofing on steel subframe to prevent structural failure can be also be implemented. Further full CFD modelling should be done. Sprinklers may not be the design solution in this case.

Greg

8/15/2022 07:54:46 am

Place of worship present unique challenges. Start with the code required "why" for sprinklers and the "fire science" why. From the code perspective there is a compulsion for a fully sprinklered occupancy. Is there any sprinkler (sidewall) or other automatic actuating head that will work for the space and achieves the aesthetic requirements? If not, move to rational from the fire science side of the problem. When would the dome sprinklers be activated? Is it most likely that fire control will occur from a heat plume somewhere along the ceiling, but not under the dome? Is it probable that (based on what is intended underneath the dome) that the dome sprinklers could even be effective in controlling a floor level fire. What if the dome sprinklers failed to activate or were delayed based on an imperfect heat plume? What would be the result, if the fire starts directly under the dome, and no sprinklers operated in the dome, could the remaining sprinklers control the fire? How large could a fire be, as domes are typically a feature designed by the architect for people to walk under. Or is this intended to house a display, is there an electrical plug for such displays?

In concluding, if the dome is ancillary to the ceiling, which it appears it is and there is not a sprinkler type that will match the space or the aesthetic requirement, that the questions above be brought out in conversation and with any additional fire features or benefits such as smoke detection (not from the standpoint of an assembly occupancy) but the early warning and emergency response.

8/15/2022 07:57:35 am

Science? (gasp) How scary and forward thinking of you.

Greg- you nailed it.

8/15/2022 12:33:53 pm

Thank you Chad,

My last paragraph seems to be missing a cut paste. opps. If not sprinklered, conclusions should match a fire science perspective and the rational shared with owner, AHJ .

8/16/2022 09:31:44 pm

Deluge?!? Are you sure the fire marshall isn’t having a bit of fun with you? I’d put a concealed ec pendant right on the center.

8/16/2022 09:36:16 pm

Absolutely sure, It was the fire marshals idea trying to satisfy the engineer.
I priced it, they decided to leave the four sprinklers and rework the dome ceiling so the pipe will be hidden (as it was originally coordinated to be).
Thank you all for your insight.

Protect Dome Using Deluge Sprinkler System?

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