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4 values, each with its units, its uncertainty, and where it came from.

Material Properties 4

Density of Dry Air at 20 °C measured

ρair=1.204 kg/m3\rho_{\mathrm{air}} = 1.204\ \text{kg/m}^{3}

kg/m³Density of dry air at 20 °C and 101.325 kPa, 1.204 kg/m³ — the standard-air value behind the 1.08 sensible-heat factor.

Thermal Conductivity of Fibreglass Batt Insulation measured

kfg=0.04 W/(m⋅K)k_{\mathrm{fg}} = 0.04\ \text{W/(m}{\cdot}\text{K)}

W/(m·K)Thermal conductivity of standard fibreglass batt at 24 °C, about 0.040 W/(m·K) — roughly R-3.6 per inch in US units.

Thermal Conductivity of Rigid Foam Board measured

kfoam=0.024 W/(m⋅K)k_{\mathrm{foam}} = 0.024\ \text{W/(m}{\cdot}\text{K)}

W/(m·K)Aged thermal conductivity of rigid polyisocyanurate or XPS board, roughly 0.024–0.029 W/(m·K), about R-5 to R-6 per inch.

Specific Heat of 30 % Propylene Glycol measured

cPG30=3850 J/(kg⋅K)c_{\mathrm{PG30}} = 3850\ \text{J/(kg}{\cdot}\text{K)}

J/(kg·K)Specific heat of a 30 % by volume propylene glycol/water mix near 40 °C, about 3850 J/(kg·K) — some 8 % below plain water.