What is the perfect building site for you is highly subjective. Some like windswept mountain tops with dramatic views, others like shady hollows. Some like open fields; others mature woods. Ideally, a house should be designed to fit the building site – or a building site found that is a perfect fit for the house design you have in mind.
In reality, most people have a house design in mind and then try to adapt it to the site they are able to afford. In some cases, this works fine, but it’s good to keep an open mind about changing the house design to truly fit the site. In any event, it is important to know what you are looking for in a building site, what are your top priority must-have’s, and what you would like to have, but can live without.
In selecting a lot, imagine where a house would fit best and where to locate the main rooms, garage, driveway, and yard space. A quick sketch on the site plan will help you visualize this. Making cut-outs to move around can be a big help. Some of the key elements to consider are discussed below:
On many smaller lots, there is little flexibility about siting the house. After accounting for the front and side-yard setbacks, the “buildable envelope” may be pretty tight. If you also needs a well and septic system, these require specific setbacks from property lines and clearances from the house, further limiting your options.
On older lots, check with the town as the lot may be “grandfathered” under more lenient zoning rules in place when the lot was originally subdivided. You can also apply for a variance or special permit (a simpler process) to bend the zoning regulations, but consider this a last resort as the process can be onerous and success is not guaranteed.
Even if the house location is set, you can still decide where to locate each room to get the best views, privacy, sunlight, and breezes. Read on.
BUILDING ON A SLOPE
A gentle slope of 10% (one foot of rise for every 10 feet across) or less is ideal. It simplifies site drainage and is easy to regrade to make a level yard if desired.
Slopes of 15% to 20% are ideal for a walk-out basement, which can be finished for relatively inexpensive living space. Beyond 20%, the slope may start to impact construction costs and may leave you with little level land for lawns and gardens.
The compass orientation of the slope acts similarly to sun exposure, as described above. A south-facing slope is particularly nice in cold climates as it tends to be warmer, and more sunny for more hours than a north-facing slope. An east slope receives more morning sun and a west slope receives more afternoon sun.
Also pay attention to whether the land is upslope or downslope from the road, assuming the lot has road frontage. On an upslope lot, you may be looking over the road at views. A downslope lot may have more privacy, but depending on the topography may feel like it’s in a pit. Also runoff from the road may end up in your yard. Again, spend some time walking the site to get a good feel for what it would be like to like to live there. See also Evaluating Sloped Sites.
Who doesn’t want a sunny house other than vampires and zombies? Anyone with the slightest interest in solar energy would love a gentle south-facing slope for their dream home. Conversely, living on the north side of a steep hill will mean very limited winter sunshine, and in cold climates, snow will remain on the ground for and extra couple of weeks in the spring, essentially making a long winter even longer. Of course, people in hot climates might find extra shade appealing, especially on the west side, where the low afternoon sun can turn any home into a slow cooker.
Sun Angles. To assess the a site’s sun exposure is not difficult, although for a precise analysis you’ll need some basic solar design tools that show sun angles throughout the year. You can do a quick assessment with the chart below, which shows the noontime sun angles throughout the year from the deep South (28° north latitude), to the northern U.S. (44° north latitude). If the winter angle shown is obstructed by tall trees, a hillside, another building, or other obstacle, you won’t get much sunshine at that time. Hardwood trees, which lose their leaves in winter, will allow a good percentage of winter sun to reach the house – the amount depending on the density of trees and branches. Pines and other conifers will block the sun year-round. Spend some time walking around the site at different times of day to get a good feeling for sun exposure.
|South-Facing Sun Angles for the Continental U.S.|
|Latitude||Cities||Sun Angle at Solar Noon*|
|June 21||March 21/Sept. 21||Dec. 21|
|28°||Tampa, San Antonio||85.4°||62.0°||38.6°|
|32°||Dallas, San Diego, Charleston||81.4°||58.0°||34.6°|
|36°||Albequerque, Nashville, Raleigh||77.4°||54.0°||30.6°|
|40°||Pittsburg, Columbus, Salt Lake City||73.4°||50.0°||26.6°|
|44°||Sioux Falls, Bangor||69.4°||46.0°||22.6°|
|* Solar noon is when the sun passes directly overhead, usually within one hour of 12:00pm standard time.|
Fixed Overhangs. The summer sun angle is useful for designing fixed overhangs or awnings to block out the summer sun (see illustration). Because of the high angle of the summer sun, special shading is usually not needed on vertical south-facing glass unless your building has extensive south glazing. Skylights and sloped glass, however, often lead to summer overheating.
Window Placement. Too many home designers and builders ignore the sun exposure when developing a floor plan and locating windows. Everyone loves a bright home with good natural daylighting, which you can maximize with south-facing glass. South-facing glass is also best for passive-solar heating as it receives the most heat gain in winter while naturally rejecting summer heat gain because of the high sun angle. Consider solar exposure when placing rooms and windows and you can have a light-filled home with natural warmth on sunny winter days.
- South Exposure.Whether or not you are designing a solar home, good south exposure is desirable in all but the hottest U.S. climate zones. For passive solar design, the southern exposure from 9 am and 3 pm are most important. To optimize solar gain, windows should be oriented within 15 to 20 degrees of true (solar) south. In a warm climate with significant cooling loads, southeast glass is better than southwest.
South-facing windows will receive the most solar heat gain in winter when the sun is low and in short supply. In summer, the sun is high in the sky at mid-day, so south windows naturally receive less solar gain. With large areas of south-facing glass, you may need the additional protection of overhangs designed to block the summer sun. One caution: Vertical glass is best. Avoid sloped south-facing glass (e.g., in a sunspace), or overuse of south-facing skylights as these are prone to overheat in summer.
In general, the total area south-facing glass should not exceed about 5% to 7% of your house’s floor area unless you use shading and thermal mass to prevent overheating on sunny days. A house with south glass up to 7% of the floor area is considered “sun-tempered”. Passive-solar homes typically have south glass equal to 9% to 12% of the floor area.
In today’s tight, well-insulated homes, too much south glass without adequate shading can cause overheating on sunny days, especially in the spring and fall. A wall of glass can also cause excessive heat loss and a chilly feeling (from radiant cooling) on winter nights. Consult an experienced passive-solar home designer who will factor in climate, glazing type, and insulation levels to come up with a workable design.
- East Exposure. If you’re a morning person, it’s nice to enjoy breakfast near east- or southeast-facing windows. Look for site with unobstructed access to morning sun.
- West Exposure. West-facing windows are the most problematic. These receive a lot of solar heat gain in the late afternoon, when houses tend to be hottest in spring, summer, and fall. I’ve been in houses that overheat from too much west-facing glass in mid-winter. These problems can be controlled to some extent by using the right type of “spectrally selective” glass that blocks much of the solar heat gain. But, unless dramatic west views demand a lot of glass on that side of your house, moderation here is advised.
- North Exposure. Artists appreciate north light for its soft, even lighting quality and lack of glare and harsh shadows. While I wouldn’t overdo it in cold climates, new high-performance glazings allow you to put windows wherever you like without worrying too much about heat loss. On the other hand, if your building site has limited north sun exposure, that should not be a problem since north lighting is rarely direct in our hemisphere.
On a hot summer day, the more wind that blows through your house the better. On a cold winter night, the a blustery wind is less appreciated. Some areas have pretty predictable prevailing winds that you can rely on for summer ventilation. Winter winds are often from a different direction, so you may be able to orient your house and windows to get the best of both worlds. You can get data on local prevailing winds from the National Oceanic and Atmospheric Administration (NOAA) website.
Traditional New England Saltboxes faced their long roof and short walls on the north to shed the winter winds, while the more open two-story south face took advantage of southern summer breezes and winter sunshine.
The same obstructions that block sunlight tend to block winds as well. Again, walk the site to get a feeling for the wind exposure. If you’re down in a hollow, don’t expect a lot of natural ventilation. If you’re on a wind-blasted hilltop, plan to build a very tight shell and minimize the number of windows on the windward side in winter.
A great view of mountains, lakes, or the Golden Gate bridge can cost a bundle. A pleasant view of fields and trees might have to do. On a heavily wooded site, it may be hard to tell what views you’ll have after clearing. I’ve climbed trees, and once climbed on a neighbor’s house to see what I could see from the future second story.
A house design can take advantage of prime views, and minimize not-so-nice views (like a nearby road or collapsing barn) by the strategic placement of windows. If you want the light, but not the view, you can also glass block or windows placed above normal view lines.
Also think about the future. Will that beautiful meadow to your south be a field of cows or a field of condos in five to ten years. Also, remember that trees tend to grow taller over time and may block your cherished view in five years. If the trees are on your land, maybe you can cut or trim them, subject to any restrictions put in place by zoning or protective covenants. If the trees are on your neighbors land, your distant water view could become a treetop view over time as the trees mature.
See also Site Planning Basics