Thermal conductivity myths and facts: Copper, plastic, air, and water


Thermal conductivity myths and facts: Copper, plastic, air, and waterCopper is the only practical and cost effective ground coil(loop field) material today, hands down. Nothing else even comes close. In fact the next closest material(plastic) used in geothermal loop fields is over 400 times less conductive than copper. If the goal is to conduct energy from mother earth, copper is without a doubt unrivaled in performance.

With renewable energy in mind is the point not to get away from oil based materials(plastic)? Why then would one even consider using an oil based, non conductive plastic(polyethylene HD) for a geothermal ground loop?

An Air source heat pump is trying to conduct into an atmospheric product(air). How can heat be conducted from air which is .024 conductive and be efficient at the same time..it cannot, the numbers do not add up. Look for yourself.

Everyone is using the same refrigerant! Freon is required for heating/cooling in every heat pump compressor(ground source, air source and water source) by government regulation on R410a heat pumps. Since freon(R-410a) is being used in every type of heat pump (regulated by EPA) which is in copper refrigerant line, why not extend these lines into the ground and take advantage of the most cost effective and efficient way to heat/cool your home, office or building. Save the work load by only circulating freon through copper. Water source is much more expensive to operate, to install, and to maintain while producing only a fraction of the work that a freon copper system would.

Ice is more conductive than plastic, air, and water!

Do not be fooled by the plastic people, the air heads and the water nuts. Do your own research and see what you find..

Silver is the only metal which out performs coppers thermal conductivity. Because silver is very expensive for such a task, copper is the only cost effective and the most efficient solution to be used as a ground source coil!

  • 1 W/(mK) = 1 W/(moC) = 0.85984 kcal/(hr moC) = 0.5779 Btu/(ft hr oF)
Thermal Conductivityk – (W/mK)
Material/Substance Temperature (oC)
25 125 225
Acetone 0.16
Acrylic 0.2
Air (gas) 0.024
Alcohol 0.17
Aluminum 250 255 250
Aluminum Oxide 30
Ammonia (gas) 0.022
Antimony 18.5
Argon (gas) 0.016
Asbestos-cement board 0.744
Asbestos-cement sheets 0.166
Asbestos-cement 2.07
Asbestos, loosely packed 0.15
Asbestos mill board 0.14
Asphalt 0.75
Balsa 0.048
Bitumen 0.17
Benzene 0.16
Beryllium 218
Brass 109
Brick dense 1.31
Brick work 0.69
Cadmium 92
Carbon 1.7
Carbon dioxide (gas) 0.0146
Cement, portland 0.29
Cement, mortar 1.73
Chalk 0.09
Chrome Nickel Steel (18% Cr, 8 % Ni) 16.3
Clay, dry to moist 0.15 – 1.8
Clay, saturated 0.6 – 2.5
Cobalt 69
Concrete, light 0.42
Concrete, stone 1.7
Constantan 22
Copper 401 400 398
Corian (ceramic filled) 1.06
Corkboard 0.043
Cork, regranulated 0.044
Cork 0.07
Cotton 0.03
Carbon Steel 54 51 47
Cotton Wool insulation 0.029
Diatomaceous earth (Sil-o-cel) 0.06
Earth, dry 1.5
Ether 0.14
Epoxy 0.35
Felt insulation 0.04
Fiberglass 0.04
Fiber insulating board 0.048
Fiber hardboard 0.2
Fireclay brick 500oC 1.4
Foam glass 0.045
Freon 12 (gas) 0.073
Gasoline 0.15
Glass 1.05
Glass, Pearls, dry 0.18
Glass, Pearls, saturated 0.76
Glass, window 0.96
Glass, wool Insulation 0.04
Glycerol 0.28
Gold 310 312 310
Granite 1.7 – 4.0
Gypsum or plaster board 0.17
Hairfelt 0.05
Hardboard high density 0.15
Hardwoods (oak, maple..) 0.16
Helium (gas) 0.142
Hydrogen (gas) 0.168
Ice (0oC, 32oF) 2.18
Insulation materials 0.035 – 0.16
Iridium 147
Iron 80 68 60
Iron, wrought 59
Iron, cast 55
Kapok insulation 0.034
Kerosene 0.15
Lead Pb 35
Leather, dry 0.14
Limestone 1.26 – 1.33
Magnesia insulation (85%) 0.07
Magnesite 4.15
Magnesium 156
Marble 2.08 – 2.94
Mercury 8
Methane (gas) 0.030
Methanol 0.21
Mica 0.71
Mineral insulation materials, wool blankets .. 0.04
Molybdenum 138
Monel 26
Nickel 91
Nitrogen 0.024
Nylon 6 0.25
Oil, machine lubricating SAE 50 0.15
Olive oil 0.17
Oxygen 0.024
Paper 0.05
Paraffin Wax 0.25
Perlite, atmospheric pressure 0.031
Perlite, vacuum 0.00137
Plaster, gypsum 0.48
Plaster, metal lath 0.47
Plaster, wood lath 0.28
Plastics, foamed (insulation materials) 0.03
Plastics, solid
Platinum 70 71 72
Plywood 0.13
Polyethylene HD 0.42 – 0.51
Polypropylene 0.1 – 0.22
Polystyrene expanded 0.03
Polyurethane foam 0.02
Porcelain 1.5
PTFE 0.25
PVC 0.19
Pyrex glass 1.005
Quartz mineral 3
Rock, solid 2 – 7
Rock, porous volcanic (Tuff) 0.5 – 2.5
Rock Wool insulation 0.045
Sand, dry 0.15 – 0.25
Sand, moist 0.25 – 2
Sand, saturated 2 – 4
Sandstone 1.7
Sawdust 0.08
Silica aerogel 0.02
Silicone oil 0.1
Silver 429
Snow (temp < 0oC) 0.05 – 0.25
Sodium 84
Softwoods (fir, pine ..) 0.12
Soil, with organic matter 0.15 – 2
Soil, saturated 0.6 – 4
Steel, Carbon 1% 43
Stainless Steel 16 17 19
Straw insulation 0.09
Styrofoam 0.033
Tin Sn 67
Zinc Zn 116
Urethane foam 0.021
Vermiculite 0.058
Vinyl ester 0.25
Water 0.58
Water, vapor (steam) 0.016
Wood across the grain, white pine 0.12
Wood across the grain, balsa 0.055
Wood across the grain, yellow pine 0.147
Wood, oak 0.17
Wool, felt 0.07
  • 1 W/(m K) = 1 W/(moC) = 0.85984 kcal/(h m oC) = 0.5779 Btu/(ft h oF)

Chart source