Passive Solar Energy

Passive solar energy is one of my favorite forms of solar energy, because it doesn't require the use of any mechanical devices! Yes, that means no moving parts to break down or wear out. :-)

There are three different types of passive solar power that can be used for your home:

• direct gain
• indirect gain
• isolated gain

Direct Gain Passive Solar

Direct gain passive solar energy involves the use of south-facing windows, normally on a large room such as a family room or parlor. A kitchen or dining nook can often also provide a large amount of solar heating, depending on their place within the home.

Direct gain solar energy involves sunlight being allowed to come into the home, normally through specially glazed windows, allowing dark masonry floors and walls to be warmed during a winter day.

Those floors and walls store heat energy that in turn will be slowly released during the nighttime hours. The glazing on the windows allows for the free movement of solar energy into the living space, while decreasing the movement of heat energy out of the house.

This form of passive solar heating is the simplest to implement, and the success or failure of the system depends entirely on the design and architechture of the building.

Indirect Gain Passive Solar Heating

Indirect gain normally involves the use of a trombe wall or another kind of material that is placed between the sun and your home.

A trombe wall is made up of a south-facing masonry wall and a single or double layer glass placed approximately one inch in front of the wall.

This glass serves the same purpose as the windows in the direct gain model, allowing solar energy to warm the dark masonry wall while trapping heat energy between the glass and wall.

Throughout the day, the wall warms and heat energy begins to move through the masonry to the interior structure. The average masonry wall is 8 inches thick and allows the movement of heat at the rate of 1 inch/hour.

Using this method, if you collect solar energy earlier in the day, let’s say around 10:00 am or so, then by 6:00 pm that evening, the effects of the warming become apparent inside the structure.

This allows the stored solar heat to move into the living areas just as you need it, when the sun is going down and heating becomes a greater priority. This is passive solar energy at its best!

Isolated Gain Solar Energy

Isolated gain is a more complex form of passive solar energy that heats air or water, which is then circulated in a loop to provide heating or cooling for your home. The isolated gain solar system is kept separate from the other areas of the home and the sunlight is passed to those areas that most need it.

One of the most common types of isolated gain systems uses a sunroom which is attached to the side of the home, combined with an air collector which helps to move air through the home to a storage system in the house.

Isolated gain systems need to be precisely calibrated to keep the home at an even temperature.

Benefits of Passive Solar Energy

• No solar panels or equipment required
• Reduce energy costs with design
• No energy consumption – energy from the sun is free
• Eliminate the need for central air conditioning units or heaters
• Passive design utilizes a completely clean and renewable energy source
• No altering of your home's appearance
• Maintenance free
• Simple to incorporate into the design of a new home
• Environmentally friendly

Disadvantages of Passive Energy for Homeowners

The biggest disadvantage is for those homeowners who want to incorporate passive solar into their existing home. It can be costly to add large windows to an existing structure or to build a trombe wall. The loop equipment required for an isolated gain system could be expensive too depending on how much is needed for heating and cooling your home.

The good news is that passive energy is still within reach for you as a homeowner, whether you have an existing home you want to add it to or if you're simply designing a new home to be built. Think of it this way – if you were going to invest in solar panels and backup system for your home, it would cost something. Compare the cost of adding brand new windows in your home to a residential solar power system and you may find that adding the passive solar features to your home will be comparable or perhaps less expensive. It pays to do the research!

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