CASE STUDIES - VILLA WÅHLIN STOCKSUND, SWEDEN

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1 CASE STUDIES - VILLA WÅHLIN STOCKSUND, SWEDEN The Villa Wåhlin is a demonstration project for a new light structure building system. The exterior walls consist of big polystyrene block elements that are connected to each other with U-formed sheet metal profiles. The house is built in two levels and gets its special character from big south facing window areas. A balanced ventilation aggregate together with a heated crawl space under the bottom floor and suspended floors in the upper floors supplies the building with fresh air and heat. SWE 1 Building type Heating generation Heating emission Cooling generation Cooling emission Storage PROJECT DESCRIPTION residential, office, school, other, other boiler, central heat pump, DH, solar, cogeneration, other radiators/convectors, floor, wall, ceiling, air heat pump, DD, other radiators/convectors, floor, wall, ceiling, air storage tank, aquifer, other GENERAL DATA Principal: Per Wåhlin Architect: Wåhlin arkitekter AB Special construction issues: Kjartan Gudmundsson, Gudni Jóhannesson Kungl Tekniska Högskolan, Building Technology Installer: TEEG AB,VVS AB Energy concept: TEEG AB Hand-over: 1999 BUILDING DATA Building envelope: U (W/m 2 K) facade 0.17 roof 0.11 floor 0.25 glazing 1.2 Air tightness: n50 = 0.7 1/h Volume: 886 m 3 Surface area: ea: 586 m 2 Specific heat load: 210 LOWEX GUIDEBOOK

2 DESCRIPTION OF INSTALLATIONS GENERAL DESCRIPTION The building is equipped with a so-called TEEG installation crawl space. The crawl space is heated and insulated / radon tight to the ground. The fresh air supply is done via balanced ventilation with an air to air heat pump, the heat from the return air is used to preheat the supply air. Warm air is supplied to the crawl space, heats the floor and flows through a gap along the edges of the floor construction into the rooms above. The heating of the two remaining floors is under-dimensioned and has to be supplemented if the heating is not sufficient. OVERVIEW Heat generation: Heat pump Emission system: Floor and air heating, heated crawl space Costs heat emission system: DHW: Ventilation: Balanced mechanical ventilation INSTALLATION SCHEME + EXPERIENCES - MEASUREMENTS MEASUREMENTS The purpose of the measurements was to display the level of the energy consumption of the Villa Wåhlin house. All further analysis of measurements and improving methods depended on the examined state of the building. The heating requirement, an important value for the thermal performance of the building, can be determined with help of the recorded energy consumption. For the examination of the heating requirement the measured energy for space heating and energy for auxiliary applications are of importance. The heating requirement depends on the building qualities (e.g. insulation, air-tightness, thermal bridges and geometrical properties) the weather conditions and the users behaviour. The starting time of this work was late spring 1999, and the measurements were carried out as soon as possible, under cold outdoor temperatures. Moreover a vacation of the occupants provided the best conditions as the energy conmsumption of users appliances was minimised. The set-point temperature of the house was left on 20 C and the room doors were kept open during the period of the measurement without occupants to preserve a sufficient air movement. The temperature were recorded at four different places. EXAMPLES OF LOWEX BUILDINGS 211

3 Figure SWE 1.1. Energy consumption and temperatures. The measured temperatures at the four sensors and the average energy consumption for the measurement periods are shown in Figure SWE 1.1. In the beginning and at the end of the measurement the temperature and energy values are unstable. In the last period the unstable energy curve is effected by the non-uniform energy use of the occupants. But the main effect is caused by solar radiation, fast temperature rising outside causes rising of the inside temperature. The set-point temperature (20 C) of the heating system was passed and the heating system turned off. Simultaneously a decrease of the heating temperature in the heated crawl space is displayed. The result is a low energy consumption in this period, the following period with less solar gains or at night-time is often influenced as well. The internal heat capacity caused an additional heat supply for the next hours which saves net heating energy. Due to the high glazing ratio the increase in the internal temperature caused by solar radiation starts almost simultaneously with the increasing outdoor temperature. The temperature decrease inside the building on the other hand is slower than the decrease in the external temperature. The reason is the good insulation and air tightness. Two temperature behaviours are conspicuous: - The internal temperature of the gallery room over 30 C is caused by inadequate solar protection of the sensor. Direct solar influences produces a unnaturally high value. A realistic but also high value is shown on the channel at the second floor. - Some short-lived high temperature increases outside, periods of about 15 minutes, one measured value, are affected by a warm air flow out of the main entrance door. This is not significant for calculating averages over 8 to 9 hours but gives a clear time point when the family left the building for holiday and when they returned. The most reliable results are from the middle 212 LOWEX GUIDEBOOK

4 Figure SWE 1.2. Energy requirement for heating (legend below) of the measurement period. A constant outdoor temperature, no occupants and less solar gains leads to constant temperature and energy curves. Figure SWE 1.3. Heat loss coefficients (theoretical (blue), measured (red), measured average (light blue)) in W/m³K. ENERGY USE The measured values are corrected to reduce the error of the energy analysis. In advance calculated or approximated values are calculated for every measured energy meter reading and summarised in Figure SWE 1.2. To pursue to the end the heat losses have to be set in dependence to the temperature difference between inside and outside. The calculated heat requirement is equal to the heat losses. The inside temperature is calculated by an average of twice the temperature of the gallery room to once the temperature of the third floor. In Figure SWE 1.3 the average of the measured heat loss coefficient (dotted blue line) is, as expected, higher than the theoretical value (dotted red line). Some measured heat loss coefficients remain under the theoretical value. This concerns only values from night periods. The reason is the saved heat energy by the thermal capacity of the building. COMFORT Averaging the temperatures of the air and surrounding surfaces give the operative temperature. This is an indicator of thermal comfort for occupants, because the temperature of surrounding surfaces influences the feeling of temperature. A cold window gives an uncomfortable feeling in spite of a sufficient air temperature. Thermal comfort is defined as the condition of mind that expresses satisfaction with the thermal environment. The house in question as shown with the thermography study has very constant indoor surface temperatures. This provided a perfect base for the thermal comfort. Due to the the good air tightness and high insulation properties of the shell, a constant climate can be produced. However, a well adapted heating system which supplies the necessary heat is important. In particular the air heating system has to be configured carefully to get no big temperature gradients. In this case the influence of the floor heating system produces additional thermal comfort. Dynamic thermal simulations have been conducted to estimate the thermal comfort EXAMPLES OF LOWEX BUILDINGS 213

5 Figure SWE 1.4. Thermal comfort of the shading study of summer reference days (simulation). within in building. With this simulation it is tried to assess thermal comfort of the building at a period of worst case. Simulations show no problems in wintertime. Some lower indoor temperatures are found but mainly at night-time. Overheating problems in January and February caused by small angle of solar incidence are prevented by chill air supply of the ventilation. The remaining problems occur in summer time. For this period the thermal parameter significant for the thermal comfort have been simulated. The calculated PMV/PPD values shown in Figure SWE 1.4 display a thermal satisfaction during the daytime with maximum operative temperatures of 26 to 27 C and a dissatisfaction at operative temperature of over 29 C. At night-time a clear dissatisfaction is calculated with this set-up. This is mainly caused by a forced cooling down of the building by ventilation. To describe interventions from the occupants in the simulation one window to the south is opened daily from 1 to 4 p.m. EXPERIENCES - USERS OCCUPANTS The family, which present lives at in Villa Wåhlin is the family of the architect Per Wåhlin, who designed his own house. There has been no complains from the occupants reported under the monitoring period, except the problem of overheating in summertime. This has been addressed in the previous chapter. Large, glazed south facing façade areas makes it necessary to prevent overheating by sunshading devices. An efficient external sunshading has still not been installed, because of high costs and special architectural expectations from the users. LITERATURE Cordes, Tobias Measurement and Simulation of Villa Wåhlin. Diploma thesis at KTH-The Royal Institute of Technology, Division of Building Technology, Stockholm, Sweden. 214 LOWEX GUIDEBOOK