Understanding the 35% Rule
For affordable and mixed-income building owners navigating Local Law 97, one distinction makes all the difference: the 35% rent-regulated threshold.
≥35% Rent-Regulated
Affordable Housing Designation
- Decarbonization plan due 2025
- Adjusted 2030 emissions caps
- Extended compliance timeline
<35% Rent-Regulated
Standard Compliance Track
- 2026 compliance deadline
- Same 2030 caps as market-rate
- No emissions adjustment
"After 2026, they will need to meet subsequent deadlines on the same timeline set for all other Covered Buildings."
Important: Tenant-Based Vouchers
Buildings relying on tenant-based vouchers (Section 8, etc.) do not qualify for any exception. These properties are fully covered under LL97 with no delay.
The Affordable Housing Challenge
Mixed-income building owners face a unique challenge: the same 2030 emissions targets as luxury towers, but without the same resources.
Limited Capital
Thin margins make major retrofits difficult
No Rent Increases
Rent-regulated units can't fund improvements
Same 2030 Cap
50% reduction required regardless
Creative Solutions
Low-cost preservation strategies exist
A Cost-Effective Preservation Strategy
For affordable housing owners facing the 2030 compliance cliff, asset preservation offers a path forward without massive capital支出.
How Scale Prevention Helps
- 12-18% immediate efficiency gain — Restore lost performance in existing boilers and heat exchangers
- 5-7 years extended equipment life — Defer costly capital replacements
- Verifiable Good Faith documentation — Meet DOB audit requirements
- Zero tenant disruption — No apartment entry, no construction
- No chemicals, no salt, no maintenance — Ideal for understaffed buildings
Recommended for Mixed-Income Buildings
For most multifamily applications, the Vulcan V5000 or S10 models provide the right capacity.
| Annual energy cost (200-unit building) | $80,000 |
| 12-18% efficiency gain from scale removal | $9,600 - $14,400 saved/year |
| Vulcan model (typical installation) | Login for pricing |
| Estimated payback period | 3-8 months* |
Pricing Note: For exact pricing tailored to your building's specifications, log in to your account or create a free account to view detailed pricing and configuration options.
* Savings and payback vary based on building size, water conditions, and existing scale buildup.
Real Proof: A Swiss Homeowner's Experience
Location: Haut-Intyamon, Switzerland
Property Type: Single-family residential home
The Challenge
Like many older homes, this property had significant mineral scale buildup in the hot water system. The scale had become "rock hard" and difficult to remove, affecting water heater efficiency and requiring frequent maintenance.
The Solution
The homeowner installed a Vulcan V5000 — the ideal model for residential applications with pipe diameters up to 2 inches and flow rates up to 35 GPM.
The Results (after 6 months)
- "Almost no trace of hard limescale was visible in our hot water tanks."
- "A simple soft brush was sufficient to clean it."
- "Before the mineral scale was rock hard."
Why This Matters for Affordable Housing: If a single-family home can achieve this level of scale removal with the V5000, imagine the impact on a 200-unit building's central hot water system. The same principle applies—scale prevention preserves equipment, reduces energy costs, and improves resident experience.
Swiss residential property — Rock-hard scale eliminated with Vulcan V5000
Finding the Right Model for Your Building
Different building sizes require different Vulcan models. Here is a quick reference for affordable housing applications:
| Building Size | Recommended Model | Pipe Diameter | Flow Rate | Typical Application |
|---|---|---|---|---|
| Small building (5-20 units) | Vulcan V5000 | Up to 2" | 35 GPM | Domestic hot water, small boilers |
| Mid-size (20-50 units) | Vulcan S10 | Up to 3" | 65 GPM | Central hot water, heat exchangers |
| Large (50-150 units) | Vulcan S25 | Up to 4" | 130 GPM | Boilers, recirculation loops |
| Very large (150+ units) | Vulcan S50 or S100 | Up to 6" | 300-530 GPM | District heating, large central plants |
Not sure which model fits your building? Contact our team for a free assessment.
Building Your Good Faith File
For buildings in the <35% category, documenting "Good Faith Efforts" is essential for penalty reduction. Here is what to include:
Required Elements
- ASHRAE-level energy audit
- Board-approved capital plan
- Financing commitments
- Permits filed with DOB
- Signed retrofit contracts
Value-Added Documentation
- Vulcan installation date (capital invested)
- Pre-installation efficiency measurements
- Post-installation delta-T improvement
- 12-18% verified efficiency gain
- Maintenance records for existing equipment
Vulcan provides all the documentation needed to demonstrate proactive equipment maintenance—a key factor DOB auditors now consider.
The Affordable Housing Math
For a fraction of boiler replacement cost, scale prevention can extend equipment life 5-7 years and reduce emissions immediately.
Pricing Note: For exact pricing tailored to your building, log in to your account or create a free account.
Taking Action Before 2030
- Step 1: Determine your rent-regulated percentage. If <35%, you are on the standard compliance track.
- Step 2: Conduct a pre-audit assessment of your mechanical systems. Measure heat exchanger delta-T and boiler efficiency.
- Step 3: Consider low-cost preservation measures like scale prevention before major capital projects.
- Step 4: Document everything for your Good Faith file—installation dates, measurements, improvements.
- Step 5: Explore financing options including C-PACE, NYSERDA incentives, and Con Edison programs.
- Need help? Contact our team for a free building assessment and model recommendation.
Supporting Affordable Housing Owners
We're here to help mixed-income buildings meet their sustainability goals while preserving valuable assets.
About the Author
Waslix- Clearly Clean Water (Vulcan Mineral Descaler) provides non-chemical, maintenance-free scale prevention solutions that help affordable housing owners protect their assets, reduce energy costs, and meet LL97 compliance goals. Create an account for detailed model specifications and pricing.
