CS81 Energy Code Feasibility Study in Amesbury, Massachusetts
Energy code feasibility study for a 296-unit Multifamily in Massachusetts. Compares multiple design paths. Recommended: ECC (All-Electric). View full study.
- Study Type
- Energy Code Feasibility Study
- State
- Massachusetts
- Units
- 296
- Building Type
- Multifamily
- Fuel Type
- All-Electric
- Recommended Path
- 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
- Amesbury, MA 01913
- 30 Buildings | 296 Units | 302,043 SF Conditioned
- New Construction | 2 high-rise, 27 low-rise buildings, and a separate clubhouse.
- All-Electric | MA Stretch Code | HERS ≤ 48 (Carbon Credit Path)
- All-Electric | MA Stretch Code | HERS ≤ 45
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
Both paths meet Massachusetts energy code and are modeled to pass on a lean margin, so the choice between them is a matter of cost and constructability rather than compliance.
ECC (All-Electric): Recommended
This is the least expensive path at approximately $45.50/sf net, and it is the more builder-friendly of the two. It keeps the project fully electric, which preserves eligibility for available incentives and aligns with the direction Massachusetts energy code is heading. For most projects, this is the right choice.
ENVELOPE (All-Electric): Alternative
At approximately $49.24/sf net, this path costs about $4/sf more than the ECC path, and it is the more labor-intensive of the two because it asks more of the envelope. It carries the same all-electric advantages, including incentive eligibility and code alignment, so the tradeoff is first cost and ease of build versus a heavier envelope package. Choose this path when that envelope emphasis matters more than trimming the last few dollars per square foot.
What Changes Between Paths
Item | ENVELOPE | ECC (Recommended) |
|---|---|---|
Exterior Walls | R-21 cavity + R-7.5 continuous. | R-21 dense-pack cellulose cavity + R-3.6 continuous low-GWP XPS. |
Slab | R-10, 2 ft vertical and 2 ft horizontal at the interior perimeter, connected for a full thermal break. | R-10 low-GWP XPS, 2 ft vertical and 2 ft horizontal at the interior perimeter, connected for a full thermal break. |
Rim Joists | R-21 rim/band insulation at floor transitions. | R-21 dense-pack cellulose rim/band insulation at floor transitions. |
Roof | Flat ceiling under vented attic: R-49. Corridor sealed attic: R-19 fiberglass batt strapped to the underside of the roof deck + R-30 continuous. | Flat ceiling under vented attic: R-49 blown cellulose. Corridor sealed attic: R-19 fiberglass batt strapped to the underside of the roof deck + R-30 continuous low-GWP XPS. |
Windows & Glass Doors | High performance, U-0.18 / SHGC 0.18. | High performance, U-0.24 / SHGC 0.24. |
HVAC | Ducted air-source heat pump, SEER2 17.5 / HSPF2 10; 1BR: 18 kBtuh; 2BR: 24 kBtuh; 3BR: 24 kBtuh; sized to the worst-case design load per bedroom count, see HVAC Design Loads | Ducted air-source heat pump, SEER2 17.5 / HSPF2 10; 1BR: 18 kBtuh; 2BR: 24 kBtuh; 3BR: 30 kBtuh; sized to the worst-case design load per bedroom count, see HVAC Design Loads |
Refrigerator | Studio / 1-bedroom: ≤ 500 kWh/yr; electric. | Studio / 1-bedroom: ≤ 550 kWh/yr; electric. |
Cost $/sf | $50.92 | $47.23 |
Incentive $/sf | $2.27 | $2.27 |
Net $/sf | $49.24 | $45.50 |
Code Path
Permit / Certificate of Occupancy Requirements
High Rise Buildings
Single Family OR Low Rise Buildings (Stretch)
3-story / low-rise (27 buildings)
MA Stretch Code | 225 CMR 22 | HERS ≤ 48 (Carbon Credit Path) or HERS ≤ 45
225 CMR 22 Stretch. All-electric HERS path. ECC = HERS ≤ 48 with the R406.5.2.1 insulation credit. ENVELOPE = HERS ≤ 45. Permitting: HERS/ERI model, IECC 2021 checklist, ENERGY STAR checklists. Certificate of occupancy: tested HERS ratings (sampling allowed).
4-story / high-rise (2 corridor buildings)
MA Stretch Code | 225 CMR 23 C407.4 | HERS ≤ 48 (Carbon Credit Path) or HERS ≤ 45
225 CMR 23 Stretch, Group R via C407.4 per-unit HERS (same ceilings: 48 with the insulation credit / 45). Permitting: HERS/ERI model, IECC 2021 checklist, ENERGY STAR checklists. Certificate of occupancy: tested HERS ratings (sampling allowed).
Clubhouse
MA Stretch Code | COMcheck
COMcheck.
Permit / Certificate of Occupancy Requirements
HERS/ERI model, IECC 2021 checklist, Energy Star checklists, COMcheck.
Certificate of occupancy: tested HERS ratings (sampling allowed) for the dwellings; COMcheck for the clubhouse.
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 ECC path.
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 already clears the threshold, so no material change is needed to earn the credit. The calculation below records it.
The result is a net 90,009 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 (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: $686,000 - $1,130,000
- MassSave Multifamily High Rise Program Energy Star Tier ($126,000) (Program Breakdown): You get this rebate for having your building(s) certified for the Energy Star MFNC v1.2 program. This requires pre-approval via an application to be submitted before construction starts. This rebate comes in the form of a check within 4 months of certification documentation being provided to MassSave, typically this is 4 months after construction is complete.
- MassSave Multifamily Low Rise Program Energy Star Tier ($560,000) (Program Breakdown): You get this rebate for having your building(s) certified for the Energy Star MFNC v1.2 program. This requires pre-approval via an application to be submitted before construction starts. This rebate comes in the form of a check within 4 months of certification documentation being provided to MassSave, typically this is 4 months after construction is complete.
- DOER Alternative Energy Credits ($0 - $444,000) (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
Essex County, MA · heating 1.0°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 |
|---|---|---|---|---|---|---|---|---|
1-Bedroom | 3.0 | — | 4.7 | 2.1 | 3.8 | 1.5 | 15.2 @ 1°F | 15.2 @ 1°F |
2-Bedroom | 2.4 | — | 4.8 | 4.1 | 5.7 | 1.9 | 18.9 @ 1°F | 18.9 @ 1°F |
3-Bedroom | 4.7 | — | 4.6 | 4.8 | 7.0 | 1.9 | 23.1 @ 1°F | 23.1 @ 1°F |
Design heat gain · components
Unit type | Solar through glazing | Envelope conduction | Internal gains | Infiltration & ventilation | Latent | Total heat gain | Sensible heat ratio |
|---|---|---|---|---|---|---|---|
1-Bedroom | 0.3 | 1.2 | 2.1 | 2.1 | 3.0 | 8.6 | 0.65 |
2-Bedroom | 2.0 | 1.7 | 2.3 | 2.6 | 3.8 | 12.3 | 0.69 |
3-Bedroom | 2.3 | 2.1 | 2.5 | 2.6 | 4.0 | 13.5 | 0.70 |
Selection
Unit type | Cooling Capacity | Minimum Heating Capacity |
|---|---|---|
1-Bedroom | 7.7 – 20.0 kBtuh | ≥ 15.2 kBtuh @ 1°F |
2-Bedroom | 11.1 – 20.0 kBtuh | ≥ 18.9 kBtuh @ 1°F |
3-Bedroom | 12.2 – 20.0 kBtuh | ≥ 23.1 kBtuh @ 1°F |
Recommended Design - Units
Item | Detailed Specifications |
|---|---|
Exterior Walls | R-21 dense-pack cellulose cavity + R-3.6 continuous low-GWP XPS. |
Below Grade Walls | N/A |
Corridor Walls | N/A |
Slab | R-10 low-GWP XPS, 2 ft vertical and 2 ft horizontal at the interior perimeter, connected for a full thermal break. |
Floor Over Unconditioned Space | N/A |
Floor Over Garage | N/A |
Floor Over Podium | N/A |
Rim Joists | R-21 dense-pack cellulose rim/band insulation at floor transitions. |
Roof | Flat ceiling under vented attic: R-49 blown cellulose. Corridor sealed attic: R-19 fiberglass batt strapped to the underside of the roof deck + R-30 continuous low-GWP XPS. |
Windows & Glass Doors | High performance, U-0.24 / SHGC 0.24. |
Doors | Opaque door, U-0.20 (R-5.0). |
Air Sealing | ≤0.27 CFM50 per sqft of enclosure (compartmentalization); tested. |
HVAC | Ducted air-source heat pump, SEER2 17.5 / HSPF2 10; 1BR: 18 kBtuh; 2BR: 24 kBtuh; 3BR: 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 well vented insulated to code minimum; ducts in conditioned space insulated to code minimum. |
Duct Sealing | ≤ greater of 80 CFM25 or 8 CFM25 per 100 sqft of conditioned floor area; tested at final. |
HVAC Grading | N/A |
Mechanical Ventilation | 1BR: In-unit ERV; 50 CFM; ≥83% recovery efficiency. | 2BR: In-unit ERV; 65 CFM; ≥81% recovery efficiency. | 3BR: In-unit ERV; 65 CFM; ≥81% recovery efficiency. |
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. |
Thermostats | Programmable thermostat (as modeled). |
DHW | Studio / 1-bedroom: In-unit all-in-one heat pump water heater (HPWH); UEF 4; 40 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 | Studio / 1-bedroom: ≤ 550 kWh/yr; electric. |
Dishwasher | ≤ 269 kWh/yr; electric. |
Clothes Washer | ENERGY STAR; electric. |
Clothes Dryer | Standard electric dryer; vented; CEF 3.93. |
Stove / Oven | Electric range. |
Lighting | 100% high-efficacy (LED). |
Solar Ready | Low-rise buildings (225 CMR 22 Appendix RB as amended): unobstructed rooftop solar-ready zone of at least 300 sf and at least 5 ft wide, with a conduit/plumbing pathway to the service panel, reserved dual-pole breaker space, structural loads shown on the construction documents, and a permanent certificate. High-rise buildings and the clubhouse (225 CMR 23 C402.3 → IECC Appendix CB): reserve and keep clear at least 40% of the qualifying roof area, with an interconnection pathway and conduit, reserved electrical service space and panel capacity, 5 psf collateral dead load in the structural design of the zone, construction documents, and a permanent certificate. |
EV Ready | At least 20% of parking spaces wired EV-ready (40-amp Level II; shared circuits with load management allowed). |
HPWH Ready | N/A |
Paperwork & Modeling | HERS/ERI model, IECC 2021 checklist, Energy Star checklists, COMcheck. |
Testing & Verification | ENERGY STAR field verification: pre-drywall and final inspections, unit air-tightness (blower door), duct-leakage, ventilation and exhaust airflow, and HVAC functional testing. |
Recommended Design - Common Areas
Item | Common Areas (Residential Building) |
|---|---|
Exterior Walls | R-21 dense-pack cellulose cavity + R-3.6 continuous low-GWP XPS. |
Below Grade Walls | N/A |
Corridor Walls | N/A |
Slab | R-10 low-GWP XPS, 2 ft vertical and 2 ft horizontal at the interior perimeter, connected for a full thermal break. |
Floor Over Unconditioned Space | N/A |
Floor Over Garage | N/A |
Floor Over Podium | N/A |
Rim Joists | R-21 dense-pack cellulose rim/band insulation at floor transitions. |
Roof | Flat ceiling under vented attic: R-49 blown cellulose. Corridor sealed attic: R-19 fiberglass batt strapped to the underside of the roof deck + R-30 continuous low-GWP XPS. |
Windows & Glass Doors | Fixed U ≤ 0.30; operable U ≤ 0.30; SHGC ≤ 0.40. |
Doors | Glazed entrance U ≤ 0.60; opaque U ≤ 0.37. |
Air Sealing | Continuous air barrier per residential air-barrier table; Grade I insulation install; penetrations, rough openings, and electrical boxes sealed; unit-to-corridor doors gasketed. Enclosed common spaces ≤ 1,500 sqft verified by inspection. |
HVAC | Ducted split HP: SEER2 15.2 / HSPF2 7.8. Ductless: 16 / 8.2. Packaged: 15.2 / 7.7. PTAC/PTHP/room AC certified to ENERGY STAR. Manual J/S sizing. |
Ductwork | Distribute conditioned air to all occupied common spaces. Ducts and air-handler units located entirely within conditioned space. Design and test to standard duct-design and duct-leakage practice. |
Duct Sealing | Per system, final test (at 25 Pa): 6 CFM per 100 sqft or 60 CFM (no return ducts); 8 CFM per 100 sqft or 80 CFM (1 to 2 return ducts); 12 CFM per 100 sqft or 120 CFM (3+ returns). Rough-in: 3/30, 4/40, or 6/60. All ducts and AHU in conditioned space. Tested. |
HVAC Grading | N/A |
Mechanical Ventilation | Outdoor air to all occupied common spaces: Lobby/Office 5 cfm/person + 0.06 cfm/sqft; Fitness 20 + 0.06; Corridor 0.06; Laundry 5 + 0.12. Installed at design airflow or above. Mandatory DCV for spaces over 500 sqft and over 25 people/1,000 sqft. Energy recovery (ERV, 70% sensible / 60% enthalpy) required for qualifying systems by runtime and outdoor-air fraction. |
Local Mechanical Exhaust | Restrooms, laundry rooms, janitor closets, mechanical equipment rooms: exhaust ducted directly to outdoors and certified to ENERGY STAR. |
Thermostats | Programmable, 5F setback |
DHW | Point-of-use electric, UEF ≥ 0.93 |
DHW Piping | R-3 (1.5 in. and smaller); R-4 (larger) |
Water Fixtures | WaterSense: Lav 1.5 GPM; Toilet 1.28 GPF; Urinal 0.5 GPF |
Refrigerator | N/A |
Dishwasher | N/A |
Clothes Washer | N/A |
Clothes Dryer | N/A |
Stove / Oven | N/A |
Lighting | 100% LED. LPD (W/sqft): Corridor 0.41; Lobby 0.84; Office 0.74; Fitness 0.72; Laundry 0.53; Stair 0.49; Mech/Elec 0.43; Storage 0.38 |
Lighting Controls | Occupancy sensors (corridors/stairs may dim to 50%); auto time switches; daylight controls where zone exceeds 100 W (primary sidelit), 300 W (sidelit), or 100 W (toplit) |
Solar Ready | Solar-ready zone per residential spec (40% roof zone, 5 PSF capacity, conduit + breaker space). |
EV Ready | 20% of installed parking spaces: 40-amp 208/240V dedicated branch circuits, 9.6 kVA minimum; AC Level I substitution allowed at 3:1 ratio. |
HPWH Ready | N/A |
Electric Readiness | N/A |
Vestibules | Self-closing vestibule at public building entrances; exempt if building under 3,000 sqft, or for employee-only/mechanical room doors, dwelling unit doors, revolving doors, or air curtains. |
Efficiency Credits | 15 credits required. Cold-climate heat pumps (COP ≥ 1.75 at 5°F, electric resistance prohibited except defrost) earn all 15 when meeting all space heating requirements. |
Paperwork & Modeling | COMcheck for common-area envelope, lighting, and mechanical (commercial compliance) plus efficiency-credit documentation. ENERGY STAR workbook, checklists, and common-space HVAC supplement (mandatory). HERS submittals at permit and CO. |
Testing & Verification | Ventilation balancing per design. Duct leakage testing at rough-in and final. HVAC functional testing by FT agent (mandatory). Lighting controls testing. Air barrier inspections. |
Amenity/Clubhouse
Item | Requirements |
|---|---|
Exterior Walls | Cavity R-21, continuous insulation none. Assembly U-0.062. 1,200 sf gross. |
Below Grade Walls | N/A |
Slab | Unheated Slab On Grade: continuous insulation R-15, 326 linear ft of perimeter. F/U-0.45. |
Floor Over Unconditioned Space | N/A |
Roof | Continuous insulation none, cavity R-49. Assembly U-0.021. 3,960 sf. |
Windows & Glass Doors | Storefront and glazing, 418 sf. U-0.30 maximum assembly U-factor. |
Doors | Opaque swinging doors U-0.37; nonswinging U-0.31. |
Air Sealing | Continuous air barrier with leakage testing per C402.5. Whole-building test per C402.5.2.1. |
Thermal Bridging | Vertical envelope performance accounts for thermal bridges: fastener derating of continuous insulation and linear bridge factors (parapets, wall-to-grade, fenestration perimeters, corners) per Table C402.7.3.1; MA Stretch COMcheck performs this automatically. |
HVAC | Cold-climate ASHP: 16 SEER2 / 9 HSPF2. |
HVAC Sizing | N/A |
Ductwork | N/A |
Economizer | No economizer provided. Basis recorded on the COMcheck mechanical certificate. |
Mechanical Ventilation | N/A |
Thermostats & Controls | N/A |
DHW | Service water heating per base 2021 IECC C404: Table C404.2 equipment efficiencies, pipe insulation, and controls. |
DHW Piping | N/A |
Water Fixtures | N/A |
Interior Lighting | Allowed LPD: Gymnasium / open play 0.94 W/sf; Fitness room (cardio/weights) 0.72 W/sf; Spin room 0.72 W/sf; Yoga room 0.72 W/sf; Restrooms (men / women) 0.63 W/sf; Corridor / lobby 0.79 W/sf; Mechanical closet 0.43 W/sf; Utility closet 0.43 W/sf; Storage closets 0.63 W/sf. |
Lighting Controls | Occupant sensor controls in offices, conference and break rooms, copy rooms, restrooms, storage rooms, locker rooms, corridors, and other enclosed spaces of 300 sf or less: auto-off within 20 minutes, manual-on or auto-on to 50 percent power. Time-switch controls elsewhere; daylight-responsive controls in daylight zones. MA lowers the daylight-responsive triggers: 100 W in primary sidelit and toplit zones, 300 W in sidelit zones. |
Exterior Lighting | Lighting zone Residential. Allowed LPD: 14 W per ft of door width. |
Solar Ready | Rooftop solar readiness is mandatory for new commercial buildings 5 stories or less: provide the Solar Ready Zone per IECC Appendix CB and show it on the construction documents. |
EV Ready | New parking includes EV Ready spaces: 20 percent for Group R and B occupancies, 10 percent otherwise; each with a 40 A branch circuit (or shared circuit with load management) wired for 6.6 kW Level II charging terminating within 6 feet of the space. |
Compliance Path | COMcheck |
Efficiency Credits | 17 of 15 required credits. Credits come from C406.2.3 (heat-pump heating at least 10% above the minimum) and C406.2.4 (heat-pump cooling at least 10% above the minimum). |
Vestibules | N/A |
Paperwork & Modeling | COMcheck |
Testing & Verification | N/A |
Exterior Wall (ECC)
Exterior Wall (ENVELOPE)
Slab on Grade (ECC, ENVELOPE)
Rim Joist (ECC, ENVELOPE)
Roof — Vented Attic (ECC, ENVELOPE)
Roof — Corridor Sealed (ECC, ENVELOPE)
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
ECC / ENVELOPE: $686,000 - $1,130,000
- MassSave Multifamily High Rise Program Energy Star Tier ($126,000) (Program Breakdown): You get this rebate for having your building(s) certified for the Energy Star MFNC v1.2 program. This requires pre-approval via an application to be submitted before construction starts. This rebate comes in the form of a check within 4 months of certification documentation being provided to MassSave, typically this is 4 months after construction is complete.
- MassSave Multifamily Low Rise Program Energy Star Tier ($560,000) (Program Breakdown): You get this rebate for having your building(s) certified for the Energy Star MFNC v1.2 program. This requires pre-approval via an application to be submitted before construction starts. This rebate comes in the form of a check within 4 months of certification documentation being provided to MassSave, typically this is 4 months after construction is complete.
- DOER Alternative Energy Credits ($0 - $444,000) (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.
Path Comparison - Net Cost Summary
Path | Total Cost $/sf | Total Incentives $/sf | Net $/sf | OpEx Factor |
|---|---|---|---|---|
ECC | $47.23 | $2.27 | $45.50 | 1.01 |
ENVELOPE | $50.92 | $2.27 | $49.24 | 1.01 |
Path Comparison - Envelope
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
Exterior Walls | ECC | R-21 dense-pack cellulose cavity + R-3.6 continuous low-GWP XPS. | $6.72 | $0.00 | $6.72 | 0.90 |
ENVELOPE | R-21 cavity + R-7.5 continuous. | $8.25 | $0.00 | $8.25 | 0.90 | |
Below Grade Walls | ECC | N/A | $0.00 | $0.00 | $0.00 | 1.00 |
ENVELOPE | N/A | $0.00 | $0.00 | $0.00 | 1.00 | |
Corridor Walls | ECC | N/A | $0.00 | $0.00 | $0.00 | 1.00 |
ENVELOPE | N/A | $0.00 | $0.00 | $0.00 | 1.00 | |
Slab | ECC | R-10 low-GWP XPS, 2 ft vertical and 2 ft horizontal at the interior perimeter, connected for a full thermal break. | $0.13 | $0.00 | $0.13 | 0.90 |
ENVELOPE | R-10, 2 ft vertical and 2 ft horizontal at the interior perimeter, connected for a full thermal break. | $0.13 | $0.00 | $0.13 | 0.90 | |
Floor Over Unconditioned Space | ECC | N/A | $0.00 | $0.00 | $0.00 | 1.00 |
ENVELOPE | N/A | $0.00 | $0.00 | $0.00 | 1.00 | |
Floor Over Garage | ECC | N/A | $0.00 | $0.00 | $0.00 | 1.00 |
ENVELOPE | N/A | $0.00 | $0.00 | $0.00 | 1.00 | |
Floor Over Podium | ECC | N/A | $0.00 | $0.00 | $0.00 | 1.00 |
ENVELOPE | N/A | $0.00 | $0.00 | $0.00 | 1.00 | |
Rim Joists | ECC | R-21 dense-pack cellulose rim/band insulation at floor transitions. | $0.20 | $0.00 | $0.20 | 0.95 |
ENVELOPE | R-21 rim/band insulation at floor transitions. | $0.20 | $0.00 | $0.20 | 0.95 | |
Roof | ECC | Flat ceiling under vented attic: R-49 blown cellulose. Corridor sealed attic: R-19 fiberglass batt strapped to the underside of the roof deck + R-30 continuous low-GWP XPS. | $1.17 | $0.00 | $1.17 | 1.00 |
ENVELOPE | Flat ceiling under vented attic: R-49. Corridor sealed attic: R-19 fiberglass batt strapped to the underside of the roof deck + R-30 continuous. | $1.17 | $0.00 | $1.17 | 1.00 | |
Windows & Glass Doors | ECC | High performance, U-0.24 / SHGC 0.24. | $7.13 | $0.00 | $7.13 | 1.00 |
ENVELOPE | High performance, U-0.18 / SHGC 0.18. | $9.27 | $0.00 | $9.27 | 1.00 | |
Doors | ECC | Opaque door, U-0.20 (R-5.0). | $0.35 | $0.00 | $0.35 | 0.95 |
ENVELOPE | Opaque door, U-0.20 (R-5.0). | $0.35 | $0.00 | $0.35 | 0.95 | |
Air Sealing | ECC | ≤0.27 CFM50 per sqft of enclosure (compartmentalization); tested. | $1.29 | $0.00 | $1.29 | 0.95 |
ENVELOPE | ≤0.27 CFM50 per sqft of enclosure (compartmentalization); tested. | $1.29 | $0.00 | $1.29 | 0.95 |
Path Comparison - Mechanical
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
HVAC | ECC | Ducted air-source heat pump, SEER2 17.5 / HSPF2 10; 1BR: 18 kBtuh; 2BR: 24 kBtuh; 3BR: 30 kBtuh; sized to the worst-case design load per bedroom count, see HVAC Design Loads | $11.52 | $0.00 | $11.52 | 1.15 |
ENVELOPE | Ducted air-source heat pump, SEER2 17.5 / HSPF2 10; 1BR: 18 kBtuh; 2BR: 24 kBtuh; 3BR: 24 kBtuh; sized to the worst-case design load per bedroom count, see HVAC Design Loads | $11.52 | $0.00 | $11.52 | 1.15 | |
Ductwork | ECC | Supply and return ducts in attic under insulation well vented insulated to code minimum; ducts in conditioned space insulated to code minimum. | $3.84 | $0.00 | $3.84 | 1.00 |
ENVELOPE | Supply and return ducts in attic under insulation well vented insulated to code minimum; ducts in conditioned space insulated to code minimum. | $3.84 | $0.00 | $3.84 | 1.00 | |
Duct Sealing | ECC | ≤ greater of 80 CFM25 or 8 CFM25 per 100 sqft of conditioned floor area; tested at final. | $0.66 | $0.00 | $0.66 | 1.00 |
ENVELOPE | ≤ greater of 80 CFM25 or 8 CFM25 per 100 sqft of conditioned floor area; tested at final. | $0.66 | $0.00 | $0.66 | 1.00 | |
HVAC Grading | ECC | N/A | $0.00 | $0.00 | $0.00 | 1.00 |
ENVELOPE | N/A | $0.00 | $0.00 | $0.00 | 1.00 | |
Mechanical Ventilation | ECC | 1BR: In-unit ERV; 50 CFM; ≥83% recovery efficiency. | 2BR: In-unit ERV; 65 CFM; ≥81% recovery efficiency. | 3BR: In-unit ERV; 65 CFM; ≥81% recovery efficiency. | $1.65 | $0.00 | $1.65 | 1.20 |
ENVELOPE | 1BR: In-unit ERV; 50 CFM; ≥83% recovery efficiency. | 2BR: In-unit ERV; 65 CFM; ≥81% recovery efficiency. | 3BR: In-unit ERV; 65 CFM; ≥81% recovery efficiency. | $1.65 | $0.00 | $1.65 | 1.20 | |
Local Mechanical Exhaust | 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. | $0.93 | $0.00 | $0.93 | 1.05 |
ENVELOPE | 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. | $0.93 | $0.00 | $0.93 | 1.05 | |
Thermostats | ECC | Programmable thermostat (as modeled). | $0.11 | $0.00 | $0.11 | 1.05 |
ENVELOPE | Programmable thermostat (as modeled). | $0.11 | $0.00 | $0.11 | 1.05 |
Path Comparison - Plumbing & Appliances
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
DHW | ECC | Studio / 1-bedroom: In-unit all-in-one heat pump water heater (HPWH); UEF 4; 40 gal. | $1.92 | $0.00 | $1.92 | 1.20 |
ENVELOPE | Studio / 1-bedroom: In-unit all-in-one heat pump water heater (HPWH); UEF 4; 40 gal. | $1.92 | $0.00 | $1.92 | 1.20 | |
DHW Piping | ECC | Supply piping insulated to R-3 minimum. | $0.66 | $0.00 | $0.66 | 0.95 |
ENVELOPE | Supply piping insulated to R-3 minimum. | $0.66 | $0.00 | $0.66 | 0.95 | |
Water Fixtures | ECC | WaterSense certified (Lavatory ≤1.2 GPM; Shower ≤2.0 GPM; Kitchen ≤2.2 GPM). | $1.65 | $0.00 | $1.65 | 1.00 |
ENVELOPE | WaterSense certified (Lavatory ≤1.2 GPM; Shower ≤2.0 GPM; Kitchen ≤2.2 GPM). | $1.65 | $0.00 | $1.65 | 1.00 | |
Refrigerator | ECC | Studio / 1-bedroom: ≤ 550 kWh/yr; electric. | $0.70 | $0.00 | $0.70 | 1.10 |
ENVELOPE | Studio / 1-bedroom: ≤ 500 kWh/yr; electric. | $0.72 | $0.00 | $0.72 | 1.10 | |
Dishwasher | ECC | ≤ 269 kWh/yr; electric. | $0.38 | $0.00 | $0.38 | 1.10 |
ENVELOPE | ≤ 269 kWh/yr; electric. | $0.38 | $0.00 | $0.38 | 1.10 | |
Clothes Washer | ECC | ENERGY STAR; electric. | $0.55 | $0.00 | $0.55 | 1.10 |
ENVELOPE | ENERGY STAR; electric. | $0.55 | $0.00 | $0.55 | 1.10 | |
Clothes Dryer | ECC | Standard electric dryer; vented; CEF 3.93. | $0.49 | $0.00 | $0.49 | 1.00 |
ENVELOPE | Standard electric dryer; vented; CEF 3.93. | $0.49 | $0.00 | $0.49 | 1.00 | |
Stove / Oven | ECC | Electric range. | $0.54 | $0.00 | $0.54 | 1.00 |
ENVELOPE | Electric range. | $0.54 | $0.00 | $0.54 | 1.00 |
Path Comparison - Electrical
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
Lighting | ECC | 100% high-efficacy (LED). | $4.00 | $0.00 | $4.00 | 0.85 |
ENVELOPE | 100% high-efficacy (LED). | $4.00 | $0.00 | $4.00 | 0.85 | |
Solar Ready | ECC | Low-rise buildings (225 CMR 22 Appendix RB as amended): unobstructed rooftop solar-ready zone of at least 300 sf and at least 5 ft wide, with a conduit/plumbing pathway to the service panel, reserved dual-pole breaker space, structural loads shown on the construction documents, and a permanent certificate. High-rise buildings and the clubhouse (225 CMR 23 C402.3 → IECC Appendix CB): reserve and keep clear at least 40% of the qualifying roof area, with an interconnection pathway and conduit, reserved electrical service space and panel capacity, 5 psf collateral dead load in the structural design of the zone, construction documents, and a permanent certificate. | $0.30 | $0.00 | $0.30 | 1.00 |
ENVELOPE | Low-rise buildings (225 CMR 22 Appendix RB as amended): unobstructed rooftop solar-ready zone of at least 300 sf and at least 5 ft wide, with a conduit/plumbing pathway to the service panel, reserved dual-pole breaker space, structural loads shown on the construction documents, and a permanent certificate. High-rise buildings and the clubhouse (225 CMR 23 C402.3 → IECC Appendix CB): reserve and keep clear at least 40% of the qualifying roof area, with an interconnection pathway and conduit, reserved electrical service space and panel capacity, 5 psf collateral dead load in the structural design of the zone, construction documents, and a permanent certificate. | $0.30 | $0.00 | $0.30 | 1.00 | |
EV Ready | ECC | At least 20% of parking spaces wired EV-ready (40-amp Level II; shared circuits with load management allowed). | $0.24 | $0.00 | $0.24 | 1.00 |
ENVELOPE | At least 20% of parking spaces wired EV-ready (40-amp Level II; shared circuits with load management allowed). | $0.24 | $0.00 | $0.24 | 1.00 | |
HPWH Ready | ECC | N/A | $0.00 | $0.00 | $0.00 | 1.00 |
ENVELOPE | 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 | ECC | HERS/ERI model, IECC 2021 checklist, Energy Star checklists, COMcheck. | $0.10 | $2.27 | $-2.17 | 1.00 |
ENVELOPE | HERS/ERI model, IECC 2021 checklist, Energy Star checklists, COMcheck. | $0.10 | $2.27 | $-2.17 | 1.00 | |
Testing & Verification | ECC | ENERGY STAR field verification: pre-drywall and final inspections, unit air-tightness (blower door), duct-leakage, ventilation and exhaust airflow, and HVAC functional testing. | $0.00 | $0.00 | $0.00 | 1.00 |
ENVELOPE | ENERGY STAR field verification: pre-drywall and final inspections, unit air-tightness (blower door), duct-leakage, ventilation and exhaust airflow, and HVAC functional testing. | $0.00 | $0.00 | $0.00 | 1.00 |
Additional Design Considerations Not Represented In This Study
- P1 ENVELOPE: An envelope-first Massachusetts Stretch Code package with no insulation carbon credit was scored through a 61-rung VE ladder from a base HERS 65. The path targeted design 43 against the HERS 45 code line. Worst-case unit W_A2_EXT_TL_1_E still sat at HERS 46 on rungs 59 through 61 after the heat-pump dryer at CEF 9, the induction range, and the convection oven were added. The ladder is exhausted one point short of code, so the path is parked and is not in this study.
- P2 MECH: A mechanical-first Stretch Code package with no insulation carbon credit was modeled to the HERS 45 line. The winning package closed on rung 30 with U-0.18 triple-pane as the compromise lever. Worst-case unit M_A1_EXT_TL_1_N scored HERS 43, and the path used a one-point fallback to a HERS 44 pass line. The package passed, but the live roster was reset to ECC versus ENVELOPE, so a mechanical-first package is not a live option.
- P3 ECC MECH: A mechanical-first package that claimed the 225 CMR 22 insulation carbon credit (code 48) was modeled with no continuous wall insulation and in-unit heat-pump water heaters. The winning rung 29 kept U-0.24 windows. Worst-case HERS 46 cleared the HERS 48 code line by two points. The live ECC path is a different package: continuous insulation capped at R-3.6, HERS 48 on the code line, and an all-in-one heat-pump water heater. A mechanical-first ECC identity is not in this study.
- P4 ECC ENVELOPE: An ECC envelope package claimed the insulation carbon credit (code 48), held the P3 envelope at the continuous-insulation cap of R-3.6, and used P1 mechanicals. A 50-gallon electric-resistance tank at UEF 0.93 and 0.94 defined that package and was not a tradable lever. The winning rung 30 added an induction range. Worst-case HERS 47 used the best-available pass line of 47. A two-point buffer at HERS 46 was never reached. The path was cut when the live roster became ECC versus ENVELOPE.
- Heat Pump Clothes Dryer: Heat-pump dryers at CEF 6.0 and CEF 9.0 were climbed on P1 rungs 58 and 59 and also appeared on the P3 and P4 ladders. Both live paths keep a vented electric dryer at CEF 3.93. The heat-pump dryer adds appliance cost and still left P1 one point short of the HERS 45 line, so it is not in this study.
- Induction Range and Convection Oven: An induction range and a convection oven were modeled on P1 rungs 60 and 61. Induction was also the closer on the P4 winning package. Both live paths keep a standard electric range. The appliance upgrade did not close the P1 HERS 45 gap and is not required for Stretch Code compliance on ECC or ENVELOPE.
- Electric Resistance DHW: A 50-gallon electric-resistance tank at UEF 0.93 and 0.94 was the DHW identity on P1 and P4. Both live paths use an in-unit all-in-one heat-pump water heater at UEF 4. Resistance DHW is not represented because the live study is the all-in-one heat-pump package, not a tank-resistance package.
- Tighter Air Sealing (0.26 and Below): Infiltration targets of 0.20 through 0.26 CFM50 per square foot of shell area were climbed on the P1, P2, and P3 ladders. Both live paths hold 0.27. Tighter sealing adds blower-door and detailing cost that did not change the live ECC or ENVELOPE packages.
- 87 to 89% ASRE ERV Recovery: ERVs at 87 to 89 percent ASRE were modeled on the parked and cut ladders, including 89 percent on P1. Both live paths keep 81 to 83 percent ASRE at 50 and 65 CFM. The higher-recovery units carry a premium that was not needed once ECC and ENVELOPE were set.
- Exterior Wall R-23 Cavity plus R-10 Continuous Insulation: P1 climbed the exterior wall to R-23 cavity plus R-10 continuous insulation. Live ECC holds R-21 plus R-3.6 CI, the credit cap. Live ENVELOPE holds R-21 plus R-7.5 CI. The heavier wall did not get P1 to HERS 45 and is above what the live packages use.
- R-60 Attic Insulation: P1 climbed the attic to R-60. Both live paths keep R-49. The extra attic insulation was part of a ladder that still finished one point short of the no-credit HERS 45 line, so it is not in this study.
- Triple-Pane U-0.15 Windows: Triple-pane glazing at U-0.15 was climbed on the P1, P2, P3, and P4 ladders. Live ECC keeps U-0.24. Live ENVELOPE keeps U-0.18. The U-0.15 premium was not warranted for the two live packages.
- Slab Perimeter R-20: P1 climbed slab perimeter insulation as high as R-20. Both live paths keep R-10 perimeter. The heavier slab detail was not needed for Stretch Code compliance on ECC or ENVELOPE.
- Refrigerator 450 kWh: P1 climbed the refrigerator to 450 kWh per year. Live ECC allows 550 kWh in studios and one-bedrooms and 650 in two- and three-bedrooms. Live ENVELOPE allows 500 and 600. The 450 kWh unit was part of an exhausted ladder that still missed HERS 45, so it is not in this study.
- Central or Split-System Heat Pump Water Heater: A central or split-system heat-pump water heater was considered as a mechanical option. It was ruled out of the live study on August 27, 2026. Domestic hot water on both live paths is an in-unit all-in-one heat-pump water heater.