Sunday, July 7, 2013

A comparison of thermal conducivity of various building materials

Thermal conductivity of some common materials and products are indicated in the table below.

  • 1 W/(m.K) = 1 W/(m.oC) = 0.85984 kcal/(hr.m.oC) = 0.5779 Btu/(ft.hr.oF)
  • Conduction will take place if there exist a temperature gradient in a solid (or stationary fluid) medium.
  • Energy is transferred from more energetic to less energetic molecules when neighboring molecules collide. Conductive heat flow occurs in the direction of the decreasing temperature since higher temperatures are associated with higher molecular energy. 
  • Fourier's Law express conductive heat transfer as q = k A dT / s (1)
  •  A = heat transfer area (m2, ft2)
  •  k = thermal conductivity of the material (W/m.K or W/m oC, Btu/(hr oF ft2/ft))
  •  dT = temperature difference across the material (K or oC, oF)
  •  s = material thickness (m, ft)

Krypton                      .0088
Argon                         .016
Acrylic                        .02
Oxygen                       .024
Cotton                        .029
Polystyrene                 .03
Polyurethane foam       .03
Styrafoam                   .033
Wool blankets            .04
Fiberglass                   .04
Fiber insulation board .048
Plywood                    .13
Pine                           .147
Oak                           .17
Gypsum                     .17
Vinyl                         .25
Water                       .58
Concrete                  1.0 - 1.8
Glass (single pane)    1.05
Slate                         2.01
Marble                     2.08 - 2.94
Ice                           2.18
Rock                        2 – 7
Stainless steel           16
Lead                        35
Carbon steel             54
Tin                           67
Platinum                   70
Nickel                      91
Brass                       109
Zinc                         116
Aluminum                 250
Gold                         310
Copper                    400

Taken from http://www.engineeringtoolbox.com/conductive-heat-transfer-d_428.html

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