Methodology

Glimpse Calculator Technical Methodology
Glimpse Calculator Technical Methodology: API
Building Stock and Portfolio Studies

Glimpse Calculator Technical Methodology

Learn how the Glimpse Calculator leverages building energy modeling, U.S. building stock data, and equipment specifications to analyze energy savings.

The Technical Methodology at a Glance

Concept	Description
Intro	Glimpse Calculator is a software technology developed by the Constellation Navigator Virtual Energy Efficiency Team. It replaces resource-heavy manual consulting processes by combining building energy modeling, U.S. building stock data, and the latest technology specs to analyze the energy savings of Energy Improvement Measures (EIM).
Energy Models	Uses live building energy models created and simulated in Energyplus. These simulate building-environment interactions at hourly/sub-hourly levels, capturing specific geometry, construction, lighting, HVAC, and DHW configurations.
Input & Scenarios	Calculations are structured at the building level. Missing user inputs are inferred from building stock data to create a “Baseline” scenario. EIMs are then applied to create “EIM” scenarios. All models are simulated for a year using the closest Typical Meteorological Year (TMY) weather environment.
Output Metrics	Produces baseline results (annual energy usage, utility cost, emissions) and EIM impact results. Optional analyses include required investment, life cycle impact, available rebates, benchmarking, and building performance standards analysis.

Public Data Sources

Data Category	Sources & Application
Building Stock Attributes	When not input by the user, Glimpse infers over 500 attributes based on age, function, climate, and main heating fuel. Major sources include DoE Commercial Reference Buildings, PNNL Residential Prototypes, EIA’s CBECS & RECS, manufacturer specs, and the American Community Survey.
Weather & Climate	TMY weather data is sourced from the official EnergyPlus database (TMY3 data). Future weather can be constructed using climate change model outputs from the WCRP’s CMIP58 multi-modal dataset.
Utility Rates & Emissions	Electric utility rates use proprietary sources, the OpenEI US Utility Rate Database, or state/industry averages from EIA databases. Emissions factors for electricity and combustible fuels come from Constellation Navigator’s Carbon Accounting API.

Reference Links

Capabilities

Methods	Features
Building Stock or Portfolio Studies Glimpse Platform Glimpse API	Energy Improvement Measures (EIMs) Building Performance Standards Rebates Lifecycle Cost and Impact Analysis Calibration to Measured Energy Usage

Glimpse Calculator Technical Methodology: API

Integrate the Glimpse Calculator directly into your own software using our comprehensive API, offering both simple (pre-simulated) and detailed (on-demand) calculations.

Developer Information

The Virtual Energy Efficiency Team maintains robust and up-to-date API documentation. Access to our endpoints, authentication guides, and schemas are readily available for approved integrators.

Resource	Details
API Documentation	Available on ReadMe. Note: This page is only accessible to API Members (Become an API member today).

Simple Building Calculations (Tier 1)

The simple API offers the same output options as the detailed API, but is designed for use cases when only a minimal amount of information is known about a building.

Faster Response Times

This method speeds up response time significantly because a model for each possible combination of the required parameters has been pre-simulated, removing energy model simulation time from the equation.

Requirement	Details
Required Attributes	Building type Zip code Year of construction or last renovation Primary heating fuel Floor area (square feet)

Detailed Building Calculations (Tier 2)

The detailed API provides access to on-demand building energy models. It creates models of the baseline and EIM scenarios, simulates them, and processes the results in real-time.

Component	Details
Inputs	Energy-relevant attributes of roofs, walls, windows, skylights, lighting systems, HVAC systems, hot water systems, elevators, and operations characteristics. (Includes Tier 1 inputs to allow the Calculator to make assumptions for missing values).
Calibration Feature	If utilizing calibration, the user must pass monthly energy usage per fuel type used in the building for each month in a representative year.
Standard Outputs	Annual energy usage, utility cost, and emissions of the baseline scenario, plus the savings of all three metrics for each of the simulated EIMs.
Optional Outputs	Economics: EIM-relevant rebate details, equipment info, and install costs. Life-cycle Analysis: Useful life, lifetime energy savings, cost savings, emissions reduction, NPV, and IRR. Building Performance Standards: State/municipal policy fines, targets, dates, compliance routes, and avoidance strategies.

Building Stock and Portfolio Studies

The Virtual Energy Efficiency team offers streamlined access to the Glimpse calculator through advisory contracts, helping businesses and municipalities gain energy efficiency insights at a massive scale.

Scale and Application

We perform large-scale analyses across a variety of geographic and commercial boundaries.

Analyses Performed On	Examples of Insights Produced
State governments’ building stocks Utility companies’ customer portfolios Solution manufacturer’s geographic markets Financial institutions’ mortgage portfolios Corporations’ commercial building portfolios	Highlighting buildings with the largest energy efficiency opportunities. Quantifying energy efficiency contributions toward Net Zero or SBTI goals. Quantifying portfolio risk regarding state/municipal Building Performance Standards. Quantifying Scope 3 emissions across a portfolio. Quantifying the impact of demand-side-management program strategies.

Insights with Just an Address

If a portfolio is represented only by a list of addresses, our team uses proprietary sources to find the necessary Tier-1 parameters (building type, heating fuel, square footage, date of construction, and zip code).

Step	Process & Resolution
1. Data Sourcing	Each address goes through a minimum of two data sources to find the required Tier-1 attributes.
2. Heating Fuel	If heating fuel is not publicly available, CBECS, RECS, or ACS data is used alongside building type and location to assign probabilities and select a fuel type via a uniform distribution.
3. Fill Blanks	If attributes (other than heating fuel) are missing, dataset averages are used to fill in the blanks based on building type or the general set.
4. Edge Cases	If an address is missing or represents a partial building (e.g., a specific apartment unit), we work with the client to resolve parameters. We can utilize public floor/unit counts to calculate unit square footage, or use the client's internal data to generate square footage assumptions.
5. Calculate	The team accesses the Glimpse Calculator through the Tier-1 API and organizes the results by building.
6. Deliver	Any subsequent, custom analyses are performed and delivered to the client.

Customization Options

Working with the Virtual Energy Efficiency team allows for deep customization of the calculation process.

Customization Type	Description
Detailed Modeling (Tier-2)	If a building dataset has additional information (e.g., known wall, window, or roof types), these are incorporated into the calculations using the Tier-2 Detailed method.
Specific EIMs	If specific hardware is being considered (e.g., installing a partner’s specific cold-climate heat pump model), that exact EIM can be built out and automated across applicable buildings.
Rates & Emissions	If specific utility rates or emissions factors apply to your portfolio, those exact figures are used to calculate resulting energy costs and emissions.

Map User Interface

The map user interface helps clients view and interact with portfolio results by adding 3D building attributes to the data set.

Geocoding: Latitude and longitude are found for each address via Google’s geocoding API. (If this fails, the building is not displayed on the map).
3D Rendering: Using the coordinates, Constellation Navigator’s geographic information vendor checks for overlapping 3D building attributes. If found, a 3D building is rendered; if not, a general building icon is shown.
Interaction: Clicking the 3D building or general icon reveals the baseline and EIM results associated with that building via a waterfall graph.

Table of contents