Steam-Heated Buildings Are the Hardest LL97 Case

Purpose and Scope

This article is written for owners, boards, and managing agents of buildings that take district steam from the utility. It explains why those buildings face the most difficult Local Law 97 (LL97) arithmetic in the 2030 to 2034 compliance period, which measures change the result, and why dividing a steam building's penalty among its occupants is harder than in other buildings.

It does not address legal questions about lease pass-throughs or condominium allocation, and it does not describe the design of any particular system. Those belong with counsel and with the building's engineers.

How LL97 Counts Steam

LL97 converts each form of energy a building uses into tonnes of carbon dioxide equivalent (tCO₂e) using a coefficient set in the law or in the Department of Buildings (DOB) rule, 1 RCNY §103-14. For calendar years 2024 through 2029 the coefficients are in Administrative Code §28-320.3.1.1. For 2030 through 2034 they are in the DOB rule.

Steam is counted at a rate per kBtu about 15 percent lower than natural gas, but it is still a fossil coefficient, and it changes very little in 2030. The electricity coefficient falls by about half because electricity is counted at the carbon intensity of the grid, and the City expects the grid to be cleaner by then. A building whose heating and cooling run on electricity receives that benefit automatically. A building whose heating, hot water, and often cooling run on steam does not.

Two other provisions of the rule matter for steam buildings. Renewable energy credits may only be deducted from emissions attributed to utility electricity, so they cannot be applied against steam. Offsets purchased through the City's Affordable Housing Reinvestment Fund are capped at 10 percent of a building's annual emissions limit.

A Worked Illustration

The following example uses hypothetical figures for a 300,000 square foot office building with district steam serving heating, domestic hot water, and a steam-driven cooling plant. The figures are illustrative and are not drawn from any specific building.

Several features of this example are typical of steam buildings.

The building is compliant today, with some room to spare, so LL97 may not have looked like an immediate concern.

Electricity does most of the improving. Electricity emissions fall by about 576 tonnes between the periods with no change in consumption. Steam emissions fall by about 42 tonnes.

Steam becomes the dominant line. It accounts for about 48 percent of emissions in the first period and about 64 percent in the second.

Reducing steam use alone is not enough. To meet the 2030 limit with electricity unchanged, steam consumption would have to fall by about 78 percent. No combination of traps, insulation, and controls produces a reduction of that size. The result has to come from moving load off steam.

The multifamily version looks similar. The Multifamily Housing factor also falls by about half, and residential steam buildings carry a large hot water load year round. For a first estimate from a building's own benchmarking data, the LL97 calculator applies the coefficients and factors for each period.

Where the Steam Goes

In most steam buildings a single utility meter measures all of the steam the building takes. That steam then serves several loads that behave differently.

The first analytical step is to separate these loads. Monthly billing data compared against heating and cooling degree days shows how much steam is weather driven and how much is baseload. Where the building has submetering or a building management system, the breakdown can be refined. Without it, a projection shows the size of the gap but not which measures close it.

The Realistic Options

The measures below are listed in the order in which they are usually considered. The right combination depends on the building's equipment, electrical capacity, and physical constraints.

1. Reduce steam consumption

Steam trap repair, pipe and tank insulation, pressure reducing station tuning, condensate management, controls, and envelope work all reduce consumption at relatively low cost, and several are among the prescriptive measures the law requires in certain buildings. They are worth doing. In a building well over its 2030 limit, they are a starting point rather than a solution.

2. Move cooling off steam

Where a building cools with steam-driven absorption chillers, replacing them with electric chillers changes the result in two ways. An electric chiller uses far less input energy for the same cooling than an absorption machine, so the energy counted falls sharply. The energy that remains is electricity, which after 2030 is counted at the lower coefficient. This measure requires electrical capacity, which has to be confirmed with the utility.

3. Move domestic hot water off steam

Heat pump water heaters, or a smaller electric plant with storage, can take the hot water load off steam entirely. In residential buildings this load runs every day of the year, so its emissions effect is larger than its share of the steam bill suggests.

4. Convert distribution to hot water and add heat pump capacity

Many steam buildings distribute steam directly to radiators or coils. Converting to a hot water loop supplied through a heat exchanger does not by itself change the fuel. It does allow a heat pump plant, air-source or water-source, to carry part of the heating load. A plant sized for a fraction of the peak can serve a large share of the heating hours, with steam carrying the coldest days. This hybrid arrangement is often the practical middle ground for buildings that cannot electrify fully before 2030.

5. Electrify fully

Full electrification removes steam from the building. In practice it depends on electrical service capacity, space for equipment, riser routing, and, in landmarked buildings, approvals for exterior equipment. Utility service upgrades follow the utility's own schedule. For many steam buildings this is a later-period measure rather than a 2030 measure.

6. Administrative pathways

DOB's rule provides for mitigated penalties where an owner demonstrates good faith efforts, and allows the Department to offer a mediated resolution to an owner who has filed, demonstrated such efforts, and can show the resolution would help the building meet its limit. These provisions are specific to the 2024 to 2029 period and carry conditions. They are not a substitute for a plan, but a documented plan is central to using them.

Why Allocation Is Contested in Steam Buildings

Our earlier article on landlord and tenant cost allocation describes the common methods for dividing a penalty among occupants. Steam buildings make each of them harder, for three reasons.

One meter, many loads. Tenant electricity is commonly submetered. Steam rarely is. The building knows how much steam it bought, but not how much went to the trading floor with a 24-hour cooling requirement, the restaurant with process steam, or the residential floors with hot water demand. An allocation by floor area treats all of these spaces alike. An allocation by modeled use depends on assumptions that each occupant can challenge.

The loads do not scale with area. A ground-floor restaurant can take a disproportionate share of hot water and process steam. A tenant with supplemental cooling off the building's steam plant can drive summer consumption. Occupants whose use is low relative to their area have a reasonable objection to an area-based share.

The limit is blended. In a mixed-use building the limit is the sum of each property type's area multiplied by its factor. The way floor area is assigned to each type changes both the building's limit and each occupant's share.

Data quality compounds this. Benchmarking submissions indicate whether each energy value was measured or estimated, and in our experience estimated values appear more often for district steam than for electricity. A projection or allocation built on an estimate inherits its uncertainty. Our article on benchmarking errors covers the checks that apply.

What a Steam Building Should Do Now

1. Confirm the data. Verify that the steam in the benchmarking record is measured, that the conversion from the utility's billing units to kBtu is correct, and that floor area and property types match the building.
2. Separate the loads. Build an end-use breakdown of steam from billing history, degree days, and whatever metering exists.
3. Project both periods. Run the 2024 and 2030 arithmetic with the correct coefficients, and show the gap in tonnes and in dollars.
4. Test the measures in order. Model consumption reductions, cooling, hot water, and hybrid heating as cumulative scenarios, with capital cost, incentive conditions, and schedule for each.
5. Confirm electrical capacity early. Every measure that moves load to electricity depends on it, and utility timelines are outside the owner's control.
6. Address allocation before 2030. Lease renewals and board discussions in the next few years are the opportunity to agree on a method while the penalty is still small or zero.

How the Work Is Organized

The managing agent holds the billing history and the benchmarking record. The building's engineers assess the steam plant, the distribution system, and the electrical service, and design any work that follows. Contractors provide pricing. Counsel advises on leases and allocation. Where DOB requires a report or plan to be certified, the certification is made by a registered design professional.

DE Energy Consultants provides technical advisory and consulting services for steam-heated buildings. We prepare the end-use breakdown, the emissions projection for each compliance period, measure-by-measure scenarios, and allocation analyses that reconcile to the building's filing. We work alongside the managing agent, the building's engineers, and its other advisors.

Next Steps

For a first estimate of a building's position in each compliance period, use the LL97 calculator. For background on the penalty calculation, see How NYC's Local Law 97 Fines Work. For how a projection becomes a capital plan, see Budgeting LL97 Into a Co-op or Condo Reserve Study.

To discuss a projection or allocation analysis for a steam building, see our services or contact us.