CS76 Energy Code Feasibility Study in Northbridge, Massachusetts
Energy code feasibility study for a 105-unit Multifamily in Massachusetts. Compares multiple design paths. Recommended: NEXTGEN-ECC (All-Electric). View full study.
- Study Type
- Energy Code Feasibility Study
- State
- Massachusetts
- Units
- 105
- Building Type
- Multifamily
- Fuel Type
- Mixed Fuel
- Recommended Path
- NEXTGEN-ECC (All-Electric)
Goal
To find the most cost-effective compliance path, this report isolates energy code related costs from total construction. We use real bid data from vendors & clients to create a reliable framework for aligning incentives and design, with all recommendations confirmed by detailed energy modeling.
Project
- Northbridge, MA
- 53 Buildings | 105 Units | 189,000 SF Conditioned
- New Construction | Multifamily Low-Rise | 53 single-story buildings, 105 age-restricted (senior living) units; 2 unit types (left/right), 1,800 SF conditioned each
- Mixed Fuel | MA Stretch Code | HERS ≤ 45 (Carbon Credit Path)
- All-Electric | MA Stretch Code | HERS ≤ 45 | ESTAR SFNH v3.2 | ESTAR NextGen v1.0
- All-Electric | MA Stretch Code | HERS ≤ 48 (Carbon Credit Path) | ESTAR SFNH v3.2 | ESTAR NextGen v1.0
Overview
Read This: This report compares different ways you can build the project and meet energy code, looking at both cost and incentives, with the ultimate goal as finding the most affordable path.
- The overview outlines the key differences between each of the paths we show in this report and why we recommend the one we picked over the others.
- The recommended design section is where we share the requirements and incentives for the path we think is best based on affordability.
- The path comparison section shows the detailed requirements and incentives for each path we compared, basically showing our work if you want to dig in.
Path Summaries
All three paths meet Massachusetts energy code and are modeled to pass on a lean margin, so the choice between them comes down to cost, constructability, and fuel preference rather than compliance.
NEXTGEN-ECC (All-Electric): Recommended
This is the least expensive path at $31.70/sf net, and it is straightforward to build with one all-electric system. It keeps the project fully electric, preserving eligibility for available incentives and aligning with the direction Massachusetts energy code is heading. For most projects, this is the right choice.
NEXTGEN (All-Electric): Alternative (Simpler Sourcing)
At $35.29/sf net, about $4/sf more than the recommended path, this path shares the same all-electric system and is equally simple to build. It keeps material sourcing normal and skips the extra credit paperwork the recommended path carries. Choose this path when simpler sourcing and paperwork are worth the extra $4/sf.
GAS-ECC (Mixed-Fuel): Alternative (Gas Service)
At $45.09/sf net, about $13/sf more than the recommended path, this is the most expensive option and the most labor-intensive to build. The premium buys gas service: heating capacity that holds steady through the coldest stretches of a Massachusetts winter, which carries weight for a senior-living population, and a fuel many buyers still ask for by name. Choose this path when dependable heat in extreme cold matters more to the project than first cost and incentive eligibility.
What Changes Between Paths
Every other line item is the same build. Price these 10 items against each other and you have the full cost difference between paths. Paths are ordered by net cost, lowest on the right.
Item | GAS-ECC | NEXTGEN | NEXTGEN-ECC (Recommended) |
|---|---|---|---|
Exterior Walls | R-21 dense-pack cellulose cavity insulation (2x6 @ 16" o.c.) with R-3.8 continuous exterior EPS/graphite insulation. Walls to the unconditioned garage: R-23 dense-pack cellulose cavity insulation (2x6 @ 16" o.c.). | R-21 cavity insulation (2x6 @ 16" o.c.) with R-3.8 continuous exterior insulation. Walls to the unconditioned garage: R-23 cavity insulation (2x6 @ 16" o.c.). | R-21 dense-pack cellulose cavity insulation (2x6 @ 16" o.c.) with R-3.8 continuous exterior EPS/graphite insulation. Walls to the unconditioned garage: R-23 dense-pack cellulose cavity insulation (2x6 @ 16" o.c.). |
Roof | Vented attic: R-49 blown cellulose insulation. | Vented attic: R-49 insulation. | Vented attic: R-49 blown cellulose insulation. |
Windows & Glass Doors | Triple pane, U-0.18 / SHGC 0.18. | Triple pane, U-0.18 / SHGC 0.18. | Double pane, U-0.30 / SHGC 0.30. |
Air Sealing | ≤0.23 CFM50 per sqft of enclosure (compartmentalization); tested. | ≤0.08 CFM50 per sqft of enclosure (compartmentalization); tested. | ≤0.08 CFM50 per sqft of enclosure (compartmentalization); tested. |
HVAC | Natural gas combi boiler (as modeled); 0.96 adjusted efficiency; also provides domestic hot water (one combi appliance, not two); cooling by a separate ducted air-source heat pump, cooling only; SEER2 18; heating sized to a 25.1 kBtuh design heat loss; cooling 2BR: 12 kBtuh; sized to the worst-case design load per bedroom count, see HVAC Design Loads | Ducted air-source heat pump, SEER2 17 / HSPF2 10; 2BR: 30 kBtuh; sized to the worst-case design load per bedroom count, see HVAC Design Loads | Ducted air-source heat pump, SEER2 17 / HSPF2 10; 2BR: 30 kBtuh; sized to the worst-case design load per bedroom count, see HVAC Design Loads |
HVAC Grading | Fan Flow Test: N/A; Watt Draw Test: N/A; Refrigerant Charge: N/A | Fan Flow Test: Grade I; Watt Draw Test: Grade I; Refrigerant Charge: Grade I | Fan Flow Test: Grade I; Watt Draw Test: Grade I; Refrigerant Charge: Grade I |
Mechanical Ventilation | In-unit ERV; 50 CFM; ≥83% recovery efficiency (Panasonic Intelli-Balance 100). | In-unit ERV; 65 CFM; ≥81% recovery efficiency (Panasonic Intelli-Balance 100). | In-unit ERV; 65 CFM; ≥81% recovery efficiency (Panasonic Intelli-Balance 100). |
DHW | Gas combi boiler with integral tankless water heater (as modeled); UEF 0.96; also provides space heating (one combi appliance, not two). | Integrated heat pump water heater (HPWH) (as modeled); UEF 3.5; 50 gal. | Integrated heat pump water heater (HPWH) (as modeled); UEF 3.5; 50 gal. |
Paperwork & Modeling | HERS energy model to the code ERI target. | ENERGY STAR energy model to the ERI target, the ENERGY STAR design-review checklist, and an HVAC design report. Plus ENERGY STAR NextGen documentation: all-electric equipment and EV-charging provisions. | ENERGY STAR energy model to the ERI target, the ENERGY STAR design-review checklist, and an HVAC design report. Plus ENERGY STAR NextGen documentation: all-electric equipment and EV-charging provisions. |
Testing & Verification | HERS field verification: pre-drywall and final inspections, blower-door and duct-leakage tests. | ENERGY STAR field verification: pre-drywall and final inspections, blower-door and duct-leakage tests, ventilation airflow, and HVAC installation grading. Plus ENERGY STAR NextGen verification: all-electric equipment and EV-charging infrastructure. | ENERGY STAR field verification: pre-drywall and final inspections, blower-door and duct-leakage tests, ventilation airflow, and HVAC installation grading. Plus ENERGY STAR NextGen verification: all-electric equipment and EV-charging infrastructure. |
Cost $/sf | $44.22 | $42.94 | $39.42 |
Incentive $/sf | $0.00 | $8.33 | $8.33 |
Net $/sf | $45.09 | $35.29 | $31.70 |
Code Path
Single Family OR Low Rise Buildings (Stretch)
Single-Family / Townhome, 1 story
MA Stretch Code | HERS ≤ 45 or HERS ≤ 48 (Carbon Credit Path)
The project is governed by the Massachusetts Stretch Code (225 CMR 22), the Commonwealth's amendments to the 2021 IECC for low-rise residential buildings, which applies in Stretch and Specialized municipalities. Compliance is demonstrated on the HERS/ERI performance path, and Table R406.5 sets the ceiling by project type. New construction is rated to HERS 42 mixed fuel or HERS 45 all electric, and to HERS 45 or HERS 48 respectively where the project takes an R406.5.2 embodied-carbon credit, with all insulation installed at Grade I and continuous balanced ventilation with heat or energy recovery. Major alterations, additions and changes of use under Sections R502.1.1 and R503.1.5 are rated to HERS 65 mixed fuel or HERS 70 all electric, and carry the other R406 provisions, including recovery ventilation and a solar-ready roof, where that component is within the project scope. Accessory dwelling units are rated to HERS 52 mixed fuel or HERS 55 all electric. The ceiling that governs this project is the one shown with the code path above.
Permit / Certificate of Occupancy Requirements
At permitting, the HERS compliance documentation is submitted with the building permit application: the projected rating with the component specifications behind it, the software and analyst, and the modeling inputs.
At certificate of occupancy, each unit is confirmed at or below its HERS ceiling: blower-door testing (attached units may use the 0.30 CFM50 per square foot of enclosure path, sampled), duct-leakage and ventilation testing by a HERS Rater or BPI professional, and the final Home Energy Rating Certificates.
Embodied Carbon Credit - Insulation
Massachusetts raises the HERS ceiling by 3 points when the insulation in the building envelope stores more carbon than its manufacture released. This credit applies to the GAS-ECC and NEXTGEN-ECC paths.
Every insulation material carries a Global Warming Potential value, measured in kilograms of CO2e per square meter at RSI-1. Foam products are positive because making them releases carbon. Plant based and recycled products are negative because the material holds carbon that would otherwise reach the atmosphere. Each assembly contributes its R-value times its area times a framing factor times its GWP value, where the framing factor is 1.0 for continuous insulation and 0.8 for cavity insulation. Add every assembly together, and a total below zero earns the credit.
The design as modeled for NEXTGEN-ECC already clears the threshold, so no material change is needed to earn the credit. The calculation below records it.
The result is a net 59,851 kg CO2e stored, which earns the 3 point credit.
Values come from Table R406.5.3 of the state code. A product specific Type III EPD may be substituted where the product performs better than the table default, in which case the declaration number is submitted with the calculation. To claim the credit the rater submits this calculation, and an approved third party verifies compliance under R406.6.
Embodied Carbon Credit - Insulation (GAS-ECC, NEXTGEN-ECC)
Recommended Design
This section outlines the design requirements, product recommendations, and incentives for the design that we believe will be the most affordable path to meeting energy code.
Recommended Design - Incentives
Incentives Available: $1,560,000 - $1,716,000
- MassSave Single-Family ENERGY STAR Certification ($1,560,000) (Program Breakdown): You get this rebate for having each townhome ENERGY STAR NextGen certified. Certification typically occurs at the end of construction around when certificate of occupancy is received. This rebate comes in the form of a check within 4 months of the certification paperwork being provided to MassSave.
- DOER Alternative Energy Credits ($0 - $156,000) (Program Breakdown): This rebate is received for installing APS eligible air source heat pumps (click here for the list). There is an extensive process to get this incentive. It comes in the form of a check approximately 6-12 months after the heat pumps are installed and fully operational.
- IMPORTANT: Although an estimate is provided, this incentive can vary widely typically between $300-1,500 per heat pump. It's based on expected kWh usage of the system as well as the market value of the alternative energy credits when sold.
- Risks: Massachusetts is rewriting this program right now. The House bill would stop the state from accepting new applications on January 1, 2028, the Senate version leaves heat pumps out of that cutoff, and the two are in conference. The application needs the equipment installed and operating, so a project that will not reach that point before the deadline should treat this as upside rather than a budgeted line.
HVAC Design Loads
Worcester County, MA · heating -2.0°F/70.0°F · cooling 90.0°F/75.0°F · loads include a bad-install allowance (UA +8%, infiltration +25%, recovery held to 60%) · all values kBtuh
Design heat loss · components
Unit type | Walls & rim joists | Roof / ceiling | Slab, floors & below grade | Windows & doors | Infiltration | Ventilation | Design heat loss | Design heat loss at selection |
|---|---|---|---|---|---|---|---|---|
2-Bedroom | 2.1 | 3.3 | 6.8 | 7.9 | 2.2 | 2.0 | 24.4 @ -2°F | 24.4 @ -2°F |
Design heat gain · components
Unit type | Solar through glazing | Envelope conduction | Internal gains | Infiltration & ventilation | Latent | Total heat gain | Sensible heat ratio |
|---|---|---|---|---|---|---|---|
2-Bedroom | 3.5 | 3.0 | 2.3 | 1.5 | 2.5 | 12.8 | 0.80 |
Selection
Unit type | Units represented | Governing model | Outdoor unit | Minimum heating capacity |
|---|---|---|---|---|
2-Bedroom | 2 of 2 · NEXTGEN-ECC-LEFT, NEXTGEN-ECC-RIGHT | NEXTGEN-ECC-LEFT heating / NEXTGEN-ECC-RIGHT cooling | 30 kBtuh | ≥ 24.4 kBtuh @ -2°F |
The selected equipment's published heating capacity at the design temperature must exceed the governing design heat loss. Verify against manufacturer expanded performance data or the NEEP cold-climate listing, not nominal capacity. Loads are whole-unit and reported as the worst case within each bedroom count; head selection requires room-by-room loads from the architectural plans.
Recommended Design - Units
Item | Detailed Specifications |
|---|---|
Exterior Walls | R-21 dense-pack cellulose cavity insulation (2x6 @ 16" o.c.) with R-3.8 continuous exterior EPS/graphite insulation. Walls to the unconditioned garage: R-23 dense-pack cellulose cavity insulation (2x6 @ 16" o.c.). |
Below Grade Walls | N/A - no below-grade walls in the model. |
Corridor Walls | N/A - borders conditioned space. |
Slab | R-20 slab-edge insulation: 2 ft horizontal and 2 ft vertical, both on the interior side of the slab and connected for a continuous thermal break. The vertical leg runs from the top of the slab down, so the slab edge is fully isolated from the foundation. |
Floor Over Unconditioned Space | N/A - no framed floors in the model. |
Floor Over Garage | N/A - no framed floors in the model. |
Floor Over Podium | N/A - no framed floors in the model. |
Rim Joists | N/A - no rim joists in the model. |
Roof | Vented attic: R-49 blown cellulose insulation. |
Windows & Glass Doors | Double pane, U-0.30 / SHGC 0.30. |
Doors | Opaque door, U-0.21 (R-4.8). |
Air Sealing | ≤0.08 CFM50 per sqft of enclosure (compartmentalization); tested. |
HVAC | Ducted air-source heat pump, SEER2 17 / HSPF2 10; 2BR: 30 kBtuh; sized to the worst-case design load per bedroom count, see HVAC Design Loads |
Ductwork | Supply and return ducts in attic under insulation poorly vented insulated to code minimum; ducts in conditioned space insulated to code minimum. |
Duct Sealing | ≤ greater of 40 CFM25 or 4 CFM25 per 100 sqft of conditioned floor area; tested at rough-in after the HVAC is installed. |
HVAC Grading | Fan Flow Test: Grade I; Watt Draw Test: Grade I; Refrigerant Charge: Grade I |
Mechanical Ventilation | In-unit ERV; 65 CFM; ≥81% recovery efficiency (Panasonic Intelli-Balance 100). |
Local Mechanical Exhaust | Bathroom(s): at least 50 CFM intermittent and up to 3.0 sones, or at least 20 CFM continuous and up to 2.0 sones.; Kitchen(s): at least 100 CFM intermittent and up to 3.0 sones, or continuous at 5 ACH.; Both: exhaust directly outdoors with ENERGY STAR certified fans. A balanced ERV or HRV serving the space may satisfy this requirement. |
Thermostats | Programmable thermostat (as modeled). |
DHW | Integrated heat pump water heater (HPWH) (as modeled); UEF 3.5; 50 gal. |
DHW Piping | Supply piping insulated to R-3 minimum. |
Water Fixtures | WaterSense certified (Lavatory ≤1.2 GPM; Shower ≤2.0 GPM; Kitchen ≤2.2 GPM). |
Refrigerator | ≤ 550 kWh/yr; electric. |
Dishwasher | ≤ 269 kWh/yr; electric. |
Clothes Washer | IMEF 1.0; ≤ 141 kWh/yr; electric. |
Clothes Dryer | Standard electric dryer; vented; CEF 3.93. |
Stove / Oven | Electric range. |
Lighting | 100% high-efficacy (LED). |
Solar Ready | Reserve an unobstructed rooftop solar-ready zone (at least 300 sq ft; 150 sq ft for small townhouses) with structural capacity, a conduit pathway, and reserved electrical-panel space. Waived if solar is already installed or the roof is heavily shaded. |
EV Ready | One 50-amp Level II EV-ready circuit per dwelling unit. |
HPWH Ready | N/A |
Paperwork & Modeling | ENERGY STAR energy model to the ERI target, the ENERGY STAR design-review checklist, and an HVAC design report. Plus ENERGY STAR NextGen documentation: all-electric equipment and EV-charging provisions. |
Testing & Verification | ENERGY STAR field verification: pre-drywall and final inspections, blower-door and duct-leakage tests, ventilation airflow, and HVAC installation grading. Plus ENERGY STAR NextGen verification: all-electric equipment and EV-charging infrastructure. |
Recommended Design - Common Areas
Item | Common Areas (Residential Building) |
|---|
Exterior Wall (GAS-ECC, NEXTGEN, NEXTGEN-ECC)
Wall to Unconditioned Garage (GAS-ECC, NEXTGEN, NEXTGEN-ECC)
Slab on Grade (GAS-ECC, NEXTGEN, NEXTGEN-ECC)
Roof (GAS-ECC, NEXTGEN, NEXTGEN-ECC)
Path Comparison
This section shows the detailed requirements and incentives for each path we compared, basically showing our work of how we determined the recommended path is the most affordable way of meeting energy code compliance.
Path Comparison - Incentives
NEXTGEN / NEXTGEN-ECC: $1,560,000 - $1,716,000
- MassSave Single-Family ENERGY STAR Certification ($1,560,000) (Program Breakdown): You get this rebate for having each townhome ENERGY STAR NextGen certified. Certification typically occurs at the end of construction around when certificate of occupancy is received. This rebate comes in the form of a check within 4 months of the certification paperwork being provided to MassSave.
- DOER Alternative Energy Credits ($0 - $156,000) (Program Breakdown): This rebate is received for installing APS eligible air source heat pumps (click here for the list). There is an extensive process to get this incentive. It comes in the form of a check approximately 6-12 months after the heat pumps are installed and fully operational.
- IMPORTANT: Although an estimate is provided, this incentive can vary widely typically between $300-1,500 per heat pump. It's based on expected kWh usage of the system as well as the market value of the alternative energy credits when sold.
- Risks: Massachusetts is rewriting this program right now. The House bill would stop the state from accepting new applications on January 1, 2028, the Senate version leaves heat pumps out of that cutoff, and the two are in conference. The application needs the equipment installed and operating, so a project that will not reach that point before the deadline should treat this as upside rather than a budgeted line.
GAS-ECC: $0
- No MassSave Incentive On The Mixed-Fuel Path ($0) (Program Breakdown): MassSave runs new construction buildings of four units or fewer through its single-family and townhome track, and that track is all-electric only. A home that heats with gas, or that makes its hot water with gas, earns nothing here no matter how far the envelope beats code. The gas boiler and the hot water it feeds are what close the door, so the money turns on the mechanical package rather than on the score. Every incentive dollar in this study comes from the all-electric designs.
- IMPORTANT: The rule reads on the whole home, not on one appliance, and there is no partial credit. Putting a gas boiler or gas water heating back into an otherwise all-electric design removes the full per-home rebate for that building.
- IMPORTANT: The four-unit line is drawn per building, not per project. A site of duplexes stays on the single-family and townhome track and its all-electric rule however many buildings are built, which is why a gas mechanical package costs the same rebate on every one of them.
Path Comparison - Net Cost Summary
Path | Total Cost $/sf | Total Incentives $/sf | Net $/sf | OpEx Factor |
|---|---|---|---|---|
NEXTGEN-ECC | $39.42 | $8.33 | $31.70 | 1.02 |
NEXTGEN | $42.94 | $8.33 | $35.29 | 1.02 |
GAS-ECC | $44.22 | $0.00 | $45.09 | 1.02 |
Path Comparison - Envelope
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
Exterior Walls | GAS-ECC | R-21 dense-pack cellulose cavity insulation (2x6 @ 16" o.c.) with R-3.8 continuous exterior EPS/graphite insulation. Walls to the unconditioned garage: R-23 dense-pack cellulose cavity insulation (2x6 @ 16" o.c.). | $5.40 | $0.00 | $5.40 | 0.95 |
NEXTGEN | R-21 cavity insulation (2x6 @ 16" o.c.) with R-3.8 continuous exterior insulation. Walls to the unconditioned garage: R-23 cavity insulation (2x6 @ 16" o.c.). | $5.14 | $0.00 | $5.14 | 0.95 | |
NEXTGEN-ECC | R-21 dense-pack cellulose cavity insulation (2x6 @ 16" o.c.) with R-3.8 continuous exterior EPS/graphite insulation. Walls to the unconditioned garage: R-23 dense-pack cellulose cavity insulation (2x6 @ 16" o.c.). | $5.40 | $0.00 | $5.40 | 0.95 | |
Below Grade Walls | GAS-ECC | N/A - no below-grade walls in the model. | $0.00 | $0.00 | $0.00 | 1.00 |
NEXTGEN | N/A - no below-grade walls in the model. | $0.00 | $0.00 | $0.00 | 1.00 | |
NEXTGEN-ECC | N/A - no below-grade walls in the model. | $0.00 | $0.00 | $0.00 | 1.00 | |
Corridor Walls | GAS-ECC | N/A - borders conditioned space. | $0.00 | $0.00 | $0.00 | 1.00 |
NEXTGEN | N/A - borders conditioned space. | $0.00 | $0.00 | $0.00 | 1.00 | |
NEXTGEN-ECC | N/A - borders conditioned space. | $0.00 | $0.00 | $0.00 | 1.00 | |
Slab | GAS-ECC | R-20 slab-edge insulation: 2 ft horizontal and 2 ft vertical, both on the interior side of the slab and connected for a continuous thermal break. The vertical leg runs from the top of the slab down, so the slab edge is fully isolated from the foundation. | $0.63 | $0.00 | $0.63 | 0.90 |
NEXTGEN | R-20 slab-edge insulation: 2 ft horizontal and 2 ft vertical, both on the interior side of the slab and connected for a continuous thermal break. The vertical leg runs from the top of the slab down, so the slab edge is fully isolated from the foundation. | $0.63 | $0.00 | $0.63 | 0.90 | |
NEXTGEN-ECC | R-20 slab-edge insulation: 2 ft horizontal and 2 ft vertical, both on the interior side of the slab and connected for a continuous thermal break. The vertical leg runs from the top of the slab down, so the slab edge is fully isolated from the foundation. | $0.63 | $0.00 | $0.63 | 0.90 | |
Floor Over Unconditioned Space | GAS-ECC | N/A - no framed floors in the model. | $0.00 | $0.00 | $0.00 | 1.00 |
NEXTGEN | N/A - no framed floors in the model. | $0.00 | $0.00 | $0.00 | 1.00 | |
NEXTGEN-ECC | N/A - no framed floors in the model. | $0.00 | $0.00 | $0.00 | 1.00 | |
Floor Over Garage | GAS-ECC | N/A - no framed floors in the model. | $0.00 | $0.00 | $0.00 | 1.00 |
NEXTGEN | N/A - no framed floors in the model. | $0.00 | $0.00 | $0.00 | 1.00 | |
NEXTGEN-ECC | N/A - no framed floors in the model. | $0.00 | $0.00 | $0.00 | 1.00 | |
Floor Over Podium | GAS-ECC | N/A - no framed floors in the model. | $0.00 | $0.00 | $0.00 | 1.00 |
NEXTGEN | N/A - no framed floors in the model. | $0.00 | $0.00 | $0.00 | 1.00 | |
NEXTGEN-ECC | N/A - no framed floors in the model. | $0.00 | $0.00 | $0.00 | 1.00 | |
Rim Joists | GAS-ECC | N/A - no rim joists in the model. | $0.00 | $0.00 | $0.00 | 1.00 |
NEXTGEN | N/A - no rim joists in the model. | $0.00 | $0.00 | $0.00 | 1.00 | |
NEXTGEN-ECC | N/A - no rim joists in the model. | $0.00 | $0.00 | $0.00 | 1.00 | |
Roof | GAS-ECC | Vented attic: R-49 blown cellulose insulation. | $1.95 | $0.00 | $1.95 | 1.10 |
NEXTGEN | Vented attic: R-49 insulation. | $1.75 | $0.00 | $1.75 | 1.10 | |
NEXTGEN-ECC | Vented attic: R-49 blown cellulose insulation. | $1.95 | $0.00 | $1.95 | 1.10 | |
Windows & Glass Doors | GAS-ECC | Triple pane, U-0.18 / SHGC 0.18. | $12.48 | $0.00 | $12.48 | 1.00 |
NEXTGEN | Triple pane, U-0.18 / SHGC 0.18. | $12.48 | $0.00 | $12.48 | 1.00 | |
NEXTGEN-ECC | Double pane, U-0.30 / SHGC 0.30. | $8.50 | $0.00 | $8.50 | 1.00 | |
Doors | GAS-ECC | Opaque door, U-0.21 (R-4.8). | $0.35 | $0.00 | $0.35 | 0.95 |
NEXTGEN | Opaque door, U-0.21 (R-4.8). | $0.35 | $0.00 | $0.35 | 0.95 | |
NEXTGEN-ECC | Opaque door, U-0.21 (R-4.8). | $0.35 | $0.00 | $0.35 | 0.95 | |
Air Sealing | GAS-ECC | ≤0.23 CFM50 per sqft of enclosure (compartmentalization); tested. | $1.40 | $0.00 | $1.40 | 0.95 |
NEXTGEN | ≤0.08 CFM50 per sqft of enclosure (compartmentalization); tested. | $2.10 | $0.00 | $2.10 | 0.95 | |
NEXTGEN-ECC | ≤0.08 CFM50 per sqft of enclosure (compartmentalization); tested. | $2.10 | $0.00 | $2.10 | 0.95 |
Path Comparison - Mechanical
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
HVAC | GAS-ECC | Natural gas combi boiler (as modeled); 0.96 adjusted efficiency; also provides domestic hot water (one combi appliance, not two); cooling by a separate ducted air-source heat pump, cooling only; SEER2 18; heating sized to a 25.1 kBtuh design heat loss; cooling 2BR: 12 kBtuh; sized to the worst-case design load per bedroom count, see HVAC Design Loads | $6.44 | $0.00 | $6.44 | 1.10 |
NEXTGEN | Ducted air-source heat pump, SEER2 17 / HSPF2 10; 2BR: 30 kBtuh; sized to the worst-case design load per bedroom count, see HVAC Design Loads | $7.25 | $0.00 | $7.25 | 1.15 | |
NEXTGEN-ECC | Ducted air-source heat pump, SEER2 17 / HSPF2 10; 2BR: 30 kBtuh; sized to the worst-case design load per bedroom count, see HVAC Design Loads | $7.25 | $0.00 | $7.25 | 1.15 | |
Ductwork | GAS-ECC | Supply and return ducts in attic under insulation poorly vented insulated to code minimum; ducts in conditioned space insulated to code minimum. | $2.56 | $0.00 | $2.56 | 1.00 |
NEXTGEN | Supply and return ducts in attic under insulation poorly vented insulated to code minimum; ducts in conditioned space insulated to code minimum. | $2.56 | $0.00 | $2.56 | 1.00 | |
NEXTGEN-ECC | Supply and return ducts in attic under insulation poorly vented insulated to code minimum; ducts in conditioned space insulated to code minimum. | $2.56 | $0.00 | $2.56 | 1.00 | |
Duct Sealing | GAS-ECC | ≤ greater of 40 CFM25 or 4 CFM25 per 100 sqft of conditioned floor area; tested at rough-in after the HVAC is installed. | $0.52 | $0.00 | $0.52 | 1.00 |
NEXTGEN | ≤ greater of 40 CFM25 or 4 CFM25 per 100 sqft of conditioned floor area; tested at rough-in after the HVAC is installed. | $0.52 | $0.00 | $0.52 | 1.00 | |
NEXTGEN-ECC | ≤ greater of 40 CFM25 or 4 CFM25 per 100 sqft of conditioned floor area; tested at rough-in after the HVAC is installed. | $0.52 | $0.00 | $0.52 | 1.00 | |
HVAC Grading | GAS-ECC | Fan Flow Test: N/A; Watt Draw Test: N/A; Refrigerant Charge: N/A | $0.00 | $0.00 | $0.00 | 1.00 |
NEXTGEN | Fan Flow Test: Grade I; Watt Draw Test: Grade I; Refrigerant Charge: Grade I | $0.00 | $0.00 | $0.00 | 1.00 | |
NEXTGEN-ECC | Fan Flow Test: Grade I; Watt Draw Test: Grade I; Refrigerant Charge: Grade I | $0.00 | $0.00 | $0.00 | 1.00 | |
Mechanical Ventilation | GAS-ECC | In-unit ERV; 50 CFM; ≥83% recovery efficiency (Panasonic Intelli-Balance 100). | $1.04 | $0.00 | $1.04 | 1.20 |
NEXTGEN | In-unit ERV; 65 CFM; ≥81% recovery efficiency (Panasonic Intelli-Balance 100). | $1.04 | $0.00 | $1.04 | 1.20 | |
NEXTGEN-ECC | In-unit ERV; 65 CFM; ≥81% recovery efficiency (Panasonic Intelli-Balance 100). | $1.04 | $0.00 | $1.04 | 1.20 | |
Local Mechanical Exhaust | GAS-ECC | Bathroom(s): at least 50 CFM intermittent and up to 3.0 sones, or at least 20 CFM continuous and up to 2.0 sones.; Kitchen(s): at least 100 CFM intermittent and up to 3.0 sones, or continuous at 5 ACH.; Both: exhaust directly outdoors with ENERGY STAR certified fans. A balanced ERV or HRV serving the space may satisfy this requirement. | $0.59 | $0.00 | $0.59 | 1.05 |
NEXTGEN | Bathroom(s): at least 50 CFM intermittent and up to 3.0 sones, or at least 20 CFM continuous and up to 2.0 sones.; Kitchen(s): at least 100 CFM intermittent and up to 3.0 sones, or continuous at 5 ACH.; Both: exhaust directly outdoors with ENERGY STAR certified fans. A balanced ERV or HRV serving the space may satisfy this requirement. | $0.59 | $0.00 | $0.59 | 1.05 | |
NEXTGEN-ECC | Bathroom(s): at least 50 CFM intermittent and up to 3.0 sones, or at least 20 CFM continuous and up to 2.0 sones.; Kitchen(s): at least 100 CFM intermittent and up to 3.0 sones, or continuous at 5 ACH.; Both: exhaust directly outdoors with ENERGY STAR certified fans. A balanced ERV or HRV serving the space may satisfy this requirement. | $0.59 | $0.00 | $0.59 | 1.05 | |
Thermostats | GAS-ECC | Programmable thermostat (as modeled). | $0.05 | $0.00 | $0.05 | 1.05 |
NEXTGEN | Programmable thermostat (as modeled). | $0.05 | $0.00 | $0.05 | 1.05 | |
NEXTGEN-ECC | Programmable thermostat (as modeled). | $0.05 | $0.00 | $0.05 | 1.05 |
Path Comparison - Plumbing & Appliances
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
DHW | GAS-ECC | Gas combi boiler with integral tankless water heater (as modeled); UEF 0.96; also provides space heating (one combi appliance, not two). | $3.50 | $0.00 | $3.50 | 1.25 |
NEXTGEN | Integrated heat pump water heater (HPWH) (as modeled); UEF 3.5; 50 gal. | $1.17 | $0.00 | $1.17 | 1.20 | |
NEXTGEN-ECC | Integrated heat pump water heater (HPWH) (as modeled); UEF 3.5; 50 gal. | $1.17 | $0.00 | $1.17 | 1.20 | |
DHW Piping | GAS-ECC | Supply piping insulated to R-3 minimum. | $0.41 | $0.00 | $0.41 | 0.95 |
NEXTGEN | Supply piping insulated to R-3 minimum. | $0.41 | $0.00 | $0.41 | 0.95 | |
NEXTGEN-ECC | Supply piping insulated to R-3 minimum. | $0.41 | $0.00 | $0.41 | 0.95 | |
Water Fixtures | GAS-ECC | WaterSense certified (Lavatory ≤1.2 GPM; Shower ≤2.0 GPM; Kitchen ≤2.2 GPM). | $1.04 | $0.00 | $1.04 | 1.00 |
NEXTGEN | WaterSense certified (Lavatory ≤1.2 GPM; Shower ≤2.0 GPM; Kitchen ≤2.2 GPM). | $1.04 | $0.00 | $1.04 | 1.00 | |
NEXTGEN-ECC | WaterSense certified (Lavatory ≤1.2 GPM; Shower ≤2.0 GPM; Kitchen ≤2.2 GPM). | $1.04 | $0.00 | $1.04 | 1.00 | |
Refrigerator | GAS-ECC | ≤ 550 kWh/yr; electric. | $0.45 | $0.00 | $0.45 | 1.10 |
NEXTGEN | ≤ 550 kWh/yr; electric. | $0.45 | $0.00 | $0.45 | 1.10 | |
NEXTGEN-ECC | ≤ 550 kWh/yr; electric. | $0.45 | $0.00 | $0.45 | 1.10 | |
Dishwasher | GAS-ECC | ≤ 269 kWh/yr; electric. | $0.24 | $0.00 | $0.24 | 1.10 |
NEXTGEN | ≤ 269 kWh/yr; electric. | $0.24 | $0.00 | $0.24 | 1.10 | |
NEXTGEN-ECC | ≤ 269 kWh/yr; electric. | $0.24 | $0.00 | $0.24 | 1.10 | |
Clothes Washer | GAS-ECC | IMEF 1.0; ≤ 141 kWh/yr; electric. | $0.27 | $0.00 | $0.27 | 1.10 |
NEXTGEN | IMEF 1.0; ≤ 141 kWh/yr; electric. | $0.27 | $0.00 | $0.27 | 1.10 | |
NEXTGEN-ECC | IMEF 1.0; ≤ 141 kWh/yr; electric. | $0.27 | $0.00 | $0.27 | 1.10 | |
Clothes Dryer | GAS-ECC | Standard electric dryer; vented; CEF 3.93. | $0.31 | $0.00 | $0.31 | 1.00 |
NEXTGEN | Standard electric dryer; vented; CEF 3.93. | $0.31 | $0.00 | $0.31 | 1.00 | |
NEXTGEN-ECC | Standard electric dryer; vented; CEF 3.93. | $0.31 | $0.00 | $0.31 | 1.00 | |
Stove / Oven | GAS-ECC | Electric range. | $0.35 | $0.00 | $0.35 | 1.05 |
NEXTGEN | Electric range. | $0.35 | $0.00 | $0.35 | 1.05 | |
NEXTGEN-ECC | Electric range. | $0.35 | $0.00 | $0.35 | 1.05 |
Path Comparison - Electrical
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
Lighting | GAS-ECC | 100% high-efficacy (LED). | $3.40 | $0.00 | $3.40 | 0.85 |
NEXTGEN | 100% high-efficacy (LED). | $3.40 | $0.00 | $3.40 | 0.85 | |
NEXTGEN-ECC | 100% high-efficacy (LED). | $3.40 | $0.00 | $3.40 | 0.85 | |
Solar Ready | GAS-ECC | Reserve an unobstructed rooftop solar-ready zone (at least 300 sq ft; 150 sq ft for small townhouses) with structural capacity, a conduit pathway, and reserved electrical-panel space. Waived if solar is already installed or the roof is heavily shaded. | $0.30 | $0.00 | $0.30 | 1.00 |
NEXTGEN | Reserve an unobstructed rooftop solar-ready zone (at least 300 sq ft; 150 sq ft for small townhouses) with structural capacity, a conduit pathway, and reserved electrical-panel space. Waived if solar is already installed or the roof is heavily shaded. | $0.30 | $0.00 | $0.30 | 1.00 | |
NEXTGEN-ECC | Reserve an unobstructed rooftop solar-ready zone (at least 300 sq ft; 150 sq ft for small townhouses) with structural capacity, a conduit pathway, and reserved electrical-panel space. Waived if solar is already installed or the roof is heavily shaded. | $0.30 | $0.00 | $0.30 | 1.00 | |
EV Ready | GAS-ECC | One 50-amp Level II EV-ready circuit per dwelling unit. | $0.38 | $0.00 | $0.38 | 1.00 |
NEXTGEN | One 50-amp Level II EV-ready circuit per dwelling unit. | $0.38 | $0.00 | $0.38 | 1.00 | |
NEXTGEN-ECC | One 50-amp Level II EV-ready circuit per dwelling unit. | $0.38 | $0.00 | $0.38 | 1.00 | |
HPWH Ready | GAS-ECC | N/A | $0.00 | $0.00 | $0.00 | 1.00 |
NEXTGEN | N/A | $0.00 | $0.00 | $0.00 | 1.00 | |
NEXTGEN-ECC | N/A | $0.00 | $0.00 | $0.00 | 1.00 |
Path Comparison - Soft Costs & Whole-Building Incentives
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
Paperwork & Modeling | GAS-ECC | HERS energy model to the code ERI target. | $0.16 | $0.00 | $0.16 | 1.00 |
NEXTGEN | ENERGY STAR energy model to the ERI target, the ENERGY STAR design-review checklist, and an HVAC design report. Plus ENERGY STAR NextGen documentation: all-electric equipment and EV-charging provisions. | $0.16 | $8.33 | $-8.17 | 1.00 | |
NEXTGEN-ECC | ENERGY STAR energy model to the ERI target, the ENERGY STAR design-review checklist, and an HVAC design report. Plus ENERGY STAR NextGen documentation: all-electric equipment and EV-charging provisions. | $0.16 | $8.33 | $-8.17 | 1.00 | |
Testing & Verification | GAS-ECC | HERS field verification: pre-drywall and final inspections, blower-door and duct-leakage tests. | $0.00 | $0.00 | $0.00 | 1.00 |
NEXTGEN | ENERGY STAR field verification: pre-drywall and final inspections, blower-door and duct-leakage tests, ventilation airflow, and HVAC installation grading. Plus ENERGY STAR NextGen verification: all-electric equipment and EV-charging infrastructure. | $0.00 | $0.00 | $0.00 | 1.00 | |
NEXTGEN-ECC | ENERGY STAR field verification: pre-drywall and final inspections, blower-door and duct-leakage tests, ventilation airflow, and HVAC installation grading. Plus ENERGY STAR NextGen verification: all-electric equipment and EV-charging infrastructure. | $0.00 | $0.00 | $0.00 | 1.00 |
Additional Design Considerations Not Represented In This Study
- Rooftop Solar At Construction: Installing rooftop solar during construction was weighed on top of the solar-ready provisions every path carries. No path needs generation to reach its ceiling. NEXTGEN lands at HERS 43 against the 45 all-electric ceiling on envelope and equipment alone, and GAS-ECC at 44 and NEXTGEN-ECC at 46 clear the 45 and 48 ceilings that the R406.5.2 embodied-carbon credit opens. Panels are capital the project does not need for compliance, so the reserved roof zone, the conduit pathway and the reserved panel space keep generation open as a later owner decision.
- Ground-Source (Geothermal) Heat Pumps: A ground-source system was compared against the ducted air-source heat pumps the two all-electric paths carry at SEER2 17 / HSPF2 10. Mass Save pays a geothermal adder of $9,000 per home on the single-family track, which is $945,000 across 105 homes and the strongest case any equipment upgrade has on this project. It stays out because the site is 53 detached buildings, so a ground loop means a bore field at each building rather than one shared field, and the air-source equipment already lands both paths under their ceilings at HERS 43 and 46. If the site work is already priced with drilling access, this is the one item on this list worth a hard quote before the mechanical package is locked.
- Sealed (Unvented) Attic At The Roof Deck: Sealing the attic at the roof deck was weighed as a way to bring the attic duct run inside the thermal boundary. Every path runs supply and return ducts through the attic, buried under the insulation, and every path reaches its ceiling that way. The sealed assembly prices at $6.28 per square foot of roof against $1.95 for the vented R-49 cellulose the carbon-credit paths carry, roughly $4.33 per square foot of building or about $818,000 across the 189,000 square foot ceiling plane, so it buys rating margin the design already holds.
- Heat Pump Clothes Dryer: A ventless heat-pump dryer in every home was considered and cut. The standard vented electric dryer at CEF 3.93 already meets the ENERGY STAR threshold, and Mass Save pays no dryer adder on the single-family track, so the ventless premium across 105 homes buys rating margin rather than compliance or incentive money. Program eligibility turns on the heating and hot water equipment, which both all-electric paths already satisfy, so the dryer choice does not move it either way.
- Induction Cooking: The design carries a radiant-coil electric range, and induction was weighed against it. Mass Save pays a $250 per home induction adder on the single-family track, worth $26,250 across the 105 homes on either ENERGY STAR path and nothing on the mixed-fuel path, which draws no Mass Save money. An induction cooktop with a convection oven prices about $177 per home above the radiant-coil range at this project's volume, so the adder covers the premium. It sits outside every path total shown here because the appliance package is not locked, and it is worth settling before that package is bought.
- Wi-Fi Connected Thermostats: Upgrading the programmable thermostat the design carries to a Wi-Fi connected stat was weighed alongside the induction question. Mass Save pays a $100 per home adder for that upgrade on the Base tier only, and this project certifies at the ENERGY STAR tier, so the upgrade earns nothing here. It costs about $26 per home more and the rating does not move on it, so the programmable stat stays on all three paths.
- Split-System Heat Pump Water Heater: A split-system heat pump water heater was weighed against the integrated 50 gallon unit both all-electric paths carry at UEF 3.5. Mass Save pays $750 per home for split-system equipment and nothing for an integrated unit, worth $78,750 across 105 homes. It stays out because a split system puts an outdoor compressor, a refrigerant line set and a wall penetration at each of 105 separate single-story homes, and the integrated tank already carries both paths to their ratings.
- DOE Zero Energy Ready Home Certification: Layering DOE Zero Energy Ready Home certification on top of ENERGY STAR was weighed. Mass Save pays a $500 per home adder for it at this project's tier, worth $52,500 across 105 homes, and it is the largest incentive available here that no path total counts. It stays outside the totals because Zero Energy Ready is a second certification with its own checklist and field verification on top of the ENERGY STAR and NextGen scope both paths already carry, and that added scope has to be priced against the adder before it earns its place. The decision belongs before registration rather than after.