basics:building_physics_-_basics:thermal_bridges:tbcalculation:ground_contact:ground_contact
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basics:building_physics_-_basics:thermal_bridges:tbcalculation:ground_contact:ground_contact [2016/08/16 13:17] – [Thermal capacity of the ground] mschueren | basics:building_physics_-_basics:thermal_bridges:tbcalculation:ground_contact:ground_contact [2022/01/18 15:29] (current) – [Thermal capacity of the ground] yaling.hsiao@passiv.de | ||
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==== Thermal capacity of the ground==== | ==== Thermal capacity of the ground==== | ||
- | In building physics, the thermal capacity of a material is given by the specific thermal capacity c. This defines the amount of energy that is required in order to increase one kilogramme of a material by one Kelvin. This means that materials can absorb a certain amount of heat and release this again depending on the changes in the applied temperature over time. The building envelope exhibits thermal inertia depending on its mass. An exterior wall which absorbs heat throughout the day releases it again during cooler temperatures. The greater the< mass of the exterior wall is, the longer the charging and discharging process will be. For most building components this time interval is relatively small. If longer time intervals are considered, such as those for the monthly method, this effect is averaged out because the number of charging phases are the same as the discharging phases. Steady-state consideration of the heat flows is therefore quite adequate. This is no longer the case for building components in contact with the ground. The following illustration shows the temperature gradient in the ground as a function of the external temperature: | + | In building physics, the thermal capacity of a material is given by the specific thermal capacity c. This defines the amount of energy that is required in order to increase one kilogramme of a material by one Kelvin. This means that materials can absorb a certain amount of heat and release this again depending on the changes in the applied temperature over time. The building envelope exhibits thermal inertia depending on its mass. An exterior wall which absorbs heat throughout the day releases it again during cooler temperatures. The greater the mass of the exterior wall is, the longer the charging and discharging process will be. For most building components this time interval is relatively small. If longer time intervals are considered, such as those for the monthly method, this effect is averaged out because the number of charging phases are the same as the discharging phases. Steady-state consideration of the heat flows is therefore quite adequate. This is no longer the case for building components in contact with the ground. The following illustration shows the temperature gradient in the ground as a function of the external temperature: |
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- | The amplitudes of the sinsoidal | + | The amplitudes of the sinusoidal |
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**Further literature on the topic of skirt insulation: | **Further literature on the topic of skirt insulation: | ||
- | **[AkkP 48]** Using Passive House technology for retrofitting non-residential buildings/ Heat losses towards the ground ; Protocol Volume No. 48 of the Research Group for Cost-effective Passive Houses, 1st Edition, Passive House Institute, Darmstadt 2012 ({{:picopen: | + | **[AkkP 48]** Using Passive House technology for retrofitting non-residential buildings/ Heat losses towards the ground ; Protocol Volume No. 48 of the Research Group for Cost-effective Passive Houses, 1st Edition, Passive House Institute, Darmstadt 2012 [[https:// |
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===== Transient or steady-state Ψ-values? ===== | ===== Transient or steady-state Ψ-values? ===== | ||
- | For calculating thermal bridges in the area in contact with the ground, a steady-state approximation suffices in many cases and dynamic simulation can be dispensed with. Although dynamic simulations provide more accurate results, they also incur additional effort. Moreover, on account of the usually only imprecisely known thermal characteristics of the ground, the expected accuracy of a one-dimensional or two-dimensional transient numerical calculation is not so high that this extra effort can also be justified (except in the case of large or research projects). Frequently, the Ψ-values calculated in a steady-state manner are therefore also used as harmonic Ψ-values (see the Ground worksheet in the [[planning: | + | For calculating thermal bridges in the area in contact with the ground, a steady-state approximation suffices in many cases and dynamic simulation can be dispensed with. Although dynamic simulations provide more accurate results, they also incur additional effort. Moreover, on account of the usually only imprecisely known thermal characteristics of the ground, the expected accuracy of a one-dimensional or two-dimensional transient numerical calculation is not so high that this extra effort can also be justified (except in the case of large or research projects). Frequently, the Ψ-values calculated in a steady-state manner are therefore also used as harmonic Ψ-values (see the Ground worksheet in the [[planning: |
==== Further literature ==== | ==== Further literature ==== | ||
- | **[AkkP 27]** **Heat losses through the ground**; Protocol Volume No. 27 of the Research Group for Cost-effective Passive Houses, \\ 1st Edition, Passive House Institute, Darmstadt 2004 ({{:picopen: | + | **[AkkP 27]** **Heat losses through the ground**; Protocol Volume No. 27 of the Research Group for Cost-effective Passive Houses, \\ 1st Edition, Passive House Institute, Darmstadt 2004 |
===== See also ===== | ===== See also ===== |
basics/building_physics_-_basics/thermal_bridges/tbcalculation/ground_contact/ground_contact.1471346228.txt.gz · Last modified: 2016/08/16 13:17 by mschueren