“A lie gets halfway around the world before the truth has a chance to get its pants on.” --Winston Churchill
Economics of Passive Solar
Solar energy is harnessed, converted and distributed using a range of ever-evolving technologies and strategies. Passive solar energy is characterized by building orientation, strategies that integrate the house with its climatic environment, and materials that have favorable thermal mass.
Although passive solar building principles are based on science and a variety of lessons learned through the years – they aren’t necessarily expensive. Passive solar construction costs can vary from no additional cost, to a little more than conventional construction to considerably more. Many forms of passive solar energy are economical because of the large savings of utility bills that can be achieved - typically in the 50 percent to 70 percent range.
Unlike “traditional” construction, it takes more thought to design with the sun’s location in mind; however, passive solar features such as additional south-facing windows, added thermal mass, larger roof overhangs, or other shading features can easily pay for themselves. In fact some modest passive solar designs like sun tempering, a design fit for cold climates, can reduce heating costs from 5 percent to 25 percent at no added cost to the construction budget.
Since passive solar designs require substantially less mechanical heating and cooling capacity, costs of the design can be offset by reduced unit size, and by reduced installation, operation, and maintenance costs. Overall, passive solar homes are often less expensive for the homeowner when the lower annual energy and maintenance costs are factored in over the life of the building.
If you are designing a new home, consider passive solar design as it is usually much more cost-effective to reduce energy use with passive solar design than it is to pay for that energy use with other forms of energy (including solar electricity).
For more information:
Passive Solar Case Study (by U.S. Department of Energy) – General Daylighting
- Daylighting—the use of windows or skylights for natural lighting and temperature regulation—is one passive solar building strategy that can save money for homeowners and businesses.
Passive Solar Case Study (by Homes Across America Program) -- Harmony Home, Flagstaff, AZ (Cost -- $200 per square foot)
- Orientation for Solar Energy Systems: The home was oriented to capture maximum solar gain to the south while maintaining views to the north.
- Orientation for Daylighting: The orientation of this single-story home with the long edge toward south and careful placement of rooms (with eastern windows) within provides ample daylighting throughout. The daylighting requirements are practically zero during daylight hours.
- Window Sizing, Location and Shading: A conflict between solar gain to the south and great views to the north was overcome with design, which carefully placed rooms to ensure all had a view as well as solar exposure. Maximum windows were installed on the southern side of the home. Windows on the north were minimized but placement allows the view to be seen from any point in a room. A roof overhang was selected to block excessive summer sun from the windows, while allowing winter sun to enter the home.
- Thermal Mass: Heat radiates from the colored concrete floors (with tile inlay), which provide thermal mass to complete the passive solar design.
Passive Solar Case Study (by Homes Across America Program) – Hopi Nation Straw Bale House, Hotevilla, AZ (Cost -- $60 per square foot)
- Straw Bale: An affordable and energy-efficient building material.
- Thermal Mass: A radiant floor heating system in the slab is augmented by passive solar. The slab acts as a thermal mass.
Passive Solar Case Study (by Homes Across America Program) – Southwest Solar, Prescott, AZ (Cost -- $175 per square foot)
- Building Envelope: This home/office was built into the hillside and uses the earth to insulate against heat and cold. A well-insulated roof reduces heating in summer while conserving heat in the winter.
- Thermal Mass: The passive/active space heating and cooling utilizes 300 tons of building mass as heat/cool storage. The mass is created using poured earth walls that utilize local soils.
- Attached Solar Greenhouse: A solar greenhouse heats the main living area from below while providing an environment for growing food.
Passive Solar Case Study (by Homes Across America Program) – The S.E.E.D. (The Super Energy Efficient Design) Home, Tucson, AZ (Cost -- $150 per square foot)
- Structural Framing: Exterior walls and roof are made of polyurethane foam core SIPS (structural insulated panels). This allows for solid and continuous foam core resulting in an R34 exterior wall. The roof is an R41.
- Roof: Standard Built Up Roofing system with Energy Star rated white roof coating.