The paper studies the energy performance of a solar chimney (SC) in a high performance two-story detached house with 220 m² floor area using EnergyPlus and the climate data of the hot summer and cold winter in China. An 8 m tall and 1.6 m wide solar chimney with a depth of 1 m is attached to the west wall to enhance building ventilation. The house uses a variable refrigerant flow (VRF) system to provide the heating and cooling and a separate ventilation system for outdoor air. The energy simulation results are compared between the house with the SC (SC case) and the same house but without SC (reference case). The results show that the SC produces larger ventilation rates than the minimum required rate most time of the year and therefore it needs to be controlled to avoid excessive outdoor air that leads to increased heating/cooling loads during the heating/cooling seasons. In this paper, a control is assumed so that the total outdoor air (through windows, doors, cracks and SC all together) is no more than one air exchange rate when the VRF system is running. The simulation shows that the SC can reduce the annual ventilation energy by 77.8% and the VRF energy by 2.3%. Overall, the annual energy saving of the SC for the studied house model is 549.0 kWh or 9.0% of the total HVAC energy consumption.

A linear model involving the solar heat gain coefficient and U value is often used to calculate the solar heat gain of traditional windows; however, it is not known if such linear model is applicable to double skin facades, which is typically featured by ventilated cavity and often with blinds inside. This paper reports on an experimental investigation into the relation between the two coefficients and the energy gain by a double skin facade without blinds. A small-scale solar calorimeter was constructed to measure the energy gain of a double skin facade window about 1.1 m high. Four tests with solar radiation intensity ranging from 205 to 793 W/m² showed that the energy gain can be represented by such linear model. The solar heat gain coefficient can be determined from the data fitting process with more accuracy than the U value, which, being a minor determinant of the heat flow in the presence of the solar radiation, may require more data for reasonable accuracy. The advantage of this linear model lies in its simplicity, which makes it easy to incorporate into present building energy simulation tools.

Double skin facades (DSFs) have gained increasing popularity worldwide for potential building energy savings. Such energy advantages are widely thought to be attributed to the ventilation feature of the DSF cavity. Keeping the cavity open to the outside, however, practically causes noise problems, dust pollution, and safety issues and thereby raising the maintenance cost of DSFs. This paper attempted to bring up this issue for more attention. We first numerically examined the thermal performance of DSF windows based on the climate of Hangzhou City featured by hot summer (>30℃) and cold winter (~4℃). Then we discussed the potential energy benefits of DSFs and the ventilation design of the cavity. Results from our simulations showed that the DSF window was more energy efficient than a double glazing window in summer regardless of the cavity open or closed. Such energy advantages were more due to the additional pane of the DSF window to reduce the solar transmittance than due to ventilation of the cavity. Although ventilation is beneficial in summer, the annual energy gain may be limited. Our simulations showed that ventilation can save annual energy by no more than 8% under Hangzhou climatic conditions. Therefore, to justify the use of ventilation in a DSF, we recommend a comprehensive evaluation to be performed by balancing the annual energy gains and investment increase associated with the open cavity.