Locating Tiny Houses for Energy Conservation
Part Two: Understanding Solar Geometry
Robert J. Kobet
November 28, 2016
Few things are more important for energy efficiency, effective day lighting and comfort in tiny houses than proper solar orientation. As early as the first century BC, Marcus Vitruvius Pollio’s Ten Books of Architecture chronicled the benefits of correct orientation to the sun. His advocacy of indigenous design and vernacular architecture has enlightened and inspired generations to remain comfortable using passive design strategies long before the advent of mechanical systems.
If properly designed and oriented on the sire, tiny homes can use solar energy effectively. This is because:
- There is usually very little area to passively heat or cool. If the building envelope is energy efficient, passive solar gain can be well utilized as a heat source.
- Tiny homes are typically rectangular in shape, resulting in a narrow “foot print” or floor plate. This benefits day lighting strategies as floor plans are shallow and do not require large window or glass doors to effectively daylight a space.
Conversely, tiny houses must carefully consider the number, type, size and placement of windows and glass doors if a tiny house is going to be a good “solar collector.” This includes:
- Purchasing or building a tiny house with high performance windows and doors that are installed to minimize infiltration around and through them.
- Providing simple shading devices that can moderate the amount of solar gain entering a space. In addition to interior shades, one should consider exterior shading devices, especially in hot climates where day lighting may be desirable, but direct solar gain is not.
- If the design can accommodate them, sliding glass doors offer the advantage of maximum ventilation area and day lighting aperture, as well as clear passage dimensions for exit and entry.
- Tiny homes should be oriented so the long axis is generally east / west. The goal is to position the tiny house so the long walls are facing to the south and north, and the short end walls are facing east and west. Keeping the long, south wall within about 20˚ east or west of true south is ideal. If possible, most glass should face south in climates with heating seasons, and north where cooling is the dominant space conditioning need.
- Solar systems should also be oriented to the south, whether roof or site mounted.
These simple considerations and the design solutions required for effective solar design vary with whether the tiny house is purchased completes, partially completed or built on site.
- Most pre-constructed tiny houses I have seen are designed from the inside out. That is, the challenges of interior layout are paramount, and window and door placement are in response to making the floor plan work. This is not always the best passive solar configuration.
- Tiny houses that are designed to be transported (not site built) are subject to width and height restrictions that limit the use of roof overhangs or shading devices that protrude horizontally. These amenities can be added once the tiny house is located on the site.
- Tiny houses typically are “light mass, quick response” structures that do not have the capability to store incoming solar energy effectively. Tile floors exposed to the winter sun are the most common materials for this purpose.
- Solar photovoltaic and solar thermal systems can be roof or ground mounted. Ground mounting allows larger solar arrays, freedom to orient the arrays independent of the tiny house, the ability to adjust the arrays seasonally, easier maintenance and less chance of roof leaks from system penetrations.
There are many resources to guide the tiny house advocate in scrutinizing the potential of a tiny house for passive solar heating and good day lighting. 84 Lumber and GreenEdge Supply have in house expertise to help you with all of your tiny house questions. Visit us at www.84tinyliving.com or www.greenedgesupply.com or stop by to view our Tiny Houses on display in Eighty Four, PA.