basics:building_physics_-_basics:what_defines_thermal_bridge_free_design
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+ | ====== What defines thermal bridge free design? ====== | ||
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+ | A building envelope is considered to be free of thermal bridges if the transmission losses under consideration of all [[basics: | ||
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+ | [{{ : | ||
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+ | The overall temperature-specific heat loss is characterised by the transmission conductance HT. It comprises the **regular losses of all areas A with their regular heat transfer coefficient U** and the thermal bridge contributions ($\varPsi \cdot l$) together with $\chi $. As the punctiform contributions are generally insignificant, | ||
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+ | <WRAP centeralign > | ||
+ | $$ | ||
+ | \Large{H_{T} = \sum_{i}A_{i}U_{i}+\sum_{k}l_{k}\varPsi_{k}+\sum_{j}\chi_{j}} | ||
+ | $$ | ||
+ | </ | ||
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+ | | ||
+ | <WRAP centeralign | ||
+ | $$ | ||
+ | \Large{\sum\varPsi \cdot l + \sum\chi | ||
+ | $$\\ | ||
+ | \\ | ||
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+ | ** [defined as thermal bridge free]** | ||
+ | </ | ||
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+ | It will then be admissible to disregard the thermal bridge effects in the PHPP, thus simplifying the calculation quite considerably. This equates to the statement $ \Delta U_{WB} \leq 0$, where $\Delta U_{WB}$ is the thermal bridge correction addend (as used in the German energy saving regulations for example)\\ | ||
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+ | ===== Simplified criterion ===== | ||
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+ | Verification using this definition of thermal bridge free design would imply that all details would have to be calculated in a multi-dimensional way. Therefore, simplified criteria for “thermal bridge free design” should be devised. It was found that for ordinary building geometries, the “thermal bridge free” requirement was almost always adequately met for all linear disturbances only if | ||
+ | <WRAP centeralign | ||
+ | $$ | ||
+ | \Large{\varPsi \leq 0.01 \quad W/ | ||
+ | $$ | ||
+ | \\ | ||
+ | **[TbCrit]** | ||
+ | </ | ||
+ | These may still result in certain positive contributions, | ||
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+ | Besides, the remaining contributions are compensated to a certain extent by other connections where there are negative linear thermal transmittances. The // | ||
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+ | With the simplified criterion, planning and construction become significantly easier: for a particular category of connection details, it only has to be verified once in advance that the // | ||
+ | On the [[http:// | ||
+ | <WRAP center 100%> | ||
+ | [{{: | ||
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+ | [{{: | ||
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+ | [{{: | ||
+ | </ | ||
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+ | <WRAP left 100%> | ||
+ | This example shows that " | ||
+ | </ | ||
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+ | ===== How to achieve a thermal bridge free design ===== | ||
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+ | The following principle demonstrates this clearly: the insulation layers should be planned in such a way that one should be able to outline the minimum insulation thickness (20 cm for the Passive House) of the whole external envelope within the insulation layers using a pencil, without a break. The following figure illustrates this principle using a sectional drawing. | ||
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+ | The purpose of “thermal bridge free design” is to substantially improve the details. | ||
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+ | There have been positive experiences with numerous construction systems in which the principle of “thermal bridge free design” has already been applied. | ||
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+ | * Solid constructions with solid bricks, | ||
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+ | * Solid constructions with low-conductivity blocks (e.g. porous concrete blocks), | ||
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+ | * Timber constructions (solid wood beams as well as lightweight beams), | ||
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+ | * Constructions using formwork elements, | ||
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+ | * Constructions using prefabricated lightweight concrete elements. | ||
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+ | Details for solid constructions, | ||
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+ | The Passive House Institute provides advice for manufacturers regarding the development of thermal bridge free constructions.\\ | ||
+ | \\ | ||
+ | In the Protocol Volume 16 “Thermal bridge free design” that has often been mentioned here, numerous other details for building envelopes with thermal bridge free connections have been presented besides that shown here. | ||
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+ | If a new building is not built in accordance with the principle of thermal bridge free design, there may be considerable heat losses as a result of the remaining thermal bridges. In various examples of building projects, there was an increase in the annual heating demand of up to 14 kWh/(m²a). For a construction project, careful planning with regard to thermal bridges can therefore be decisive for achieving the Passive House standard in the first place.\\ | ||
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+ | <WRAP centeralign 90% > | ||
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+ | </ | ||
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+ | ===== References ===== | ||
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+ | **[AkkP 16]** Wärmebrückenfreies Konstruieren ; Protokollband Nr. 16 des Arbeitskreises kostengünstige Passivhäuser, | ||
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+ | **[Kaufmann 2002]** Das Passivhaus – Energie-Effizientes-Bauen, | ||
+ | Reihe 1: Entwurf und Konstruktion Teil 3: Wohn- und Verwaltungsbauten Folge 10: Passivhaus – Energie-Effizientes-Bauen, | ||
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+ | **[Kaufmann 2009]** [[http:// | ||
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+ | ===== See also ===== | ||
+ | [[basics: | ||
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+ | [[basics: | ||
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+ | [[basics: | ||
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basics/building_physics_-_basics/what_defines_thermal_bridge_free_design.txt · Last modified: 2022/02/15 19:13 by admin