Atsushi Iwamae

The Humidity Variation in Crawl Spaces of Japanese Houses

We found that many houses experience summer condensation in the crawl spaces. These houses are constructed in compliance with the Japanese Building Code requirements for crawl space ventilation and contain ground covers. The humidity in the crawl space affects durability of the house. We have monitored the temperature and humidity variations of 36 houses in Japan over two years and confirmed the annual variations of hygro-thermal conditions in the crawl spaces by the numerical analysis. Numerical calculations using a one-dimensional heat transfer model agreed well with the measured results. These results show that during the summer, houses in this region of Japan have extremely high humidity in crawl spaces. The daily average of crawl space vapor pressure is nearly equal to that of the outdoors. The effects of floor thermal resistance and ground moisture are also estimated in this paper.

A STUDY ON CONVECTIVE HEAT-TRANSFER COEFFICIENT AT SLAB-CONCRETE SURFACE AND FLOOR-UNDER SURFACE UNDER THE CONDITION OF CRAWL-SPACE HEATING BY WIND TUNNEL TEST

‘Crawl-space heating’ is a heating system using the crawl space as a duct for heat transport from a heat pump. The purpose of this study is to grasp the convective heat-transfer coefficient at the slab-concrete surface and the floor-under surface, under the condition of crawl-space heating. When the crawl-space heating is operated, the air velocity in the crawl space is generally 0.05-0.20m/s and the heat transfer is caused by both the forced convection and the natural convection. We measure the convective heat-transfer coefficient by the wind tunnel test. It is revealed that the convective heat-transfer coefficient at the slab-concrete surface is about 1.0-4.0W/m2K and that at the floor-under surface is about 6.0-10.0W/m2K.

A STUDY ON CRAWL SPACE HEATING WITH SENSIBLE THERMAL STORAGE MATERIALS

We present a heating system with thermal storage using a heat pump which supplies heat to the thermal storage installed in a crawl space of a residential house insulated at the foundation walls. We used sensible thermal storage materials. This system can charge heat by using cheap nighttime electricity and discharge the stored heat at daytime. It is revealed by experimental studies that thermal behavior of the room is greatly influenced by the heat capacity of the thermal storage. We constructed a computer simulation program of this heating system and showed the ratio of the stored heat for generated heat by the heat pump with the volume of the thermal storage materials. We showed the way to determine the volume of the thermal storage materials and the capacity of the heat pump.

A STUDY ON CRAWL SPACE HEATING WITH LATENT THERMAL STORAGE MATERIALS

We present a heating system with thermal storage using a heat pump which supplies heat to the thermal storage installed in a crawl space of a residential house insulated at the foundation walls. We used latent thermal storage materials. This system can charge heat by using cheap nighttime electricity and discharge the stored heat at daytime. We showed equations to determine the air volumes of the heat pump and the ventilator, and equations to determine the phase transition temperature and the amount of the latent thermal storage materials to keep the room setting temperature. We constructed a computer simulation program of this heating system and confirmed the validity of these equations.