User Tools

Site Tools


basics:internal_heat_capacity

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
basics:internal_heat_capacity [2014/09/18 18:19]
127.0.0.1 external edit
basics:internal_heat_capacity [2019/02/21 10:13] (current)
cblagojevic
Line 14: Line 14:
 In order to obtain the results given below, many simulations based on the entire year were carried out for various residential buildings with respectively controlled varying characteristics. In order to obtain the results given below, many simulations based on the entire year were carried out for various residential buildings with respectively controlled varying characteristics.
   * In the first part, the internal heat capacity was varied,   * In the first part, the internal heat capacity was varied,
 +
   * in the second part, the externally applied thermal protection was varied.   * in the second part, the externally applied thermal protection was varied.
  
Line 29: Line 30:
  
   * **Why is the influence so small?​** ​ A Passive House is only heated in the middle of winter. ​ During this period, the external temperature is almost always considerably less than the indoor temperature and the solar gains are usually very small. ​ The internal heat capacity cannot contribute much towards the efficient utilisation of solar energy - this is already being used to almost 100 %.   * **Why is the influence so small?​** ​ A Passive House is only heated in the middle of winter. ​ During this period, the external temperature is almost always considerably less than the indoor temperature and the solar gains are usually very small. ​ The internal heat capacity cannot contribute much towards the efficient utilisation of solar energy - this is already being used to almost 100 %.
 +
   * **Why is the influence so high all the same?** In fact, for this building there is a certain seasonal storage effect. ​ In the transition from autumn into winter, the house has temperatures of 22 to 23 ° C, this delays the start of the heating operation. ​ The more heat capacity there is inside, the more pronounced this effect is.   * **Why is the influence so high all the same?** In fact, for this building there is a certain seasonal storage effect. ​ In the transition from autumn into winter, the house has temperatures of 22 to 23 ° C, this delays the start of the heating operation. ​ The more heat capacity there is inside, the more pronounced this effect is.
  
Line 40: Line 42:
  
   * The frequency of overheating events (left axis, red curve) as a percentage of the hours in a year in which the operative temperature exceeds 25 °C. This is a measure of the “discomfort” or more correctly, the length of the periods in which comfort does not prevail.   * The frequency of overheating events (left axis, red curve) as a percentage of the hours in a year in which the operative temperature exceeds 25 °C. This is a measure of the “discomfort” or more correctly, the length of the periods in which comfort does not prevail.
 +
   * The annual heating demand (right axis, green curve). This hardly varies and is nothing new; it confirms the result already obtained above.\\   * The annual heating demand (right axis, green curve). This hardly varies and is nothing new; it confirms the result already obtained above.\\
 \\ \\
Line 60: Line 63:
  
   * **Why is the influence still so great?** It is a widely held view that insulation that is “even thicker” than the good insulation already present initially serves no purpose, (because the insulation does not have any effect on other heat losses which predominate). This view is incorrect, as proven by the analysis shown. The reason for this is that in the energy balance of a Passive House, it is actually the transmission heat losses that are still dominant or recurrently predominant – ventilation heat losses are very small due to the heat recovery; and the losses through windows are over compensated by their solar gains.   * **Why is the influence still so great?** It is a widely held view that insulation that is “even thicker” than the good insulation already present initially serves no purpose, (because the insulation does not have any effect on other heat losses which predominate). This view is incorrect, as proven by the analysis shown. The reason for this is that in the energy balance of a Passive House, it is actually the transmission heat losses that are still dominant or recurrently predominant – ventilation heat losses are very small due to the heat recovery; and the losses through windows are over compensated by their solar gains.
 +
   * **Why don’t we recommend even better insulation in spite of this?** It is not worthwhile to increase the level of insulation above that which is necessary for achieving the Passive House Standard. Although thicker insulation continues to save additional heating energy (even down to zero, if insulated thickly enough), saving from 2007 kWh/a to 791 kWh/a only "​gives"​ savings of 100 €/a. In contrast, the insulation previously invested in for achieving the Passive House Standard does not only save heating costs, but also reduces the technical expenditure for building services.\\   * **Why don’t we recommend even better insulation in spite of this?** It is not worthwhile to increase the level of insulation above that which is necessary for achieving the Passive House Standard. Although thicker insulation continues to save additional heating energy (even down to zero, if insulated thickly enough), saving from 2007 kWh/a to 791 kWh/a only "​gives"​ savings of 100 €/a. In contrast, the insulation previously invested in for achieving the Passive House Standard does not only save heating costs, but also reduces the technical expenditure for building services.\\
 \\ \\
Line 67: Line 71:
  
   * The frequency of overheating events (left axis, red curve) as a percentage of the hours in a year on which the operative temperature exceeds 25 °C.  This is a measure of the “discomfort” or more correctly, the length of the periods in which comfort does not prevail.   * The frequency of overheating events (left axis, red curve) as a percentage of the hours in a year on which the operative temperature exceeds 25 °C.  This is a measure of the “discomfort” or more correctly, the length of the periods in which comfort does not prevail.
 +
   * The annual heating demand (right axis, green curve). ​ This varies almost in line with the U-value, and is nothing new, it confirms the result already obtained in the last section.\\   * The annual heating demand (right axis, green curve). ​ This varies almost in line with the U-value, and is nothing new, it confirms the result already obtained in the last section.\\
 \\ \\
Line 81: Line 86:
 However, the internal heat capacity is not the most important influencing parameter for summer comfort. However, the internal heat capacity is not the most important influencing parameter for summer comfort.
   * Possibilities for increased ventilation,​   * Possibilities for increased ventilation,​
 +
   * shading from high solar gains   * shading from high solar gains
 +
   * and restriction of internal heat loads   * and restriction of internal heat loads
 are the more important parameters. ​ For example, even a very large internal heat capacity cannot compensate for a lack of shading for large glazing areas in summer. are the more important parameters. ​ For example, even a very large internal heat capacity cannot compensate for a lack of shading for large glazing areas in summer.
basics/internal_heat_capacity.txt · Last modified: 2019/02/21 10:13 by cblagojevic