###### Abstract  
The application of attached sunspace passive solar heating systems (ASPSHS) for farmhouses can improve building performance, reduce heating energy consumption and carbon dioxide emissions. In order to take better use of the attached sunspace to prevent heat transfer or promote natural ventilation, this paper presented a zero-state response control strategy for the opening and closing time of active interior window in the APSHS. In order to verify the application of this strategy, an attached sunspace was built in an actual farmhouse. A natural ventilation heat exchange model was built based on the farmhouse with attached sunspace. The proposed zero-state response control strategy was implemented in TRNSYS software. Field measurement in living lab was carried out to inspect the distribution of the thermal environment in the farmhouse with attached sunspace under a zero-state response control strategy in the cold region of northern China. The experimental results show that, even under \(-\)5.0-2.5 \({}^{\circ}\)C ambient temperature, the application of zero-state response control strategy effectively increases the internal temperature to an average of 25.45 \({}^{\circ}\)C higher than the outside, with 23% indoor discernible temperature differential in the sample daytime. The whole-season heating performance was evaluated by simulating the model for the heating season in 2020-2021. The simulation demonstrates that the APSHS under zero-state response control strategy can maintain a basic indoor temperature of 14 \({}^{\circ}\)C for 1094 h during the heating season, with a daytime heating guarantee rate of 73.33%, thus ensuring higher indoor heating control during the day. When compared to a farmhouse with an attached sunspace under the zero-state response control strategy, the energy savings rate can be enhanced by 20.88%, and carbon emissions can be reduced by 51.73%. Overall, the attached sunspace with the zero-state response control strategy can effectively increase the indoor temperature when the solar radiation is intensive and create a suitable thermal environment for the farmhouse in the cold region of northern China. attached sunspace passive solar heating systems; energy consumption; indoor thermal environment; zero-state response control strategy +
Footnote †: journal: Applied Sciences  
make it suitable for the development of passive solar heating technology [4]. Therefore, a suitable construction of passive solar heating systems (PSHS) for new constructions or reconstructions of existing farmhouse buildings in northern China has tremendous energy-saving renovation potential for reducing energy consumption in winter heating [5]. Currently, research on PSHS is mostly focused on Trombe walls, direct-gain room, and attached sunspace and other types of solar room [6]. Trombe walls have been investigated by several experts over the last few decades as an essential passive solar heating device. [PERSON] et al. [7] analyzed Trombe walls' classification, testing, modeling, and evaluation. Trombe walls' heat storage and thermal resistance performance have been much enhanced thanks to advances in material technology, particularly the use of heat storage materials and aerogel materials. However, due to its structure, it combines absorption, heat storage, heat release and less internal air buffering, which leads to insufficient thermal resistance, and losses of significant quantities of heat to the outside during its operation are inevitable. The direct-gain room, as the most basic PSHS model, offers the advantages of a simple design and inexpensive cost. However, because of its single adjustment mechanism and weak heat storage efficiency, it is prone to glare and significant indoor temperature swings when in operation. [PERSON] et al. [8] proposed a new double-layer transparent enclosure structure with changeable thermal resistance that uses a step control operating technique.