Passive building design strategy utilizes natural assets, like solar power and wind patterns, to design and construct comfortable buildings that limit or eliminate purchased energy needs. Passive architecture aims to achieve a carbon-neutral, comfortable, and healthy built environment by curbing the destructive forces impacting Earth’s climate and, ultimately, healing the damaged natural environment.

Through thoughtful architectural design, custom residential and commercial projects can:

• Minimize construction site disturbance
• Mitigate Additional Community Infrastructure (e.g., energy, roads, water supply, etc.)
• Optimize Natural Resources (e.g., sun exposure, climate, recycled material, etc.)

Keep reading to learn about the five critical points of a passive building and the potential strategies an architect can apply for a successful design.

1. Air Control

Air-Tight

An air-tight structure is fortified against inward and outward air leakage from unintentional leakage points (cracks, holes, etc.). Air-tight buildings with adequate ventilation:

• Reduce heating and cooling demands,
• prevent mold and rot, and
• lessen the number of drafts, creating a more comfortable space.

Indoor Air Quality (IAQ)

IAQ refers to the concentration of contaminants that affect occupants’ health and comfort in an enclosure. Superior IAQ is achievable with intelligent interior material selection and optimum ventilation strategy.

HVAC air filters capture air particles (i.e., pollutants). MERV ratings, set by the EPA, represent a filter’s efficiency at capturing a specific range of particle sizes. A higher MERV rating indicates an ability to capture smaller air particles, enhancing how efficiently a filter extracts pollutants from a building’s ventilation system.

Heat-Recovery Ventilation (HRV)

An HRV unit, or heat exchanger, is a ventilation fixture in a home’s basement or attic. Two air flows pass each other in this unit: (1) pre-heated, fresh outdoor air and (2) warm, extracted, stale indoor air. The system separates the heat from the outgoing stale air, transferring it to the fresh incoming air.

Energy-Recovery Ventilation (ERV)

Like HRVs, ERV systems are mechanical ventilation systems that maintain a continuous flow of fresh outdoor air while extracting stale indoor air simultaneously. While HRV units only transfer heat from the outgoing stale air, ERVs exchange heat and moisture. The additional moisture is particularly helpful in colder, dry climates.

Natural Cross-Ventilation

Natural cross-ventilation occurs when air enters a building through openings (e.g., windows, doors, etc.) on one side, then crosses the room and exits through the opposite side, producing a stream or current of cool air across the room.

A similar force can occur vertically via the stack effect—air movement in and out of a building via unsealed openings like chimneys and flu-gas stacks.

Differences between the moisture and temperature of the building’s interior and the exterior environment facilitate the effect. The more significant the contrast between the interior and exterior thermal environments and the taller a structure’s height (e.g., chimney), the stronger the stack effect.

2. Moisture Control

Green Roof

Also known as living roofs, green roofs partially or wholly cover a building’s roof by planting indigenous vegetation spread across root barriers and drainage layers over a waterproofing membrane. Becoming more common in urban locations, green roofs contribute to:

• Consistent Cool Building Temperatures via Evapotranspiration
• Rainwater Filtration
• Roof Membrane Protection
• Storm Water Retention Mitigation
• Urban Heat Island Effect Reduction

Automated irrigation systems make for convenient green roof maintenance.

Permeable Paving

Permeable paving aids in stormwater management using either porous materials or non-porous blocks, allowing stormwater to flow through the pavement or between strategically placed gaps.

Permeable pavement surfaces include:

• Paving Stones and Interlocking Pavers
• Pervious Concrete
• Porous Asphalt

Rainwater Harvesting

A rainwater-harvest system collects rainwater from a building’s roof or a roof-like surface, transferring it into a tank, reservoir, cistern, or other storage container. Harvested rainwater is an excellent solution for off-setting freshwater demands for tasks such as:

• Washing Applications
• Toilet Flushing
• Ornamental Pond and Fountain Filling
• Landscape Irrigation

3. Radiation Control

Passive Solar 

Passive solar design aims to exploit sun exposure and the natural properties it triggers from a building’s materials and the climate, efficiently and sustainably heating and cooling living spaces.

Examples of passive solar design include:

• Automatic Exterior/Interior Window Blinds
• Deep Roof Overhangs
• Operable Window Placement for Ideal Heat Gain (in winter)
• Solar Chimneys (for cooling and heating)
  

High Albedo Roofing

High albedo roof materials reflect sunlight, limiting the heat a building’s roof absorbs and impacting a building’s heating and cooling loads, particularly in the attic and top-floor areas.

While the reduction in solar heat gain may increase a building’s heating load during winter, this “penalty” is often offset by the summer energy savings. A light-colored roof can help moderate cooling loads during summer—slashing cooling costs and maintaining a comfortable interior.

High-Efficiency Windows

High-efficiency windows are air-sealed, typically double- or triple-glazed, offering first-rate thermal performance. Double- and triple-glazed windows are highly efficient due to the insulating gas between panes (argon or krypton) and low-E coating. Frame materials like fiberglass and wood further reduce thermal energy transmission.

4. Thermal Control

Above-Code Insulation

Above-code insulation is conducive to energy conservation. Energy-consultant-recommended insulation (based on R-values) for cold climates are:

• R-60 – ceilings
• R-40 – above-grade walls
• R-20 – basement walls
• R-10 – below and surrounding basement slab perimeters

Property owners can maximize comfort and energy savings with continuous, above-code insulation encompassing the whole structure, reducing heating/cooling needs.

Insulated Concrete Forms (ICF)

ICF refers to formwork blocks comprised of insulative materials. These blocks are stacked and poured over with concrete, filling spaces in and around the ICF blocks, resulting in beneficial insulating properties, minimal thermal bridging, and continuous air-tight seals.

• Thermal Bridge – an area that offers a “path of least resistance” for heat transfer compared to surrounding materials, creating a “path of least resistance.” By eliminating thermal bridges, designers can minimize interior mold-grow risks.

Thermal Mass

A material’s thermal mass represents its ability to absorb, store, and release heat. Concrete is a “thermally massive” building material with a high capacity to store excess heat and provide inertia against temperature fluctuations. Thermal Mass materials also absorb excess humidity.

5. Waste Control

Adaptive Reuse

Adaptive reuse is the process of repurposing something we no longer need to fulfill a new function—making the most of what we have by up-cycling old materials or altering an existing building’s previous intended use. When we reuse construction materials, we keep stuff out of landfills and save energy and resources by reducing the quantity of new, manufactured products.

Exterior Materials

Passive, design-friendly building exteriors should be durable and natural (organic)— cladding materials and treatments that are resilient to weathering and favorable to enhancing a building’s longevity. Once the materials are no longer in use, ideally, they may return to the biosphere with a positive effect.

Choose Top Architects for Responsible, Sustainable Designs

Mitchell Wall Architecture & Design’s innovative architecture and design professionals provide customized design and project management services. The result? Custom builds that sit at the cutting edge of architectural advancements while maintaining the client-specific personalization that makes a custom home or commercial space worth the investment.

When you choose Mitchell Wall to create your dream design, your custom project can achieve everything you want and more. To learn more about our services, please call us at (314) 576-5888 or complete our online contact form at https://mitchellwall.com/contact/.