In the countries with tropical climates such as Malaysia, humidity and hot weather are well-regarded; this weather can affect the heat conditions and indoor room. The effects of the poor thermal condition are non-conducive human activities and a comfortable environment in the room. They improved the tilt angle for roof building or house design with insulation to achieve comfort and reduce the indoor temperature. Thermal insulation is one of the methods to reduce heat transmission through the room by applying proper material and installation. The main objective of this study is to test Glasswool insulation in different orientations of the roof for Malaysian houses. The insulation material has been tested by airflow simulation using SolidWorks software which applies to the rooftop on the east and west orientations, where the indoor temperature of the house has been reduced from (29°C - 27°C East and 30°C - 28°C West) without considering any air movement. The simulation result shows the temperature reduction before and after applying the insulation corresponds, while the reduction is 2°C temperature (7.4% reduction) at both orientations. The significant reduction helped the occupants to reach their comfort zone and save the cost of the electrical bill.