Subscribe

2.2 Design Considerations & Objectives

1. Economic Performance Analysis

Construction costs and capital cost reduction are common drivers of mechanical insulation practices. However, it is important to note that this approach does not consider the operations and maintenance costs. Economic performance should include both capital, operating and maintenance costs over the life of the equipment.

Overall economic performance will be determined primarily by:

  • Capital costs of insulation materials and labour
  • Energy consumption costs, which are related to thermal performance of the insulation
  • System maintenance costs, which are related to the mechanical insulation materials and installation
  • Costs associated with space requirements of mechanical insulation.

 

The greatest energy benefits from mechanical insulation are found in systems that have the highest rates of heat transfer; this occurs where temperature difference is the greatest. The following table shows typical levels of heat loss based on system type, insulation thickness, and surface temperature, assuming a constant ambient temperature.

 

 

 

Table 2.2.1 – Example Heat Transfer Rates[1]

System

Surface Temp (ºC)

Insulation Thickness (mm)

Heat Transfer Rate

Energy Losses

(kWh/yr)

Example Lost Energy Cost[2] ($/yr)

Duct System—heating

49

0

249 W/m2

2,181

$180

25

31 W/m2

272

$22

50

17 W/m2

149

$12

Duct System—cooling

10

0

102 W/m2

894

$74

25

15 W/m2

131

$11

50

8 W/m2

70

$6

Piping System—heating (40 mm NPS)

82.2

0

119 W/m

1,042

$86

25

18 W/m

158

$13

50

11 W/m

96

$8

Piping System—chilled water (40 mm NPS)

4.4

0

25 W/m

219

$18

25

5 W/m

44

$4

50

3 W/m

26

$2

Piping System—condenser water (100 mm NPS)

29.4

0

21 W/m

184

$15

25

4 W/m

35

$3

50

2 W/m

18

$1


Notes:

All cases above (where insulation thickness is greater than 0) assume jacketed mineral fibre insulation.



[1] Note heat transfer units shown are different for ducts and pipes (per unit area vs. unit length respectively); similarly, energy losses and energy costs are referenced to the same units – i.e., per m2 or per m.

[2] Energy costs are estimated assuming electrical power at approx. $0.08/kWh, the same across all cases for simplicity. The values shown are for comparative purposes, and will change over time as energy prices change.

2. Key Design Objectives

In addition to minimum Code and regulatory requirements (e.g., fire, smoke & safety), insulation in commercial and institutional buildings such as schools, shopping centers, warehouses, hospitals, hotels and other public buildings is designed primarily to reduce energy consumption and/or prevent condensation. Appearance is another objective that is typically most important in mechanical rooms. The types of mechanical systems commonly insulated in commercial buildings vary only slightly from project to project, and involve a relatively narrow temperature range. The following table provides guidance on the primary mechanical insulation design objectives that apply to a range of system types*.

 

Table ?2.2.2 - Key Design Objectives by System Type and Temperature Range

System

Temperature Range

Typical Design Objectives

Personnel Protection*

Fire*

Vapour Retarder

Thermal

Noise

Appearance

Plumbing 13°C to 80°C

X

X

X

X

Ducts and housings 15°C to 43°C

X

X

X

X

Steam and condensate 100°C to 185°C

X

X

X

Outdoor air intake seasonal outdoor temp range

X

X

X

X

Roof drains 1°C to 15°C

X

Hot water heating 80°C to 100°C

X

X

X

Chilled water 5°C to 13°C

X

X

X

Engine exhaust approximately 675°C

X

X

X

X

Kitchen exhaust ducts approximately 1100°C

X

X

X

X

Refrigerant suction -40°C to 10°C

X

X

X

X

 

*All fire, smoke and safety objectives for any system types must conform to the BC Building Code and any other applicable regulations and standards; the above table does not supersede requirements of the BC Building Code or other regulations.

3. Green Building Rating Frameworks

There are opportunities to support achievement of green building rating system points and meet minimum requirements through increased mechanical insulation thickness and material selection. This includes:

  1. Improving thermal performance can help meet energy performance objectives within green building rating systems. For example, “Optimize Energy Performance” credits within LEED® (Leadership in Energy and Environmental Design) Canada – NC 1.0, or NC/CS 2009. Note that there are different pathways to validate energy performance within LEED; for example, if a whole building energy modelling path is chosen, the modelling method would need to recognize the energy gains provided by mechanical insulation, in order to benefit the LEED performance.
  2. Materials chosen for mechanical insulation may need to meet specific requirements. For example, the Living Building Challenge [17] includes a “Red List” of prohibited materials and chemicals [18], which will restrict the acceptable mechanical insulation materials. In this case, suppliers and manufacturers product specifications will need to be consulted to confirm compliance.

 


[17] The Living Building Challenge is currently a program under the International Living Future Institute, and has been endorsed by the Canada and US Green Building Councils.

[18] The framework allows for some temporary exceptions.

4. Applicable Systems and Components

The following table provides a list of system elements that should be considered for mechanical insulation in a commercial or institutional project, organized by system type (across columns), to help practitioners in identifying all elements that may require mechanical insulation.

Table 2.2.3 - Mechanical Insulation Commercial and Institutional System Components Check List

Plumbing

Ducts and housings

Steam and condensate

Hot water heating

Chilled water

Engine exhaust

Kitchen exhaust ducts

Refrigerant suction

Cold Water High Pressure Supply Steam (High, Medium and/or Low Pressure) Hot Water Heating Supply/Return Chilled Water Supply/Return Generators Kitchen Exhaust Refrigeration Piping, Drains and Equipment
Hot Water Low Pressure Supply Condensate (from trap to receiver tank) Pumps (chilled/hot) Refrigeration Suction Breechings/Flues
Hot Water Circulating Return Air Pumped Condensate (from receiver to boiler or feed water heater) Expansion Tanks Cooling Tower
Soil, Waste, Vent and/or Drain Lines Mixed Air Boiler Feed Water Air Eliminators Condensate Drain Lines
Cold Water Storage Tanks Plenums and Housings Cold Water Make-up Boilers Chillers
Horizontal Suspended Roof Drain Piping and/or Roof Sumps VAV and Terminal Units, and Mixing Boxes Flash Tanks Converters/Heat Exchangers
Drops to Diffusers and/or Flexible Ducts Condensate Receivers, Deaerator and Feed Water Tanks
Exhaust (from dampers to outside louvers)

NOTE: If any of the above items are factory insulated, it should be so noted in the project insulation specification.

5. Analysis Tools

Software analytical tools can help designers to determine the appropriate amount of insulation in order to optimize thermal performance and cost.

.1            3E Plus® Insulation Thickness Computer Program

The 3E Plus® Insulation Thickness Computer Program is an industrial energy management tool developed by the North American Insulation Manufacturers Association (NAIMA) to simplify the task of determining how much insulation is necessary to use less energy, reduce plant emissions and improve system process efficiency. The 3E Plus program can:

  • Calculate the thermal performance of both insulated and uninsulated piping, ducts and equipment
  • Translate BTU losses into actual dollars
  • Calculate greenhouse gas emission and reductions

 

.2            Whole Building Design Guide

The online Mechanical Insulation Design Guide, part of the WBDG, provides several tools related to economic and financial performance.

These two tools provide a simple to use calculation of energy savings and payback for different design options:

  • Energy Calculator for Equipment (Vertical Flat Surfaces)
  • Energy Calculator for Horizontal Piping

This tool provides project cash flows, return on investment, and NPV, from energy savings and other inputs:

  • Mechanical Insulation Financial Calculator

The WBDG also provides a “time to freezing” calculator, which estimates the time for a long, water-filled pipe or tube (with no flow) to reach the freezing temperature.