Table of Contents
Life Cycle energy balances, Embodied energy and the Passive House Standard
Cumulated primary energy demand (CED)
A full comparison must take place over the entire life cycle period. In the work mentioned, the cumulated primary energy demand (CED) was compared over an 80-year usage period for various building standards (Fig.1).
- For poorly insulated buildings, the energy required for their construction accounts for only about 5% in comparison with the energy required in the form of natural gas and for domestic electricity.
- The importance of electricity and natural gas consumption during the period of use in the low-energy house is about the same with 45% for each. Improvement is possible mainly through the efficient use of electricity.
- The heating consumption of the Passive House is so small due to the excellent thermal protection that there is no need for a separate heating system. The energy required for the construction of a new Passive House can thus be even less than that of ordinary new buildings.
- The cumulated primary energy demand for energy-autarchic houses is higher than that for Passive Houses, due to the large amount of primary energy required for the production and renewal of complex technical systems [Röhm 1993] .
Vergleich: KEA über 80 a = Comparison CED over 80 years
KEA Strom = cumulated energy demand (CED) for electricity;
KEA Gas = CED for gas
E-HEA = energy demand for production and renewal
HEA = energy demand for production
70-80% Einsparung = 70-80% energy savings
Kumulierter Primärenergie-Aufwand KEA
= Culuated energy demand CED
WSchVO 84 = 1984 German thermal protection regulations
Niedrig-Energie-Haus = low energy house
Passivhaus = Passive House
Energieautarkes Haus = energy-autarchic house
|Fig. 1: Comparison of the cumulated primary energy demand(based on: The first Passive House in Darmstadt-Kranichstein), [Feist 1997] ;
Material data based on [Köhler 1995] and [SIA 0123] .
The basic data for the consumption of electricity and gas in the Passive House are measured values (see Primary energy – quantifying sustainability)
Fig.2 shows the temporal course of the cumulated primary energy demand (CED) for 3 variants over an 80-year usage period.
- The “starting points“ of the German thermal protection regulations (MEE 1171 kWh/m²), low-energy house (1220 kWh/m²) and the Passive House (1391 kWh/m²) are very close together.
- After two years the cumulated energy demand of the reference house is already greater than that of the low-energy house and that of the Passive House.
- The primary energy levels finally develop away from each other proportional to the different consumptions during the period of use; the expenditure for the renewal of solar collectors and ventilation systems in the Passive House can also be seen (peaks every 20 years or every 30 years respectively).
- It can be seen clearly that the ecological benefit in the transition from the low-energy house to the Passive House is much greater than it is in the transition from the reference house based on the regulations to the low-energy house.
|Fig. 2: Temporal development of the cumulated primary energy
demand over a 80-year usage period in the reference house
based on the 1984 German thermal protection regulations,
low-energy house and Passive House [Feist 1997] .
Embodied energy... Does super-insulation make sense?
Fig. 3.shows how the manufacturing energy demand changes when only the insulation thickness is varied (the rest of the data is the same as for the Passive House).
- It is interesting that the MED initially decreases for insulation thicknesses of up to 5 cm, although the manufacture of insulation requires energy. The reason for this is that due to the reduced maximum heat load, the heating surfaces (steel) are now smaller.
- For this house, the Passive House Standard can be achieved with an insulation thickness of about 23 cm. The heat distribution system and the remaining heating surfaces can be dispensed with, resulting in a peak in the curve.
Please note: in this diagram, the zero-point has been suppressed. The given value of 44 kWh/m² is just 3.5 % of the total manufacturing primary energy.
However, taking into account the MED alone is misleading. Fig.4 shows the cumulated primary energy demand over a period of 80 years (CED 80) depending on the thickness of the insulation material in the Passive House. It is clear here that the primary energy demand dominates across the entire
range during the period of use and that this decreases considerably with thicker insulation (the energy demand for the production of one additional centimetre would exceed the savings achieved only if the total thickness exceeds 105 cm (!)).
|Fig. 4 Cumulated primary energy demand (80a) for a Passive House,
depending on the insulation thickness.
The Passive House is a proven building standard that can be easily and practically implemented. It enables significant savings in running costs
and provides energy savings during the period of use. The additional energy expenditure for manufacturing that is necessary is small in comparison with the energy saved during the whole life cycle; this has been confirmed by other authors in independent verification calculations [Mossmann, Kohler 2005] .
With energy-efficient construction, the primary energy demand for the application of electricity during the period of use, as well as the embodied energy of the building materials become increasingly significant. Further improvement can be achieved here by increasing the production efficiency of building materials as well as through efficient use of materials; but this should not be at the expense of increasing operating energy again, as this still predominates.
Optimisation of Passive House planning is appropriately carried out using the Passive House Planning Package (PHPP), which is a comprehensive tool for determining the energy balance of buildings.
- This brief online summary has been compiled from the article Life-cycle energy analysis: Comparison of low-energy house, Passive House, self-sufficient house which can be found in the Protocol Volume Number 8 of the Research Group for Cost-efficient Passive Houses.
- The data has not changed significantly since the original Study; the measured data of the reference Passive House hasn’t changed anyway, but neither have the specific primary energy values for building materials changed appreciably, according to the latest easily accessible databases. This may change in future, as the energy costs are much higher today than they were 10 years ago and more efficient production methods are now paying off. However, it was not the subject of this article to investigate this.
- If statements are found in any literature that appear to contradict the findings of this article in part, attention should be paid to the following points for an accurate comparison:
Has the period of use (this is dominant) been taken into consideration at all?
Which approach has been chosen for the life cycle?
Was the renewal energy demand taken into account?
Which apparent density of the insulation materials was assumed and which insulation materials were considered?
[Feist 1997] Feist, Wolfgang: Lebenszyklusbilanzen im Vergleich: Niedrigenergiehaus, Passivhaus, Energieautarkes Haus, In: Arbeitskreis Kostengünstige Passivhäuser, Protokollband Nr. 8: “Materialwahl, Ökologie und Raumlufthygiene“, Hrg.: Wolfgang Feist, Passivhaus Institut, Darmstadt, 1997, S. V/1 – V/11. (A comparison of life cycle balances: Low-energy house, Passive House, energy-autarchic house; in the Research Group for Cost-efficient Passive Houses Protocol Volume No. 8: “Material selection, ecology and indoor air hygiene”, published by Wolfgang Feist, Passive House Institute, Darmstadt 1997, pages V/1-V/11 )
[Köhler 1995] Kohler, N.: Baustoffdaten, Ökoinventare; ifib Karlsruhe; HAB Weimer; ESU-ETH Zürich; 1995 (Building material data, Life Cycle Inventories, ifib Karlsruhe; HAB Weimer; ESU-ETH Zürich; 1995)
[Mossmann, Kohler 2005] Mossmann, Cornelia; Kohler, Nikolaus; Jumel, Stéphanie: Lebenszyklusanalyse von Passivhäusern; Im Tagungsband der 9. Passivhaustagung, Ludwigshafen-Darmstadt 2005, S. 333-338 (Life cycle analysis of Passive Houses, in the Conference Proceedings of the 9th International Passive House Conference, Ludwigshafen-Darmstadt 2005, pages 333-338)
[PHPP 2007] Feist, W.; Kah, O.; Kaufmann, B.; Pfluger, R.; Schnieders, J.: Passivhaus Projektierungs Paket 2007, Passivhaus Institut Darmstadt, 2007. (Passive House Planning Package 2007, Passive House Institute, Darmstadt 2007)
[Röhm 1993] Röhm, T.: Der Energieaufwand zur Herstellung des Energieautarken Solarhauses Freiburg; Diplomarbeit, Universität Karlsruhe, 1993 (The maufacturing energy demand for the energy-autarchic Solar House in Freiburg, Thesis, University of Karlsruhe, 1993)
[SIA 0123] SIA: Hochbaukonstruktionen nach ökologischen Gesichtspunkten; SIA-Dokumentation 0123; Zürich 1995 (SIA (Swiss Engineers and Architects Association): Structural engineering based on ecological aspects, SIA Documentation 0123; Zürich 1995)