Understanding Objectives: The First Step in Designing Insulation Systems
Most engineers, architects, and end users are familiar with the use of insulation to reduce heating and cooling loads and control noise in building envelopes or residential structures. They may not be as familiar with mechanical insulations systems used for pipes, ducts, tanks, and equipment. The installed cost of these insulation systems is usually a small part of the total cost of a project, but yield significant results and savings. However, mechanical insulation is often overlooked, undervalued, or improperly specified and maintained in commercial and industrial construction projects.
Designing insulation systems can be complicated. Insulation systems are intended to satisfy a number of design objectives. In some projects, multiple design objectives must be satisfied simultaneously. For example, the objective may be to minimize energy use and to avoid surface condensation on a chilled-water line. The chilled-water line may pass through various spaces within the project. Since the various spaces may have differing temperature and humidity conditions, it is likely that different insulation materials, thicknesses, and coverings may be required for a single line. Since projects may involve many lines operating at various service temperatures in various environmental conditions, it is obvious that a systematic approach is required for all but the simplest projects.
In engineering schools, students are taught that the design process is divided into a number of phases along these lines:
- Identify the need or define the problem;
- Gather pertinent information;
- Identify possible solutions;
- Analyze and select a solution; and
- Communicate the solution.
For a mechanical insulation design project, these phases could be expanded and restated as follows:
- Identify the design objectives (Why insulate?);
- Identify what is to be insulated (What?);
- Identify the location and appropriate ambient design conditions (Where?);
- Identify the materials and systems available (How?);
- Analyze and determine the acceptable solutions (How to and how much?); and
- Write the specification.
For mechanical insulation, the design process boils down to developing answers to 6 basic questions:
- How to?
- How much?
The critical first step in the design process is answering the question, why insulate? Insulation has many purposes and may be used to satisfy one or more of the following design objectives.
- Energy conservation and thermal system regulation: minimizing unwanted heat loss/gain from systems. There are 3 primary reasons to conserve energy:
- Minimizing the use of scarce natural resources;
- Maximizing return on investment and minimizing the life cycle cost; and
- Minimizing the GHG emissions associated with energy usage.
- Personnel protection: controlling surface temperatures to avoid contact burns (hot or cold).
- Fire safety: protecting critical building elements and slowing the spread of fire in buildings.
- Condensation control: minimizing condensation and the potential for mold growth by keeping surface temperature above the dew point of surrounding air.
- Process control: minimizing temperature change in processes where close control is needed.
- Increasing equipment life: extending the life of your equipment which saves money over time.
- Freeze protection: minimizing energy required for heat tracing systems and/or extending the time to freezing in the event of system failure.
- Noise control: reducing/controlling noise in mechanical systems.
In addition to these design objectives, there are a number of design considerations that may require attention when designing a mechanical insulation system:
- Abuse resistance;
- Corrosion under insulation (CUI);
- Indoor air quality;
- Regulatory considerations;
- Service and location; and
- Service life.
A thorough understanding of the design objectives and recognition of the design considerations are the first steps in the successful design of a mechanical insulation system.