approach

building systems

heating strategies

     solar collection
     heat storage
     heat distribution
     heat conservation

cooling strategies

policy strategies

consumer notes

Heating Strategies

Our designs try to benefit from solar energy in the colder months. The process by which this happens includes the following steps: solar collection, heat storage, heat distribution, and heat conservation.

solar collection

To trap solar gains during cold months to serve as free heat, is the goal of solar collection. This is achieved through careful consideration of orientation, transparency, and placement of windows. South-facing surfaces receive less solar radiation in summer months and more solar radiation in winter months compared to other orientations. This is advantageous since it matches seasonal heating requirements. In addition to windows, walls, and floor slabs may serve to collect heat. Thus, insulating walls - depending on climate and orientation - can become necessary to prevent against heat loss.

Another method for solar collection is utilizing the greenhouse effect, which transforms short-wave solar energy into long wave radiation through a process which first collects solar energy and then traps the radiation inside, causing a rise in temperature. The greenhouse effect should exist without auxiliary heating, to insure that the sunspace is an energy saving feature. In addition, this space should be separated from other areas of the house, and any fenestrations should be closed when possible. During the summer months, it is best to have a shading strategy in order to prevent overheating.

heat storage

The second phase to achieve successful heat gains is to store the heat which has been collected, for distribution at the appropriate time. Materials such as concrete, brick, and water are good for direct storage of solar radiation due to their high storage capacities. Other factors, such as location, sun angle, color, are also important. In summer months, due to the high incident of angle, much of the floor is in shadow. Darker colors are better absorbers of heat gains than lighter colors, which tend to reflect radiation.

heat distribution

Heat distribution is possible through convection or radiation transmitted by a storage element such as a wall. One can take advantage of natural circulation achieved by air's tendency to rise when heated to distribute heat from one zone of a building to another. Mechanical ventilation is also possible through the use of fans and pumps.

heat conservation

Finally, a final step toward optimization of heating strategies in cooler months is the conservation of heat, often caused by instances of infiltration, ventilation, or thermal conduction, convection, and radiation processes. This can be achieved through the use of insulation, reduced surface area of building, and better windows. Another strategy is to reduce the temperature difference between interior and exterior through the use of buffer zones with reduced temperatures.

For example, one can place rooms which require less heat on the north of a building, such as laundry rooms and cellars, so that heat loss is minimized due to the reduced temperature difference. Basement and attics can serve the same purpose. In these situations, insulation should be placed between the buffer space and the interior, rather than between the buffer zone and the exterior. In addition, it is helpful to place the areas of the house which require the most heat, toward the center of the building area.

A higher thermal resistance of a wall, or R-value, is an important factor affecting the resistance to heat loss. Wall thickness, insulation, material selection, and thermal conductivity will affect the R-value of a given wall, roof or floor slab. Also important are the transmission properties of the glazing. Double-glazed windows provide significantly greater heat conservation than single-glazed windows. Current advances in technology have developed double-glazed units that reduce heat loss by ten times over single-glazed units.

We have found in our studies, that infiltration proves to be a large factor in energy loss. While it is important to have some levels of infiltration for renewal of air, excessive amounts can contribute to heat loss. Thus, attention should be paid to seal windows and doors which are located on the building envelope, and minimize gaps between building components.

 

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Last modified on December 13, 2000 by china@juintow.com.
 
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