Where the cold weather shelter needs dead air to retain the user's body heat, the hot weather shelter needs to breather and have as much air circulation as possible. An effective hot weather shelter can be made simply by erecting a sloped light-proof roof over a frame, leaving the sides, front and back open to allow any air currents to pass unobstructed. The space blanket works very well here. The roof should face south to keep out as much sun as possible, and travelling through open country MUST be restricted to the hours between dusk and dawn. The shade provided by the roof will be approximately 10 degrees cooler than the outside temperature and should be comfortable enough to allow the survivalist to sleep throughout the heat of the day.
Perspiration wastes water.
The earth is the world's best heat sink and it will absorb a human's body heat faster than it can be generated, resulting in hypothermia that can range from mild to life threatening. They need not to be fancy or difficult to make. My own favourite winter bed is made from lengths of dead poplar or cottonwood logs. These dead trunks are easy to break off and several of them laid side by side on the snow with a thick covering of pine boughs will provide as much insulation from the ground as possible. Building a fire on a similar platform next to the bed will allow you to keep warm while sleeping outside in clear weather.