When deciding to build a home or place a modular/mobile home on a site, it is most common to orient it to the road or entrance. This makes the curb appeal as high as possible.; most housing developments utilize this approach. Although it may provide for a visually appealing or space efficient layout, more often than not this orientation will not provide the most energy-efficient setup. Orienting your home and its interior layout properly can save anywhere from 10-40% of energy costs. That is by far the most cost-effective energy option, and the initial cost is ZERO!
Magnetic South vs Solar South
Before we get into the nitty-gritty of orienting a home to reap the solar benefits, one must understand the difference between magnetic south and solar (or true) south. A compass will point to magnetic south. Due to the molten core of the Earth moving around, along with ore deposits in the Earth’s crust, one must factor in variation to determine true south. The NOAA (National Oceanic and Atmospheric Administration) provides a great calculator for finding this variation; look at the value for solar declination. This value is the difference between true south and magnetic south. You want your home to follow the true directions, not the magnetic directions.
For a more low-tech approach, you can go on-site on a clear night, and follow some simple steps to find true north. This in turn will give you true south. Follow these steps:
- Wait for a clear sky with the stars easily visible. Identify the North Star. For help with this, check out this guide from SurvivalTopics.com.
- Pound a 4’-5’ post into the ground, approximately in the area of where you want to build.
- Stand 50’ back from the post in the general direction of south, and, kneeling down, sight the North Star just over the top of the post. Move left to right to line up the post and the star.
- Once you have them lined up vertically, pound another post where you are standing
- The orientation from the 1st post to the 2nd post will give you a pretty accurate idea of true south and is a good reference for orienting your home.
Calculating True North from Magnetic North Using a Compass Rose
The compass rose shown here from a nautical chart gives an example of the difference between true and magnetic north. The outer ring of the rose depicts true north, while the inner ring is magnetic north.
In this case the variation is 4º15’ W with an annual decrease of 8’. The rose was printed in 1985 so we need to run some calculations to determine the current variation. See below for how to do this.
First calculate the difference in years from the current year and when the rose was printed:
2014 – 1985 = 29 yrs
Now multiply the difference in years by the annual decrease:
29yrs × 8’= 232′ of variation
Convert this number of minutes to degrees by dividing by 60 (60 minutes in 1 degree):
232′ ÷ 60′ = 3.867º
Now convert the decimal degrees to degrees minutes:
0.867 x 60 = 52′ which equates to 3º52′ annual decrease
Lastly, take the variation for the area, and subtract the annual decrease we calculated:
4º15′ Variation – 3º52′ Total Decrease = 0º 23′ W Total Variation
Once true south is found, out we can begin figuring out which way to orient the home. Typically, a rectangular home is the most advantageous shape, with the longer side in an east/west orientation. By putting a large number of windows in the south wall, a home will reap the maximum amount of solar gain; these windows will be facing the sun throughout the day.
One feature to include in the home design is extended overhangs, especially on this southern facing wall. The overhangs will block the hot summer sun as it travels high in the sky, but they will allow the light through the windows in the winter. By not letting this sun in, the thermal mass of the home is not rising. Therefore, it will need less cooling via mechanical means. In the winter when the sun is low and is able to sneak under the overhangs, the light will heat up the home and reduce the need for mechanical heat input. One step further is to utilize stone, tile or concrete floors in these southern rooms for maximum thermal mass impact.
To get the most out of orienting your home this way, designers try to arrange the interior layout in conjunction with the sun’s daily travels. Dark spaces such as closets and garages are placed on the northern side of the home. A common example is the placement of the master bedroom/bathroom on the east side of the home with windows facing east. Traveling from east to west, the next room is the kitchen, with southern facing windows. A living room or den follows, with both southern and western facing windows, along with any guest rooms facing west as well. One can see how, as the sun moves across that southern wall, there is an attempt to have the sun light up the rooms that would be most commonly at certain times of the day. Natural light reduces the need for energy consuming light bulbs, and it also has positive effects on your health.
UCLA has created a great, free calculator application that can be downloaded to help analyze passive solar information for your home. Spend some time playing with it; the data it provides can be invaluable.
HEED: Home Energy Efficient Design Calculator
Orienting your home along the sun’s path is the most important factor, but with some clever designs one can also harness the natural wind patterns for cooling breezes in the summer. Be sure to include opening windows or doors on opposing sides of the home that run parallel with the normal wind direction in your area. Having windows that can open at the top of a vaulted ceiling (similar to the setup in the picture above) will allow the rising, warm air in the home to vent out as cool, breezy air enters the home.
Window Quantity and Quality
The last thing to factor into your home design is the quantity and quality of the windows. There is a delicate balance between having enough windows but not so many that you overheat in the summer or overcool in the winter. The number of windows actually needed is probably less than one might think. To properly know, it is recommended that an engineer do the necessary calculations factoring in location, build materials of the home, window quality, etc.
Speaking to quality, windows come in a wide variety of materials and features. Some of these features are more cost-effective than others, and proper diligence should be used when determining what to use. One option that is mostly standard these days is to use double-glazed, or dual-pane, windows. These windows use two panes of glass with a sealed space between them to create an insulating effect. Also available are features like triple-glazed, argon-filled and Low E glazing. Each of these features has their own merits and needs to be weighed against their cost; their actual effects on the home may be minimal compared to their costs. If the cost to add one of these features won’t actually give you a good return on efficiency, there is no sense spending money that could otherwise be spent on extra insulation, solar power equipment or be kept in your bank account.
Hopefully this post has opened your eyes to some of the simple things that can be done with design and orienting your home. These steps can give your house a unique look and feel, while also saving you lots of money heating or cooling your home The principles outlined here should be researched thoroughly, and should be vetted by engineers or experts in the field of passive solar design. As always, be sure to check out other posts on Land University for great information on living off the grid and setting up utilities for your home.