Discussion from the Standpoint of Heat and Moisture Balance for Cattle Barns using Low-cost Materials

Studies on a counterplan preventing dew from falling on the inner roof surface of large-size cattle barns suitable for warm districts in Japan for fatting

Abstract

The roof structure of large-size and low-cost cattle barns (hereafter called the example barn), which has an attic space used for fodder store, is investigated from the standpoint of environmental design, for the main purpose of establishing some conditions for avoiding falling dew.
First, a laboratory experiment is carried out using similar materials used for the roofing of the example barn. As a result, the heat transfer coefficient of the natural convection of the material can be obtained suitably as 2.3 W/(m²·K). By use of this value, the improvement of the roof structure used low-cost materials can be proposed as the example barn.
Second, using the data obtained by the investigation of the example barn with falling dew, the ventilation estimate is done by means of three stationaly methods consisting of heat and moisture balance and the architechtural method for the example barn.
As a result, these three values estimated roughly agree with each other.
Third, the physical values of the low-cost cattle barn are simulated as an object of the estimations, obtained by means of using the heat balance equation with the environmental data investigated and the ventilation done. As a result, a rate of increase of more than 50% of the ventilation and a rise in the air temperature can be estimated.
Last, it should be able to say conclusively that, the example barn can not avoid falling dew on the inside part of its roof. Then, as a counterplan to avoid falling dew on the inside part of its roof, a new low-cost structural design of the roof, another look at the size and position of the ventilation should be looked into. Moreover, a fan should be installed for free circulation of the air inside of the barn.