What is Passive Solar?
Passive solar means using the building’s Windows, walls, and floors to collect, store and distribute solar energy in the form of heat in the winter, and rejecting solar energy (heat) in the summer. It is called “passive” because it does not use mechanical means to distribute heat, but rather takes advantage of natural convection, radiation, and air flow.
If you’re adding energy-efficient features into an older home (built before 1993) that currently has little insulation, less energy-efficient Windows, and non-EnergyStar appliances, you may be able to reduce heating and cooling costs by up to 50-60%. That savings will pay for itself year after year, and many of the passive solar design features also add aesthetically to the house and increase the house’s market value (see “Going Green Can Add Value to Your Home”).
Ways To Incoprporate Passive Solar
If you are not building a new home from scratch, you may not be able to take advantage of all of the suggestions below, but, the more you can do, the more you’ll save.
- Use wide overhangs on your house to shield the house from the sun in summer. Western or eastern-facing Windows are particularly vulnerable to overheating in summer, so these should be shaded using overhangs and large leaf-bearing shade trees that shed their leaves in the fall.
- Have south-facing Windows that have an unobstructed view of the sun (no big trees or tall buildings in the way). Keep these Windows clean and keep the drapes, blinds, or shutters open during the cooler months while the sun is shining. In the warmer months, place a removable reflective film on these Windows or keep the drapes, blinds or shutters closed to block the sun. Remember: if light can get in, so can radiant heat.
- Capture and store the sun’s heat in thermal masses inside the house. This can be concrete, brick, stone, or tile which is used on walls or floors. The thermal mass absorbs heat from sunlight during the heating season, and absorbs heat from the air during cooling season. You can easily create a thermal mass by having a brick or stone fireplace which extends up the entire wall, or adding tile or decorative concrete flooring in the room containing the best sun exposure.
- Take advantage of the “chimney effect” (natural convection). Since heat rises, install operable skylights (skylights that open) in the upper-most areas of the house, such as an upper floor or vaulted ceiling.
- Use clerestory and transom Windows or light tubes to let natural light in year-round, so you minimize the use of electric lights. Convert all lights in the house to LED bulbs, which radiate far less heat.
- An open floor plan takes advantage of passive solar the best, as do open stairwells and atria.
- Install EnergyStar-certified appliances and fans throughout the home, and energy-efficient double or triple glazed Windows. Casement Windows offer the best air flow.
- Add insulation to your attic. This will help year-round (see our post “5 of the Best HVAC Investments You Can Make”).
- Make your roof reflective with a light color paint, or by using reflective paint, shingles, or tiles. Roofs receive the majority of solar radiation delivered to a house, so a cool roof will dramatically cut air-conditioning bills.
- Allow the landscape design to work in your favor. Use evergreen hedges and shrubs as windbreaks. Use deciduous trees (trees that drop their leaves in fall) near the house, to provide shade in summer and allow light in in winter.
The real joy comes in living in an energy-efficient, eco-friendly, passive solar house that is not only beautiful, but saves you money every single day.
If you live in the Nashville or surrounding area, Interstate AC Service can help with all your heating and cooling needs. Call on us at 615-832-8500. We’re here for you!
How Does a Passive Solar Heating System Work?
Passive solar heating is the process of using a certain building system to regulate internal temperature carefully and benefit from the sun’s heat energy.
So, the purpose of a passive solar heating system is to store the sun’s heat energy during days within the building’s elements or materials and use it during the night.
A comfortable temperature inside the living space should be maintained during the absorption of the sun’s heat energy. This means preventing possible overheating of the living space during the daytime.
Passive solar heating offers a comfortable living area, reduces energy consumption, and minimizes maintenance. It is applicable and suitable for small buildings, especially if the envelope design of the building controls the energy demand.
What is Passive Solar Heating System?
The essential elements of a passive solar heating system include facing a number of Windows placed in the house toward the direction where the sun’s heat strikes the most. For instance, facing Windows toward the south for North America is best. The availability of thermal mass to absorb, store, and distribute heat is another vital element of a passive solar heating system.
The thermal mass is made of a construction material that is capable of holding heat energy, such as concrete, bricks, ceramic tiles, and stone. The stored heat can be dispersed by radiation, convection, or conduction into the living space.
Radiation is the movement of heat in the form of waves. Convection is the transfer of heat through the air, which can be seen as ragged lines in the air during hot days, and conduction is the transfer of heat from storage to another mass. For example, touching a hot surface and burning is the transfer of heat through conduction.
A passive solar heating system is suitable for low-rise buildings in a temperate and cold climate, barracks, lobbies, hallways, break rooms, and large maintenance facilities. This system can reduce heating energy consumption by 25-75% compared with conventional structures.
Passive Solar Heating Techniques
Three approaches are available to implement passive solar heating:
In the direct gain system, the living space collects, absorbs, and distributes the sun’s heat energy.
The south-facing glass allows solar energy into the living space, where it directly and indirectly strikes thermal mass materials like masonry walls and floors.
The thermal mass takes solar radiation during the daytime and emits heat energy at night into the living space. The direct gain uses around 60-75% of the sun’s heat that strikes the window.
In this system, the thermal mass is between the sun and living space. The thermal mass absorbs heat energy from the sun and conducts it to the living space.
The direct gain system utilizes 30-45% of the sun’s heat energy that strikes the window. Three indirect gain solar passive heating techniques are available namely: thermal storage wall systems (or Trombe wall), water wall, and roof pond.
The thermal storage wall system absorbs and stores heat during the daytime. Excess heat is transferred by air between wall and glass through the thermosyphon principle into the living space. During the night, vents of the trombe wall are closed, then heat energy is dispersed into the interior space.
The water wall consists of transparent containers filled with water. During the day, the water absorbs and stores the sun’s heat and disperses it into living space at night.
Solar passive heating roof pond system uses water which is encased in plastic beds and placed on roofs, see Figure-4 and Figure-5. The system is the only indirect gain approach that provides heating and cooling.
During the daytime, in hot seasons where the cooling effect is desirable, movable cover or insulation covers the roof pond to minimize solar heat absorption from outside. As a result, water absorbs heat from the living space which subsequently provides a cooling effect.
During the nighttime, the movable insulation is removed, and the water disperses heat outside the living room.
In the winters, when solar heating is desirable, the movable insulation cover is removed during the day to allow water to absorb and store heat. During the nighttime, moveable insulation is used to cover the roof pond to prevent heat loss. As a result, the water releases heat in the living room and raises the temperature.
The integral parts of the isolated passive solar heat gain system are isolated from the main living area. The isolated gain uses solar energy to passively move heat to or from the living space through water or air by natural or driven convection.
An example of an isolated passive solar heat gain system is a sunroom, see Figure-8. The sunroom uses both direct gain and indirect gain features. It consists of a solar collector, storage area, and transfer medium.
The flat plate solar collector uses air or liquid to collect the heat energy from the sun. The collected heat is moved through pipes or ducts by natural convection to the storage area, where cooled fluid or air is displaced and driven back to the collector.
The storage consists of a tank when liquid is used as medium transfer or rock known as bin when air is used as a medium transfer.
Passive solar heating is the process of using a specific building system to regulate internal temperature carefully and benefit from the sun’s energy.
Direct gain2. Indirect gain2. Isolated gain
A building must be well-insulated for a passive solar heating system to work properly.
Small buildings such as low-rise buildings in a temperate and cold climate, Barracks, 2. Lobbies, 3. Hallways, 4. Break rooms, 5. Large maintenance facilities.
Incorporating a passive solar heating system into a building will increase its total cost by around 0-3%.
The Science Behind Passive Solar Design:
The scientific basis for passive solar building design is based on a combination of climatology, thermodynamics (particularly heat transfer: conduction (heat), convection, and electromagnetic radiation), fluid mechanics/natural convection (passive movement of air and water without the use of electricity, fans, or pumps), and human thermal comfort based on heat index, psychrometrics, and enthalpy control for buildings to be inhabited by humans or animals; sunroofing.
The following aspects are given special consideration: the building’s site, location, and solar orientation; the local sun path; the prevailing level of insolation (latitude/sunshine/clouds/precipitation); design and construction quality and materials; window and wall placement/size/type; and incorporation of solar-energy-storing thermal mass with heat capacity.
While these concerns may be applied to any structure, getting an optimal cost-performance solution necessitates thorough, holistic, system integration engineering of these scientific concepts. Modern refinements through computer modeling (such as the comprehensive U.S. Department of Energy Energy Plus building energy simulation software) and the application of decades of lessons learned (since the 1970s energy crisis) can achieve significant energy savings and environmental damage reduction without sacrificing functionality or aesthetics. In reality, passive-solar design elements such as a greenhouse, sunroom, or solarium may significantly improve a home’s usability, sunshine, vistas, and value at a cheap cost per unit of area.
Since the 1970s energy crisis, much has been learnt about passive solar building design. Many costly, illogical, intuition-based building initiatives have sought and failed to reach zero energy — the complete removal of heating and cooling energy expenditures.
Although passive solar building construction is not difficult or expensive (using off-the-shelf existing materials and technology), scientific passive solar building design is a non-trivial engineering effort that necessitates significant study of previous counter-intuitive lessons learned, as well as time to enter, evaluate, and iteratively refine the simulation input and output.
The use of thermography with digital thermal imaging cameras for a formal, quantitative scientific energy audit has been one of the most beneficial post-construction evaluation techniques. Thermal imaging can be used to document poor thermal performance locations, such as the negative thermal impact of roof-angled glass or a skylight on a chilly winter night or a hot summer day.
The scientific insights learnt over the previous three decades have been encoded in sophisticated computer software systems for complete building energy modeling (like U.S. DOE Energy Plus).
Solar labs is one of the best solar design software widely used by industry experts. It helps you design a highly accurate design in under 15mins.
A beginner will find it difficult to develop a scientific passive solar building with quantitative cost benefit product optimization. The degree of complexity has resulted in continued poor architecture and numerous intuition-based, unscientific building experiments that disappoint their designers and spend a considerable portion of their construction budget on incorrect concepts.
What Are The 5 Main Elements Passive Solar Design?
The wide glass space that allows sunshine to enter the structure. During the heating season, the aperture(s) should face within 30 degrees of true south and should not be shadowed by other buildings or trees from 9 a.m. to 3 p.m. everyday.
The storage element’s rough, black surface. The surface, which might be a stone wall, floor, or water container, is directly in the path of the sun. Heat is absorbed as a result of sunlight striking the surface.
Materials that absorb or store the heat generated by sunshine. The thermal mass is the substance beneath and behind the absorber, which is an exposed surface.
The process through which solar heat travels from collecting and storage locations to various regions of the home. A purely passive design will rely only on the three natural heat transmission mechanisms of conduction, convection, and radiation. Fans, ducting, and blowers may be used in some applications to transfer heat around the house.
During the summer, roof overhangs can be employed to shade the aperture area. Electronic sensing systems, such as a differential thermostat that signals a fan to switch on, as well as movable vents and dampers that allow or limit heat flow, low-emissivity blinds, and awnings, are other features that regulate under and/or overheating.
Design, Options, And Cost:
A passive solar home is an exceptional home, differing from standard construction in the thermal integrity of its shell and its well-considered design. The design options, employing the principles and methods described here are endless. However, workmanship is always extremely important when installing insulation, air sealing the building envelope, and installing the Windows. Most successful passive solar homes are very airtight. As a result, they may require mechanical ventilation systems to maintain good indoor air quality. Heat-recovery ventilator (HRV) is often the best choice to conserve the home’s hard-won solar heat. An HRV takes heat from the departing indoor air and transfers this heat to the entering outdoor air.
Passive solar technology may still be new to many designers and builders. So you`re sometimes required to pay extra for them to master unfamiliar design and construction details. But if you’re lucky enough to be working with an experienced solar designer and builder who are committed to excellence, a passive solar home may cost no more than a conventional one or even less in some situations. Also, properly sized heating equipment, which are typically smaller in passive solar homes, will sometimes offset the cost of the passive solar features.
Passive solar heating and cooling
Passive solar heating and cooling, sometimes referred to simply as passive solar design, is the process of using specific building systems to help regulate internal temperature by using the Sun’s energy selectively and beneficially in an attempt to improve the energy efficiency. In these systems, the building itself or some element of it takes advantage of the natural energy characteristics of materials when exposed to the Sun. Generally these passive systems are simplistic with few moving parts, thus requiring minimal maintenance. 
The engineering required to create these systems includes carefully selecting materials for the building envelope. including the building’s walls, floors, roofs, Windows and their glazing materials. and determining their proper orientation. Passive heating and cooling strategically captures or shades against solar radiation. 
How They Work
Solar heating and cooling systems take advantage of natural processes such as conduction, convection and radiation to warm or cool a building. Because of this, they require little to no external energy to function and can contribute to the energy efficiency of a home. When the Sun shines, the solar radiation heats buildings. This solar energy is converted into heat and transported by hot air or water into the building.  By strategically capturing or shading against this radiation, the temperature of a home can be regulated. 
Additionally, the heat gain from the solar insolation can be stored for future use. Capturing solar radiation in the winter helps to warm up the space, and shading from solar radiation in the summer cools the space. Hence, the use of insulation and thermal mass is crucial to prevent over-cooling of a space in the winter.  Likewise, the use of shading technologies in combination with Windows and glazing is equally important in preventing over-heating of a space in the summer.
Passive Solar Technologies
Passive heating and cooling systems are used to avoid using air conditioning or a heater. Many of the most advanced techniques for home temperature control use passive methods to accomplish energy efficiency. There are a variety of different technologies that selectively harness or shield against the Sun’s energy to heat or cool a building without using a heater or air conditioner. These technologies include operable Windows, solar chimneys, solar walls, and trombe walls. 
These technologies regulate internal space temperatures by capturing or venting heat from solar radiation. Shading technology can also be used strategically to reduce heating. By creating places where shade can be increased or decreased, the amount of solar radiation entering a space is reduced, therefore keeping the room cool without the use of an air conditioner.
These technologies can be used for a newly built structure and can also be incorporated into existing structures. Local climate is always the biggest factor when designing and implementing passive solar heating and cooling systems. 
Here’s an article with a more in depth discussion of architecture in passive solar heating and cooling.
Examples Of Passive Solar Heating
We’ve selected 10 case studies of passive solar heating in action to showcase how passive solar heating works. The following homes are great examples of sustainable homes. However, we’ll be looking specifically at their passive solar heating principles.
Harmony House || Design For Place Australia
The Stonelea House is a home in Australia that incorporates 4 passive solar heating principles. These are:
- Overhanging eaves
- Timber battens for shading
- Thermal mass
- Passive Windows
You’ll find that these 4 elements are often the most used in homes.
The overhanging eaves block the harsh summer sun but allow the low winter sun to warm the rooms.
Passive Windows to the north reduce heat loss during the winter and increase heat gain. Additionally, the timber battens act as shading over the room Windows, allowing passive light in but not direct sunlight.
Finally, the timber-cladding concrete walls and floors capture the heat during the day and release it through the night.
Green School South Africa || GASS Architecture Studios
Built in the Western Cape of South Africa, the Green School has to deal with cold winters and hot summers.
This building achieves this by using passive heating and cooling principles that work hand in hand.
Clerestories face north, capturing the direct sunlight and filtering the warmth into the classrooms. Towards the south, Windows made from colorful recycled glass create playful lighting.
The buildings are made from locally-sourced rammed earth; they use thermal mass to warm the classrooms during the winter. In addition, the school takes advantage of the heat created by learners. Capturing this heat inside warms up the rooms more than you’d expect.
Finally, the central courtyards allow direct sunlight to reach into each classroom, warming them during the cold winters.
Project Kilcunda || Ecoliv
Built near the edge of Lake Tahoe, U.S.A, this home has to withstand snowy winters by using passive solar heating.
Important note: this home is prefabricated, which means that builders paid close attention to sealing all the joints. Doing this prevents any unwanted heat loss during the winter.
Large Windows and sliding doors allow southern light to reach the home, warming the living spaces during the winter. Additionally, the main living space is double volume and connects to another living space on the second floor. The second living space also takes advantage of the southern light, creating a joint space with a warm climate throughout the home.
Cowboy Modern Desert Eco-Retreat || Jeremy Levine Design
This 3955 square foot home is built in San Bernardino’s High Desert. It uses a passive solar design to stay warm during cold nights and cool during the day.
As previously discussed, passive heating goes hand in hand with passive cooling, so passive solar design is crucial even though this home is located in a desert.
The design stores heat during the day to keep the house warm at night. The house achieves this by using thermal mass in the walls and concrete floor. Additionally, overhangs prevent direct sunlight from entering the home, keeping it cool during the day — this also prevents the house from overheating during the night.
The open living space doesn’t just prevent cold s of air from forming but also allows for passive cooling during the day.
Is A Home With Passive Solar Heating Expensive?
According to a study by Southern Illinois University Carbondale, an energy-efficient home costs 99/square foot. However, when compared to a price of 100/square foot provided by HomeAdvisor, the cost of passive heating is on par.
In this case study, passive solar heating replaced 23% of the energy needed to heat the home. This saved the owners 825 annually. It was cost-effective to build this home, but it also saved the owners money in the long run.
However, depending on the amount of passive heating desired, implementing these elements can cost up to 3% more. Therefore, the price would increase by 6780 to build a home that costs 226,100.
Forking out the extra money to install passive solar heating elements may seem unnecessary, especially in today’s economy. Still, passive solar design is always a good investment, and it will pay off in the future.
Passive solar heating is an age-old concept that we can use in today’s homes.
By implementing simple elements like passive Windows, shading devices, and insulation, you can make your home much more energy-efficient. This will decrease your carbon footprint and turn your home into an eco-home.
By spending 3% more on building costs, you’ll be able to create a passive home that uses solar heating. Installing these elements will save you money in the long run, decreasing your utility bill by 40%.
We hope you found this guide helpful, and feel free to ask any questions in the Комментарии и мнения владельцев below.