Experimental Study on the Combined Effect of Outdoor Thermal-Environment and Ventilation Patterns on Indoor Thermal-EnvironmentControl for Summer

If thermal insulation and solar control ofbuilding envelopes are appropriately made forindoor thermal environment control, then themoderate air current becomes relativelyeffective for thermal comfort especially inresidentional buildings in summer seasons.To clarify the ways of natural ventilation withsufficient thermal insulation and solar control,we examined four cases of natural ventilation.We use an experimental house designed withthe concept of symbiosis in Tsukuba for tendays in August, 2007. There are three rooms onthe ground floor; the outdoor space in fiont ofthese rooms was equipped with shading devicesfor solar control. We examined the case of noventilation, nighttime ventilation only, thenighttime and daytime ventilation with upperopening, and the nighttime ventilation withupper opening and daytime ventilation withhorizontal openings. The transmitted verticalsolar issadiance in the rooms was smaller thanincident vertical solar irradiance. To describe the thermal environment provided by the casesof ventilation, we used exergy concept. Cool exergy contained by the room air duringdaytime in the case of the nighttime ventilation only was the largest, but wet exergy was alsoavailable in the large amount. In the case ofboth nighttime and daytime ventilation withupper opening, cool exergy contained by theroom air was larger than that in the case ofnighttime ventilation with upper opening anddaytime cross ventilation. Cool exergycontained by the room air decreased as the rateof air change increased. The average of the rateof air change was 7 timeslh in the case of bothnighttime and daytime ventilation with upperopening, and 13 timeslh in the case of nighttimeventilation with upper opening and daytimecross ventilation. The air current velocity in therooms during the nighttime was larger than thatof daytime even if the wind velocity outdoorsduring nighttime was smaller than that duringdaytime. This is considered to be caused bybuoyancy due to the difference in airtemperature between indoors and outdoors. It isimportant to control the rate of air changeduring daytime ventilation to keep the coolnessstored by nighttime ventilation by buoyancy.