Freeze protection: Multifamily

Educational Overview: NFPA Guidelines and Freeze Protection in Multifamily Settings

This document provides an overview of NFPA guidelines and recommendations for freeze protection in multifamily buildings, with a focus on designing and installing reliable fire sprinkler systems. Below, we outline key installation methods to clarify best practices.

Unconditioned exterior spaces requiring sprinkler protection, such as exterior corridors and balconies, are particularly vulnerable to freezing temperatures and wind exposure. These conditions present unique design and installation challenges. For wet systems, two common solutions include the use of dry barrel sprinklers or dry flexible sprinklers.

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Dry Barrel Sprinklers:

Freeze breaks commonly occur on north-facing balconies where wet pipes are installed in exterior walls or within close proximity to uninsulated areas. Special attention must be given to the appropriate sizing of the dry barrel sprinkler at these locations.

NFPA 13 Chart 8.4.9.1(a) provides guidance on sizing such sprinklers, but it can be confusing.

Key Points from NFPA Chart 8.4.9.1(a):

Discharge End Temperature: Determined by the coldest expected temperature for the building's location:

San Antonio: 20°F

Austin: 10°F

Dallas: 0°F

Below is a diagram showing measurements for dry barrel Installation “if” done inside the exterior wall:

Typical wall cavity dimensions:

R11 or R13 insulation is 3.5” (Insulation takes up all 3.5” of a 2x4 wall as shown in Diagram 4

Sprinkler head tee: 1.72” (excluding threads)

Clearance behind tee: 0.75” (Shown below in green in Diagram 3)

Total distance to install 0” dry barrel is 5.97”

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2x4 wall has 3.5” -negative 2 ½”

2x6 wall has 5.5”-negative ½”

2x8 wall has 7.5” available - 1 ½” exposed barrel

Conclusion:

Lack of space for proper insulation often leads to annual freeze breaks when a wet system is installed inside an exterior wall. Additionally undersized or improperly sealed dry barrel sprinklers are not a reliable method of protection from freezing temperatures.

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Flexible Dry Sprinklers:

DFW Area Challenges:

Minimum 12” of interior truss space in DFW area We require wet pipes to maintain 20” from exterior wall.

Southern Regions:

In warmer areas like Houston and San Antonio, these problems are rarely observed as long as 4” of hose is used inside the truss.

Fully blown insulation in midfloor settles after a few years, wet sprinkler pipe freeze breaks will show up later. NFPA requires 12” of hose in the truss in DFW area and 4” in southern applications. However, based on field observations we recommend wet pipes not be installed within 20” of exterior walls.

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Below are improperly installed flexible dry sprinklers (Wet portion of system too close to exterior walls):