Amid growing concerns over the dangers of climate change, the built industry is seeing growing interest in net-zero construction. In essence, this means building structures that can generate as much energy as they consume each year.
This isn’t a new concept. Danish researchers referenced zero-energy homes in a 1976 study on solar heating. Arguably the first nearly net-zero construction was an 1893 Norse polar ship. But history shows that interest has mostly been prevalent in colder climates. That needs to change as our world heats up.
The warming world incentivizes net-zero
The summer of 2021 saw a record-breaking heatwave across the Pacific Northwest, a region full of structures ill-prepared to deal with such extreme conditions. Many buildings lacked air conditioning, and concrete-filled cityscapes baking under atmospheric heat domes created an urban heat island effect.
Residents should certainly talk to their HVAC contractors about having better cooling systems installed. But we live in a warming world, and extreme weather events are likely to be more frequent and strike even areas with little or no historical precedent. This calls for more than just damage control or measures to mitigate the immediate impacts of climate change.
We need to seek remedies for the source of emissions, and the built industry is a major contributor in that area. Net-zero energy buildings (NZEBs) offer a long-term solution. They give back as much energy as they consume. Conscientious developers can also balance the upfront emissions cost by purchasing equivalent carbon offsets.
And though a warming world isn’t good news, it creates an added incentive to quickly adopt NZEB construction. In warm climates, there’s a lower temperature differential between the outdoor environment and what we consider as comfortable indoor conditions. This means that we use less energy for thermoregulation in such areas, making it easier to achieve net-zero goals.
Balancing size versus scope
The bulk of past research into NZEBs has been centered on construction projects in cooler areas. It’s no surprise that most successful case studies so far have come from moderate climates like California. Developers in warmer, more humid areas may hesitate to aim for ambitious targets like net-zero. They don’t have many precedents to refer to and are worried about the costs and returns.
A study by Building Design+ Construction in the Texas Gulf Coast looked at different types of structures designed to achieve green certification. Their analysis of net present values (NPVs) showed that all but one structure proved a positive investment at the 25-year mark. The larger ones, in particular, could yield ROI between as little as 9-13 years.
The generalization here is that larger structures make for more profitable NZEBs. They can take advantage of the economies of scale involved in deploying various technological solutions and design features. They also enjoy a generally lower occupancy-to-space ratio.
This doesn’t rule out net-zero for small structures, however. Homes can also be feasible NZEBs. Owners have to be willing to take a long-term approach. And over time, the cost of net-zero solutions will decrease, while local tax credits may also increase to improve returns.
Exploring methods, materials, and technology
In a warm climate, instead of focusing on heating solutions, you want to explore ways to keep the indoors cooler than it is outdoors. Yet as with their cool-environment counterparts, the approach with these buildings can be broken down into passive and active strategies.
Passive design tries to take advantage of things like the movement and angle of the sun, minimizing the structure’s absorption of solar heat while maximizing its airflow. This presents a unique challenge because NZEBs generally want to harness the greater amount of sunlight and use PV solar cells for energy capture. Also, natural ventilation techniques will still require occupants to acclimatize, wearing clothes suitable for the season.
Using reflective roofing materials, such as white metal or tile, can effectively keep the heat off low-rise structures when features such as environmental shade aren’t available. In this case, PV panels could be laid out around the boundary of the property instead.
Alternatively, a high-rise structure could take advantage of technology such as wind turbines built into an open atrium, generating significant wind energy even with low ground level wind speed. Another source of renewable energy could be geothermal, captured by the use of ground source heat pumps. The use of phase change materials in a building’s envelope also has demonstrated the potential to significantly reduce indoor peak temperatures.
NZEB construction in warm, humid areas hasn’t reached the same level of maturity as in cooler climates. But the techniques, technologies, and materials are all available. It’s time for truly sustainable buildings to be laid down where it matters most in the era of climate change.
Meta title: The Case for Net-zero Construction Where It Matters Most Right Now
Meta desc: As the world heats up, the warmer parts of our world will need buildings that use less energy in cooling if we’re to start reversing the tide of climate change.