Heating and DHW systems in Passive Houses - Overview

The fundamental concept of the Passive House which relates to improving the energy-efficiency so that that significant investment cost savings can be achieved for the heating system, has already been published several times (e.g. [PHI 1996] , [Feist 1998] ). Thus it is possible to change the heating demand from that of low-energy houses to an economically optimal demand of less than 15kWh/(m²a). This difference is primarily due to the fact that a conventional heat distribution system is no longer required. Further savings are also possible through a lower output of the heat generator and if applicable, less storage volume. This article will discuss specially adapted systems which combine high efficiency with minimum installation engineering.

The high level of efficiency in the Passive House particularly with regard to heating results in a uniformity of the annual load duration curve, because the importance of the year-round hot water supply increases proportional to the remaining energy for heating. The following boundary conditions must be set for the heat generator in the Passive House:

Heating:

• Heating demand ≤15kWh/(m²a)
• Heating load ca 10W/m²

Domestic hot water:

• Heat demand of the hot water system 12 - 35kWh/(m²a) (depending on the number of occupants and distribution losses)
  

The location and time of the heat gains are no longer of any significance in the Passive House due to the large time constant of the building and the particularly small thermal coupling coefficients from the inside towards the outside in relation to the conductances between the individual areas of the building.

If gas (natural or liquefied gas) is used for the heat generator, it is also possible to use it for cooking. In doing so, a final energy demand of around 380kWh/a per household can be assumed, which can be met more economically in terms of either direct electricity or primary energy, by using gas.

When classifying heating systems in terms of final energy, a distinction should be made between the variants with electricity, fossil fuels, regenerative energy and the different types of combined heat and power generation in conjunction with district/local heating if applicable.

Table 1: The main final energy sources that can be used for heat generation in Passive Houses

From the article about the statistical evaluation of supply variants in the Passive House in this Protocol Volume, it is evident that all the variants mentioned in Table 1 have actually been implemented already in practice, but with a substantially different frequency of occurrence. The frequency of occurrence of the energy source in the Passive House also differs significantly from the average frequency of use in many countries such as Germany. The reason for this lies in the suitability of the respective energy sources for smaller outputs, the availability of relevant heat generators and the basic costs for grid-based systems. In this article therefore, systems which have been specially adapted for use in the Passive House will be discussed in particular. In addition, generally the whole range of conventional supply technologies can be applied in the Passive House.

The specific PE value - parameters

Systems adapted for the Passive House

Experiences with Passive House heating systems over many years show that compact units have considerable advantages. Besides the economic benefits due to synergetic effects, positive aspects include the fact that less time is required for installation and start-up (and there are fewer error sources), as well as less installation space in the room. Compact units with small heat pumps which use the extract air as a heat source are now quite common, new developments with ground-coupled brine pipes are especially suitable for multi-storey buildings.

Until now, larger systems have always been assembled from modular individual components, often by different manufacturers. The fundamental idea of the compact unit can be effective here too, and common rules can at least be developed for all components.

In principle, the compact unit approach can also be used for fuel-operated systems, the first gas and pellet devices are already being tested. For the use of oil as a fuel there weren’t any small-output burners available, now modulating systems are about to be introduced onto the market.

As for fuel-operated systems, the question arises, whether the buffer storage can be omitted when no solar heating is used. Research and initial developments have been taken up in this respect.

[AKKP 20] Feist, W.: Varianten für die Wärmeversorgung von Passivhäusern im Vergleich, Beitrag im Protokollband Nr. 20, Arbeitskreis kostengünstige Passivhäuser, Phase II, Darmstadt, 2000 (S. 91-176).
Feist, W.: A comparison of heat supply variants in Passive Houses, Article in Protocol Volume No. 20 of the Research Group for Cost-effective Passive Houses Phase II; Darmstadt 2000 (pages 91-16)

[AKKP 26] Neue Passive House-Gebäudetechnik mit Wärmepumpen, Protokollband Nr. 26, Arbeitskreis kostengünstige Passivhäuser Phase III, Darmstadt, 2004
New Passive House Building Services Using Heat Pumps, Protocol Volume No. 26 of the Research Group for Cost-effective Passive Houses Phase II; Darmstadt 2004.

[AKKP 6] Feist, W.: Anforderungen an die Haustechnik im Passivhaus; Rochard, U., Werner, J.: Entwicklung eines Kompaktaggregats zur Lüftung und Wärmeversorgung in Passivhäusern / Arbeitsbericht. In: Haustechnik im Passivhaus, Protokollband Nr. 6, Arbeitskreis kostengünstige Passivhäuser, Darmstadt, 1997.
Feist, W.: Requirements for building services in the Passive House; Rochard, U., Werner, J.: Development of a compact unit for ventilation and heat supply in Passive Houses/Working Report in Building services in the Passive House, Protocol Volume No. 6, Research Group for Cost-effective Passive Houses; Darmstadt 1997

[Bley 2007] Bley, H..; Petersdorff, C.; Krämer, G.: Entwicklung eines Kompaktgerätes auf Gasbasis, Tagungsband zur 11. internationalen Passivhaustagung, Bregenz 2007.
Bley, H..; Petersdorff, C.; Krämer, G.: Development of a gas-based compact unit, Conference Proceedings of the 11th International Passive House Conference, Bregenz 2007.

[DIN 624] DIN EN 624:2001-06 Festlegungen für flüssiggasbetriebene Geräte - Raumluftunabhängige Flüssiggas-Raumheizgeräte zum Einbau in Fahrzeugen und Booten, Deutsche Fassung EN 624:2000.
DIN EN 624:2001-06 Specifications for liquefied gas operated appliances – Room-sealed liquefied gas space heating equipment for installation in vehicles and boats, German version EN 624:2000.

[Drexel 2007] Drexel, C.: Ökonomie und energetische Performance von semizentralen Konzepten, Tagungsband zur 11. internationalen Passive Housetagung, Bregenz 2007.
Drexel, C.: Economy and energy-relevant performance of semi-central concepts, Conference Proceedings of the 11th International Passive House Conference, Bregenz 2007

[Feist 1996] Feist, W.: Passivhäuser – Behaglichkeit ohne Heizung. Im Tagungsband zur 1. Passivhaustagung. Passivhaus Institut, Darmstadt 1996
Feist, W.: Passive Houses – Comfort without heating. In the Conference Proceedings of the 1st Passive House Conference. Passive House Institute, Darmstadt 1996

[Feist 1998] Feist, W.: Innovative Haustechnik im Passivhaus. Fachinformation PHI 1998/4 Passivhaus Institut, Darmstadt 1998
Feist, W.: Innovative building services in the Passive House. Technical Information PHI 1998/4 Passive House Institute, Darmstadt 1998

[PHI 1996] Passive House Institute: Tagungsband zur 1. Passive Housetagung in Darmstadt. Passive House Institut, Darmstadt 1996
Passivhaus Institut: Conference Proceedings of the 1st Passive House Conference. Passive House Institute, Darmstadt 1996

[PHI 1998] Passivhaus Institut: Tagungsband zur 2. Passivhaustagung in Düsseldorf. Passivhaus Institut, Darmstadt 1998
Passive House Institute: Conference Proceedings of the 2nd Passive House Conference in Duesselsdorf. Passive House Institute, Darmstadt 1998

[PHPP 1998-2007] Passivhaus Projektierungspaket PHPP 2007. Passivhaus Institut, Darmstadt, 1998 - 2007
Passive House Planning Package PHPP 2007. Passive House Institute, Darmstadt, 1998 - 2007

[Strauß 2007] Strauß, R.: Kompaktgeräte auf Pelletsbasis, Beitrag im Protokollband Nr. 36, Arbeitskreis kostengünstige Passivhäuser, Phase IV, Darmstadt 2007.
Strauß, R.: Pellet-based compact units, article in Protocol Volume No. 36, Research Group for Cost-effective Passive Houses, Phase IV, Darmstadt 2007.