Passive solar design involves using sunlight without active mechanical systems whereas active solar heating systems involve the use of mechanical and electronic devices. Regions with temperate climate face moderate rainfall, mild to warm summers, and cool to cold winters. While designing for these regions, the passive design should aim to reject solar heat in the summer and collect, store and distribute solar energy in the winter.
Here are 6 passive design strategies for temperate climates
- Orientation and General Building Design
- Trombe wall
- Kachadorian Floor
- Earth Shelter
1. Orientation and general building design
- The building can be oriented a few degrees to the east to capture sunlight during the daytime.
- The building can be extended in the east-west axis.
- The size of the windows should be such that it captures the midday sun in the winter while avoiding the harsh sun in the summer.
- The windows on the west side can be avoided. Overhang on windows should be such that it prevents overheating in the summer but allows low winter sun to penetrate.
- Vents between rooms ensure that heat is transferred from heated to unheated rooms in the winter.
2. Trombe wall
- It is a wall that is painted a dark color with glass on the outside and an insulating air gap between the two.
- The dark wall absorbs the thermal energy from the sunlight and traps it in the air gap by the greenhouse effect.
- The heat is then conducted through the wall into the building by radiation and convection.
- These walls are thick and made of high-heat capacity materials. The heat flow from the warm outer wall to the inner surface is slow. This delay in heat transfer causes heat absorbed during the day to be transmitted to the interiors during the evening.
- Sufficiently thick Trombe walls may also transmit heat up till the night.
- The wall is limited to one facade and may not have an effect on the entire building.
- The interiors behind the Trombe wall must have other ways of receiving daylight or they might become claustrophobic.
3. Kachadorian floor
- This passive heating method solves the drawback of Trombe walls, namely uneven heating of living spaces.
- It consists of a concrete floor with concrete ducts beneath it.
- Solar heat from south-facing windows and skylights is stored and distributed throughout the house using ducts.
- A sunspace uses the methods of direct heat gain and thermal storage.
- It consists of a glazed collecting space that faces south, attached to the main building via a thick thermal storage wall.
- Solar radiation that enters the sunspace heats up the air which reaches the living space through the thermal wall.
- Shutters can be used to avoid overheating in summer and heat loss in winter.
- Sunspaces can alternatively include plants with humidity control measures to avoid the growth of molds.
- Deciduous trees are best suited for temperate regions as they provide shade during summers and shed their leaves allowing the sun to shine through in the winters.
- Trellis pergolas with vines can be used for summer shading.
- Nondeciduous shrubs can be planted to break chill winter winds.
- Driveways, cloth drying areas, and other yard activities should be located away from the north edge as the north part of the garden is the best place for outdoor living in the winter.
6. Earth shelter
- Earth sheltering is achieved by covering walls, roofs or an entire building with earth(soil)
- For the northern hemisphere, a building facing south with the other sides covered by the earth is most effective.
- Earth acts as thermal mass, helping in maintaining ambient indoor temperature.