> What is Passive Solar? - Page 3

3. Isolated Gain
The integral parts of an isolated solar heating system are separate from the main living area of a house. The most common isolated-gain passive solar home design is a sun space or sun room. The isolated gain system will utilize 15-30% of the sunlight striking the glazing toward heating the adjoining living areas. Solar energy is also retained in the sun room itself. Sun rooms may experience high heat gain and high heat loss through their abundance of glazing. The temperature variations caused by the heat losses and gains can be moderated by thermal mass and low-emissivity windows. Heat is distributed to the house by means of conduction through a shared mass wall in the rear of the sun room, or by using ceiling and floor level vents, windows, doors, or fans that permit the air between the sun room and living space to be exchanged by convection.

Passive collectors use a south (or North) facing air collector to naturally convect air into a storage area. Convective air collectors are located lower than the storage area so that the heated air generated in the collector naturally rises into the storage area and is replaced by return air from the lower cooler section of the storage area.

The sun room has advantages in that it can provide additional usable space to the house and plants can be grown in it effectively.

Some points on Thermal Mass and Passive Solar

The thermal mass you have in your building must be able to interact with its environment, what this means is if it is the floor, you cannot carpet it or put rugs all over it. If it is the wall you cannot cover it in gyprock!

Also make sure your thermal mass is actually made out of material with a high thermal density. Concrete or bricks are ideal. Autoclaved aerated concrete (AAC), sandwiched insulation panels, or ICFs on the other hand have very low thermal density (hence why they insulate so well), so are very bad as the thermal mass. Also straw bales are not usable as thermal mass, in fact, we recommend that straw bales are not used within the internal construction of a property as they can breakdown and cause other problems and effect your resale value.

What this usually boils down to is that concrete floors are employed with tiles on them, and thermal mass internal walls are made from brick.

Note: Of course insulation has its place, you need to use it to help isolate the internal environment from the external environment to get maximum benefit from the thermal mass you put in the property (i.e. help it regulate the temperature by having to deal with less external effects).

What must also be understood is that we are looking for sufficient thermal mass in a building to be able to regulate the temperature and allow you to open windows to refresh the air. Opening windows is something you should do in a property on a regular basis anyways, otherwise humidity and 'bad air' can accumulate and you end up with a sick building with sick people in it. If a thermal mass property is designed right there should be no need for air heat exchangers and other fancy heat recovery systems to ensure you have fresh air - the natural daily solar cycle will be sufficient to help keep your property at a comfortable temperature for the majority of the time.

We hope this article on Passive Solar Design and the practical aspects of how to achieve it has given you a useful understanding. Given the effectiveness of Passive Solar Design in saving on energy costs, we consider it one of the first things you should consider when designing a new home.

If you would like to learn more, please look at the related articles below.

Passive Solar Design Related Articles

• Keeping your home Cool in Summer or Warm in Winter for free! - tips and techniques on how to keep comfortable for little or no cost.
• What is convection and how it effects your heating costs - what convection is and why we term it the 'heat thief'.
• The importance of building orientation - how the correct orientation of a building can reduce heating costs by up to 30%.
• What is a Trombe Wall and how can you use one? - how a simple wall and some glass can be used to reduce your heating costs.
• Solar water heating, how it works and options available