Passive houses: A comfortable solution to lowering GHG

Live comfortably and eliminate the need for air conditioning.

The built environment contributes to 40% of all greenhouse gases (GHG). We are in crisis, and passive houses are a part of the solution.

Crisis

a: an unstable or crucial time or state of affairs in which a decisive change is impending, especially one with the distinct possibility of a highly undesirable outcome: a financial crisis, the nation’s energy crisis

b: a situation that has reached a critical phase: the environmental crisis, the housing crisis

Contributing factors to GHG in today’s dwellings.

We are exhausting our materials and energy resources. The depletion of these resources combined with the pollution they create is propelling us towards the most catastrophic global climate event since the Ice Age. Extreme weather patterns are in the news daily, fires, floods, hurricanes, blizzards, extreme heat, and drought. Wildfires are raging, hurricanes are wiping out urban areas, reservoirs are drying up, and Hydro Plants are shutting down, sending people into blackouts during unprecedented heat. And, we are in a housing crisis; we need to build the equivalent of 40 New York City’s every month for the next 40 years. We can’t waste any more time or resources. Passive houses are a necessity for our future.

The idea of optimizing a dwelling’s orientation to take full advantage of the sun, rain, and wind has been around since humans began building structures. Unfortunately, the practice fell by the wayside in the Industrial Revolution with the advancement of heating and cooling systems. It seemed like a good idea at the time. But, now we must harness the simple elegance of passive house design with innovative construction methods and materials to reduce greenhouse gases before it is too late.

“Here’s the rub; the warmer it gets, the more we use air conditioning. The more we use air conditioning, the warmer it gets.”

According to the Climate Institute, “while our planet is warming, using and producing air conditioning equipment exacerbates climate change. The organic compound Hydrofluorocarbon (HFC) is the primary refrigerant used in air conditioning and refrigeration units. HFCs are a much more potent greenhouse gas than carbon dioxide and are leaked from manufacturing air conditioning equipment to installation to disposal. Additionally, air conditioning and refrigeration units run on electricity that relies primarily on fossil fuels to generate power. As the need for cooling rises, so too will the need for electricity.”

Fortunately, by adopting Passive House design, we can circumnavigate the need for air conditioning units and keep people healthy and comfortable while also reducing climate pressures.

What is a Passive House?

Passive houses utilize sustainable building materials and designs to provide:

• Comfort (maintains an ideal ambient temperature)
• Indoor Air Quality (filters out, pollution, allergies, wildfires)
• Efficiency (reduces operational energy cost and GHG))
• Tranquility (increased insulation and reduced air leakage create a quiet and peaceful dwelling)
• A solid, easily maintained, and sustainable living environment.

While the term ‘passive house’ implies usage in single-family dwellings, the passive house design can be implemented in any building. And it is currently the industry standard in low-energy building design and architecture. The passive house design upholds stringent measures to reduce fuel consumption and maintain an ideal carbon footprint. In addition, passive houses are extraordinarily comfortable and employ an ingenious use of natural energy sources such as; body heat, incident solar heat, light, etc.

The idea of simultaneously maximizing living comfort and energy efficiency long seemed an impossibility. But recent innovations and actionable models put forth by passive house institutions like the Passive House Alliance U.S (PHAUS) have proven that sustainable architecture is more comfortable, more affordable, and better for the environment.

Standards for Passive Houses

The design standards for passive houses eliminate the need for traditional heating and cooling sources like furnaces and air conditioners. As a result, passive houses require 90% less energy than conventional structures.

According to the Passive House Institute, passive houses must meet the following energy usage criteria:

• Space Heating Demand: The energy required for heating should be lower than 15 kW/m2 of living space per year. The peak demand at any given time should not exceed 10 W/m2. In comparison, a conventional house requires around 100 kW of energy per m2 per year.
• Space Cooling Demand: Roughly matches the heat demand with an additional, climate-dependent allowance for dehumidification.
• Primary Energy Demand: Not to exceed 120kWh annually for heating, cooling, hot water, and household electricity per square meter of usable living space.
• Airtightness: Maintain a high degree of airtightness. This means that these houses should experience no more than 0.6 air changes per hour at a pressure of 50 pascals.
• Thermal Comfort: Finally, passive houses must have extreme thermal stability. The temperature in a passive house does not exceed 25 degrees Celsius for more than 10% of the hours in a year.

You can find the white paper on Passive House Standards here.

These stringent design standards help passive houses maintain their excellent energy efficiency levels. Apart from these, there are no predefined aesthetic limitations for passive houses; they can adopt whatever style the owner prefers.

Construction Standards for Passive Houses

Passive houses use sustainable building materials and designs that offer excellent natural insulation. Further, by positioning to maintain an optimum balance of wind, shade, and direct sunlight, operating energy is significantly reduced. The following construction standards are required to achieve the desired attributes of a passive house:

• No thermal bridging: Thermal bridging is when a thermally conductive material creates a path of least resistance for heat transfer, creating a significant source of energy loss. These thermal loss highways are present in all conventional stick construction as studs, headers, and posts. Thermal bridging reduces with innovative design (hollow walls), choosing less conductive materials (wood instead of metal), and increasing insulation. BamCore is an example of a building design that eliminates over 80% of thermal bridging.
• Using high-quality insulation: Low-quality insulants tend to dissipate some heat, defeating the entire purpose of thermal insulation. Passive house buildings employ high-quality nontoxic insulation like wool, stone wool, hempcrete, and even mycelium. The more insulation, the better; this can be accomplished by utilizing a hollow wall design and increasing the building envelope (space between the inner and exterior walls). Proper insulation protects the residents against external climatic conditions while also reducing the need for electronic heating and cooling devices. This high degree of insulation or ‘superinsulation’ makes a passive house highly comfortable and functional.
• High-quality windows: Passive house windows need to have low thermal conductivity and excellent transparency. The windows also serve to diverge incident light to light the entire room slightly better.
• Airtight design: No uncontrolled flow of air should take place in or around the house. The cost to heat or cool buildings is significantly impacted by the air leakage of the building envelopment. Air leakage is often an underlooked component in construction and design.
• Mechanical ventilation: A passive house has apt ventilation that recovers heat from used air and transfers it to fresh incoming air. Further, these vents make the most out of body heat, and the heat dissipated from light sources inside the house, thereby creating a Heat Recovery Ventilation or HRV system. This helps retain energy and maintain good air quality.

Thermal Bridging show in stick construction vs BamCore Prime Walls

Utilizing BamCore in Passive House design

The Generation 3 BamCore framing solution provides a superior thermal envelopment to help meet the rigorous passive house construction standards.

Eliminating Thermal Bridging and Air Leakage

By utilizing timber bamboo’s tensile and compressive strength, the patented BamCore framing solution eliminates over 80% of cross-cavity framing members (studs, headers, and posts) where thermal bridging and air leakage occur.

The total amount of framing material in a wall is called the framing factor. California ranges from a low of around 25% on a simple single-story building to approximately 40% in multistory buildings or areas with strong wind or seismic activity. Due to BamCore’s innovative design and material, the dual-panel nearly hollow load-bearing system meets building code in climate-stressed areas without adding to the overall thermal bridging. In addition, wall thickness can be economically increased to 2×12 for the minimal cost of wider plates and extra insulation. Gone is the need for expensive double framing to achieve high thermal performance. This efficiency in building material and method contributes to the passive house construction standard, lowers operational energy costs, and sequesters more embodied carbon.

A word about Zero Net Energy (ZNE) buildings.

In 1978, California adopted the Energy Efficiency Standards for Residential and Nonresidential Buildings to reduce California’s energy consumption. The state has been on a progressive path to tighten building energy efficiency with each three-year cycle of the state’s building code. The 2019 building code, which became effective in 2020, completes the progression by requiring all new residential and low-rise buildings to perform at ZNE levels. By 2030 all commercial buildings (low-rise and high-rise) must also reach ZNE energy performance levels. Zero Net Energy is reached when a dwelling generates at least as much energy as it consumes during the year.

This means that all new residences will pursue a mix of three tactics to reach ZNE:

1. install ample solar power systems,
2. upgrade the structural building envelope to achieve high performance,
3. upgrade the fenestration (doors and windows) to high-performance levels. Improving fenestration performance is usually the most expensive, so the primary focus is on installing the solar and improving the envelope. BamCore’s super-efficient Prime Wall envelope makes a significant contribution to improving the overall building envelope performance.

In closing.

Building with the BamCore framing solution contributes to a quieter, safer, healthier, thermally superior dwelling that lowers GHG.

The BamCore data in this article is from tests performed on Generation 2 BamCore panels. The Generation 3 Panels are undergoing testing. We expect them to perform similarly or better than Generation 2 when testing is complete.