Passive Solar Home Design
Passive Solar Design consists of architectural elements such as windows and building layouts that seek to take advantage of sunlight in order to heat or power a building. Collection, storage, and use of the sun's heat reduces energy bills and carbon emissions from more traditional energy sources.
Types
There are three different ways to approach passive solar design. Direct Gain allows sun to directly penetrate a building via windows and uses heat absorbing materials to soak up the ambient warmth. Indirect Gain absorbs sunlight and stores it for later use, but does not allow for any direct access into a building. Isolated Gain concentrates heat to a specific area of the living space and elements are often stored apart from the main building structure.
General Passive Design Rules
Optimal passive design relies on a south facing building that receives direct sun during the day and installation of windows on the south side to maximize passive heat collection. Buildings should also be built in more of a rectangular shape to provide additional south facing space. Floor plans should be open to allow for free flow of air and even heat distribution. Sloping roofs will limit heat loss from northern walls of a building.
Direct Gain
Direct Gain passive solar design uses livable space as a solar collector and will convert between 60% to 75% of the sun's energy into usable heat. Direct Gain relies on multiple windows and heat absorbing construction materials, such as concrete walls or floors, to collect the sun's heat. Direct Gain design precludes the use of carpet since concrete must be exposed to absorb heat. In general, for each square foot of south facing glass, 150 pounds of concrete will be used.
Indirect Gain
Indirect gain passive solar design collects the sun's heat outside of the living space and then conducts it where desired. This method of passive solar design uses between 30 to 45% of the sun's heat. Trombe walls, solar panels, and roof ponds are examples of indirect passive design methods. Roof Ponds use 6 to 12 inches of water on the roof and word best in regions with low humidity. Trombe walls use thick wall construction to store heat and vents to distribute it and solar panels use sunlight to give silicon an electric charge which generates heat or electricity.
Isolated Gain
Isolated Gain refers to passive solar design where heat collection is focused on one specific area apart from the main living space. A sun room is an example of Isolated Gain solar collection and so is a closed system that uses water to collect heat outside a building and then move heated water inside. Isolated Gain utilizes just 15 to 30% of the sun's energy. Sunrooms should be vented and built with appropriate wall thickness to maximize heat absorption.
