CS75 Energy Code Feasibility Study in Provincetown, Massachusetts

Energy code feasibility study for a 16-unit Multifamily in Massachusetts. Compares multiple design paths. Recommended: Path 2 - Final Design (All-Electric). View full study.

Study Type: Energy Code Feasibility Study
State: Massachusetts
Units: 16
Building Type: Multifamily
Fuel Type: All-Electric
Recommended Path: Path 2 - Final Design (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

Provincetown, MA
1 Building | 16 Units | 12,967 SF Conditioned
New Construction | Multifamily Low-Rise | 3 stories, 16 units (mix of 1-story and 2-story units), slab-on-grade, all-electric
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

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 and constructability rather than compliance.

What Changes Between Paths

Exterior Walls: R-21 dense-pack cellulose in a 2x6 cavity with no continuous insulation on Final Design, stepping to R-23 cavity plus R-7 continuous exterior insulation (wood fiberboard or EPS Type I) on Carbon Credit, and R-23 cavity plus R-9 continuous exterior insulation (conventional rigid board) on HERS No GWP.
Slab: R-10 rigid insulation, full sub-slab plus turned up at the inside slab edge, on all three paths; only the product changes, low-GWP rigid on Final Design and Carbon Credit, conventional rigid on HERS No GWP.
Rim Joists: R-21 on Final Design, stepping up to R-23 on both Carbon Credit and HERS No GWP.
Roof: Vented attic blown cellulose steps from R-49 on Final Design to R-60 on Carbon Credit and HERS No GWP; the sealed flat-roof portion holds R-30 on all three but shifts from cavity insulation on Final Design to continuous low-GWP XPS on Carbon Credit to continuous conventional rigid board on HERS No GWP.
Windows & Glass Doors: Final Design uses one building-wide spec, U-0.27 and SHGC 0.29; Carbon Credit and HERS No GWP are identical to each other, triple pane U-0.18 and SHGC 0.18 in Units 2 and 15 with double pane U-0.24 and SHGC 0.24 everywhere else, glass doors matching.
Air Sealing: Tested enclosure leakage tightens from 0.27 CFM50 per square foot of enclosure on Final Design to 0.23 on Carbon Credit to 0.20 on HERS No GWP, lower being tighter.
HVAC: Final Design runs one ductless multi-split heat pump per unit (HSPF2 9, SEER2 20), 20 kBtuh two-zone in the one-bedroom units and 24 kBtuh three-zone in the two-bedroom units; Carbon Credit and HERS No GWP are identical to each other and split into three systems by unit type, two-story units pairing a ductless mini-split on Floor 1 (HSPF2 12, SEER2 23) with a ducted mini-split on Floor 2 (HSPF2 8.8, SEER2 16, attic ducts buried under insulation), and one-story units on a ductless mini-split (HSPF2 10, SEER2 20).
Ductwork: Final Design has no distribution ductwork at all; Carbon Credit and HERS No GWP add metal ducts with R-12 insulation buried in the attic under the blown insulation, for the two-story Floor-2 ducted systems only, with every other system ductless.
Duct Sealing: Final Design has no ducts to test; Carbon Credit caps total duct leakage at 80 CFM or below tested at final inspection; HERS No GWP is more demanding both ways, total and to-outside leakage at 40 CFM or below tested at rough-in, right after the air handler goes in.
Mechanical Ventilation: Final Design runs one in-unit ERV spec building-wide at 50 CFM, 89 percent or better recovery in the one-bedroom units and 90 percent or better in the two-bedroom units (Panasonic Intelli-Balance Elite Plus+); Carbon Credit and HERS No GWP are identical to each other and keep the bedroom split, one-bedroom units on a 60 CFM ERV at 63 percent or better recovery (Panasonic WhisperComfort) and two-bedroom units on a 120 CFM ERV at 80 percent or better (Panasonic Intelli-Balance Elite Plus+).
Clothes Washer: Same IMEF 1.84 electric washer on all three paths; only the annual energy cap changes, 99 kWh per year or less on Final Design against 120 kWh per year or less on Carbon Credit and HERS No GWP.
Clothes Dryer: Same ventless heat pump dryer on all three paths; Final Design requires CEF 9, Carbon Credit and HERS No GWP drop to CEF 6.4.

Price these twelve items against each other and you have the full cost difference between paths.

Path 2 - Final Design (All-Electric): Recommended

This is the least expensive path at approximately $62.89/sf net, about $14/sf below the next option, and it is also the most straightforward of the three to build. The simpler build protects the schedule and reduces how much has to be executed precisely in the field. It stays fully electric, which carries the same incentive eligibility as the other two paths and aligns with the direction Massachusetts energy code is heading.

Path 3 - HERS No GWP (All-Electric): Alternative (Conventional Materials)

At approximately $77.15/sf net, this path costs about $14/sf more than the Final Design, and it asks the most of the field crew of the three. Its advantage is procurement: everything it calls for is conventional and readily available, so nothing on the schedule waits on a special order. Choose this path when sourcing certainty matters more than first cost and construction speed.

Path 1 - Carbon Credit (All-Electric): Alternative (Low Carbon Materials)

At approximately $78.04/sf net, this is the most expensive path, about $15/sf above the Final Design, and it lands within a dollar per square foot of the other alternative. It is somewhat easier to execute in the field than that path, but it depends on products that have to be ordered in rather than pulled off the shelf, so it trades one kind of risk for another. Choose this path when the project wants the low carbon material commitment and can lock in sourcing early.

Code Path

Single Family OR Low Rise Buildings (Stretch)

Multifamily Low-Rise, 3 stories

MA Stretch Code | HERS ≤ 48 (Carbon Credit Path) or HERS ≤ 45

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 Path 1 - Carbon Credit and Path 2 - Final Design 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 Path 2 - Final Design already clears the threshold, so no material change is needed to earn the credit. The calculation below records it.

The result is a net 46,341 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 (Path 2 - Final Design)

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: $28,000 - $52,000

MassSave Multifamily Low Rise Program Base Tier ($24,000) (Program Breakdown): You get this rebate for having your building(s) meet energy code. 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.
In-Unit Heat Pump Water Heater Adder ($4,000) : A MassSave market transformation adder of $250 per unit for installing a heat-pump water heater in each dwelling unit. 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 - $24,000) (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.

Recommended Design - Units

Item	Detailed Specifications
Exterior Walls	R-21 dense-pack cellulose in a 2x6 @ 16 in. o.c. cavity, no continuous insulation.
Below Grade Walls	N/A - no below-grade walls in the model.
Corridor Walls	N/A - borders conditioned space.
Slab	R-10 low-GWP rigid insulation, full sub-slab plus turned up at the inside slab edge for a continuous thermal break.
Floor Over Unconditioned Space	N/A - borders conditioned space.
Floor Over Garage	N/A - borders conditioned space.
Floor Over Podium	N/A - borders conditioned space.
Rim Joists	R-21 rim/band insulation at floor transitions.
Roof	Vented attic: R-49 blown cellulose. Sealed flat-roof portion: R-30 cavity insulation.
Windows & Glass Doors	High performance, U-0.27 / SHGC 0.29.
Doors	All exterior doors are glass; no opaque doors (see Windows & Glass Doors).
Air Sealing	≤0.27 CFM50 per sqft of enclosure (compartmentalization); tested.
HVAC	Ductless multi-split cold-climate air-source heat pump, HSPF2 9 / SEER2 20; 1BR: 20 kBtuh 2-zone; 2BR: 24 kBtuh 3-zone; sized to the worst-case design load per bedroom count, see HVAC Design Loads
Ductwork	N/A - ductless system; no distribution ductwork.
Duct Sealing	N/A - ductless system (no ducts to test).
HVAC Grading	Fan Flow Test: N/A Watt Draw Test: N/A Refrigerant Charge: N/A
Mechanical Ventilation	1BR: In-unit ERV; 50 CFM; ≥89% recovery efficiency (Panasonic Intelli-Balance® Elite Plus+ ERV). \| 2BR: In-unit ERV; 50 CFM; ≥90% recovery efficiency (Panasonic Intelli-Balance® Elite Plus+ ERV).
Local Mechanical Exhaust	Code minimum local exhaust in kitchens and bathrooms, vented directly outdoors.
Thermostats	Smart thermostat (as modeled).
DHW	1BR: Integrated heat pump water heater (HPWH) (as modeled); UEF 3.88; 40 gal. \| 2BR: Integrated heat pump water heater (HPWH) (as modeled); UEF 3.88; 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	≤ 476 kWh/yr; electric.
Dishwasher	≤ 224 kWh/yr; electric.
Clothes Washer	IMEF 1.84; ≤ 99 kWh/yr; electric.
Clothes Dryer	Heat pump dryer; ventless; CEF 9.
Stove / Oven	Electric induction cooktop; convection oven.
Lighting	100% high-efficacy (LED).
Solar Ready	Reserve an unobstructed rooftop solar-ready zone (at least 300 sq ft) 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	At least 20% of parking spaces wired EV-ready (40-amp, 240-volt Level II).
HPWH Ready	N/A
Paperwork & Modeling	HERS/ERI energy model to the required rating, energy-code compliance documentation, and incentive paperwork.
Testing & Verification	Blower-door, duct-leakage, and ventilation-airflow testing, with pre-drywall and final inspections.

Recommended Design - Common Areas

Item	Common Areas (Residential Building)
Exterior Walls	Wood-frame: R-13 + R-7.5 CI or R-20 + R-3.8 CI or R-30. Steel-frame: R-13 + R-7.5 CI (CI mandatory).
Below Grade Walls	R-7.5 continuous insulation.
Corridor Walls	Common area wall insulation governs; refer to Exterior Walls.
Slab	R-10 edge, extending 4 feet or 24 inches below grade (whichever is greater).
Floor Over Unconditioned Space	R-13 cavity with R-17 CI, or R-30 cavity only, or R-19 cavity with R-5 CI.
Floor Over Garage	R-13 cavity with R-17 CI, or R-30 cavity only, or R-19 cavity with R-5 CI.
Floor Over Podium	R-30 continuous insulation.
Rim Joists	Insulation and air barrier continuous through rim joint; seal with caulk or foam; match wall R-value above and below grade.
Roof	R-30 continuous insulation at deck; or R-49 in attic with air barrier and Grade I insulation installation.
Windows & Glass Doors	U-factor ≤ 0.30 (fixed and operable); HERS model governs actual unit windows.
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	Heat pump (ducted split, ductless, or packaged): SEER2 15.2 / HSPF2 7.8 (ducted); 16 / 8.2 (ductless); 15.2 / 7.7 (packaged). 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. DCV and ERV are optional for common-space systems on this path.
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. No prescriptive LPD limits in common areas.
Lighting Controls	Dimmer, occupancy sensor, or built-in control on permanent fixtures.
Solar Ready	Solar-ready zone where roof area between 110 and 270 degrees exceeds 600 sqft and is not fully shaded; exempt if PV installed.
EV Ready	20% of installed parking spaces: 40-amp 208/240V dedicated branch circuits, 9.6 kVA minimum; AC Level I (120V, 3.3 kVA) substitution allowed at 3:1 ratio.
HPWH Ready	N/A
Electric Readiness	N/A
Vestibules	Standard entrance doors satisfy this path.
Efficiency Credits	N/A
Paperwork & Modeling	HERS/ERI models and certificates at permit and CO. ENERGY STAR workbook and checklists if certifying ESTAR.
Testing & Verification	Ventilation balancing per design. Duct leakage testing at rough-in and final. Lighting controls check. Rough-in and final air barrier inspections.

Exterior Wall (Path 1 - Carbon Credit)

Exterior Wall (Path 2 - Final Design)

Exterior Wall (Path 3 - HERS No GWP)

Slab on Grade (Path 1 - Carbon Credit, Path 2 - Final Design)

Slab on Grade (Path 3 - HERS No GWP)

Rim Joist (Path 1 - Carbon Credit)

Rim Joist (Path 2 - Final Design)

Rim Joist (Path 3 - HERS No GWP)

Roof — Vented Attic (Path 1 - Carbon Credit, Path 3 - HERS No GWP)

Roof — Vented Attic (Path 2 - Final Design)

Roof — Flat Sealed Section (Path 1 - Carbon Credit)

Roof — Flat Sealed Section (Path 2 - Final Design)

Roof — Flat Sealed Section (Path 3 - HERS No GWP)

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

Path 1 - Carbon Credit / Path 2 - Final Design / Path 3 - HERS No GWP: $28,000 - $52,000

MassSave Multifamily Low Rise Program Base Tier ($24,000) (Program Breakdown): You get this rebate for having your building(s) meet energy code. 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.
In-Unit Heat Pump Water Heater Adder ($4,000) : A MassSave market transformation adder of $250 per unit for installing a heat-pump water heater in each dwelling unit. 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 - $24,000) (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
Path 2 - Final Design	$63.74	$2.16	$62.89	1.02
Path 3 - HERS No GWP	$77.53	$2.16	$77.15	1.02
Path 1 - Carbon Credit	$78.40	$2.16	$78.04	1.02

Path Comparison - Envelope

Item	Path	Detailed Specifications	Cost $/sf	Incentive $/sf	Net $/sf	OpEx
Exterior Walls	Path 1 - Carbon Credit	R-23 dense-pack cellulose in a 2x6 @ 16 in. o.c. cavity plus R-7 continuous exterior insulation (2 in. wood fiberboard or EPS Type I).	$10.29	$0.00	$10.29	0.95
	Path 2 - Final Design	R-21 dense-pack cellulose in a 2x6 @ 16 in. o.c. cavity, no continuous insulation.	$7.18	$0.00	$7.18	0.95
	Path 3 - HERS No GWP	R-23 cavity insulation plus R-9 continuous exterior insulation (conventional rigid board; product per builder).	$9.20	$0.00	$9.20	0.95
Below Grade Walls	Path 1 - Carbon Credit	N/A - no below-grade walls in the model.	$0.00	$0.00	$0.00	1.00
	Path 2 - Final Design	N/A - no below-grade walls in the model.	$0.00	$0.00	$0.00	1.00
	Path 3 - HERS No GWP	N/A - no below-grade walls in the model.	$0.00	$0.00	$0.00	1.00
Corridor Walls	Path 1 - Carbon Credit	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	Path 2 - Final Design	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	Path 3 - HERS No GWP	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
Slab	Path 1 - Carbon Credit	R-10 low-GWP rigid insulation, full sub-slab plus turned up at the inside slab edge for a continuous thermal break.	$0.97	$0.00	$0.97	0.90
	Path 2 - Final Design	R-10 low-GWP rigid insulation, full sub-slab plus turned up at the inside slab edge for a continuous thermal break.	$0.97	$0.00	$0.97	0.90
	Path 3 - HERS No GWP	R-10 rigid insulation, full sub-slab plus turned up at the inside slab edge for a continuous thermal break (conventional product).	$0.88	$0.00	$0.88	0.90
Floor Over Unconditioned Space	Path 1 - Carbon Credit	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	Path 2 - Final Design	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	Path 3 - HERS No GWP	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
Floor Over Garage	Path 1 - Carbon Credit	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	Path 2 - Final Design	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	Path 3 - HERS No GWP	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
Floor Over Podium	Path 1 - Carbon Credit	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	Path 2 - Final Design	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	Path 3 - HERS No GWP	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
Rim Joists	Path 1 - Carbon Credit	R-23 rim/band insulation at floor transitions.	$0.21	$0.00	$0.21	0.95
	Path 2 - Final Design	R-21 rim/band insulation at floor transitions.	$0.20	$0.00	$0.20	0.95
	Path 3 - HERS No GWP	R-23 rim/band insulation at floor transitions.	$0.21	$0.00	$0.21	0.95
Roof	Path 1 - Carbon Credit	Vented attic: R-60 blown cellulose. Sealed flat-roof portion: R-30 continuous low-GWP insulation (XPS Low GWP).	$1.25	$0.00	$1.25	1.10
	Path 2 - Final Design	Vented attic: R-49 blown cellulose. Sealed flat-roof portion: R-30 cavity insulation.	$0.90	$0.00	$0.90	1.10
	Path 3 - HERS No GWP	Vented attic: R-60 blown cellulose. Sealed flat-roof portion: R-30 continuous insulation (conventional rigid board).	$1.18	$0.00	$1.18	1.10
Windows & Glass Doors	Path 1 - Carbon Credit	Units 2 and 15: triple pane, U-0.18 / SHGC 0.18. All other units: double pane, U-0.24 / SHGC 0.24. Glass doors carry the same requirement.	$14.55	$0.00	$14.55	1.05
	Path 2 - Final Design	High performance, U-0.27 / SHGC 0.29.	$11.91	$0.00	$11.91	1.05
	Path 3 - HERS No GWP	Units 2 and 15: triple pane, U-0.18 / SHGC 0.18. All other units: double pane, U-0.24 / SHGC 0.24. Glass doors carry the same requirement.	$14.55	$0.00	$14.55	1.05
Doors	Path 1 - Carbon Credit	All exterior doors are glass; no opaque doors (see Windows & Glass Doors).	$0.00	$0.00	$0.00	0.95
	Path 2 - Final Design	All exterior doors are glass; no opaque doors (see Windows & Glass Doors).	$0.00	$0.00	$0.00	0.95
	Path 3 - HERS No GWP	All exterior doors are glass; no opaque doors (see Windows & Glass Doors).	$0.00	$0.00	$0.00	0.95
Air Sealing	Path 1 - Carbon Credit	≤0.23 CFM50 per sqft of enclosure (compartmentalization); tested.	$1.40	$0.00	$1.40	0.95
	Path 2 - Final Design	≤0.27 CFM50 per sqft of enclosure (compartmentalization); tested.	$1.29	$0.00	$1.29	0.95
	Path 3 - HERS No GWP	≤0.20 CFM50 per sqft of enclosure (compartmentalization); tested.	$1.55	$0.00	$1.55	0.95

Path Comparison - Mechanical

Item	Path	Detailed Specifications	Cost $/sf	Incentive $/sf	Net $/sf	OpEx
HVAC	Path 1 - Carbon Credit	Three heat-pump systems by unit type: 2-story units Floor 1 ductless mini-split, HSPF2 12 / SEER2 23; 2-story units Floor 2 ducted mini-split, HSPF2 8.8 / SEER2 16 (attic ducts, buried under insulation); 1-story units ductless mini-split, HSPF2 10 / SEER2 20. All-electric.	$22.19	$0.00	$22.19	1.18
	Path 2 - Final Design	Ductless multi-split cold-climate air-source heat pump, HSPF2 9 / SEER2 20; 1BR: 20 kBtuh 2-zone; 2BR: 24 kBtuh 3-zone; sized to the worst-case design load per bedroom count, see HVAC Design Loads	$15.85	$0.00	$15.85	1.15
	Path 3 - HERS No GWP	Three heat-pump systems by unit type: 2-story units Floor 1 ductless mini-split, HSPF2 12 / SEER2 23; 2-story units Floor 2 ducted mini-split, HSPF2 8.8 / SEER2 16 (attic ducts, buried under insulation); 1-story units ductless mini-split, HSPF2 10 / SEER2 20. All-electric.	$22.19	$0.00	$22.19	1.18
Ductwork	Path 1 - Carbon Credit	Metal ducts, R-12 insulation, run in the attic buried under the blown insulation; 2-story Floor-2 ducted systems only. All other systems ductless.	$2.60	$0.00	$2.60	1.05
	Path 2 - Final Design	N/A - ductless system; no distribution ductwork.	$0.00	$0.00	$0.00	1.00
	Path 3 - HERS No GWP	Metal ducts, R-12 insulation, run in the attic buried under the blown insulation; 2-story Floor-2 ducted systems only. All other systems ductless.	$2.60	$0.00	$2.60	1.05
Duct Sealing	Path 1 - Carbon Credit	Total duct leakage ≤ 80 CFM, tested at final inspection.	$0.44	$0.00	$0.44	1.00
	Path 2 - Final Design	N/A - ductless system (no ducts to test).	$0.00	$0.00	$0.00	1.00
	Path 3 - HERS No GWP	Total and to-outside duct leakage ≤ 40 CFM, tested at rough-in (after the air handler is installed).	$0.67	$0.00	$0.67	1.00
HVAC Grading	Path 1 - Carbon Credit	Fan Flow Test: N/A Watt Draw Test: N/A Refrigerant Charge: N/A	$0.00	$0.00	$0.00	1.00
	Path 2 - Final Design	Fan Flow Test: N/A Watt Draw Test: N/A Refrigerant Charge: N/A	$0.00	$0.00	$0.00	1.00
	Path 3 - HERS No GWP	Fan Flow Test: N/A Watt Draw Test: N/A Refrigerant Charge: N/A	$0.00	$0.00	$0.00	1.00
Mechanical Ventilation	Path 1 - Carbon Credit	1BR: In-unit ERV; 60 CFM; ≥63% recovery efficiency (Panasonic WhisperComfort). \| 2BR: In-unit ERV; 120 CFM; ≥80% recovery efficiency (Panasonic Intelli-Balance® Elite Plus+ ERV).	$2.72	$0.00	$2.72	1.25
	Path 2 - Final Design	1BR: In-unit ERV; 50 CFM; ≥89% recovery efficiency (Panasonic Intelli-Balance® Elite Plus+ ERV). \| 2BR: In-unit ERV; 50 CFM; ≥90% recovery efficiency (Panasonic Intelli-Balance® Elite Plus+ ERV).	$3.42	$0.00	$3.42	1.25
	Path 3 - HERS No GWP	1BR: In-unit ERV; 60 CFM; ≥63% recovery efficiency (Panasonic WhisperComfort). \| 2BR: In-unit ERV; 120 CFM; ≥80% recovery efficiency (Panasonic Intelli-Balance® Elite Plus+ ERV).	$2.72	$0.00	$2.72	1.25
Local Mechanical Exhaust	Path 1 - Carbon Credit	Code minimum local exhaust in kitchens and bathrooms, vented directly outdoors.	$1.57	$0.00	$1.57	1.05
	Path 2 - Final Design	Code minimum local exhaust in kitchens and bathrooms, vented directly outdoors.	$1.57	$0.00	$1.57	1.05
	Path 3 - HERS No GWP	Code minimum local exhaust in kitchens and bathrooms, vented directly outdoors.	$1.57	$0.00	$1.57	1.05
Thermostats	Path 1 - Carbon Credit	Smart thermostat (as modeled).	$0.19	$0.00	$0.19	1.05
	Path 2 - Final Design	Smart thermostat (as modeled).	$0.19	$0.00	$0.19	1.05
	Path 3 - HERS No GWP	Smart thermostat (as modeled).	$0.19	$0.00	$0.19	1.05

Path Comparison - Plumbing & Appliances

Item	Path	Detailed Specifications	Cost $/sf	Incentive $/sf	Net $/sf	OpEx
DHW	Path 1 - Carbon Credit	1BR: Integrated heat pump water heater (HPWH) (as modeled); UEF 3.88; 40 gal. \| 2BR: Integrated heat pump water heater (HPWH) (as modeled); UEF 3.88; 50 gal.	$3.37	$0.31	$3.06	1.20
	Path 2 - Final Design	1BR: Integrated heat pump water heater (HPWH) (as modeled); UEF 3.88; 40 gal. \| 2BR: Integrated heat pump water heater (HPWH) (as modeled); UEF 3.88; 50 gal.	$3.37	$0.31	$3.06	1.20
	Path 3 - HERS No GWP	1BR: Integrated heat pump water heater (HPWH) (as modeled); UEF 3.88; 40 gal. \| 2BR: Integrated heat pump water heater (HPWH) (as modeled); UEF 3.88; 50 gal.	$3.37	$0.31	$3.06	1.20
DHW Piping	Path 1 - Carbon Credit	Supply piping insulated to R-3 minimum.	$1.11	$0.00	$1.11	0.95
	Path 2 - Final Design	Supply piping insulated to R-3 minimum.	$1.11	$0.00	$1.11	0.95
	Path 3 - HERS No GWP	Supply piping insulated to R-3 minimum.	$1.11	$0.00	$1.11	0.95
Water Fixtures	Path 1 - Carbon Credit	WaterSense certified (Lavatory ≤1.2 GPM; Shower ≤2.0 GPM; Kitchen ≤2.2 GPM).	$2.77	$0.00	$2.77	1.00
	Path 2 - Final Design	WaterSense certified (Lavatory ≤1.2 GPM; Shower ≤2.0 GPM; Kitchen ≤2.2 GPM).	$2.77	$0.00	$2.77	1.00
	Path 3 - HERS No GWP	WaterSense certified (Lavatory ≤1.2 GPM; Shower ≤2.0 GPM; Kitchen ≤2.2 GPM).	$2.77	$0.00	$2.77	1.00
Refrigerator	Path 1 - Carbon Credit	≤ 476 kWh/yr; electric.	$1.24	$0.00	$1.24	1.10
	Path 2 - Final Design	≤ 476 kWh/yr; electric.	$1.24	$0.00	$1.24	1.10
	Path 3 - HERS No GWP	≤ 476 kWh/yr; electric.	$1.24	$0.00	$1.24	1.10
Dishwasher	Path 1 - Carbon Credit	≤ 224 kWh/yr; electric.	$0.77	$0.00	$0.77	1.10
	Path 2 - Final Design	≤ 224 kWh/yr; electric.	$0.77	$0.00	$0.77	1.10
	Path 3 - HERS No GWP	≤ 224 kWh/yr; electric.	$0.77	$0.00	$0.77	1.10
Clothes Washer	Path 1 - Carbon Credit	IMEF 1.84; ≤ 120 kWh/yr; electric.	$0.74	$0.00	$0.74	1.10
	Path 2 - Final Design	IMEF 1.84; ≤ 99 kWh/yr; electric.	$0.79	$0.00	$0.79	1.10
	Path 3 - HERS No GWP	IMEF 1.84; ≤ 120 kWh/yr; electric.	$0.74	$0.00	$0.74	1.10
Clothes Dryer	Path 1 - Carbon Credit	Heat pump dryer; ventless; CEF 6.4.	$1.64	$0.00	$1.64	1.00
	Path 2 - Final Design	Heat pump dryer; ventless; CEF 9.	$1.83	$0.00	$1.83	1.00
	Path 3 - HERS No GWP	Heat pump dryer; ventless; CEF 6.4.	$1.64	$0.00	$1.64	1.00
Stove / Oven	Path 1 - Carbon Credit	Electric induction cooktop; convection oven.	$1.20	$0.00	$1.20	1.05
	Path 2 - Final Design	Electric induction cooktop; convection oven.	$1.20	$0.00	$1.20	1.05
	Path 3 - HERS No GWP	Electric induction cooktop; convection oven.	$1.20	$0.00	$1.20	1.05

Path Comparison - Electrical

Item	Path	Detailed Specifications	Cost $/sf	Incentive $/sf	Net $/sf	OpEx
Lighting	Path 1 - Carbon Credit	100% high-efficacy (LED).	$4.00	$0.00	$4.00	0.85
	Path 2 - Final Design	100% high-efficacy (LED).	$4.00	$0.00	$4.00	0.85
	Path 3 - HERS No GWP	100% high-efficacy (LED).	$4.00	$0.00	$4.00	0.85
Solar Ready	Path 1 - Carbon Credit	Reserve an unobstructed rooftop solar-ready zone (at least 300 sq ft) 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
	Path 2 - Final Design	Reserve an unobstructed rooftop solar-ready zone (at least 300 sq ft) 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
	Path 3 - HERS No GWP	Reserve an unobstructed rooftop solar-ready zone (at least 300 sq ft) 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	Path 1 - Carbon Credit	At least 20% of parking spaces wired EV-ready (40-amp, 240-volt Level II).	$0.52	$0.00	$0.52	1.00
	Path 2 - Final Design	At least 20% of parking spaces wired EV-ready (40-amp, 240-volt Level II).	$0.52	$0.00	$0.52	1.00
	Path 3 - HERS No GWP	At least 20% of parking spaces wired EV-ready (40-amp, 240-volt Level II).	$0.52	$0.00	$0.52	1.00
HPWH Ready	Path 1 - Carbon Credit	N/A	$0.00	$0.00	$0.00	1.00
	Path 2 - Final Design	N/A	$0.00	$0.00	$0.00	1.00
	Path 3 - HERS No GWP	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	Path 1 - Carbon Credit	HERS/ERI energy model to the required rating, energy-code compliance documentation, and incentive paperwork.	$2.36	$1.85	$0.51	1.00
	Path 2 - Final Design	HERS/ERI energy model to the required rating, energy-code compliance documentation, and incentive paperwork.	$2.36	$1.85	$0.51	1.00
	Path 3 - HERS No GWP	HERS/ERI energy model to the required rating, energy-code compliance documentation, and incentive paperwork.	$2.36	$1.85	$0.51	1.00
Testing & Verification	Path 1 - Carbon Credit	Blower-door, duct-leakage, and ventilation-airflow testing, with pre-drywall and final inspections.	$0.00	$0.00	$0.00	1.00
	Path 2 - Final Design	Blower-door, duct-leakage, and ventilation-airflow testing, with pre-drywall and final inspections.	$0.00	$0.00	$0.00	1.00
	Path 3 - HERS No GWP	Blower-door, duct-leakage, and ventilation-airflow testing, with pre-drywall and final inspections.	$0.00	$0.00	$0.00	1.00

Additional Design Considerations Not Represented In This Study

Building-Wide Triple-Pane Windows: Triple-pane glazing was weighed for all sixteen units. The carbon credit and no-GWP paths carry triple pane at Units 2 and 15 only, and the final design reaches HERS 46 on U-0.27 / SHGC 0.29 glazing throughout, glass doors included, so building-wide triple pane buys rating margin the design already holds.
Rooftop Solar at Construction: Installing rooftop solar during construction was weighed on top of the solar-ready provisions every path carries. All three paths reach their ratings of HERS 42.96, 46, and 47.37 on envelope and equipment alone. The capital cost and the exposed coastal roof in Provincetown put solar on a later owner decision, held open by the reserved 300 sq ft rooftop zone with its conduit pathway and panel space.
Ground-Source (Geothermal) Heat Pumps: A ground-source (geothermal) system was weighed against the air-source heat pumps carried on all three paths. The air-source equipment already lands the paths at HERS 42.96 to 47.37 at a fraction of the first cost of a drilled ground loop, so the design stays all air-source.
Central Heat-Pump Water Heating: A shared central heat-pump water-heating plant was considered in place of the in-unit heat pump water heaters. The in-unit HPWHs at UEF 3.88 already carry the HERS 46 result on the chosen path, while a central plant would add a dedicated mechanical room and a recirculation loop that loses heat around the clock, so in-unit water heaters stayed on all three paths.