Overhang / Solar Control

An overhang, or some sort of solar control or solar shading, is a crucial element in passive solar design because it blocks the sun’s heat energy when it is not desired. Because the sun travels different paths across the sky in the winter (low) and summer (high) time, an overhang can be constructed to utilize and manipulate the heat energy from the sun.  The overhang can be a fixture on the outside of the house, or it can be a type of shading, overhang, or some type of control that can be utilized and and managed from inside or outside of the house.

This picture was taken shortly after the Spring Equinox. In the summer, the building is completely shaded. In the winter, the building receives full sun.

The overhang or solar control, is used to keep the building’s thermal mass in the shade. This will help keep the house cooler in the summertime.

In order to better illustrate this principle in action: Think of how cool, shaded tile or marble can feel on bare feet on a hot summer day. As long as a material that has thermal mass is shielded from a heat source, the sun, it will stay cool because of its density.

This density, along with the object’s heat capacity (also called thermal capacitance) is referred to as its thermal mass. When a material has high density, it resists rapid temperature fluctuations. It desires and seeks to stay a stable temperature. Thus if shaded, will tend to stay cool.

Find out more about the overhang and other qualities of the off the grid passive solar building to the left.

Different elements of passive solar design work together to warm a building in the winter and keep it cool in the summer.
 
 
 

This diagram shows how an overhang can be constructed to allow the winter sun in, while it keeps the summer sun from hitting the dwelling.

There is an additional outline showing the possibility of having sloped south wall with glazing (glass). While having sloped glass allows for the greater potential of winter heat energy storage from the sun, care must be taken to keep the building from overheating in the summertime.
 
 
 
 

Shutters as a type of control in a passive solar sun room


 
 

This shows a shutter system in a sun room acts as a control to help keep the summer sun out of the house. It can be controlled from the inside of the house.

The shutters to the far side have been shut, while others are open.  This allows the owner to open the shades in the winter to take advantage of the sun’s heat energy, while in the summertime, the shades can all be closed to help to keep the sun out, keeping the building cooler.

The possibilities of passive solar design are endless, will have different impacts on heating, cooling and how it affects living areas and quite beautiful in action and possibility.

 

 

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