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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====
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 {{ :picopen:erdreichtemp.jpg?nolink&600 |}}
-The amplitudes of the sinsoidal temperature gradients clearly decline with increasing soil depth. Simultaneously, a phase shift takes place so that external air temperature peaks reach the deeper regions much later on. The amplitude peaks of 21.5 °C (on 21.07) in the test reference years shown here only has an impact 91 days later at a depth of 5 m. Here the peak temperature was still 13.1 °C on 20.10. With increasing depth, an almost constant temperature at the level of the mean annual temperature is reached. The high phase shifts no longer allow a purely steady-state consideration of the transmission heat losses for the monthly method since the charging and discharging processes may extend over several months. Heat storage in the ground and the resultant damping action and phase shifting of the ground temperature under the floor slab is therefore of significance when calculating heat losses through the ground.
+The amplitudes of the sinusoidal temperature gradients clearly decline with increasing soil depth. Simultaneously, a phase shift takes place so that external air temperature peaks reach the deeper regions much later on. The amplitude peaks of 21.5 °C (on 21.07) in the test reference years shown here only has an impact 91 days later at a depth of 5 m. Here the peak temperature was still 13.1 °C on 20.10. With increasing depth, an almost constant temperature at the level of the mean annual temperature is reached. The high phase shifts no longer allow a purely steady-state consideration of the transmission heat losses for the monthly method since the charging and discharging processes may extend over several months. Heat storage in the ground and the resultant damping action and phase shifting of the ground temperature under the floor slab is therefore of significance when calculating heat losses through the ground.
 {{ :picopen:superpositionsprinzip_erdreich.jpg?nolink&600 |}}
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 **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:faxb.pdf|Link zur Publikationsliste des PHI}})
+**[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://shop.passivehouse.com/en/products/48-einsatz-von-passivhaustechnologien-bei-der-modernisierung-von-nichtwohngebauden-66/|Link to PHI Publication]]
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 ===== 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:calculating_energy_efficiency:phpp_-_the_passive_house_planning_package |PHPP]]). However, for thermal bridges of areas in contact with the ground which are far away from the ground surface, this assumption is will usually be quite pessimistic. Whether it is worthwhile to perform a time-dependent calculation is easily determined by setting the harmonic Ψ-value in the [[planning:calculating_energy_efficiency:phpp_-_the_passive_house_planning_package |PHPP]] to the same value as the steady-state Ψ-value one time, and equal to zero another time and then observing the influence on the final result. A steady-state calculation under the mentioned boundary conditions can also give pessimistic results with respect to the surface temperatures.
+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:calculating_energy_efficiency:phpp_-_the_passive_house_planning_package |PHPP]]). However, for thermal bridges of areas in contact with the ground which are far away from the ground surface, this assumption will usually be quite pessimistic. Whether it is worthwhile to perform a time-dependent calculation is easily determined by setting the harmonic Ψ-value in the [[planning:calculating_energy_efficiency:phpp_-_the_passive_house_planning_package |PHPP]] to the same value as the steady-state Ψ-value one time, and equal to zero another time and then observing the influence on the final result. A steady-state calculation under the mentioned boundary conditions can also give pessimistic results with respect to the surface temperatures.
 ==== 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:faxb.pdf|Link to list of PHI publications}})
+**[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  [[https://shop.passivehouse.com/en/products/27-warmeverluste-durch-das-erdreich-45/|Link to PHI publications]]
 ===== See also =====