How much skin do you have in the game? Having “skin in the game” is good for business deals, but not for homes. In home design, “skin” is another name for the shell of the building (i.e. exterior walls, roofs and floors). This is a classic example of “Less is More”, but why is this true, why does it matter?
There are at least 3 primary reasons:
1. The first reason is easily illustrated by an analogy to the human body. The more your skin is exposed to the elements, the more uncomfortable you are, and the more energy you expend trying to remain comfortable. Anyone that steps outside to get the newspaper on a cold day or hot sunny one, is painfully aware of this reality. A home is no different except its skin is exposed to the elements ALL the time.
Therefore, with other design attributes being equal, a home with more skin will cost more to heat and cool than one with less skin.
2. A home with more skin is more expensive to build and maintain, since the skin represents an expensive assembly of structural framing, insulation, water, and weather barriers. The skin of the home has always been a relatively expensive part of the assembly, but with the need for energy efficiency, the building science of the home skin has gotten more complex, making it even more expensive to design, build, and maintain properly.
3. When you reduce the amount of building skin you also reduce the size of your home’s footprint. This allows you to have a more spacious yard, which is especially helpful on small lots that are common in the city.
To compare apples to apples, it is most helpful to look at the ratio of skin to usable square footage. The ratio of skin to number of bedrooms is another interesting comparison, but perhaps more on that in a later blog.
Consider these three homes, the smaller the number, the better the ratio.
Skin to usable floor area ratio = 3.0
Skin to bedroom ratio = 1722
Graphics by Marcelo Valdes
Skin to usable floor area ratio = 2.4
Skin to bedroom ratio = 1240
Graphics by Marcelo Valdes
Skin to usable floor area ratio = 1.8
Skin to bedroom ratio = 1190
Graphics by Marcelo Valdes
3 general categories of home massing are represented by these examples:
- A = single story.
- B = combination of 1 and 2 stories
- C = full 2 stories.
If you analyzed more home shapes within any one of these categories, you will find that the closer the house footprint is to a square shape, the better the ratio. Also, unless the shape of the floor plan is an extremely irregular shape, the ratio within any one category does not change significantly as the house shape changes.
Does this bring to mind any known house form? If you are familiar with existing housing stock, you are probably thinking the American Four Square, and you are right!
Here is a classic example located in St. Charles, MN dating to the early 1900’s.
This is an example of a more contemporary approach to a 4 Square designed by Dale Mulfinger.
Any good architect knows that different topography, homeowner lifestyle, accessibility needs, climate, and views are just some of the design considerations that also influence the optimal home shape on any given project. These typically add complexity to home shapes, so starting your planning with a more simple form can often be a good approach. As you can see in this ad from 1910, some of these designs are tried-and-true (and go up in value!)
The biggest lesson in all of this is that when planning your house, if you want to keep as much skin out of the game as possible, you should divide your space needs into two or three relatively equal groups that can be stacked into a 2 or 3 story mass. This will put you on the path to the most efficient, cost effective, sustainable house possible, and all without compromising daylight, views or natural ventilation.
Marc Sloot has an extensive background in sustainable design and is currently the Minnesota GreenStar Board President. For more information on Minnesota Green Star and the process of design that includes an emphasis on sustainability, read an interview with Marc HERE. To see more of Marc's sustainable research and experience put to use on projects, visit his profile page!