Building Science 101: How size & shape impact home performance
Custom designed home by BrightBuilt Home.
Keep it simple
By Parlin Meyer
Photos: C.A. Smith Photography
MINIMIZING ENVIRONMENTAL impact has become a paramount objective for designers, builders, and homeowners alike. While intricate designs and complex structures may initially captivate the eye, simplicity holds the key to unlocking the true potential of sustainable living. Not only do simple structures lend themselves to high performance design, but they can also be aesthetically appealing, celebrating the beauty of clean lines. Let’s delve into the significance of structural simplicity when designing a green home and explore the benefits it offers in terms of energy efficiency, resource conservation and long-term sustainability.
Great Diamond design by BrightBuilt Home.
STRUCTURAL SIMPLICITY
A structure that is simpler will have fewer opportunities for failure than one that is more complex. In the context of a green home, failure primarily means air and/or water leaks. The more transitions a home has, such as corners and connections between the walls and roof, the more likely it is that unwanted water and air will be able to enter your home. Implications related to water leaks can be substantial, including water damage, mold and insect infestation. Air leakage is a concern when building green homes because when warm air inside escapes to the colder outside air, mechanical systems have to work harder to maintain the desired temperature. The same is true when warm air comes into the house in summer, and cooling systems have to run more frequently. This leads to more energy consumption, higher utility bills and a bigger environmental footprint.
To reduce air leakage, the exterior of a green home should have no more than three to four roof planes and six to eight corners. To put that in visual terms, a cube or rectangle has four corners, an L-shaped building has six, and a U-shaped building has eight. Additional features like dormers and bay windows add more corners and roof planes, adding complexity and increasing the chance that warm air will leak out of—or into—your home.
It’s worth noting that simpler structures also cost less to build because fewer materials are required. You not only get the benefits of long-term savings from less energy consumption, but you also save on construction costs.
SURFACE AREA-TO-VOLUME RATIO
In addition to the number of surfaces, the surface-area-to-volume ratio is an important consideration when building a green home. The more surface area a home has—the total area of the exterior walls, roof, and floors—the more opportunity there is for heat to escape or enter. Thus, the higher the ratio, the greater the risk of loss.
The geometric shape that has the minimum surface-area-to-volume ratio is a sphere, but that’s hardly practical for a house. A cube is the most reasonable, compact shape for a home to minimize heat transfer.
Of course, other factors come into play, such as optimizing glass area on the south-facing wall and ensuring that sufficient light can penetrate to the interior spaces, often making a rectangular shape more desirable than a cube. Plus, sloped roofs make more sense in regions that receive a lot of snow, such as New England.
The key is to strike the right balance between all of these factors to produce a green home that’s right for you and your building site. An architect with a background in green building can use sophisticated modeling tools to calculate how adjusting various factors, including surface area and volume, will impact the performance of the building.
To illustrate why this metric is so important, consider two shapes that have the same volume but a very different surface area (as shown in the illustration on the right). Both a 10’ x 10’ x 10’ cube and a 10’ x 50’ x 2’ rectangle have a volume of 1,000 cubic feet, but the surface area is quite different. The cube’s surface area is 600 square feet, and the rectangle’s is 1,240 square feet. That’s more than twice the opportunity for heat loss on the rectangular building. The rectangle in this example also requires more building materials for the walls, roof, slab, and flooring, which translates to higher building costs.
MATERIAL CONSERVATION AND LIFECYCLE SUSTAINABILITY
Designing green homes with simplicity in mind allows for efficient use of building materials. By focusing on essential features and minimizing excess, designers can curtail resource consumption during both construction and operation phases. Fewer materials are needed for construction, leading to reduced environmental impact. Additionally, simplified designs often result in less waste generated during the building process (particularly for modular construction), contributing to a more sustainable construction industry.
A well thought out simplified structure also enhances a green home’s long-term sustainability by facilitating adaptability and resilience. With a flexible design, homeowners can easily modify or expand their living spaces without significant structural modifications. This adaptability minimizes the need for new construction and reduces the overall environmental footprint. Steering clear of complex and bespoke features in design thus enhances the durability and longevity of the building, ensuring its continued functionality and reducing the need for frequent renovations or replacements.
Simplicity in green home design can enhance visual appeal by creating clean, harmonious spaces that complement the natural environment. There are many other opportunities to incorporate unique design features without modifying the simple shape of the home; examples include decks, porches or large banks of southerly facing windows. A minimalist approach to design aligns with the principles of biophilic design, which promotes a connection between occupants and nature. By incorporating ample natural light, using sustainable materials and creating spaces that evoke a sense of tranquility, the right designer can create a green home that is both visually pleasing and ecologically sound.
Simplicity is key to sustainability. By embracing the design advantages and opportunities in simplicity, designers have an opportunity to maximize a home’s value and longevity, and minimize its impact.
This article appeared in the Fall 2023 edition of Green & Healthy Maine HOMES. Subscribe today!
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