INcoming SOLar radiATION is the portion of the sun’s radiation that is received by the earth. Most of the energy of the earth comes from radiation from the sun. In fact, were it not for this solar radiation, life as we know it on earth could not exist.

The Seasons

The Earth rotates on its axis at an angle of 23½ ° with respect to a line perpendicular to its orbit, which means that regardless of the position of the earth in its orbit, its axis always points to the same position in space. As the Earth revolves around the sun the direction of its axis with respect to the sun varies, so that in the northern hemisphere the northern axis points away from the sun in winter and towards the sun in summer. This causes the rays of the sun to strike the earth at a sharp angle in winter and a more upright angle in summer. The rays are more concentrated in summer and more spread out in winter, resulting in much greater intensity in summer. Also the “total daylight hours” are much greater in summer because of the Earth’s position on its axis with respect to the sun. This cycle of variations creates the different seasons of the year.

The Greenhouse Effect

Direct shortwave radiation (mostly visible light) readily passes through the atmosphere. As it strikes an object it radiates as long waves. The Earth’s surface acts much like the glass of a greenhouse and blocks this long wave radiation from escaping, thus warming the Earth.


Maximum Solar Heat Gain

1. Facing true south attains maximum solar heat.
2. Facing + or -20° of south loses only 4%.
3. Facing + or -30° of south loses about 10%.
4. Facing + or -45° of south loses about 18%.

Passive Solar Heating

Capturing the sun’s energy in a sunroom can add significant heat to your home. Just as the Earth captures solar radiation on a large scale (The Greenhouse Effect) you can capture significant solar energy all winter in a sunroom, even enough to heat your home.

Sunroom Science Winter
Sunroom Science Spring
Sunroom Science Summer
Sunroom Science Fall