Multi-Comfort House an example of the building concept for sustainability

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1 Multi-Comfort House an example of the building concept for sustainability Kimmo Lylykangas M.Sc.(arch.), Kimmo Lylykangas architects, Finland ( Abstract Multi-Comfort House is a building concept, which includes energy performance criteria set in accordance to the Finnish Passive House definition. The term Passive House refers to a voluntary target for the energy performance of a single building, aiming at significant reduction of heating energy demand compared to the current construction practices. As an approach to sustainable building, it emphasizes energy-savings by an air-tight and well-insulated building envelope as well as an effective heat recovery in the ventilation. The simulation results of the first Finnish Multi-Comfort pilot building, a single-family house in Nummela, indicate that the criteria for the energy performance can be met in an average-sized house in the Southern Finland. The energy demand of the pilot building was calculated with the dynamic simulation software IDA ICE 4.0, which was also used for the analyses of the thermal comfort inside the house. Keywords: Passive House, Multi-Comfort, energy-efficiency 1. Introduction: The Passive House approach Within the various approaches to sustainability, the Passive House aims at significant reduction of heating energy demand by improving the properties of the building envelope and by introducing an efficient heat recovery in the ventilation. The definition is based on the total energy approach, which will be applied in the Finnish building code in The heating energy demand of a Passive House is low enough for ventilation heating. [1] In the Northernmost parts of the Europe the international Passive House criteria lead to solutions, which are not economically viable. For this reason Sweden [2], Norway [3] and Finland have introduced their own, national Passive House definitions. The VTT researchers introduced the suggestion for the Finnish Passive House definition in the research project PEP Promotion of European Passive Houses in The Finnish Passive House is defined by three criteria, which are: Heating energy demand kwh/(m²a) depending on the location Total primary energy demand kwh/(m²a) depending on the location Air-tightness n /h

2 The floor area used in the definition is gross floor area. [4] The first pilot buildings meeting the criteria of the definition were completed in Figure 1. The International Passive House criteria and the Finnish Passive House definition as suggested by the VTT researchers in the research project PEP Promotion of European Passive Houses. The floor area is calculated as treated floor area (wohnfläche) in the international Passive House definition and as gross floor area in the Finnish Passive House definition. 2. The Multi-Comfort concept Multi-Comfort is a concept by Isover Oy for new constructions. It sets a requirement for the energy performance of a building in accordance to the Finnish Passive House definition. The heating energy demand of a Multi-Comfort house is max kwh/(m²a) according to the location, as in the Finnish Passive House definition. As the national primary energy factors are not confirmed, the Multi-Comfort concept does not at this stage set any criteria for the total primary energy demand, but the calculated total energy consumption should not exceed 130 kwh/(m²a). The total energy consumption is calculated as so called ET-value according to the Finnish building code. In addition, the Multi-Comfort concept gives recommendations for air-tightness (max /h) and maximum heating power (20 30 W/m² depending on the location). The calculation tool is not specified by the concept. [5] The first project targeting to meet the criteria of the Multi-Comfort concept is a singlefamily house located in Nummela, 50 km North-West from Helsinki center. In the Southern parts of Finland the Multi-Comfort house criteria for the heating energy demand is max. 20 kwh/(m²a), and in addition the Multi-Comfort concept recommends the heating power of max. 20 W/m².

3 Figure 2. The Finnish Passive House definition and the criteria of the Multi-Comfort concept. The only requirement of the Multi-Comfort concept is the maximum heating energy demand. Values given for the maximum heating power, total energy consumption and air-tightness are recommendations. The concept also defines the internal heat gains (3.1 W/m²) for the calculations. 3. The solutions of the pilot project Figure 3. Illustration of the Multi-Comfort pilot project in Nummela, Southern Finland. The Multi-Comfort pilot project is a single-family house, 179 m² in gross floor area, characterized by the large north-facing windows, which the client family wanted to have for the lake view on the northern side of the house. The rooms are organized in one

4 storey for functional reasons, leading to a relatively high shape factor (A/V) of 1.3 m²/m³. The recommended shape factor of a single-family Passive House is max. 0.8 m²/m³. [6] The architectural design was an interactive process with the energy simulation. The early simulation results of the sketches indicated, that the heating energy demand would be too high, about 27 kwh/m²a. The architect listed changes, which would decrease the heating energy demand. The changes were simulated and applied in the plan in the order of the client family priorities. The target value for the heating energy demand was achieved by reduction of the window surface area and the room height, improvements of the U-values and introduction of the occupancy-time-based control in the ventilation. Figure 4. Floor plan of the Multi-Comfort pilot project. The mechanical ventilation has a heat recovery system with a regenerative heat exchanger and the annual efficiency of 74 %. Heat is distributed through floor heating and ventilation. The heating energy for the domestic hot water and the floor heating is generated by an air-to-water heat pump with the COP of 2.6. The load-bearing exterior walls are constructed of prefabricated wall elements with LVL (laminated veneer lumber) frame. The facade materials are oak panelling with white translucent finish and plaster rendering on ventilated plasterboard. The thermal insulation for the roof and for the floor was installed on site. The ventilated floor structure consists of hollow concrete slabs with thermal insulation on top. The U-value of the relatively large window surface area was improved by using sealed quadruple glazed units fixed onto the wall frame. This solution was applied wherever an opening window is not necessary and the glass surfaces can be easily washed on both sides. The price per square meter of this 4K-glass unit filled with Argon is less than half the price of a regular Passive House window.

5 Figure 5. Building envelope properties of the Multi-Comfort pilot.

6 4. Simulation results The energy consumption of the Multi-Comfort pilot building was simulated by Equa Simulation Finland with the dynamic simulation software IDA Indoor Climate and Energy 4.0 using the climate data of Helsinki. Figure 6. IFC-model of the pilot building imported in the IDA ICE simulation software. The building information model includes the properties of the building envelope such as the sizes of the doors and windows, U-values and the material layers of the structures. The value used for the internal heat load is 3.1 W/m² as required in the Multi-Comfort concept. For the calculation of the indicative primary energy demand, the value 2.1 was used as the primary energy factor for electricity. This has been one of the recent suggestions, although in many countries the primary energy factor for electricity is higher than this. The terrace roof provides shading for the south-facing windows. The simulation results showed, however, that the summertime room temperatures would be relatively high due to the large windows in the west facade. Thermal comfort was improved by adding external blinds on the west-facing windows. This decreased the percentage of hours when the operative temperature is above 27 C from 25 % down to 13 %. The simulation model did not include the trees, which will provide some extra shading from the low sun angles from west.

7 Figure 7. Simulation results of the final design. The table shows the supplied energy and the primary energy. The heating energy demand (without DHW) is 18.6 kwh/(m²a) including both the heating in the spaces and in the ventilation unit. The heating energy is produced in an air-to-water heat pump with a COP of 2.6 resulting to the heating energy consumption of 7.1 kwh/(m²a). The total primary energy demand was calculated as an indicative value, though the Multi-Comfort concept does not set a requirement for the total primary energy demand and the Finnish primary energy factors are not defined yet. With the factor of 2.3 (for electricity) the primary energy criteria of a Finnish Passive House (max. 130 kwh/(m²a) in the Southern Finland) could still be met.

8 Figure 8. Indication of the savings gained: a comparison of the pilot building solutions and the minimum requirements of the Finnish building code 2008 (SRakMK C3 2007). With the current solutions the simulated heating energy consumption of the pilot building is 84 % smaller than with the 2008 minimum requirement level without any compensation. Respectively, the total energy consumption is reduced by 39 % compared to the building code minimum requirements. The COP value 2.6 of the heat pump is applied in both cases. Energy performance is calculated in both cases using a reference value for the air-tightness. 5. Conclusions The energy performance criteria of the Multi-Comfort concept were proved to be viable for an average-sized single-family house in Southern Finland. Despite the relatively high A/V ratio, large window surface area and the north orientation of the windows, the criteria for the energy performance can be met. With higher U-values or less effective heat recovery the target level would not be achieved, and the compensation would probably require reduction of the window surface area and compromising the wishes of the client family. The simulation results also show that the thermal comfort of the interior spaces would be poor without the external shading of the west-facing windows. In the buildings with high level of thermal insulation, extra attention must be paid to the thermal comfort and shading of large windows. Mechanical cooling of spaces would increase the annual energy consumption.

9 Figure 9. Based on the simulation results, the energy performance criteria of the Multi- Comfort concept can be met in the pilot building. The pilot building is located in the climatic zone I. The air-tightness will be measured in a standard blower-door test in a pressure difference of 50 Pascal. References [1] Feist, Wolfgang: Passive Houses Worldwide Energy Efficiency Takes Hold. Conference Proceedings. 12th International Conference on Passive Houses April 2008 Nuremberg. Darmstadt p [2] Kravspecifikation för Passivhus. Version Framtagen inom Energimyndighetens program för Passivhus och lågenergihus. Juni Forum för Energieffektiva Byggnader 2009 p. 6. [3] Dokka, Tor Helge; Andresen, Inger: Passive Houses in cold Norwegian climate. Conference Proceedings. 10 th International Conference On Passive Houses 2006, 19 th 20 th of May 2006, Hannover. Darmstadt, p.228. [4] Lylykangas, Kimmo & Nieminen, Jyri: What is a Passive House in Finland. In Conference Proceedings. 12 th International Conference on Passive Houses April 2008 Nuremberg. Passivhaus Institut, Darmstad, Germany pp [5] Energiatehokas rakentaminen. Kirja fiksusta asumisesta. Saint-Gobain, s.l.s.a. [6] Rongen, Ludwig: Very Small Passive Houses. In Conference Proceedings. 12 th International Conference on Passive Houses April 2008 Nuremberg. Passivhaus Institut, Darmstadt, Germany p. 411.