By Joe Emerson and Bruce Sullivan
The Zero Energy Project is a strong advocate for and supporter of net zero homes (and buildings) and has been for more than a decade. These super green homes are a huge step forward on the path to zero carbon and healthy living. The most powerful attribute of net zero homes, unlike many green home concepts, is that zero is quantifiable through energy modeling and/or tracking energy bills. As the concept of zero evolves, moving to the next iteration of these homes — Zero 2.0 — will be central to ensuring that we positively address the climate disruption, pollution, and financial challenges of the 21st century. Zero 2.0 must reduce the overall carbon impact of homes and buildings to zero while enhancing occupants’ health, security, resilience, and financial stability. Zero 2.0 is both a vision for the future of buildings and a roadmap that we must start implementing immediately.
Challenges and Upgrades for Net Zero Homes
To ensure that net zero homes truly get us on the path to zero carbon and zero negative impacts, they must more effectively address several challenges that faced the first generation of zero energy homes. Here are those challenges and the innovations needed to reach Zero 2.0.
#1 The Use of Natural Gas. Using fossil methane gas for space heating, cooking, and water heating can no longer be an option if we are to prevent the worst of global warming. Zero 2.0 homes and buildings must be all electric. If electric grids source 100% renewable energy, then all-electric, zero energy ready homes will then be net zero, and existing zero energy homes can produce excess renewable energy to contribute power to electric vehicles, batteries, and the grid.
#2 The Disconnect between Solar Production and Home Energy Use. Solar electric panels produce the most power around midday, even though the homes they power consume the most power in late afternoon and evening — creating a disconnect between supply and demand. Zero 2.0 must include smart home controls that integrate with a smart grid, operating dishwashers, laundry, water heaters, and car chargers during times most advantageous for grid stability and low retail pricing. As battery prices come down, Zero 2.0 must include sufficient on-site energy storage to manage appliances’ energy use in a demand-response program to even out energy loads as grids use more renewables.
#3 Most Solar Systems Provide No Power During Outages. Most grid-tied solar electric systems cannot draw on their own solar production during power outages, even when solar power is abundant. As currently configured, they do not enhance resiliency as extreme climate events become more common. Zero 2.0 must include battery back-up for critical survival needs.
#4 Some Zero Energy Homes Rely Too Heavily on Solar. With the price of solar panels dropping, some homes employ only minimal energy-efficiency measures, such as improved insulation, air sealing, and advanced windows. When climate-related emergencies result in power outages that disable solar systems, leaky uninsulated homes will not weather emergencies as well. Zero 2.0 must be designed to the highest efficiency standards. Making all homes as energy-efficient as possible will keep healthy temperatures for days during a power outage. This is especially true for homes without solar potential that need to subscribe to off-site renewable energy.
#5 Most Zero Energy Homes Ignore Transportation and Other Home Energy Uses. Few zero energy homes are designed or equipped to generate enough renewable energy production to supply energy for transportation, yard and garden equipment, and possible luxury items like a hot tub, pool, or sauna. Zero 2.0 must be designed and equipped for 100% zero energy living. This means installing sufficient solar collectors to power all energy use associated with the building, including charging electric vehicles. To increase the area available for solar production, use solar panels to cover patios and parking areas. Alternatively, you can purchase community solar or use renewable energy purchase programs.
#6 Most Zero Energy Homes Do Not Account for Embodied Carbon. Zero energy homes are currently defined by operational energy and do not take into account embodied greenhouse gas emissions from materials, construction, appliance refrigerants, and more. Zero 2.0 must use carbon accounting software and low GWP refrigerants. The design-build team should use a carbon accounting software program to minimize embodied carbon in construction materials and focus on the least carbon intensive and least expensive methods for getting to zero carbon by using energy modeling. All heat pump equipment, including mini-splits, heat pump water heaters, refrigerators, and freezers should use the latest low-GWP refrigerants, such as hydrofluoroolefin (HFO).
#7 Most Zero Energy Homes Are Not Designed for Resilience in Extreme Climate Events. They do not directly address local climate threats to home safety and health from extreme climate events, such as wildfire, wind, and floods. Zero 2.0 must design for resiliency in the face of the most likely local pollution and climate threats. For fire, use fire resistant materials and landscaping. For smoke and air pollution, specify high levels of air tightness and controlled ventilation, and use HEPA or MERV-16 filters integrated to an ERV and air purification system. For floods, specify appropriate foundation height, water resistance, and ventilation, For wind and earthquakes, specify structural integrity. For water shortages, use low water-use showers and faucets, drip irrigation, reuse of greywater, and if appropriate, rainwater harvesting roofs with cisterns.
#8 Most Zero Energy Homes Do Not Provide the Highest Standards of Indoor Air Quality (IAQ) Management. These homes do not always address health threats from local environmental pollution, wildfire smoke, gas appliances, and the use of off-gassing materials during construction. Zero 2.0 must design and build to the highest IAQ standards. New homes must include features and equipment that meet or exceed advanced indoor air quality standards, such as non-toxic materials, high levels of air tightness, and HEPA or MERV-16 filters integrated into the air purification and ERV/HRV system. Go all electric, with no gas heating, water heating, or appliances, to eliminate pollutants released indoors from fossil fuel burning appliances.
Zero 2.0 Starts Now
In order to meet the extraordinary climate and environmental challenges of the 21st century, these eight upgrades to Zero 2.0 must be steadily integrated into the definition, planning, and implementation of zero. With net zero energy use, zero carbon footprint, and zero health impact, designing and building these resilient Zero 2.0 homes will ensure that the housing industry is doing all it can to get us on the path to zero carbon, zero health impact, and zero risk homes — but to be effective, these upgrades must be started now.