The passive house PH+ concept is applied to a series of typical office building geometries and possibilities for on-site renewable energy production to reach zero net energy buildings are explored with the following assumptions:

• PV installation on the roof and facades (with total efficiency of 11%)

• Solar thermal system installation on roof and/or south facing facade (total efficiency of 56%)

• Roof cover 90%, facade cover 40%

The results of the parametric study are summarized in Figure 4. Here, energy consumption figures are shown in MWh/a in order to be able to balance the energy with on-site generation. It can be seen that only four building geometries provide enough floor and facade area to produce enough energy to balance the energy demand of the design. It can further be seen that energy concept PH requires only a small amount of heating energy but a large amount of electrical energy. The energy concept with reduced internal gains (PH+) reduces overall energy consumption but increases the amount of heating energy demand. This is still beneficial for zero net energy buildings since PV and solar thermal systems can be applied to the building envelope. Depending on the building form there is enough roof and faqade area to generate renewable energy necessary fulfilling the ZNE definition. In Figure 4 building forms and energy concepts with ZNE (without red and white columns) are buildings with 2 floors (1a and 1b) and 3 floors (2a and 2b). All other building forms do not provide enough building envelope to fulfil ZNE definition. Here, other energy concepts might be applicable in order to reach ZNE.

3. Conclusion

Newly introduced building regulations aim to reduce energy consumption in buildings. In heating dominated climates like Norway this implies more stringent building envelope requirements to reduce heat losses. Insulation and air tightness of the building envelope ensures this but can as a result lead to overheating problems during the summer period. Consequently, especially in buildings with high internal loads like commercial buildings, cooling equipment may be needed that uses additional energy. This will have consequences for the design of energy efficient buildings in Norway in the near future. Bioclimatic design strategies which focus on avoiding active cooling might be applied more regularly. Especially architects and engineers have to be

aware of the consequences of design decisions in regard to building form and envelope. It is proposed that thermal comfort criteria should be developed and coupled to energy calculations. Especially thermal comfort in (a hotter) summer will be reduced and should be put in focus when designing buildings and energy concepts.

The results show that the air tightness of the building envelope and the efficiency of the heat recovery system are the most sensitive parameters (together with the outdoor climate). Therefore, the energy concepts focused on those two parameters. With appropriate energy concepts applied to different building geometries it could be shown that ZNE office buildings are possible. There are some difficulties in implementing the passive house standard to office buildings due to differences in internal heat loads and occupation hours, resulting in differences in heating and cooling demand. Consequently, internal heat loads were reduced (PH+) and this resulted in more building shapes that allow for ZNE.

Another challenge is that climate change predictions for Norway forecast an increase in mean temperature and precipitation [8]. This has the potential to increase the overheating problems in future summer periods and might even extend it to autumn and spring seasons. Especially in western parts of Norway this may also lead to hot and humid summer periods. Further work is needed in order to quantify the extent of energy related implications. Also cost implications have to be studied in order to be able to optimize the design options.

References

[1] I. Andresen, 0. Aschehoug, Bell, M. Thyholt, Energy-Efficient Intelligent Facades. A state-of-the-Art, in: SINTEF (Ed.), SINTEF Building and Infrastructure, Trondheim, 2005.

[2] K. A. Dokka, T. H. Dokka, User Guide SCIAQ version 2.0, SCIAQ Pro — Simulation of Climate and IndoorAir Quality, 2004.

[3] T. H. Dokka, I. Andresen, Passive Houses in cold Norwegian climate, 10th International passive house conference, 2006.

[4] T. H. Dokka, Hermstad, Energieffektive boliger for fremtiden — En handbok for planlegging av passivhus og lavenergiboliger, SINTEF Byggforsk, SINTEF Byggforsk, Trondheim, 2006.

[5] Enova, Bygningsnettverkets energistatistikk 2006, enovas bygningsnettverket, enova, Trondheim, 2007.

[6] M. Haase, I. Andresen, Energy-efficient office buildings in Norway — from low energy standard to passive house standard, Passivhus Norden, Trondheim, Norway, 2008.

[7] M. Haase, I. Andresen, Key issues in energy-efficient building envelopes of Norwegian office buildings, in: C. Rode (Ed.), 8th Nordic Symposium on Building Physics, Copenhagen, Denmark, 2008.

[8] K. R. Lise, A. G., S. Eriksen, K. H. Alfsen, Preparing for climate change impacts in Norway’s built environment, Building Research & Information 31 (3-4) (2003) 200-209.

[9] K. J. Lomas, H. Eppel, Sensitivity Analysis Techniques for Building Thermal Simulation Programs, Energy and Buildings 19 (1) (1992) 21 — 44.

[10] PHI, PHPP 2004: Passive House Planning Package 2004, in: T. P.H. Institute (Ed.), The Passive House Institute, Darmstadt, 2004.

[11] I. Sartori, A. G. Hestnes, Energy use in the life cycle of conventional and low-energy buildings: A review article, Energy and Buildings 39 (3) (2007) 249-257.

[12] TEK, Energi — Temaveiledning, in: StatensBygningstekniskeEtat (Ed.), Vol. TEK 2007, Norsk Byggtjenestes Forlag, 2007.

[13] P. Torcellini, S. Pless, M. Deru, D. Crawley, Zero Energy Buildings: A Critical Look at the Definition, National Renewable Energy Labratory, 2006.

[14] K. Voss, G. Loehnert, S. Herkel, A. Wagner, M. Wambsganss, Buerogebaeude mit Zukunft, Solarpraxis, Karlsruhe, 2006.

[15] T. Wigenstad, T. H. Dokka, T. Pettersen, l. Myhre, Energimerking av nsringsbygg, SINTEF Building and Infrastructure, Trondheim, 2005.