Passive solar house design considerations.

Passive Solar house plan

Passive Solar house plan provides the most cost effective means of day-lighting and solar heating and cooling of the house by utilizing and controlling the sun’s heat without using any additional mechanical or electrical devices.

There is an erroneous belief that using solar energy for your home means you need solar panels on your roof, converter and other technological gadgets. While the Solar Residential System planning does need these items, solar energy can also be harnessed through proper passive solar house design. To minimize energy use passive solar home takes advantage of the building’s site, climate of its location and materials. Well-designed passive solar house plan reduce heating and cooling costs through energy-efficient strategies. The passive solar home design to heat and cool your home can be both environmentally friendly and cost effective. In many cases, by passive solar heating your heating costs can be reduced to less than half the cost of heating a typical home!

The basics of passive solar house plan

Passive solar energy system refers to the use of the sun’s energy for heating and cooling of living spaces by exposure to the sun. Basically, in a passive solar home, the heat energy from sunlight is captured, stored and transmitted or released directly during the winter months, and minimizes the overheating effects of solar radiation through shading or generating air flows with convection ventilation during hot summer days. In order to take full advantage of solar energy in this way, well designed passive solar house plans are needed. In such planning the windows, walls, and floors of passive solar buildings are designed to collect, store, and distribute solar energy in the form of heat in the winter and reject solar heat in the summer. Unlike active solar heating systems, passive solar house design does not make use of additional mechanical or electrical devices, such as pumps, fans, or electrical controls for using the solar energy.

In passive solar house plan south facing windows, walls, and floors are made to collect heat as the sun shines and to retain it in materials that store heat, known as thermal mass. A properly designed passive solar home provides daylight all the year and comfort during the cooling season through carefully designed overhangs and reflective coatings on windows, exterior walls, and roofs. The above passive solar house design is done in such a way that the solar heat-flow is by natural means, such as radiation, convection, and conduction, and the thermal storage is in the structure itself. Thus, passive solar heating and cooling can save electricity bills significantly.

Basic elements needed in passive solar house design

To be effective, passive solar house design needs the following basic elements to make the best use of passive solar energy:

• Properly oriented windows;
• Thermal mass;
• Distribution mechanisms;
• Control strategies;

Properly oriented windows: Properly-oriented, large size south-facing windows to collect sun’s heat energy from sunlight;

Thermal mass:  ‘High Thermal mass’ building components (dense materials that retain or store the heat produced by sunlight) such as stone, brick, concrete or ceramic tile forming the walls, floors, or partitions that sit in the direct path of sunlight for absorption and storage of heat energy from sunlight;

Distribution mechanisms: For distribution of the stored solar heat energy back to the different living areas of the building during the winter months, through the mechanisms of natural heat transfer modes i.e. conduction, convection and radiation;

Control strategies: For controlling the overheating effects of solar radiation through roof overhangs or shading or generating air flows with convection ventilation during hot summer months;

Passive Solar house plan – major considerations

You can harness solar energy to heat and cool your home through passive solar home design. The three major options for utilizing solar energy in passive solar house plan are, day-lighting, passive solar heating and passive cooling.

Day-lighting    

Day-lighting is the controlled admission of natural sunlight and diffuse skylight—into a building to illuminate building’s interior rather than relying solely on electric lighting during the day. Successful day-lighting can provide substantial energy saving, reduce building peak loads, increase visibility, and improve overall lighting quality. Climate and geographical position, as well as building type, use and orientation, are big factors in designing a successfully day-lit building.

A good day-lighting system in passive solar house plan takes several factors into consideration such as,

• The general orientation and planning of areas to be lit;
• Location, form and dimensions of the apertures and openings through which the daylight will pass;
• Choosing the shape and size of windows and a mix of window types depending on the building’s orientation;
• Choosing the glazing and shading systems;
• Placement and orientation of room surfaces so that reflectance values for room surfaces are kept as high as possible;
• Location of movable or permanent objects which provide protection from excessive light or glare;

Passive solar heating

Passive solar heating, on its most basic level, works like this – rays from the sun enter a building through properly oriented windows and get the heat energy absorbed by the masonry floors and/or walls that have a high thermal mass. ‘Thermal mass’ can be defined as a material’s ability to absorb, store and release heat. High thermal mass include materials that are dense, such as stone, brick, concrete or ceramic tile. These materials absorb and store the solar heat during the period of time that the sun shines on them. As the air cools at night, the absorbed heat slowly releases into the building throughout the night-time and maintains a comfortable temperature.

Passive cooling

The cooling system in passive solar home design focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort during summer months with almost no energy consumption. Specially, utilizing passive cooling strategies like shading, generating air flows with convection ventilation and air cooling can reduce the demand for mechanical cooling while maintaining thermal comfort. Shading devices, fixed or adjustable, reduce solar radiation. We can shade a building by natural vegetation and by using special glazing in windows. External heat gain can also be minimized by good insulation, reduced window size and by the use of reflective materials in the walls and roof. A well designed overhang also can shade south facing windows from the high summer sun, while still allowing the low winter sun to shine in and provide welcome solar heating. Thermal mass is also used in a passive cooling design to absorb heat and moderate internal temperature rise on hot days. During the night, thermal mass can be cooled using ventilation, allowing it to be ready the next day to absorb heat again.

At their simplest, passive solar cooling systems include overhangs or shades on south facing windows, shade trees, thermal mass and cross ventilation.

Advantages of passive solar home

• Passive solar home is Eco-friendly. When homeowners harness the power of the sun, they don’t have to rely too much on fossil fuels. As a result, the passive energy system helps in saving the earth’s non-renewable energy resources and reducing greenhouse gasses in the atmosphere;
• Passive solar energy uses an energy source that occurs naturally and is almost always available free of cost. Passive solar home may involve initial costs, but the reduction in utility bills will more than offset the cost in the long run;
• Compared to the equipment needed in active solar energy (such as solar panels, inverters, wires, etc.), the materials required in passive solar house plan is relatively cheap. This is great advantage for homeowners who don’t have a large budget to create an eco-friendly home;

Before I conclude let me also address some of the questions often asked by the people related to passive solar house design.

How much does it cost to build a passive solar house?

A Passive solar home can cost between $150 and $500 per square foot depending on the level of finishing materials.

Can you open windows in a passive house?

You can open windows in a passive house whenever you want. However, as with all houses, if windows are left open for longer periods with extreme outdoor temperatures, the inside air temperature will be affected and energy consumption for heating/cooling will increase.

How does passive solar heating work?

For passive solar heating a living space needs to be exposed to sunlight so that the sun’s rays can heat the area. Passive solar house design takes the advantage of how the sun moves throughout the day in order to warm the living spaces, without requiring any mechanical devices or fuel to do so.

Conclusion

To sum up, passive solar house plan is region-specific. This is because each building site has its own weather and temperature patterns, as well as a unique topography that affects heating and cooling. But despite regional differences, there are a handful of strategies at the heart of passive solar house design for best utilization of passive solar energy. The key issues and strategies are:

• Building site and its orientation;
• Shape of the building and its thermal envelope (outer walls, roof, foundation, windows and doors) which prevents heat transfer form interior of a house to its exterior in winter and vice versa in summer;
• Size, type, and location of windows;
• Use of high thermal mass (ability of a material to absorb and store heat energy) materials to moderate interior temperature swings;
• Design of roof overhangs that shade windows and doors;