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  • Writer's pictureTim Rhodes, RA., AIA

Design for a Hotter Climate

Summer is upon us. The global news feed is burning with stories about unseasonably hot weather and climate change.

The Pacific Northwest is in a temperate climate zone and yet we too are seeing changes to our climate resulting from global warming. More than 50% of homes in warmer temperate climates use air conditioning and that percentage is increasing. Often this is due to poorly designed buildings that open to heat-absorbing materials (unshaded paving, for example), a lack of greenspace, insufficient ventilation, dark heat-absorbing materials, and buildings that orient to southern and western sun with inadequate sun control.

We have built good examples of residences that use passive strategies to moderate a warming climate and stay cool and comfortable. These same strategies also work to keep us warm and reduce energy costs during colder months such as in the Fish Hatchery, Uberti, Medina + Seola Beach Residences featured here which employ building elements for summer sun control while allowing lower winter sun to reduce heating needs and promote daylight in colder months.

As air conditioning is used to counter poor design, our homes use more energy, generate more heat output as a result and amplify the cycle of climate change. According to Seattle City Light, the city gets over 80% of its electricity from clean, carbon-free hydroelectric projects (dams) on Washington rivers, 5% from wind generation and 5% from nuclear facilities. Dams have consequences too: changes to rivers, reduction of carbon sinks downstream, destruction of fish habitats, and in the cost of construction, production of the materials used and maintenance over time. The best design strategies reduce the use of electricity in our buildings and the need for additional power generation which saves utility costs and reduces environmental heat.

As each design is envisioned, Rhodes Architecture + Light considers foundation, orientation, ventilation, layout, adjacent greenspaces and daylighting-coupled with sun control.

In our temperate local PNW climate, design strategies can be employed to enhance energy efficiency. These include using earth coupled slab-on-grade concrete foundations to make the most of cooling breezes and cross-ventilation resulting from open plans. Instead of relying on air conditioning, the use of ceiling and whole-house fans can effectively cool the spaces. Additionally, choosing lighter colored materials for roofs and walls, and integrating accessible, well-located, and landscaped, outdoor greenspaces and living areas, all contribute reduce energy use. Incorporating shade, bries soleil, and overhang designs that permit winter sunlight, while blocking excessive sunlight during summer, subsequently diminishes the need for electricity for both heating and interior lighting, which may often be unnecessary.

Foundations: Earth-coupled slab-on-grade concrete foundations (and exposed concrete floors) tap lower earth temperatures to help cool an interior space in summer and keep it warmer in winter (mean annual Seattle soil temperatures are 47-52 degrees Fahrenheit). The thermal mass of concrete slab-on-grade construction can house a radiant heating system as well for highly efficient winter heating. Heated concrete floors feel warmer in winter than traditional flooring and cooler in summer when the outside temperature is higher­–a win-win. Exposed concrete can be ground, colored, and become a beautiful tough flooring material without the added cost of a flooring finish; Our Mukilteo, Norway Hills and Wingspan projects are good examples which employ colored and ground concrete floors.

"We walk barefoot around the house most of the time, even in the winter. We'll even sit on the floor and have dinner at the low table. In the winter, the concrete floors provide nice, uniform heat. The house is comfortable all the time." –Homeowner

Orientation: Designing the longer sides of our homes to face south yields better daylighting and passive solar radiation for free heating in cold months. South and west-facing doors and windows, however, must be protected from high-angled summer sun.

A layout that orients major spaces to southern sunlight results in better daylit living space and improves our well-being, reducing symptoms of seasonal affective disorder (SADs) which the Mayo Clinic notes “is a type of depression that's related to changes in seasons — seasonal affective disorder (SAD) begins and ends at about the same times every year.”

Understanding where our clients spend their time within their homes is a key to orientation and the layout of their living space; we utilize a series of programmatic and experiential questionnaires prior to beginning design. The Point Roberts Residence used orientation to maximize daylighting while controlling solar gain in hotter months; the North Lake Washington Residence oriented to southern light and a “living” court.

Ventilation: Well-oriented courtyard houses can achieve better cross-ventilation, open to access greenspace and outdoor living areas, and encourage those using the home to open doors and windows and turn a/c off. The more narrow and linear open plans of the “wings” of courtyard homes are simpler to cross-ventilate than a compact plan that stacks rooms, creating a deeper, and more difficult to ventilate, plan. A lush, planted courtyard creates a microclimate which can be cooler than the surrounding air temperature. That cooler air can be selected by well-designed ventilation for indoor comfort-without electricity. We use low operable awning windows in courtyards facing in the direction of predominant winds (in Seattle typically south-southwest) coupled with high ventilating windows on the opposite side of the residence to encourage cross-ventilation. At the Johnson Point Residence we carefully grouped lower windows on courtyards and upper ventilating openings to facilitate better cross-ventilation.

"The house has been successful at maintaining climate control since we bought it 20 years ago. We go about 360 days of the year without supplemental cooling. With climate change though, we've started bringing fans in over the last 10 years for cross ventilation and we open a lot of windows. The overhangs help offset the heat from our abundant glass." –Homeowner

Good, natural cross ventilation using operable windows and doors is supplemented in our homes with whole-house and ceiling fans extending the comfortable season when a/c can be left off. There are now several manufacturers of high-quality whole-house fans (Panasonic is a favorite) and ceiling fans (Big Ass Fans makes high-quality fans for buildings) when efficient powered ventilation is an aid to cooling without air conditioning. Adding an energy-recovery ventilation (“ERV”) system (one that harvests heat from the air being exhausted) is a good way to increase energy efficiency in ventilation in the heating season (ERV’s often feature air filtration as well for higher air quality). Wingspan, a 5-Star Built Green residence, was designed with energy recovery ventilation and high-efficiency reverse heat pump heating/cooling- all powered by the sun.

Adjacent Greenspaces: Opening to well-designed greenspaces, vegetated courtyards, and exterior living areas (with carefully controlled pavement) is a great way to reduce the energy use of a home while improving well-being. “Greenspace is multifunctional–it provides social, economic and environmental benefits”, according to studies by Forest Research UK. Many current studies are showing that living with access to greenspace improves mood while adding to quality of life and even increasing cognitive function. Building greenspace into our designs has clear environmental benefits (adding cooling trees and plants to our environment) while outdoor living areas adjacent to our indoor space beckon us to live outside, to open our dwellings, and are also beneficial as green views outside when weather forces us indoors. Well-landscaped courtyards, such as those that are the focus of our Norway Hills Residences, reduce the temperature of our surrounding environment and allow manually operated windows and doors to bring cooler air into our homes for natural ventilation. The key is the landscaping the building opens to–trees and other shade plants are far more beneficial than a mowed lawn, reducing temperatures by as much as 9 degrees Fahrenheit.

The Seattle Times recently reported a study of greenspace temperatures: “Seattle Parks and Recreation said it joined 12 other cities last summer to study the cooling potential of urban green spaces. The study from the Natural Areas Conservancy found that air and surface temperatures vary across types of urban green space.” Adding water to our courtyards, as the residences at The Glade and the Spring Hill Residence do, is another winning solution.

Daylighting Coupled with Sun Control: We recently wrote about the benefits of daylighting including the resulting reduction in the use of powered lighting together with the improvement of the wellness of users of spaces. Using the sun for natural lighting benefits the occupant while reducing energy use at the same time.

“There’s lots of windows and natural light. And the artificial lighting wasn’t overdone …it was just right. Not overkill, but exactly right for the space.” –Homeowner

Using simple design principles- foundation, orientation, ventilation, layout, adjacent greenspaces, and daylighting, coupled with sun control, Rhodes Architecture + Light strives in all our designs to make the same elements that reduce energy use work for the benefit and wellness of those whose daily lives these important buildings nurture.

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