Furthermore, research indicates that the market share of sustainable (green) single-family residential construction is continuing to grow. This includes single-detached houses and single-family dwellings that share one or more walls with another unit.

The National Association of Home Builders’ (NAHB) authoritative SmartMarket Brief: Green Multifamily and Single-Family Homes 2017, indicates that while the market share of single-family homes was a mere 2% in 2005 it had climbed to 33% in 2017 and is set to climb to 38% this year (2019) and to continue climbing to 44% by 2022. The figures for single-family remodelers are similar, climbing from 20% in 2017 to an estimated 35% by 2022.

Affiliated with 700 local and state home builders associations in the U.S., the NAHB undertakes ongoing research relating to green building and sustainability and they report that 80% of home buyers of all ages, from millennials to seniors, are positively influenced by energy-efficient strategies when deciding which property to buy. The most important factors mentioned are above-code insulation, and ENERGY STAR windows and appliances; but there are, of course, many other elements.

NAHB’s most recent report is encouraging. Of the builder respondents committed to sustainability:

  • 88% believed customers appreciated the prospect of getting a better quality product.
  • 76% said it was simply due to customer demand.
  • 73% believed customers recognized the value of sustainable homes.

But what makes a single-family home sustainable, and what do buyers want?

Sustainability of Residential Buildings
Sustainable home buildings operate with reduced carbon emissions, minimize all forms of environmental impact, and promote renewable energy.

A screen shot of the NGBS website.
A screen shot of the NGBS website.

The National Green Building Standard (NGBS) was launched in 2008 and designed to rate and certify residential buildings, including single-family home buildings. There are various other green certification systems including the U.S. Building Council’s Leadership in Energy and Environmental Design (LEED), the U.S. Environmental Protection Agency’s (EPA) ENERGY STAR, and A Net Zero Residential Energy Sector By 2040 (RESNET) HERS, but the NGBS is the only green building rating system for homes that is approved by the American National Standards Institute.

Due the third update in 2020, the NGBS currently has six green practice categories that align with important areas of sustainability.

  1. Site design, preparation, and development, which is where sustainability starts. The aim is to have low-impact development strategies and/or a green infrastructure designed to handle storm events. Transit features are important for townhouses and cluster housing.
  2. Resource efficiency, which involves using required percentages of recycled materials, including precut, precast, and preassembled products. Resource efficiency also embraces size, with smaller homes being potentially more sustainable than larger homes.
  3. Energy efficiency is key to the sustainability of all buildings, including our houses and apartments. In essence, it relates to mechanical systems for heating, ventilation, and air conditioning (HVAC) designed for living spaces and heating of water, as well as cooking and refrigeration, and all the other activities we need power for including washing and drying clothes, dishes. For this reason, the use of ENERGY STAR appliances and fittings is important. Energy efficiency also relates to lighting and incorporates everything from the type of light bulbs used to building design that exploits the use of natural sunlight. Of course, other vital factors that ensure energy-efficiency relate to insulation, fenestration, U-factors, and solar heat gain coefficients for exterior doors, windows, and skylights. Too specialized for the average building owner, these technicalities are usually taken care of by an experienced city, for instance, a New York or Chicago engineering firm that specializes in mechanical, engineering, and plumbing (MEP) designs.
  4. Water efficiency both inside the home and in the yard. This incorporates the used of low-flow showerheads, energy-efficient appliances, including washing machines and dishwashers, and irrigation control systems. The use of gray or recycled water and harvesting of rainwater adds to the sustainability of the dwelling. Water for fire protection systems and automatic sprinklers are other elements that need to be carefully considered in terms of sustainability.
  5. Indoor environmental quality, which includes air quality (including return ducts in parking garages and air handling equipment), heating, and cooling. It also relates to the need for avoidance of building materials including paints, adhesives, sealants, and so on that contain volatile organic compounds (VOCs).
  6. The operation, maintenance, and education of building owners.

The most recent version of the regularly updated NAHB book, What Home Buyers Really Want, reveals that energy-saving features and whole-house certification are hugely important to home buyers. Based on a survey of about 4,000 home buyers, it also shows that people are downscaling in size and reducing their demand for upscale features like three-car garages. Instead of focusing on curb appeal, most respondents (63%) wanted a home that utilizes passive solar design for both cooling and heating. A relatively large percent (32) said they were concerned about the environment but admitted it wouldn’t affect their home purchase. A larger percentage (36) wanted a sustainable, eco-friendly home, but weren’t prepared to pay a higher cost. Only 14% were prepared to pay more – slightly less than the 18% who didn’t have any environmental concerns.

Strategies for Sustainable Single-Family Homes

CINDY SHEBLEY / Courtesy Adobe Stock/CloverCity
CINDY SHEBLEY / Courtesy Adobe Stock/CloverCity

The strategies required to make single-family homes sustainable are no different from those employed for other residential buildings, or indeed commercial or industrial buildings.

There is absolutely no doubt that energy-efficiency ranks right at the top in terms of expectations, and with good reason. More and more people are recognizing the need for a healthier indoor environment, so this is also of vital importance, as is the need for homes to be resilient and durable. Single-family respondents included in the NAHB SmartMarket report ranked these top three practices 95%, 63%, and 50% respectively. Feedback relating to multifamily residents shows a lower percentage (90%, 52%, and 31%) probably because these are more likely to be commercial properties that generate an income for owners. On the other hand, most single-home owners regard their houses as the biggest investment they will ever make.

Other important strategies include the efficient use of natural resources, water efficiency, and a reduced carbon footprint – an element that cannot be ignored.

Additionally, the use of all types of renewable technology continues to grow, particularly solar photovoltaics and ground-source heat exchange, both of which are being used by about 25% of single-family home builders. As demand increases, costs are beginning to decrease, helping to drive the goal towards net-zero homes. Wind power hasn’t been embraced by owners of single-family homes, for obvious reasons, primarily cost and logistics.

An NAHB Green Practices Survey undertaken in 2017 shows that resource efficiency and the site or lot design are currently the most challenging aspects of maintaining sustainable building practices. This has a direct effect on eligibility for certification in terms of the NGBS.

The Cost of Sustainable Building
One of the greatest challenges for green building is the perception (by consumers) that it involves higher upfront costs compared to conventional buildings, particularly in terms of building materials and fittings. Other factors relate to additional time and costs required for research, training, documentation, and design by all professionals including those offering HVAC engineering services in Chicago, New York, London, Paris, and all the other big cities worldwide.

There is also a perception in some parts of the world, including the United Kingdom and Australia, that a green approach is only suitable for high-end projects, probably because of the perceived cost factor.

Additionally, the NAHB report identified a very important shift in the market that shows 30% of single-family home builders and remodelers who identified themselves as “dedicated green builders” who were committed to sustainability had lower incremental costs. Only 15% of those who had less commitment achieved lower costs. What this clearly means is that an increase in experience will inevitably lead to lower costs.

Whether customers will pay a higher price for sustainable homes is a moot point, but 91% of dedicated “green” single-family builders believe they will, presuming the premium increase is only between 5% and 10%. Most don’t believe customers will be willing to pay more than this.

There doesn’t seem to be any single factor that drives demand for sustainable housing, but there is agreement among single-family builders and remodelers that when it comes to marketing, the terms operating efficiency and long-term utility cost savings are the most effective. Buyers also respond well to reference to healthier homes, quality construction, and high performance. Perhaps ironically, the term sustainable is the least effective!

Now the challenge is to encourage more single-family home builders to build net-zero ready homes that meet the building envelope performance and other standards required to meet the upcoming goals of zero carbon emissions globally.