Designing a passive solar home

In order to consume as little energy as possible, passive solar architecture makes the most of a building’s location, temperature, and materials.An energy-efficient passive solar home reduces its heating and cooling requirements before supplying all or part of those requirements with solar energy. Modern homes have relatively low heating loads, so it’s crucial to avoid oversizing south-facing glass and make sure it’s correctly shaded to avoid overheating and increasing cooling loads in the spring and fall.

First, energy efficiency

Prior to incorporating solar features into your new home design or existing home, keep in mind that improving energy efficiency is the most economical way to lower heating and cooling costs. Work with building experts that have experience designing and developing energy-efficient homes to maximize the energy efficiency of your house. The first step in redesigning an existing home is to conduct a home energy audit to identify the most affordable energy efficiency upgrades.

Site choice

A piece of the south side of your home must have an unobstructed “view” of the sun if you’re designing a new passive solar home. Think about potential uses for the land south of your site; little trees can grow to be large ones, and a future multi-story structure could obstruct your home’s access to the sun. Solar access for landowners may be safeguarded in some locations by zoning or other land use laws. Find a property that is deep from north to south and build the house on the north end if solar access is not protected in your area.

How a Passive Solar Home is Constructed

In layman’s words, a passive solar home absorbs heat from the sun as it enters through south-facing windows and stores it in thermal mass—materials that can hold onto heat. The passive solar fraction, which is based on the glazing area and the quantity of thermal mass, is the portion of the home’s heating load that the passive solar design can satisfy. Each environment has a different optimal thermal mass to glazing ratio. The use of nocturnal ventilation in well-designed passive solar dwellings also ensures comfort during the cooling season and daylight throughout the year.

A effective passive solar home design must have a few fundamental components that complement one another:

• Correctly positioned windows. Typically, windows or other solar energy-collecting components should face south or south-southeast within 30 degrees, and they shouldn’t be covered by other structures or trees from 9 a.m. to 3 p.m. every day throughout the heating season. The windows should be shaded in the spring, fall, and cooling season to prevent overheating. Window glass should always be kept clean.

• Thermal weight. In a passive solar home, thermal mass, which is typically made of concrete, brick, stone, and tile, absorbs heat from the sun during the heating season and from warm indoor air during the cooling season. While water and phase change products are more effective at storing heat than other thermal mass materials, masonry has the advantage of serving as both a structural and/or finishing material. The thermal mass present in drywall and household furnishings may be adequate in well-insulated homes in mild regions, negating the need for extra thermal storage materials. Make sure that nothing blocks the sun from reaching thermal mass materials.

• Distribution systems Conduction, convection, and radiation are the methods used to move solar heat from the location where it is gathered and stored to other parts of the house. Small fans and blowers can assist spread heat in some homes. When two items in direct contact with each other transfer heat through conduction, like when your bare feet are warmed by a sun-heated floor, for example. Passive solar homes frequently use convection to move air from warmer locations — a sunspace, for example — into the rest of the house. Convection is the transmission of heat through a fluid like air or water. When you stand next to a wood stove or a sunny window and feel the warmth of it on your skin, that is radiation. Darker colors are preferable for thermal mass in passive solar dwellings since they absorb more heat than lighter hues do.

• Control techniques. Summer shade can be provided for vertical south windows by correctly sized roof overhangs. Others include operable vents and dampers that permit or restrict heat flow, operable low-emissivity blinds, operable insulating shutters, and awnings. Electronic sensing devices, such as a differential thermostat that instructs a fan to switch on, are also used in other control strategies.

Developing the Concept

Though conceptually straightforward, a successful passive solar housing necessitates the balancing of many little features and variables. An expert designer can simulate the specifics of a passive solar home in many configurations using a computer model until the design suits the site as well as the owner’s budget, aesthetic preferences, and performance needs.

The designer will take into account a number of factors, including:

• Airtightness and insulation.
• Location of windows, glazing types, and window coverings.
• The type and placement of thermal mass.
• Systems for additional heating and cooling.

These components will be utilized by the designer using direct gain, indirect gain, and isolated gain passive solar design strategies.

Specific Gain

Through south-facing windows, sunlight enters the home and strikes brick walls and/or floors, absorbing and storing solar heat. This is known as a direct gain design. The thermal mass transfers heat into the home as the room cools during the night.

To capture and store solar heat, some home builders and owners place water-filled containers inside the living area. Although water thermal storage requires carefully planned structural support, it may store twice as much heat per cubic foot than masonry materials. If the building can handle the weight, water thermal storage has the benefit of being able to be put in an existing residence.

Reverse Gain (Trombe Wall)

The thermal storage of an indirect-gain passive solar home is located between the living areas and the south-facing windows. A Trombe wall is the commonest indirect-gain strategy.
On the south side of a house, there is a masonry wall that is 8 to 16 inches thick. Solar heat is absorbed by a single or double layer of glass installed one inch or less in front of a dark wall, which is then stored in the mass of the wall. Through the wall, the heat radiates into the living area. The heat absorbed on the exterior of an 8-inch thick concrete wall at noon will enter the inner living space at around 8 p.m. because heat moves through masonry walls at an average rate of one inch per hour.

Undiluted Gain (Sunspaces)

A sunspace that may be partitioned off from the house by doors, windows, and other operable openings is the most popular isolated-gain passive solar home design. A sunspace can be incorporated into the design of a new home or added onto an existing one. It is also referred to as a sunroom, solar room, or solarium.

Not to be mistaken with greenhouses, which are used to cultivate plants, are sunspaces. Sunspaces have three major purposes: they offer supplemental heating, a sunny location for plant growth, and a comfortable living environment. These three functions need very distinct design considerations, thus serving them all necessitates making concessions.

Designing a Passive Solar Home for Summer Comfort

In addition to planning for winter heating, seasoned passive solar home designers also consider summer comfort. A careful design and placement are necessary for a passive solar home, and these factors depend on the local climate.

In the majority of regions, blocking summer solar heat gain will need the use of an overhang or other structures like awnings, shutters, and trellises. Additionally, landscaping can contribute to the comfort of your passive solar home throughout the cooling season. Consult an architect experienced in passive solar design if you’re thinking about using it for a new house or a significant remodel.