basics:summer
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| basics:summer [2014/09/18 18:19] – external edit 127.0.0.1 | basics:summer [2020/08/05 16:14] – [Base case of a Passive House with tilted windows when required] wfeist | ||
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| ===== Summer climate in the Passive House – an important issue ===== | ===== Summer climate in the Passive House – an important issue ===== | ||
| - | The question of low-energy buildings overheating in summer "due to their high level of insulation" | + | The question of low-energy buildings overheating in summer "due to their high level of insulation" |
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| **Thermal building simulations** are used to determine the summer characteristics of Passive Houses built according to **different construction methods** and having a **different orientation** – taking account of the type and level of shading and ventilation. The first systematic investigation was carried out in the " | **Thermal building simulations** are used to determine the summer characteristics of Passive Houses built according to **different construction methods** and having a **different orientation** – taking account of the type and level of shading and ventilation. The first systematic investigation was carried out in the " | ||
| - | In this paper some parts of the study are summarised and substantiated based on existing measurement results. | + | In this paper some parts of the study are summarised and substantiated based on existing measurement results. |
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| The analyses are based on plans of the inhabited Passive House in Darmstadt-Kranichstein. | The analyses are based on plans of the inhabited Passive House in Darmstadt-Kranichstein. | ||
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| |//**__Fig. 2__: cross-section of the Darmstadt Kranichstein Passive House including the individual zones.**// | |//**__Fig. 2__: cross-section of the Darmstadt Kranichstein Passive House including the individual zones.**// | ||
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| The model parameters have been documented in detail in the study [[basics: | The model parameters have been documented in detail in the study [[basics: | ||
| - | |{{ :picopen:phpp_daten_004.gif }}| | + | |{{:picprivate:pb15_02_table_2a.png?/ |
| - | |// | + | |// |
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| ==== Evaluation based on operative temperatures ==== | ==== Evaluation based on operative temperatures ==== | ||
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| //__**Fig. 4**__// shows the daily mean values of the indoor temperatures during the year for the ** reference case of the " Darmstadt-Kranichstein Passive House – without any shading or window ventilation" | //__**Fig. 4**__// shows the daily mean values of the indoor temperatures during the year for the ** reference case of the " Darmstadt-Kranichstein Passive House – without any shading or window ventilation" | ||
| * the heat recovery | * the heat recovery | ||
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| * in the summer (more exactly: from 15th April to 30th September) the ventilation system is operated only as an exhaust system with air changes of 0.475 h< | * in the summer (more exactly: from 15th April to 30th September) the ventilation system is operated only as an exhaust system with air changes of 0.475 h< | ||
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| > If temperatures in the house exceed 21 °C __and__ the external temperature is lower than the indoor temperature, | > If temperatures in the house exceed 21 °C __and__ the external temperature is lower than the indoor temperature, | ||
| - | The tilted position of the window leads to considerably higher average air changes. //__**Fig. 7**__// shows that due to this, the temperatures in the house sink perceptibly to constantly comfortable levels during the summer.\\ | + | The tilted position of the window leads to considerably higher average air changes. //__**Fig. 7**__// shows that due to this, the temperatures in the house sink perceptibly to constantly comfortable levels during the summer. This is one of several reasons, why we always recommend to have at least one window in each room openable and also have a tool to keep it fixed at a specific level (e.g., a " |
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| * about 30% with triple glazing and low-e coating | * about 30% with triple glazing and low-e coating | ||
| * about 25% with " | * about 25% with " | ||
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| good values can still be achieved without temporary sunshades in the Passive House. | good values can still be achieved without temporary sunshades in the Passive House. | ||
| * In contrast, with a glazing proportion of | * In contrast, with a glazing proportion of | ||
| * over 42% with triple glazing and low-e coating | * over 42% with triple glazing and low-e coating | ||
| * over 35% with " | * over 35% with " | ||
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| there are such high solar gains in the summer in the base case under consideration that additional measures have to be taken. | there are such high solar gains in the summer in the base case under consideration that additional measures have to be taken. | ||
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| * The annual heating demand (between 10 and 12 kWh/ | * The annual heating demand (between 10 and 12 kWh/ | ||
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| * Then however, overheating events as well as the heating demand increase noticeably. | * Then however, overheating events as well as the heating demand increase noticeably. | ||
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| * This hardly changes with further deviation from the southern orientation, | * This hardly changes with further deviation from the southern orientation, | ||
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| * In a Passive House the annual heating demand does not change with overhangs of up to 1.25m depth (it is different for low-energy houses). | * In a Passive House the annual heating demand does not change with overhangs of up to 1.25m depth (it is different for low-energy houses). | ||
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| * In contrast, the frequency of overheating events in summer decreases noticeably with horizontal overhangs | * In contrast, the frequency of overheating events in summer decreases noticeably with horizontal overhangs | ||
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| In //**__Fig. 16__**// shows how, based on the DYNBIL simulation, the annual heating demand is reduced if the useable heat sources increase: | In //**__Fig. 16__**// shows how, based on the DYNBIL simulation, the annual heating demand is reduced if the useable heat sources increase: | ||
| * At first the heating demand decreases almost in line with the additional usable free heat, with a utilisation factor of about 80 %. | * At first the heating demand decreases almost in line with the additional usable free heat, with a utilisation factor of about 80 %. | ||
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| * However, the curve quickly levels out with higher gains. | * However, the curve quickly levels out with higher gains. | ||
| => This would be equivalent to an additional internal energy conversion of 8470 kWh/a; this is neither economically nor ecologically sound.\\ | => This would be equivalent to an additional internal energy conversion of 8470 kWh/a; this is neither economically nor ecologically sound.\\ | ||
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| Each additional internal heat source also has an extremely unfavourable effect on the summer comfort, (see //**__Fig. 16__**//). | Each additional internal heat source also has an extremely unfavourable effect on the summer comfort, (see //**__Fig. 16__**//). | ||
| - | * At first, the frequency of overheating events also increases almost in line with the internal heat sources; doubling of the sources equates to about 2.3 times more hours of overheating. | + | * At first, the frequency of overheating events also increases almost in line with the internal heat sources; doubling of the sources equates to about 2.3 times more hours of overheating. |
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| * The frequency of overheating events increases disproportionately with internal heat sources of more than 5 W/ | * The frequency of overheating events increases disproportionately with internal heat sources of more than 5 W/ | ||
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| The daily mean temperatures during the course of the year as shown in //**__Fig. 17__**// with the same floor plans, ventilation technology and window sizes and glazing qualities as the Passive House built in Darmstadt, but using only lightweight timber building components. | The daily mean temperatures during the course of the year as shown in //**__Fig. 17__**// with the same floor plans, ventilation technology and window sizes and glazing qualities as the Passive House built in Darmstadt, but using only lightweight timber building components. | ||
| * The annual heating demand is 12.8 kWh/(m²yr) | * The annual heating demand is 12.8 kWh/(m²yr) | ||
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| * The frequency of overheating events is 17.7%. | * The frequency of overheating events is 17.7%. | ||
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| Both are the result of the lower storage mass of the building, due to which the time constant is reduced. | Both are the result of the lower storage mass of the building, due to which the time constant is reduced. | ||
| * no window ventilation and | * no window ventilation and | ||
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| * only minimal summer shading | * only minimal summer shading | ||
| takes place.\\ | takes place.\\ | ||
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| At first, this result is apparently in contrast with the excellent indoor climate in summer in the Passive House in Kranichstein. | At first, this result is apparently in contrast with the excellent indoor climate in summer in the Passive House in Kranichstein. | ||
| * The contradiction is resolved if the excessive temperature frequencies are considered using a different and practically-oriented **summer ventilation strategy** (//**__Fig. 21__**//): if the windows are tilted in summer when required, the excessive temperature frequencies decrease quite considerably for this solid construction. | * The contradiction is resolved if the excessive temperature frequencies are considered using a different and practically-oriented **summer ventilation strategy** (//**__Fig. 21__**//): if the windows are tilted in summer when required, the excessive temperature frequencies decrease quite considerably for this solid construction. | ||
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| * Not only that: also the thermal protection level of the roof and wall has the reverse effect. | * Not only that: also the thermal protection level of the roof and wall has the reverse effect. | ||
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| * **With regard to the insulation level: | * **With regard to the insulation level: | ||
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| * **With regard to ventilation: | * **With regard to ventilation: | ||
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| * **With regard to glazing:** apart from the ventilation, | * **With regard to glazing:** apart from the ventilation, | ||
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| * **With regard to shading:** In contrast with an ordinary low-energy house, for south-oriented windows, horizontal fixed shading (balcony overhangs) with a depth that is not too large(1.2 to 1.6 m for room-height windows) is very effective for sun protection in summer, without increasing the annual heating demand too much. Temporary shading equipment on the outside and also shading in the outer space between the glass panes of the triple-glazing is very effective. | * **With regard to shading:** In contrast with an ordinary low-energy house, for south-oriented windows, horizontal fixed shading (balcony overhangs) with a depth that is not too large(1.2 to 1.6 m for room-height windows) is very effective for sun protection in summer, without increasing the annual heating demand too much. Temporary shading equipment on the outside and also shading in the outer space between the glass panes of the triple-glazing is very effective. | ||
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| * **With regard to the building mass:** In Central Europe, it is easier to keep buildings with a larger effective internal mass at cool temperatures than purely lightweight buildings. | * **With regard to the building mass:** In Central Europe, it is easier to keep buildings with a larger effective internal mass at cool temperatures than purely lightweight buildings. | ||
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| * **With regard to the temperature amplitude ratio TAR:** With the insulation quality of the Passive House the stationary attenuation is already so large that the dynamic attenuation and thus the TAR no longer play a role. \\ | * **With regard to the temperature amplitude ratio TAR:** With the insulation quality of the Passive House the stationary attenuation is already so large that the dynamic attenuation and thus the TAR no longer play a role. \\ | ||
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| * Type and amount of additional summer ventilation, | * Type and amount of additional summer ventilation, | ||
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| * Type and cap factor of the temporary summer shading equipment for each window, | * Type and cap factor of the temporary summer shading equipment for each window, | ||
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| * Applicable maximum temperature limit for summertime. | * Applicable maximum temperature limit for summertime. | ||
basics/summer.txt · Last modified: 2021/10/13 10:44 by corinna.geiger@passiv.de