The Universal Low-Carbon Building Standard Does Six Things
This is the third article in a five-part series introducing a comprehensive, universal carbon standard for buildings. Part One explains how “net zero” has failed us. Part Two introduces the six building blocks of a proposed low-carbon standard. And Part Three (this one) provides details on each of those six things.
Part Four explains why we need to prohibit offsets and RECs, and eliminate other distractions, and Part Five offers a condensed recap as well as a path toward adoption of this comprehensive low-carbon standard across the building sector.
We need to decarbonize the building sector rapidly, at scale, and together.
But to do that, we first need to deconstruct the whole mess we know as “net zero.” We then must rebuild it as a science-based standard that we expect every building in every portfolio to achieve.
In doing so, we need to include all emission sources and remove all use of renewable energy certificates (RECs) and offsets. Remember, the intent is not to showcase the top performers, but rather to act as a requirement for all new construction projects and, in the longer term, existing buildings so that the industry is aligned with a 1.5ºC warming scenario—i.e., a science-based target.
Demonstrating leadership and high performance and being an early adopter of new technologies are still important, so we should continue to recognize and certify cutting-edge projects. The difference is that the Universal Low-Carbon Building Standard is intended for all building projects, attainable everywhere, and meant to be adopted universally—as part of the building code, as a foundational prerequisite in any certification program, and by corporate entities, universities, and local governments.
To scale this one critical slice of what building certifications now do, we need to cut through the ambiguity of myriad systems and align around a single, relatively simple set of metrics and targets.
The first step for all projects within the Universal Low-Carbon Building Standard would be to quantify the emissions and emissions intensity associated with the five greenhouse gas (GHG) emission sources. (As established previously, these are onsite fossil fuel use, electricity use, transportation, embodied carbon, and refrigerants.) This not only creates a baseline for existing buildings but also builds awareness of the different sources of emissions and their relative magnitude.
All of these emissions should be expressed in carbon dioxide equivalents per square foot per year (CO2e/SF/year).
To calculate emissions from electricity use, projects should use a current grid emission factor from eGrid (which is really a year or so old) as well as one representing the future grid (preferably a 20-year average, which can be estimated using the National Renewable Energy Lab’s Cambium tool) to estimate the projected impact of a decarbonizing grid over the project’s lifetime.
This is what it would look like for a semi-urban office building in Colorado referencing the U.S. grid:
In the past year, a couple of tools have popped up to enable these calculations—like ZeroGuide from NBBJ, although it doesn’t yet include refrigerant emissions. As a result, all projects should start with an understanding of what their emissions look like today as well as how those emissions are likely to change as a result of a changing grid.
Once these buildings start operating, just like with other existing buildings, they would need to curb actual emissions to zero. Existing buildings would use the same six categories of the standard as levers to reduce emissions, in line with an industry-wide science-based target: a 50% reduction by 2030, proceeding linearly toward zero emissions by 2050.
Once emissions have been quantified, all new buildings would be required to comply with each of the six areas of the standard explained below.
Any zero-carbon or zero-energy program for buildings that doesn’t include transportation in a major way would be a profoundly incomplete standard. Transportation is the biggest source of emissions in the US. Transportation is also the biggest source of emissions for most new building projects.
Perhaps most importantly, transportation and land-use patterns determine housing affordability and availability for most people.
I understand why most net-zero standards have left transportation off their lists to date: if you’re a building owner or developer, the way that people get to and from your building is often beyond your control.
That logic might have flown in the pre-scope 3 days of emission accounting, or the pre-2020 equity movement, or the U.S.’s ongoing and widespread housing crisis, but now it’s a pretty glaring omission. You just can’t have a carbon program without addressing transportation in a serious way.
To reduce transportation GHG emissions, you need to do two things:
- reduce vehicle miles traveled (VMT)
- electrify everything else with a clean grid
To reduce VMT—and also address the housing crisis—our main tools are density, walking and biking infrastructure, and transit access.
And to electrify, we need charging infrastructure and a way to reduce barriers to EV access, especially for those in multifamily buildings and dense urban settings.
A low-carbon program for buildings and building portfolios should require that all non-residential, non-urban buildings include a transportation demand-management (TDM) plan. Such a plan outlines how a building owner will facilitate a reduction in the use of single-occupancy vehicles. TDM plans are fairly standard for development projects in the context of a rezoning effort or other city requirements, and already include estimates of trip reductions.
The carbon standard I’m proposing would require a minimum of 10%–20% reduction in single-occupancy trips or in VMT per year relative to a non-TDM baseline. Urban non-residential projects with a baseline mode split below a certain single-occupancy-vehicle (SOV) percentage, say fewer than 30% SOV trips, would be exempt from this requirement.
If you’re building dense, transit-oriented housing, you’re already reducing a region’s transportation footprint. If you’re building anything else, and the baseline is that most people drive to get there, you need to come up with a plan that reduces that footprint. That could be a work-from-home policy, home deliveries for retailers, access to transit passes, first- and last-mile ride benefits, electric bike access, or whatever creative solution has the intended result for a given location and project type.
Addressing vehicle electrification would be as simple as meeting both Option 1 and Option 2 of the LEED v4.1 Electric Vehicles credit for commercial and multifamily buildings. Option 1 requires Level 2 charging capability for 5% of parking spaces; Option 2 requires EV-ready infrastructure for an additional 10%.
- separately meter EV loads
- utilizing charge-management software to enable demand management
- time-of-use-based charging
- enabling multiple vehicle owners to access charging spaces over the course of a day
We tend to gloss over how challenging it is to electrify heating and hot water loads in cold climates and in certain building types.
One could argue that figuring out how to electrify commercial and multifamily buildings in cold climates is the most important building engineering and architectural challenge of the decade. Doing so is non-trivial, and our ability to universally electrify not just new but also existing buildings will require significant progress, lessons learned, and massive expansion of the heat pump industry before electrification is a given.
A low-carbon standard should require that new buildings, at least, prohibit onsite combustion as a first principle: you can’t ever reach zero emissions if you continue to burn fossil fuels. Yet both LEED and ASHRAE 228, Standard Method of Evaluating Zero Net Energy and Zero Net Carbon Building Performance, have shied away from banning onsite combustion.
While discussion may be warranted about whether certain fossil fuel uses should continue to be allowed—such as for commercial cooking, although I would prohibit the use of gas in these situations as well—electrification of HVAC, domestic hot water (DHW), and residential cooking should be non-negotiable.
Once you establish electrification as a requirement, a couple other things fall into place.
- First, assuming you are using heat pumps and induction cooking, you’ve made huge gains—as well as positive health impacts—in your HVAC, DHW, and cooking efficiency because heat pumps work in the 3 to 5 coefficient of performance (COP) range for heating, meaning they are 300%–500% more efficient than their gas or electric-resistance counterparts. And induction ranges are about twice as efficient as gas.
- Another thing that happens is that project teams have implicit incentives not to build inefficient, high-peak-load buildings. Certain poor-envelope buildings can create high heating and cooling loads but can squeak through energy-code compliance using the whole-building approach (these would also be prohibited, as described in the following Efficiency section). If these are required to be electric buildings, the first cost of obtaining electrical service can be formidable, so project teams must resort instead to passive strategies. If you’re using a ground-source system, then the motivation to have low peak loads is to avoid drilling expensive wells that could otherwise be avoided, despite the lucrative incentives available for ground-source projects through the IRA.
For the purposes of a low-carbon standard, there should be limits, however, like a minimum heating-season average COP of 2 or higher. That would preclude buildings like Climate Pledge Arena, which is heated primarily via electric-resistance boilers (an irony, given its name), from meeting this proposed standard.
What about existing buildings?
Because the goal is to reduce total emissions by a certain amount by a certain date, electrification becomes a tool to get there rather than a prescribed requirement, because the grid will be getting cleaner as time goes on (and gas won't be).
It may also make more sense to electrify most of an existing building’s fossil energy use while continuing to permit limited combustion. Allowing a gas boiler for peak loads in some cases would likely reduce the need for as much electrical-service upsizing, be easier on the grid, and still allow the building to reduce to zero in the timeframe prescribed by the Science Based Targets initiative.
How efficient must a building be to meet the Universal Low-Carbon Building Standard I’m proposing?
The most popular and widely respected net-zero-carbon standard is probably ILFI’s Zero Carbon certification, and it requires modeled performance 25% better than ASHRAE 90.1-2010.
But because this new standard would require electrification via heat pumps, there are already built-in efficiency gains as well as an incentive to minimize peak loads, as described above.
Therefore, the simplest approach would be to require compliance with the current IECC or ASHRAE 90.1 and then move on. However, to prevent all-too-common gaming of the code, I would add that buildings independently meet the envelope aspects of the energy code, at least the envelope-wide insulation (area- weighted U-Value method) and solar heat gain values. ASHRAE 90.1-2022 is already moving in this direction, as have a handful of states around the country in what they refer to as the “envelope backstop.”
Why not go beyond code efficiency? Energy codes are sufficiently stringent that over-focusing on efficiency for new buildings would lead to diminishing returns—especially since we're requiring envelope compliance and have already eliminated combustion and dealt with peak loads that drive the need for more grid infrastructure.
For existing buildings, though, efficiency remains as important as ever. But in this standard, they wouldn't need to hit a certain EUI, GHGi, or Energy Star score to comply with the standard. They would only need to deploy efficiency to meet their science-based target.
In our renewable energy future, where is the best place to put solar PV? Would you choose a utility-scale project, rooftops, parking lots, or landscape areas?
I’m in the all-but-the latter camp. Yes, utility-scale solar is significantly cheaper ($1/watt vs. $2–$3/watt for rooftop PV vs. $4–$5/watt for s parking canopy), but distributed production provides direct value to end users in the form of reduced utility bills and resilience (when coupled with onsite storage).
Similarly, we shouldn’t assume that an infinite area of land exists that we can easily develop and tie into the grid, which involves lengthy interconnection queues and costly permitting processes, and which will eventually require difficult tradeoffs in terms of developing pristine or otherwise valuable areas like agricultural land.
Furthermore, having distributed renewables supports the increased utilization (capacity factor) of the transmission system, so combining distributed and utility-scale production yields a more cost-effective system overall.
In other words, we should continue to prioritize onsite solar. But we should also be mindful that onsite solar may have project-specific limitations.
A simple approach would be to create a watt-per-square-foot requirement for available roof space, keeping in mind that roof space can (and maybe should) be prioritized for other uses, such as occupiable space or vegetation. My three P’s of rooftop prioritization are people, plants, and PV.
So we first define occupiable roof space as roof area minus setbacks, minus shading, minus greenspace, minus occupiable areas. And we then require solar capacity of 15 watts per square foot for that area (a conservative range of PV power density).
These approaches maintain the emphasis on onsite solar while allowing other uses to take priority, and they also recognize that it might just be a poor site because of shading from trees or other buildings.
One might also advocate for including a similar requirement for unshaded surface-parking areas, even though these are more expensive solar installations. While expensive, this might rightfully help disincentivize surface parking, contributing in turn to VMT reductions, so that should be an area for further consideration.
At this point, the building industry is slowly getting familiar with whole-building life-cycle assessment (WBLCA) as an approach to reducing embodied carbon in much the same way as we look at operational energy models. We can create baselines and evaluate reduction opportunities from a cost–benefit perspective and then make informed decisions about the highest-value reduction opportunities.
In today’s projects, most of the reductions tend to come from dematerialization driven by structural design optimization, low- or no-cost changes to concrete mixes, the use of recycled-content steel, use of low-GWP insulation and finishes, or the use of wood in certain applications.
However, we need to keep in mind that the end goal of reducing embodied carbon is to transform heavy industry, namely cement and steel production—which represent >10% of global GHG emissions (see the chart).
Therefore, the goal of embodied carbon reductions should be not just to find ways to reduce a given project’s footprint, but to help transform these sectors to a decarbonized state. There simply isn’t enough recycled-content steel to meet global demand, and supplementary cementitious materials (SCMs) can only replace a small percentage of the concrete mix (meaning GHG reductions are limited to that percentage as well).
The real prize will be when we are able to manufacture steel and concrete without the associated emissions, and there is a lot of early-phase activity in this space with companies like CarbonCure, CarbonBuilt, Prometheus, and Blue Planet on the concrete side of things alone, all emerging in the past few years (for a full treatment of currently viable low-carbon concrete options, see Brent Ehrlich’s piece “Using Low-Carbon Concrete on Your Next Project”).
So what can developers do to help create their own low-carbon supply chain?
The obvious thing is to support credible low-GWP products and materials as they continue to emerge, and be willing to pay a premium for doing so. This would effectively act the way RECs were originally intended—as a market signal to suppliers—only in this case for a building material rather than a wind or solar farm.
Another option would be to mirror what the corporate virtual-power-purchase agreement (VPPA) did for renewables, namely, to de-risk the market for those materials by guaranteeing a standard price per unit output (e.g. $ per ton of green steel or cement), and then utilizing a contract for differences to determine the ultimate cost or revenue for doing so.
In other words, once you remove the goal of attaining offsets, one can still maintain the investments in, and support the demand for, those low-emissions materials – such as Volvo is doing for green steel – to ensure they become available and that they have a stable market when they do so.
Until those materials are available, the Universal Low-Carbon Building Standard would require all projects to use WBLCA to demonstrate reductions from a baseline in the 20% range (which is what ILFI’s Zero Carbon certification requires), and then ratchet that number down over time as lower-carbon materials become more and more available. Doing so will help build awareness of embodied carbon, support the transition to low-carbon concrete, facilitate the integration of structural design as part of the low-carbon approach, and drive more demand-side interest in low-carbon materials.
It’s worth noting that embodied carbon has a component that takes place when the building is originally built and a use-phase component that reflects ongoing churn and material replacement.
The low-carbon standard would manage the former through the WBLCA reduction requirement. For the latter, a building would be assigned a use-phase embodied carbon budget based on typical material purchases and would be given the chance to reduce that budget through the use of more durable materials, fewer materials, and low-carbon-material procurement.
The problem of fluorinated refrigerants is an area where we will likely see a lot of progress in the coming years.
Already there are replacement refrigerants coming onto the market for high-global-warming-potential (GWP) offenders. R32, for example, can replace R410a at one-third the GWP. There are also forays into the use of CO2 and ammonia (the OG of refrigerants), with GWPs of 1 and 0 respectively, in place of conventional equipment.
And ultimately the U.S. Environmental Protection Agency’s (EPA) regulation and phaseout of HFCs over time—aligning the US with the global Kigali Amendment to the Montreal Protocol—should effectively transform refrigerants to a point where we can take them off the list.
But in the meantime, we have to deal with the fact that more and more projects are using variable refrigerant flow (VRF) as their HVAC electrification solution. Compared with centralized chillers and heat pumps, VRF systems:
- require a lot more refrigerant
- come with a higher risk of leakage
- have not to date moved away from R410a
It is because of this tradeoff with VRF systems in particular—achieving electrification but with additional refrigerant leakage—that it is so important to include refrigerants in any low-carbon building standard.
Fortunately, doing so is one of the easiest things on this list, and it’s odd that it’s been omitted from other zero-carbon certification programs to date. LEED has had a totally sufficient low-GWP refrigerant credit since version 2.2, so the simplest approach would be to require projects to meet the current LEED v4.1 Enhanced Refrigerant Management credit with the intent of bringing down the life-cycle direct global warming potential (LCGWP) metric over time.
This would effectively preclude VRF projects that use R410a from qualifying, and it would promote awareness of considering refrigerant GHG impacts in building designs.
The six areas above would be the basis for the Universal Low Carbon standard. All projects would be required to meet all six of these requirements.
Next time, we’ll talk about what’s not in this standard: namely the use of renewable energy certificates (RECs) or offsets, and time-of-use (TOU) emissions accounting.
You can link to the other parts of this series here:
- Net Zero Has Failed. We Need a Universal Carbon Standard for Buildings.
- This is the Universal Low-Carbon Building Standard We Need
- The Universal Low-Carbon Building Standard Does Six Things (this one)
- The Universal Low-Carbon Building Standard Avoids RECs and Unnecessary Complications
- The Universal Low-Carbon Building Standard’s Path to Adoption
 For some reason, the GHG accounting industry does not include emission factors for upstream methane leakage, and that should be added to the scope 3 sources. This would add at least a 25% penalty to the GHG emissions resulting from the combustion of the gas.
 In many cases, a company’s work-from-home policy might already be providing the intended TDM effect. Bringing people back to work will be a great opportunity to rethink the TDM opportunity.
 Denver has introduced an EUI-target-based program by asset type. It also includes an electrification bonus. The $0.30/kBtu penalty for non-compliance is an excellent motivator for building owners to improve their efficiency and electrify their systems. To use one example, office buildings have a 2030 EUI target of 48.3. If I have a 200k SF office building with an EUI of 60, then I would pay 11.7*$0.3*200,000 = $700,000 per year.
Radoff, J. (2023, September 6). The Universal Low-Carbon Building Standard Does Six Things . Retrieved from https://www.buildinggreen.com/op-ed/universal-low-carbon-building-standard-does-six-things