Recommend Antifreeze for Assisted Living Attic?

10/4/2024

I have a client who owns multiple assisted living facilities. It's residential construction with attic insulation on the roof trusses' bottom chord, and louvered gable ends with ridge vents.

They have existing wet pipe sprinkler systems in the attic and have experienced busted sprinkler lines in the past. They want to heat the attics to prevent this with electric heaters.

I have done the heat loss calculations and have determined the heating load would be more than their current electrical service can support. The only options I see available are heat trace, anti-freeze, or conversion to a dry system. Anti-freeze with UL-listed anti-freeze was my first thought, but it looks like a backflow preventer would have to be added.

Does anyone have experience with this and/or have recommendations on how to address this?

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10 Comments

Pete H

10/4/2024 07:09:21 am

You pretty much nailed the options I'd see.

Either the dry system addition (would not personally recommend full conversion, would recommend disconnecting your main feeding the attic from your wet system and reconnecting it to a new dry valve and keeping everything below the attic wet for maintenance) or the antifreeze should probably require installation of a backflow assembly if one is not present. In which case I'd just advise reviewing the existing system and calculations to make sure the additional loss from a backflow prevention device is something the system can absorb. Especially if the area would call for an rpz instead of a double check. Similarly remember that a dry system, especially an attic dry system is going to be significantly more hydraulically demanding than the existing wet (possibly residential) system.

If the system can take the hit and the compressor is not somewhere where residents would complain, I'd separate the attic and add the dry valve. If that's not an option, I'd go antifreeze.

If the system cannot take the hit of the backflow prevention device at all, let alone for a dry system calculation, now heat tracing seems a lot more fiscally practical.

Daryl Lovejoy

10/4/2024 10:35:57 am

Don't forget pipe will all have to be pitched on a dry system in accordance with NFPA 13 !

Dan Wilder

10/4/2024 07:53:29 am

Most AHJ's/Water purveyors require a Reduced Pressure Backflow when the water downstream is being introduced with any chemicals, FYI. This can push a tight calc into not being accepted with the additional PSI loss.

You did not include if the attic system is independent, or it feeds rooms below, material used (steel vs CPVC/Copper) and what NFPA you're expected to follow. Also, roof construction will need to be reviewed for area increases and decreases (Sloped 30%▲, QR used up to 40%▼, Dry system 30%▲), if it's flat there may be a combustible concealed option.

For a dry system, NFPA 13 has trip times that are much more lenient, pending the system size, for light hazard vs residential. Change in C-Factor of piping (standard air - If using N2 or other approved inhibitor you can keep the C-Factor of 120 in later editions), pipe sloping, aux drains, additional electrical for compressors, ability to drain drops, and return bends are all in the mix.

For Anti-Freeze the size of the system will also be a factor as 500 gallons is about the largest anti-freeze system you can have. The RPBF will also be a need along with filling and testing means.

Any chance to split the upper and lower systems?

The last couple times we have been approach for options; it was a several page proposal with pricing options showing pros & cons for each path.

Brett

10/4/2024 07:57:38 am

I concur with Pete's comment but I'd also like to add that the existing piping material could cause a wrinkle. If the piping in the attic is plastic and the intent is to reuse as much pipe as possible, then a dry system is out of the question and for heat trace you would need to make sure the cable is listed to protect plastic piping.

If this were new construction, typically the cheapest option is antifreeze with plastic piping. If you convert to dry or antifreeze know that you have to calc the system either way. Dry systems require a larger area and antifreeze systems (assuming this isn't a very small attic space) are required to be calculated with the Darcy-Weisbach equation. Darcy-Weisbach calcs in a cold area are typically more demanding than than a Hazen-Williams calc.

Also, anecdotally I've heard that heat trace simply isn't reliable in the long term and is a maintenance headache.

Jimmy

10/4/2024 08:50:09 am

Sounds like you need to upgrade the system completely.
Depending on the area involved height, roof pitch and square footage. There are newer heads designed for just for attic protection that can cover way more area than standard heads.

This means fewer heads and less piping,
It needs to be a dry system and maybe in zones using smaller dry valves for "zone protection" to keep the demand down.

Even if you need to replace all the piping the end cost result in coming years is the ultimate goal,... right?

Jonathan Griffin

10/4/2024 09:33:37 am

I would suspect that your Wet Pipe system serves the rooms/areas below the ceiling, not the Attic. The order of consideration here is:

1. Tent & insulate the piping within the Attic (Plastic or Steel)
2. Convert Plastic pipe system to Anti-freeze system
3. Convert Steel to Anti-freeze system
4. Convert to a steel Dry-pipe system; plan on making all Pendent drops Dry-barrel pendents

Good luck!

Glenn Berger

10/4/2024 09:44:42 am

You got the options stated correctly. I would recommend the heat trace system as long as power is deemed reliable.

Dave

10/4/2024 10:52:19 am

And for branch lines, using heat-tracing specifically listed for use on branch lines. (NFPA '19, #16.4.1.4.1)

Jack G

10/4/2024 07:17:44 pm

Dave and Glenn have the best options.
I would heat trace the pipe— wrap it with insulation to avoid excessive energy to keep pipe at 40 degrees F. Add blanket insulation where possible.
No rpz required. No recalculations, if the piping remains the same configuration, no breaking it up into 2 or more systems,,( heat traced wet system) .
I would also add unit heaters with digital probe into ( wet heat traced pipe in the attic) that would operate if the water in the system reaches 40 degrees, which it shouldn’t . This would make it fail safe if the power was more than reliable.
I did this on a military installations ( specified) for the same scenario as above.

Todd E Wyatt

10/7/2024 08:41:44 am

You may consider checking the attic exemptions for providing an automatic sprinkler system (ASPS) in a Group I-1 Assisted Living Facility per the scoping Code (e.g. IBC-2021) :

IBC-2021
Chapter 9 Fire Protection and Life Safety Systems
Section 903 Automatic Sprinkler Systems
903.3.1.2.3 Attics
Attic protection shall be provided as follows:
1. Attics that are used or intended for living purposes or storage shall be protected by an automatic sprinkler system.
2. Where fuel-fired equipment is installed in an unsprinklered attic, not fewer than one quick-response intermediate temperature sprinkler shall be installed above the equipment.
3. Where located in a building of Type III, Type IV or Type V construction designed in accordance with Section 510.2 or 510.4, attics not required by Item 1 to have sprinklers shall comply with ONE of the following IF the roof assembly is located more than 55 feet (16 764 mm) above the lowest level of fire department vehicle access needed to meet the provisions in Section 503.
1. Provide automatic sprinkler system protection.
2. Construct the attic using noncombustible materials.
3. Construct the attic using fire-retardant-treated wood complying with Section 2303.2.
4. FILL THE ATTIC WITH NONCOMBUSTIBLE INSULATION.
The height of the roof assembly shall be determined by measuring the distance from the lowest required fire vehicle access road surface adjacent to the building to the eave of the highest pitched roof, the intersection of the highest roof to the exterior wall, or the top of the highest parapet, whichever yields the greatest distance. For the purpose of this measurement, required fire vehicle access roads shall include only those roads that are necessary for compliance with Section 503 of the International Fire Code:
4. Group R-4, Condition 2 occupancy attics not required by Item 1 to have sprinklers shall comply with one of the following:
1. Provide automatic sprinkler system protection.
2. Provide a heat detection system throughout the attic that is arranged to activate the building fire alarm system.
3. Construct the attic using noncombustible materials.
4. Construct the attic using fire-retardant-treated wood complying with Section 2303.2.
5. Fill the attic with noncombustible insulation.

903.3.1.2.3-3(4) … FILL THE ATTIC WITH NONCOMBUSTIBLE INSULATION … is a solution I have seen approved by AHJs.

Recommend Antifreeze for Assisted Living Attic?

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