The Goldilocks Effect: Getting Sustainable Systems “Just Right”

by Matt Woo, P.E., RCDD, LEED AP BD+C

This article is part of Wood Harbinger’s newsletter series.

A sustainable or green building designation means that the structure and the systems within it are designed to be environmentally responsible and resource-efficient throughout the building’s entire life-cycle: from siting to design, construction, operation, maintenance, renovation, and demolition. Whether new construction or a renovation project, sustainable buildings should include systems that are long-lasting; flexible for future additions and use changes; applicable to the facility’s function; and correctly sized to meet current and future demand; and avoid wasted cost, under-utilization, and inefficient operation. A “right-sized” approach finds the correct balance between building use, system performance, and environmental responsibility in order to meet building demand requirements, while not affecting user productivity and comfort or creating negative impacts on the environment. This requires close collaboration between the owner, design team, and construction team through all stages of a project. A well-designed, sustainable building achieves this balance between all building life cycle elements, including economy, utility, durability, and comfort.

Weighing Options

We’ve talked about the general benefits of some of the most popular sustainable system choices in previous articles. Here, we’ll explore “right sizing” of these systems, looking at how the benefits apply to various scenarios and when these systems might not work or be worth it.


We’ve talked about the important role that lighting plays in our health, wellness, and productivity and the many benefits of LEDs. The strongest selling point for LEDs is that they are universally beneficial, as they are readily available for most all interior and exterior lighting applications and are an easy, cost-effective retrofit upgrade for existing building fluorescent lighting. Almost all of Wood Harbinger’s recent project experience includes use of LEDs—the new SR-520 floating bridge systems and even theatre lighting systems we designed for an elementary school’s multi-purpose space. Whether for full-building retrofits or small-scale applications, LED works well and increases energy efficiency. We use it for ambient lighting, task lighting, architectural lighting, and industrial lighting.

Ground or Water Source Heat Pumps

As my colleague Jeff has shared before, a ground-source heat pump system is considered a renewable resource by the State of Washington for Energy Life Cycle Cost Analysis (ELCCA) purposes. The system takes advantage of the temperature consistency of below-ground soil or water, making it more efficient than traditional air-source heating and cooling, which is affected by fluctuating air temperatures. The ground or water acts as the heat rejection/heat absorption medium; heat is absorbed from the ground or water when building heating is required, and heat is rejected to the ground or water when the building requires cooling. While such a system presents a higher first cost, the energy cost savings that it can accrue over its life cycle proves its worth. Wood Harbinger recently designed a ground-source heat pump system for an elementary school project. Our energy analysis showed that this system could enable a low energy use index (EUI) of 18.

The challenge with a ground-source heat pump system is the site space required for the underground geothermal loops wells. This system is only a viable option for projects with some land available at the site. But if you have the space, it’s an innovative HVAC solution!

Geothermal “slinky” loops.

Geothermal “slinky” loops. They can also be designed in vertical loops. Photo by Mark Johnson via Wikimedia Commons, licensed as public domain.

Natural Ventilation

Natural ventilation provides a way to ventilate and cool a building with little to no mechanical (and therefore energy consumption) influence. Most natural ventilation applications require some mechanical ventilation (e.g., fan assisted exhaust and ceiling fans) to adequately and uniformly ventilate a building. Ceiling fans provide an economical way to cool a building space by pulling cooler outside air into a space and circulating it around. Likewise, a ceiling fan can reverse its direction and circulate warmer ceiling air down to the occupants below to warm them. Ceilings fans work great in high-bay ceilings as well as typical-height ceilings and can blend in with or augment the building aesthetic. Natural ventilation requires a temperate climate in order to be effective—it’s not applicable in either extreme heat and humidity or cold weather environments. In the Pacific Northwest, we can utilize natural ventilation more effectively west of the Cascades, but it’s not as viable an option in all locations.

Water Reclamation Systems – Rainwater and Greywater

A water reclamation system reduces water demand by using rainwater for certain plumbing fixtures (e.g., flushing toilets) or greywater for irrigation or vehicle-washing systems. We successfully utilized a rainwater-harvesting system for a bus-washing system at a school district’s support-services facility. You need to have both the supply and demand for a water reclamation system in order for it to be effective. It’s probably not a good sustainable system choice if a building is very small, does not have many plumbing fixtures, or has very little landscaping. Rainwater harvesting is also only effective if there is sufficient and sustained rainwater to capture. Again, in the Pacific Northwest west of the Cascades, it’s a great option, but not so much in desert climates.

Rainwater Collection System at Lake Washington School District’s Juanita High School

Rainwater Collection System at Lake Washington School District’s Juanita High School. Photos by Wood Harbinger staff.

Compostable Toilet System

To minimize water demand, reduced or no-water plumbing fixtures can be used for sinks, urinal, and toilets. Composting toilet systems require much less potable water and wastewater treatment, while providing a nutrient-rich compost, which may be used for horticulture or agricultural soil enrichment after having gone through a curing stage to reduce potential phytoxins. This option can also be used where there is no water supply or sewer system and where access to a sewage treatment plant is not available, such as roadside facilities, state and national parks, and rural homes. Compostable toilet systems can be more costly at the outset and more complicated to maintain, but the savings of not having to bring water and sewer to a remote site can potentially justify its work.

Solar Systems: Photovoltaic-Power Generation and Hot-Water Heating

Renewable energy systems, such as a solar-photovoltaic panels and a solar-hot-water heaters, help offset electrical and water-heating demands. The return on investment can be about five years for a solar-photovoltaic panels and the same for a solar-hot-water heaters, after you factor in tax credits, net metering energy savings from local utility providers, and other incentives and rebates. One may think that solar-energy systems wouldn’t be viable in our area with its reputation for clouds and rain, but you’d be surprised. The key to making solar-energy systems effective is sizing for your needs. A grid-tied, solar-photovoltaic system, which is oversized for the building’s electrical demand costs more and will not gain any more revenue from a Renewable Energy Production Payment program. Excess energy produced by the solar- photovoltaic system will offset demand on the utility grid at the expense of the building owner.

Solar-photovoltaic panel systems at Lower Columbia College's Health and Science Building (left) and Lake Washington School District's Redmond High School (right)

Solar-photovoltaic panel systems at Lower Columbia College’s Health and Science Building (left) and Lake Washington School District’s Redmond High School (right). Photos by Wood Harbinger staff.

Thinking for the Future

Master planning and forward thinking are key steps in providing right-sized systems for current as well as future needs. Some systems can be operated efficiently at reduced capacity, so it’s possible to build in a sustainable system in anticipation of future demand or provide flexibility for future space program or use changes. For example, variable speed drives on fan motors can turn down to match current needs but ramp up as demand increases. It’s also possible to plan ahead for sustainable systems by provisioning with space, infrastructure, and capacity to facilitate a future sustainable system addition.

A common concern when designing and constructing sustainable buildings is their higher costs. However, the premium in cost for materials, equipment, and design for sustainable buildings tends to be less than 2%, yet can reduce greenhouse gas (GHG’s) pollutants and yield a significant financial payback over the entire life of the building, including increased rent or sales price and reduced utility costs. Other benefits include increased occupant comfort, increased lighting quality, and reduction of pollutants, eliminating potentially toxic building materials and creating a heathier environment. Also, a sustainable building and its systems can be a great educational tool for employees and students as well as an effective marketing tool.

Goldilocks and the Three… Engineers

Smart system selection takes into consideration a host of factors, such as first costs and life cycle costs, physical feasibility, and location considerations. The skill to balance all the parameters and deliver the best system fit for the project—as well as assure it is designed and implemented correctly—is a major reason why it’s important to have experienced engineers and designers on your team!

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