Fiberglass Insulation for Chilled Water Systems

08-11-2023

Hydronic cooling systems (also known as chilled water systems) are closed-loop, tempered water systems that convey heat away from a conditioned space or process, using water as the heat transfer medium. These systems use standard compressed refrigerant in tubes or coils, or evaporative cooling, to cool the water. The cooled water is pumped through the system piping to an end-point heat exchanger/cooling coil. The heat exchanging coil surface is cooled by the chilled water.

In an air-to-air heat exchange, a fan moves air across the coil, removing heat from the air, providing cooled air to the building’s space or to the process being chilled. In a direct exchange chilled water cooling process, heat is removed from the process by the direct contact of the heat exchanger with the product being cooled, whether a liquid or solid material.

Insulating these systems is important to satisfactory operation. Fiberglass insulation has a long and successful history of being the most selected insulation material for chilled water systems. The areas of a chilled water cooling system that typically need to be insulated are the chiller barrels and heads, pumps, piping, and piping specialties. Insulating these components delivers:

Energy savings equaling reduced operating costs
Reduced machine usage and wear equaling reduced operating costs
Increased system effectiveness equaling happier occupants
Condensation control equaling reduced moisture-induced problems

The Science of Condensation Formation in Mechanical Systems

Ever present water vapor molecules in the atmosphere are attracted to any colder surfaces, where they cohere to form liquid water. The warmer water vapor molecules lose energy to the colder surface. These water molecules gather on the cold surface in enough quantity to form a liquid that sits on the surface of any construction that will not allow water vapor to pass.

The Basics of Condensation Control

Two key parameters in an installation must be met to control condensation formation on mechanical systems, including piping, duct and equipment.

First, the total amount of insulation used must have enough resistance to the flow of heat energy to hold the surface temperature of the insulation system higher than the atmospheric dew point, no matter what the atmosphere temperature, relative humidity, and dewpoint (the temperature at which condensation forms).

Second, the insulation system must include a material that is classified as a vapor retarder, either a separate system solely meant as the vapor retarder, or an insulation material that has vapor retarding properties. A vapor retarder is a material that resists all or a significant amount of water molecule penetration, in the form of vapor. If the insulation system does not offer both a sufficiently low thermal conductance and a low water vapor permeance, condensation can still form.

Control Condensation Options for Ducts & Pipes

Different combinations of two key insulation system components, the insulation and the finishing system, can be used to achieve the goal of impeding condensation formation on the surface of insulated mechanical systems.

Fiberglass insulation has differing rates of heat energy flow, depending on the density and thickness of the product. A denser, thinner fiberglass insulation may deliver as much insulating value as a thicker less dense fiberglass insulation. The finish systems used for mechanical insulation have different levels of emissivity, changing the rate of energy flow of the system. Highly-reflective finishes require thicker fiberglass for the system to work than non-reflective finishes. This is an important consideration when selecting system components, in conjunction with site conditions that may restrict selections.

Drawbacks of Ineffective Chilled Water Insulation Installation

Ineffective chilled water insulation system installation can result in negative impacts such as:

Yields damaged assets, including damage to architectural finishes and the development of moisture in building assemblies, requiring corrective costs
Contributes to excessive energy consumption increasing operational expense
Causes excessive machine wear increasing repair expense
Maylead to mold and mildew growth in facilities requiring remediation cost
Duplicate costs to prematurely remove and replace insulation installations

Keys to an Effective Installation

There are a few key details to watch in an insulation installation for chilled water systems: Correct thickness for the worst expected temperatures, relative humidity and air movement combinations. Many times, the wrong thickness is chosen for a multitude of reasons. Longitudinal seam/joints, butt joints/seams, fitting insulation, hanger insulation, and vapor sealing are the most common features of an insulation system that need special focus. Proper completion of each of these details is as important as the others. Details for completing installations that will deliver satisfactory performance can be found in the North American Insulation Manufacturers’ Association GUIDE TO INSULATING CHILLED WATER PIPING SYSTEMS WITH MINERAL FIBER PIPE INSULATION or the North American Commercial and Industrial Insulation Standards Manual.

The Importance of the Vapor Retarder and Correct Installation

Water vapor finds the smallest entry points through compromised vapor retarding materials or systems. The vapor retarder system on an insulation installation is key to making a successful installation. As previously mentioned, the correct insulation thickness combined with a well-executed vapor retarder makes the use of fiberglass insulation on chilled water highly preferred. Higher-performance, premium ASJ vapor retarder jacketing– now being supplied on Knauf fiberglass pipe insulation products– provides a water vapor permeance of 0.01 perm. Knauf refers to this as All Service Jacketing (ASJ+), a flexible laminate composite of multiple layers typically consisting of foil, paper, film and reinforcements. ASJ+ or ASJ butt strip tape completes the jacketing system to seal the joints between sections of pipe insulation.

Appropriate vapor dams or vapor seals must be installed, including all terminations. Fitting insulation must have vapor retarder treatment applied as part of or before applying protective finishes. Seal the throat seam and circumferential edges of PVC fitting covers with PVC vapor seal or adhesive/solvent to all joints. Any damage or voids in the vapor retarder materials must be repaired.

Principles and Practices Apply to Industrial Product and Process Cooling

When thinking of chilled water installations, most think of commercial building HVAC comfort cooling systems. Many industrial processes use chilled water as well to cool product or maintain a process temperature. These same principles for a winning fiberglass insulation installation apply to the industrial chilled water system, as well as the HVAC chilled water system.

In Summary

Fiberglass insulation forms the basis of a highly-effective and economical system for insulating all kinds of chilled water cooling systems. Following sound installation practice, especially related to the vapor retarder features, is key to success, correctly specified and installed fiberglass systems having been used for many years for chilled water systems. Knauf Earthwool 1000°F Pipe Insulation, ASJ+/SSL+ with ECOSE and Knauf Pipe & Tank Insulation with ECOSE provide reliable performance and a high level of sustainability for chilled water cooling when done completely and thoroughly.

Additional Industry Resources:

Midwest Insulation Contractors Association

North American Commercial and Industrial Insulation Standards Manual

North American Insulation Manufacturers Association

GUIDE TO INSULATING CHILLED WATER PIPING SYSTEMS WITH MINERAL FIBER PIPE INSULATION

American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE)

Handbook of Fundamentals

ASTM International

Standard Guide for Industrial Thermal Insulation