How we calculate grades

Blueprint reads official public records for a building and turns them into a single A to F grade. This page explains, in plain English, how that calculation works, so you can understand what the grade means and what it does not. Blueprint is part of Vasly.

The two steps

Every grade comes from the same two-step process:

• 1. A severity-weighted point total. Each relevant record is weighted by how serious it is, and the weighted records are added up into a single point total for the building.
• 2. Normalize and grade against similar buildings. The total is divided by the number of units, then compared against thresholds that depend on the building's size, so a large building is not penalized simply for having more records.

Step 1: severity weights

Not every record means the same thing. An open, most-serious housing violation matters far more than a single closed one or a routine complaint, so each record type carries a weight. The point total is the sum of (count × weight) across all records that fall within a recency window, so older, resolved issues count for less.

The exact weights vary by city, because each city publishes its records differently, but they all follow the same severity logic. The table below uses New York City as the worked example, since it has the most detailed records:

Step 2: per-unit normalization and size cohorts

A 100-unit building will naturally have more records than a two-family home, even if it is run well. To make the comparison fair, the point total is divided by the number of units to get a per-unit score. That per-unit score is then compared against thresholds that depend on the building's size cohort.

A building earns a grade when its per-unit score is below the value listed for that grade. If it is above the D threshold, it grades F.

When the unit count is unknown

Sometimes the public records do not say how many units a building has. In that case Blueprint cannot do the per-unit normalization, so it falls back to grading the raw point total against absolute thresholds:

• Total below 2 → A
• Total below 10 → B
• Total below 28 → C
• Total below 60 → D
• Otherwise → F

When this fallback is used, the grade is flagged as approximate, because it is based on the total alone rather than a per-unit comparison.

The 0 to 100 score

Alongside the letter, Blueprint shows a 0 to 100 score as a companion number on the same scale. It is a display value pegged to the letter grade, so the two always agree:

• A - 80 to 100
• B - 60 to 80
• C - 40 to 60
• D - 20 to 40
• F - 0 to 20

A worked example

Take a 12-unit New York City building, looking at records over roughly the last three years. Suppose it has:

• 2 open Class C violations - 2 × 5 = 10
• 3 other open housing violations - 3 × 2 = 6
• 4 closed housing violations - 4 × 0.3 = 1.2
• 1 executed eviction - 1 × 6 = 6
• 5 311 complaints - 5 × 1 = 5

That adds up to a point total of 28.2. Divided by 12 units, the per-unit score is 28.2 / 12 = 2.35. The building is in the 11 to 50 unit cohort, where 2.35 falls between the B threshold (1.8) and the C threshold (4.0), so it grades C - a 0 to 100 score of about 55.

International grades

The A to F grade above is a Blueprint condition grade, built from a building's own permit, violation, and complaint records. It is offered in select cities where that record-level data is open. Outside those cities, each country publishes different records, so Blueprint grades each country on its own terms and labels honestly what the grade measures. We never let an energy grade read as a condition grade, and a grade in one country is not comparable to a grade in another. Every graded country is calibrated within that country against its own national scale.

• Native energy grades (surfaced as-is). Some countries run an official, public, keyless building-energy register with its own letter scale. Where one exists, Blueprint shows that official letter unchanged, clearly marked as an energy grade.
• Area and risk views. For markets without a keyless per-building grade, Blueprint shows planning, permit, hazard, and neighborhood data as an area view rather than inventing a letter grade.

France: the DPE energy grade

For a French address, Blueprint surfaces the building's DPE (Diagnostic de Performance Energetique), France's official national energy-performance label, on its own A to G scale where A is the most efficient home and G the least. The letter is taken directly from the public ADEME DPE register and is shown unchanged. It is an energy grade about heating and energy cost, not a structural condition grade, and it is not comparable to a Blueprint A to F grade or to an energy label in any other country. Because the register is keyed by certificate rather than by every address, the certificate shown is the nearest one on file and may belong to a neighbouring unit; the report says so. Alongside the DPE, the French report shows the CO2 (GES) label and the Georisques hazard layers (radon potential, seismic zoning, clay shrink-swell, and nearby classified industrial sites) as context, not as part of the energy grade. Source: ADEME DPE register and Base Adresse Nationale, both free and keyless. See the data sources page for the exact endpoints.

Italy (Lombardy): the APE energy grade

For an address in the Lombardy region, Blueprint surfaces the building's APE (Attestato di Prestazione Energetica), Italy's official energy performance certificate, on the national A4 to G scale where A4 is the most efficient home and G the least. The letter is taken directly from Regione Lombardia's open CENED register and shown unchanged. It is an energy grade, not a structural condition grade, and it is not comparable to a Blueprint A to F grade, to France's DPE, or to any other country's label. Because the register is keyed by certificate, the grade shown is the most recent certificate on that street and may belong to a neighbouring unit; the report says so. APE certificates are published openly only for the Lombardy region, so the grade resolves for Lombardy addresses; elsewhere in Italy the address still geocodes but shows no energy grade. Source: Regione Lombardia CENED open data, free and keyless. See the data sources page.

Singapore: BCA Green Mark (a certification, not a grade)

For a Singapore address, Blueprint shows recent HDB resale prices as a neighborhood view, and, when the building holds one, its BCA Green Mark certification tier (Certified, Gold, GoldPlus, or Platinum) from data.gov.sg. Green Mark is a voluntary green-building certification, so we show it only as a fact when present. Its absence does not mean a building is poor, so we never turn it into a letter grade. Source: data.gov.sg (BCA Green Mark), free and keyless.

The neighbourhood area-risk score

For markets that do not have a per-building grade, Blueprint shows a neighbourhood area-risk score from 0 to 100, where 100 is the lowest risk. It is deliberately not an A to F condition grade and not about the building itself: it summarizes risk in the surrounding area. It combines one global, keyless signal, air quality (the European AQI from Open-Meteo, available at any coordinate on Earth), with whatever official risk layers that country already publishes openly, such as flood-risk zones, seismic zoning, radon potential, clay shrink-swell, nearby classified industrial sites, or aircraft noise. Each factor is scored on a simple low-to-high band, the factors are averaged, and the result is mapped to a band: 75 to 100 Low, 50 to 74 Moderate, 25 to 49 Elevated, below 25 High. The report lists the exact factors that fed the score. It is calibrated to absolute risk bands, not ranked between countries, so it reads the same way everywhere, and it is a starting point for your own research, not a verdict on the building.

What's not in the grade

Blueprint also shows a national, area-level risk layer drawn from hazard data such as FEMA, USGS, and EPA sources. That is a separate area-risk overlay about the surrounding area, and it is not part of the building's A to F grade. The grade reflects the building's own records; the risk layer is context about the area around it.

Corrections

Records can be wrong, incomplete, or delayed at the source. If a record or a grade looks wrong, head to Support and email us the address and what you believe is incorrect. We will check the underlying source. The grade is an estimate, not an official rating - always verify in person.