Can Net-Zero keep us at 1.5?

Admittedly, while individual energy consumption may not alter the fate of humanity, a change in how the masses consume energy will undoubtedly affect the overarching power big-oil has on our environment. The ultimate goal being to move communities off the traditional grid and onto renewable energy sources, thereby eliminating carbon output from new and existing buildings. Luckily for us, we’re currently living in a time where solar and wind power are as cheap as, if not cheaper than natural gas (natural gas, by the way, is oil).

IEA (international energy agency) estimates that solar costs 98 euros per megawatt hour (a megawatt hour is 1,000 kilowatts of electricity used for an hour. The average household uses a little less than one megawatt hour a month). Another way to look at it, solar panels can deliver one megawatt-hour costing between $31 and $111 depending on demand to 650 homes. By comparison, natural gas peaking plants, which utilities can turn on and off quickly to meet surging demand, deliver power at $122 to $162 a megawatt-hour. While many energy providers argue they are unable to switch to 100% renewables citing the need to “switch on” natural gas during peaks, battery storage now has the ability to store such great numbers that the argument feels more like a blatant refusal to add new machinery than anything else.

How does this affect the construction and development industry? Well, we’re fortunate enough to have the ability to design buildings that don’t need to rely on antiquated natural gas grids. We can develop new Zero Carbon homes and Zero Energy Buildings (ZEB’s) as well as repurpose existing infrastructure to meet those same energy goals (for repurposing see previous passivehouse post).

Net Zero Carbon Homes / Zero Energy Buildings (are becoming more and more popular for new construction. Net zero (carbon) according to the UKGBC Renewable Energy Procurement Guidance is operational energy that covers energy used for heating and cooling, cooking, lighting and plug loads but excludes commercial process loads and transport (electric vehicle charging). Essentially, the building or dwelling produces enough renewable energy to meet its own annual energy consumption requirements.

Currently, 21% of the UK’s total emissions are attributable to building space heating and hot water with approximately 75% of the heating demand met by natural gas. Likewise, of the US’s total emissions are attributable to electricity production with 34% of that coming directly from natural gas. The CCC’s (Committee of Climate Change) report on UK housing recommended that by 2025 at the latest, no new homes should be connected to the gas grid. However, new buildings only account for a small proportion of the challenge; approximately 80% of buildings that will be operating in 2050 have already been built. This means existing stock must rapidly improve on their energy efficiency and transition to non-fossil fuel based heating.

With that in mind, the industry has two major tasks ahead of them. First, for new construction. ZEB’s and Net Zero homes have the immediate advantage of starting fresh. These buildings, once completed should be able to claim:

• Utilization of 100% renewable energy
• Subsisting off traditional energy grids ( less impact during outages )
• Extremely low energy bills
• Healthier interior building atmosphere
• Overall lower environmental impact

New construction can achieve the above in a few different ways. Adding solar panels (directly on-site or sourcing community solar/wind), facing south to maximize on direct photovoltaic sunlight, adding energy efficient air source heat pumps, using local materials, pre fabricating off-site, adding rainwater collection systems and ensuring a tight building envelope. The methods stated above do not take into account carbon created during construction (i.e. transportation of goods and manufacturing of goods). For a truly net-zero building to exist, carbon-offsetting pre and post construction needs to be considered — a topic to review in another post.

Second, the updating of existing buildings. In a previous post I discussed adapting Passivehouse principles for existing homes. Similar to new construction, repurposing existing buildings will follow the above guidelines with the exception of maximizing on direct sunlight (given its preexisting potentially non-southern facing location). Alternate areas that will have the most impact on reducing carbon emissions are:

• Sealing the building envelope with a high R-value — door casings, new double or triple paned windows, insulating the foundation and any attic space as well as exterior walls
• Adding a Heat-recovery ventilator (HRVs) — this will capture heat in outbound air and reuse that energy to condition (heat or cool) inbound fresh air. The ventilator is tied to exterior vents at two locations: an upper vent that exhausts stale air, and a lower vent collects fresh air.
• Changing any interior finishes to those that are low VOC, low formaldehyde wood, and local.

Given the task of refurbishing existing homes requires funding from individuals (or smaller companies), the likelihood of these happening quickly are low. Government incentives, ones which aren’t fully flushed out yet, will inevitably need to come to fruition in order to get the masses on board and to assist in funding to the point of being able to carry these ideas out. Until then, those who can afford to further insulate their homes and switch to renewable energy providers should do so immediately. Those small but mighty steps will ultimately bring them that much closer to a true net-zero building.

For new builds, we have no excuses. With renewable energy costs continuing to decline and more building material manufacturers finding better ways to produce low-carbon products, it’s hard to imagine any new build that isn’t designing towards net-zero. We have the ability to eliminate nearly 40% of the annual carbon emissions and reduce energy costs for our communities — shouldn’t we strive for the ideal instead of being stuck in the past?

Originally published at https://www.alexhirschdesign.com on November 16, 2020.