Thermal Lag

Thermal lag is the time delay for heat to be conducted through a material. A material with high heat capacity and low conductivity will have a high thermal lag.

Thermal lag times are influenced by: * Temperature differentials between each face. * Exposure to air movement and air speed. * Texture and coatings of surfaces. * Thickness of material. * Conductivity of material. Thermal lag can be used to ease out internal/external diurnal temperature variations. In temperate climates, external wall materials with a minimum time lag of 10 to 12 hours can be very effective to reduce internal/external temperature variations during day and night. If it is required to keep the heat for a longer time, a layer of insulation can be added to slow the rate of heat transfer and moderate temperature differentials.

== Units and Measures ==

Thermal lag can be measured as the amount of time taken for a material to absorb and then release the heat energy.

Units for measuring thermal lag is generally Hours

== Example Units ==

The following table indicates the relative thermal lag of some common building materials. Insulated Brick Veneer - 5.0 Hours Concrete (250) - 6.9 Hours Concrete (250) - 6.9 Hours Double Brick (250) - 7.0 Hours AAC (200) - 7.0 Hours Adobe (250) - 9.2 Hours Rammed Earth (250) - 10.3 Hours Compressed Earth Blocks (250) - 10.5 Hours Sandy Loam (1000) - 30 days

== References ==

http://www.yourhome.gov.au/technical/fs45.html#mass http://www.ecospecifier.org/knowledge_base/technical_guides/thermal_mass_building_comfort_energy_efficiency