The Most Efficient Building Form

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By Mark Lundegren


Do you wonder if common building forms or approaches are the most efficient possible?

Since much of architecture and design today, as in the past, is concerned with aesthetics, norms, status, expression, and therefore communication, you may suspect the answer is no, and even strongly no.

But before you answer, let me point out that when we think of form or design efficiency, we can mean more than the direct costs or immediate resources and energy involved in constructing and using buildings, along with the larger settings they create in combination, as important as this is to determining efficiency.

In a complementary and informing way, we also can consider the indirect costs of buildings and developed areas. This crucial but less obvious category of costs or efficiency factors is often substantially overlooked, taken as separate from or beyond the scope of building and development, or expediently treated as “free” to some degree – thereby becoming externalities, or public or unborn costs, in the terminology of economists.

Importantly, indirect building and development costs can be as significant as direct ones. They include the often unexamined costs of pollution, dislocation, future inflexibility, sprawl, resource degradation, eventual obsolescence, and the potential for blight. As a practical matter, such indirect and commonly overlooked costs are essential to understanding the true cost, and thus the true efficiency, of any design, building, or developed area.

Fortunately, we can simplify this complex topic for a general discussion by recognizing that two basic design principles or features often substantially predict both types of costs, and thus the general efficiency of building and development. The first of these principles is that development, buildings, and spaces that are more compact or reduced in scope will tend to be less resource-intensive, less costly overall, and therefore more efficient, as long as they meet essential needs or are effective solutions overall.

The second principle is that buildings, infrastructure, and material inputs using renewable resources – and failing this, readily recyclable or reusable ones – will tend to be less costly and more efficient overall as well, by often producing fewer externalities or indirect costs for others to contend with in time. There are of course exceptions to these two rules. But overall, it is a much more difficult general case to advocate for expansive and non-renewable building and development on efficiency grounds, even as this is still our most common approach to building today.

With these ideas in mind, let’s examine a few instructive studies in or candidates for the most efficient building form possible, notably by looking at: 1) available building profiles or basic shapes, 2) possible plans, layouts, or distributions of buildings, and 3) the potential for solar energy collection or production by buildings and developed areas (click to enlarge each exhibit).

Efficiency of Building Shapes

For our first study, examining building profiles, or their basic shape or street view, I have begun with the sphere in my first exhibit. As you likely know, this shape is naturally or geometrically the most efficient in terms of minimizing surface area for a given volume, and thus can be relatively efficient in terms of enclosing interior space, and heating and cooling space too.

But spheres and their variations suffer from natural drawbacks or inefficiencies, on the earth or water, and even in space. They of course are naturally likely to roll and thus require steadying, can be difficult or intricate to build unless constructed monolithically or geodesically, and often require extra effort or otherwise prove inefficient to partition, furnish, equip, and modify for human use.

Solving some of these natural inefficiencies are the next two forms in the exhibit, domed and arched-shaped buildings. These shapes are also very efficient in terms of surface to volume ratio, and as with spheres, are often superior when seeking to span large areas and enclose space homogeneously. But the two forms similarly can be less practical and efficient for many applications. Domes and arches also frequently waste or leave unusable internal space, and often prove less effective as overall solutions for modern and generally rectilinear human living.

These issues lead us to the square or rectangular building profiles that are the mainstay of settled human life, and also notably to the hybrid form that is the cylindrically shaped building (which generally blends the advantages and disadvantages of curved and rectangular forms). Overall, rectilinear building forms are less efficient from a surface-to-volume standpoint and are naturally weaker structurally than spheres, domes, and arches, but they can be much simpler and thus more efficient to build and use in many cases (again excepting buildings requiring large spans and having homogeneous interiors).

Importantly, square and rectangular forms also can be much easier, or more efficient, to modify, expand, or adapt over time than spherical and curved structures, and this is likely a crucial driver of their ubiquity in human life. However, one important disadvantage of perfectly rectilinear buildings is their flat roofline, a widely unnatural and inefficient approach to providing shelter from precipitation. In practice, this drawback of course is mitigated via the use of special materials and pitched roofs of various slopes – which we can view as variations on or extensions of basic rectilinear forms, as I have indicated in the exhibit.

Efficiency of Development Plans

Our second study moves from considering the efficiency of basic building shapes or profiles to that of overall building distributions, or the general organizing plans, layouts, or top-down views of buildings and developed areas. As the first graphic in the second exhibit highlights, round, spherical, and cylindrical buildings, rooms, and other spaces are most efficiently planned in an alternating honeycomb format, though this still leaves significant unused space between buildings, even when they touch.

As you can see in the next graphic in the exhibit, one solution to this natural inefficiency is to use hexagonal or other tiling polygons for building plans, which reduce unused exterior space and also have a natural beauty or aesthetic appeal. But this approach suffers from many of the drawbacks of spherical and cylindrical buildings mentioned above – including potential added complexity of construction and frequent interior spatial mismatches for many applications. In addition, the lack of direct or straight entry and exit from hexagonal and similar grids may disadvantage them from an efficiency of access and use standpoint in many applications (though this feature can advantage them in others, as I will touch on).

Once again, these natural trade-offs bring us to the ubiquitous human form that is the rectilinear building plan and larger grid layout, whether buildings are square or rectangular, along with potential variations such as triangular grids (but which have many of the same properties as hexagonal and other non-square grid patterns). Overall, rectilinear grids often waste less space both inside and outside of buildings, and thus can be more spatially efficient across many human applications. But one disadvantage of rectilinear and similar grids is that they can be too regimented or belittling experientially, and thereby emotionally unappealing or unsettling. That is, they may be aesthetically inefficient amid their practical and geometric efficiency.

As shown in the last graphic in the second exhibit, a solution to this aesthetic, emotional, or experiential limitation is to alternate, honeycomb, or otherwise stagger rectilinear buildings in one plan or layout dimension. This has the effect of reducing access efficiency somewhat, but can produce a more effective solution overall in many applications, including the development of neighborhoods and other intimate public, semi-public, and private spaces.

Efficiency of Energy Production

Our third study considers building profiles and layouts in combination – in street, side, or profile view once again – and in particular, resulting opportunities for solar energy collection or production. Owing to this, it therefore considers the potential for transformative modern building efficiency from new design profiles and layouts, even to the point where buildings might produce or capture more energy than is consumed in their construction and use.

Intuitively, and as the first two graphics in the third exhibit illustrate, any building will cast an amount of shadow in sunlight, and of course in proportion to its overall shape, size, and height. When buildings require no energy input or benefit from shade, such shadowing is not a problem or source of inefficiency, and even may result in efficiency gains.

However, if we wish to collect solar energy along the sides or walls of buildings, this will necessitate a wider distribution or layout of buildings, spaces, or building elements than might otherwise be the case. In other words, it will involve new optimization of building shape and layout based on the relative efficiency benefits afforded by compactness on one hand and renewability considerations on the other.

As shown in the second pair of graphics in the exhibit, a natural solution to the problem of unwelcome shading from plan compactness is to design for solar collection on the tops of buildings only (roofs and upper walls). This approach allows for close placement of buildings without the unwelcome shading of solar collectors, and also with perhaps beneficial shading of building walls in warm climates, but it does require relatively uniform or otherwise sun-friendly building profiles overall.

Depending on building energy demands, limiting solar collection to the tops of buildings may be an ideal solution, but it is clear that building height and occupancy will be limited overall, especially if 100 percent solar power is a goal, and simply given natural spatial constraints. In this approach, and in a way that is still quite unusual today, building height would be primarily determined by rooftop solar gain potential, system efficiency, and expected building energy use patterns, instead of structural or aesthetic considerations.

Key Takeaways

I hope these ideas and analysis are helpful to you, and will help you to explore, pursue, and encourage more optimal natural design and development in its many potential forms.

Provocatively, our discussion suggests three overall efficiency ideals for solar-powered building, leaving aside industrial and other high-span applications: 1) low-rise buildings placed closely together and primarily using rooftop solar collection, 2) mid-rise buildings placed a moderate distance apart, and using roof and wall solar collection, and 3) high-rise structures spaced even more widely apart and also collecting energy on both roofs and walls. Importantly, the ideas we have examined further suggest that rectilinear buildings and rectilinear grids, significantly compacted in shape and layout,  will be most efficient as well – though again, perhaps with the use of partially staggered or honeycombed layouts in some applications to improve aesthetics, appeal, or spatial intimacy.

Of course, there are other factors or application demands, beyond solar energy production and building autonomy, that will determine which building profiles and development formats are best or most efficient in particular cases. But I want to end our discussion by pointing out that much of our traditional and contemporary built environment does not match the above archetypes, and also often is not substantially compact as well. Given this, many historical and ongoing approaches to building and development are likely to prove less efficient and desirable, as we move to greener or more ecologically-friendly development, and especially as we switch to naturally more distributed, decentralized, and thus democratic sun-based energy production.

As you can readily observe, nearly everywhere we look today, we see tall and mid-rise buildings packed closely together, low buildings often far apart and sprawling into the landscape, and similarly wandering and inefficient building shapes, especially in the latter case. There are numerous reasons for these patterns of development, including historical building practices and inherited community zoning practices. But if we are serious about renewable, sustainable, and efficient human building and development, this must change.

I would welcome your comments and questions on this crucial and far-reaching set of design ideas.

Mark Lundegren is the founder of ArchaNatura. 

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