CS70 Energy Code Feasibility Study in Shrewsbury, Massachusetts

Energy code feasibility study for a 36-unit Multifamily in Massachusetts. Compares multiple design paths. Recommended: NO HPWH (All-Electric). View full study.

Study Type: Energy Code Feasibility Study
State: Massachusetts
Units: 36
Building Type: Multifamily
Fuel Type: All-Electric
Recommended Path: NO HPWH (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

Shrewsbury, MA
3 Buildings | 36 Units | 36,748 SF Conditioned
New Construction | Multifamily Low-Rise | 2 residential buildings, 3 stories each, 36 units; plus a separate 1-story 5,625 sf retail building
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.

What Changes Between Paths

HVAC: both paths use a ducted air-source heat pump, and the ratings shift: NO HPWH runs SEER2 17 with HSPF2 10 in every unit, while HPWH runs HSPF2 9 with SEER2 17.5 in the one-bedroom units and SEER2 17 in the two-bedroom units
DHW: the water heater changes, an electric resistance storage tank at UEF 0.93 and 50 gallons on NO HPWH, against an integrated heat pump water heater at UEF 3.5 with 50 gallons in the one-bedroom units and 65 gallons in the two-bedroom units on HPWH
Refrigerator: the allowance holds at 550 kWh per year on HPWH, while NO HPWH drops the one-bedroom units to 500 kWh per year and keeps the two-bedroom units at 550

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

NO HPWH (All-Electric): Recommended

This is the least expensive path at approximately $46.61/sf net, and it is the simpler of the two to build: one equipment package repeats across every unit, so there is less to coordinate in the field and fewer parts to procure. It keeps the project fully electric, which lines up with the direction Massachusetts energy code is heading. For this project, it is the right call.

HPWH (All-Electric): Alternative (Compliance Margin)

At approximately $47.74/sf net, this path costs about $1.13/sf more than the recommended path and asks for more coordination in the field, since more of the build varies by unit type. What it buys is headroom: it clears the compliance target with room to spare instead of landing right on the line. Choose this path when protecting against late design changes matters more than the last dollar per square foot.

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: each dwelling unit is rated to the code ceiling of HERS 42 mixed fuel or HERS 45 all electric (48 on the R406.5.2 embodied-carbon path), with all insulation installed at Grade I and continuous balanced ventilation with heat or energy recovery.

Commercial, 1 story

MA Stretch Code | IECC-C Prescriptive (COMcheck)

This structure complies prescriptively: COMcheck envelope, lighting, and mechanical certificates with the plan review checklist, plus the mandatory air-leakage testing. The prescriptive path serves nonresidential buildings up to 20,000 sf; larger buildings comply through a performance pathway.

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.

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: $0 - $74,000

SELCO Commercial Heat Pump Rebate ($0 - $20,000) (Program Breakdown): You get this rebate for installing air source heat pumps in a building served by SELCO, Shrewsbury's municipal electric utility. Shrewsbury does not pay into the Mass Save charge, so SELCO runs its own program in its place, and new construction qualifies for this one. It pays $750 per ton of heating capacity and caps at $20,000 per customer or developer, so a project of this size reaches the cap on heating capacity alone. The rebate comes in the form of a check after the equipment is installed and verified.
- IMPORTANT: SELCO has to pre-approve the rebate in writing before any work begins. Starting the work first gives it up entirely, so the application belongs in the pre-construction schedule.
- Risks: SELCO funds only a handful of projects a year out of a limited budget, first come and first serve, so this is worth pursuing as upside rather than carrying it as a budgeted line. The $20,000 cap is written per customer or developer, so a second building under a related entity is unlikely to claim it twice. Buildings that take natural gas service from Eversource are not eligible for this program at all.
DOER Alternative Energy Credits ($0 - $54,000) (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-30 cavity insulation (2x6 @ 16" o.c.), 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 fully insulated slab.
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-30 rim/band insulation at floor transitions.
Roof	Sealed attic: R-19 insulation + R-30 continuous insulation.
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 (as modeled); SEER2 17; HSPF2 10.
Ductwork	Supply and return ducts in conditioned space insulated to code minimum.
Duct Sealing	≤ greater of 80 CFM25 or 8 CFM25 per 100 sqft of conditioned floor area.
HVAC Grading	Fan Flow Test: N/A Watt Draw Test: N/A Refrigerant Charge: N/A
Mechanical Ventilation	In-unit ERV; 50 CFM; ≥83% recovery efficiency (Panasonic Intelli-Balance 100).
Local Mechanical Exhaust	Code minimum local exhaust in kitchens and bathrooms, vented directly outdoors.
Thermostats	Programmable thermostat (as modeled).
DHW	Electric resistance storage water heater (as modeled); UEF 0.93; 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	1BR: ≤ 500 kWh/yr; electric. \| 2BR: ≤ 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) 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.

Retail Space (5,625 SF)

Item	Requirements
Compliance Path	Prescriptive compliance is available for nonresidential buildings up to 20,000 sf: COMcheck envelope, lighting, and mechanical certificates plus the plan review checklist. Larger buildings comply through a performance pathway (Targeted Performance TEDI, ASHRAE 90.1 Appendix G, Passive House, or HERS for Group R).
Exterior Walls	Wall compliance is by assembly U-factor: wood-framed walls U-0.051 max, with continuous insulation derated for fasteners and linear thermal bridges per C402.7 (MA Stretch COMcheck applies the derating automatically).
Roof	Insulation entirely above deck U-0.032 (R-30 continuous; tapered systems rated 1 inch above minimum thickness). Attic assemblies U-0.021 (R-49).
Slab	Unheated slab-on-grade F-0.52 (R-15 perimeter, 24 inches below; Group R R-20); the slab insulation installation rule applies without exception.
Windows & Glass Doors	Fixed fenestration U-0.30 and operable U-0.32 (MA amendment), documented by NFRC label or simulation report; SHGC per base Table C402.4: 0.38 fixed / 0.33 operable at projection factor under 0.2.
Doors	Opaque swinging doors U-0.37; nonswinging U-0.31.
Air Sealing	Third-party air-leakage testing is mandatory: whole-building 0.35 cfm/sf at 75 Pa or better (diagnostic evaluation and sealing path between 0.35 and 0.45); continuous air barrier designed, documented, and field verified; enclosed vestibules at building entrances serving spaces of 3,000 sf or more.
HVAC	Equipment meets the C403.3.2 minimum efficiencies with the 2024 IECC heat pump tables; ventilation energy recovery per the CZ5A rows of Tables C403.7.4.2(1)-(2) (70 percent sensible at heating design).
Economizer	Air or water economizer on fan systems of 54,000 Btu/h or more (Group R 270,000 Btu/h or more) and all dedicated outdoor air systems; chilled-water triggers per Table C403.5(1).
DHW	Service water heating per base 2021 IECC C404: Table C404.2 equipment efficiencies, pipe insulation, and controls.
Lighting	Interior lighting power within Table C405.3.2(2) space-by-space allowances; typical values: corridor 0.41 W/sf, lobby 0.84, laundry 0.53, stairwell 0.49, storage 0.38, enclosed office 0.74, restroom 0.63. COMcheck documents the calculation.
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.
Additional Efficiency Credits	Achieve 15 credits from Tables C406.1(1)-(5); MA menu highlights for CZ5A: cold-climate heat pump space heating 15 credits, heavy timber or low-GWP concrete or net-zero-GWP insulation 8 credits each, reduced air leakage at 0.20 cfm/sf tested.
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.
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.

Exterior Wall (HPWH, NO HPWH)

Slab on Grade (HPWH, NO HPWH)

Rim Joist (HPWH, NO HPWH)

Roof (HPWH, NO HPWH)

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

HPWH / NO HPWH: $0 - $74,000

SELCO Commercial Heat Pump Rebate ($0 - $20,000) (Program Breakdown): You get this rebate for installing air source heat pumps in a building served by SELCO, Shrewsbury's municipal electric utility. Shrewsbury does not pay into the Mass Save charge, so SELCO runs its own program in its place, and new construction qualifies for this one. It pays $750 per ton of heating capacity and caps at $20,000 per customer or developer, so a project of this size reaches the cap on heating capacity alone. The rebate comes in the form of a check after the equipment is installed and verified.
- IMPORTANT: SELCO has to pre-approve the rebate in writing before any work begins. Starting the work first gives it up entirely, so the application belongs in the pre-construction schedule.
- Risks: SELCO funds only a handful of projects a year out of a limited budget, first come and first serve, so this is worth pursuing as upside rather than carrying it as a budgeted line. The $20,000 cap is written per customer or developer, so a second building under a related entity is unlikely to claim it twice. Buildings that take natural gas service from Eversource are not eligible for this program at all.
DOER Alternative Energy Credits ($0 - $54,000) (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
NO HPWH	$46.19	$0.00	$46.61	1.01
HPWH	$46.89	$0.00	$47.74	1.02

Path Comparison - Envelope

Item	Path	Detailed Specifications	Cost $/sf	Incentive $/sf	Net $/sf	OpEx
Exterior Walls	HPWH	R-30 cavity insulation (2x6 @ 16" o.c.), no continuous insulation.	$3.90	$0.00	$3.90	0.95
	NO HPWH	R-30 cavity insulation (2x6 @ 16" o.c.), no continuous insulation.	$3.90	$0.00	$3.90	0.95
Below Grade Walls	HPWH	N/A - no below-grade walls in the model.	$0.00	$0.00	$0.00	1.00
	NO HPWH	N/A - no below-grade walls in the model.	$0.00	$0.00	$0.00	1.00
Corridor Walls	HPWH	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	NO HPWH	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
Slab	HPWH	R-10 fully insulated slab.	$0.82	$0.00	$0.82	0.90
	NO HPWH	R-10 fully insulated slab.	$0.82	$0.00	$0.82	0.90
Floor Over Unconditioned Space	HPWH	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	NO HPWH	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
Floor Over Garage	HPWH	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	NO HPWH	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
Floor Over Podium	HPWH	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
	NO HPWH	N/A - borders conditioned space.	$0.00	$0.00	$0.00	1.00
Rim Joists	HPWH	R-30 rim/band insulation at floor transitions.	$0.25	$0.00	$0.25	0.95
	NO HPWH	R-30 rim/band insulation at floor transitions.	$0.25	$0.00	$0.25	0.95
Roof	HPWH	Sealed attic: R-19 insulation + R-30 continuous insulation.	$2.09	$0.00	$2.09	1.10
	NO HPWH	Sealed attic: R-19 insulation + R-30 continuous insulation.	$2.09	$0.00	$2.09	1.10
Windows & Glass Doors	HPWH	High performance, U-0.24 / SHGC 0.24.	$2.00	$0.00	$2.00	1.00
	NO HPWH	High performance, U-0.24 / SHGC 0.24.	$2.00	$0.00	$2.00	1.00
Doors	HPWH	Opaque door, U-0.20 (R-5.0).	$0.35	$0.00	$0.35	0.95
	NO HPWH	Opaque door, U-0.20 (R-5.0).	$0.35	$0.00	$0.35	0.95
Air Sealing	HPWH	≤0.27 CFM50 per sqft of enclosure (compartmentalization); tested.	$1.29	$0.00	$1.29	0.95
	NO HPWH	≤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	HPWH	1BR: Ducted air-source heat pump (as modeled); SEER2 17.5; HSPF2 9. \| 2BR: Ducted air-source heat pump (as modeled); SEER2 17; HSPF2 9.	$13.60	$0.00	$13.60	1.15
	NO HPWH	Ducted air-source heat pump (as modeled); SEER2 17; HSPF2 10.	$14.21	$0.00	$14.21	1.15
Ductwork	HPWH	Supply and return ducts in conditioned space insulated to code minimum.	$4.74	$0.00	$4.74	1.00
	NO HPWH	Supply and return ducts in conditioned space insulated to code minimum.	$4.74	$0.00	$4.74	1.00
Duct Sealing	HPWH	≤ greater of 80 CFM25 or 8 CFM25 per 100 sqft of conditioned floor area.	$0.81	$0.00	$0.81	1.00
	NO HPWH	≤ greater of 80 CFM25 or 8 CFM25 per 100 sqft of conditioned floor area.	$0.81	$0.00	$0.81	1.00
HVAC Grading	HPWH	Fan Flow Test: N/A Watt Draw Test: N/A Refrigerant Charge: N/A	$0.00	$0.00	$0.00	1.00
	NO HPWH	Fan Flow Test: N/A Watt Draw Test: N/A Refrigerant Charge: N/A	$0.00	$0.00	$0.00	1.00
Mechanical Ventilation	HPWH	In-unit ERV; 50 CFM; ≥83% recovery efficiency (Panasonic Intelli-Balance 100).	$2.03	$0.00	$2.03	1.20
	NO HPWH	In-unit ERV; 50 CFM; ≥83% recovery efficiency (Panasonic Intelli-Balance 100).	$2.03	$0.00	$2.03	1.20
Local Mechanical Exhaust	HPWH	Code minimum local exhaust in kitchens and bathrooms, vented directly outdoors.	$1.15	$0.00	$1.15	1.05
	NO HPWH	Code minimum local exhaust in kitchens and bathrooms, vented directly outdoors.	$1.15	$0.00	$1.15	1.05
Thermostats	HPWH	Programmable thermostat (as modeled).	$0.10	$0.00	$0.10	1.05
	NO HPWH	Programmable thermostat (as modeled).	$0.10	$0.00	$0.10	1.05

Path Comparison - Plumbing & Appliances

Item	Path	Detailed Specifications	Cost $/sf	Incentive $/sf	Net $/sf	OpEx
DHW	HPWH	1BR: Integrated heat pump water heater (HPWH) (as modeled); UEF 3.5; 50 gal. \| 2BR: Integrated heat pump water heater (HPWH) (as modeled); UEF 3.5; 65 gal.	$2.41	$0.00	$2.41	1.20
	NO HPWH	Electric resistance storage water heater (as modeled); UEF 0.93; 50 gal.	$1.07	$0.00	$1.07	0.90
DHW Piping	HPWH	Supply piping insulated to R-3 minimum.	$0.81	$0.00	$0.81	0.95
	NO HPWH	Supply piping insulated to R-3 minimum.	$0.81	$0.00	$0.81	0.95
Water Fixtures	HPWH	WaterSense certified (Lavatory ≤1.2 GPM; Shower ≤2.0 GPM; Kitchen ≤2.2 GPM).	$2.03	$0.00	$2.03	1.00
	NO HPWH	WaterSense certified (Lavatory ≤1.2 GPM; Shower ≤2.0 GPM; Kitchen ≤2.2 GPM).	$2.03	$0.00	$2.03	1.00
Refrigerator	HPWH	≤ 550 kWh/yr; electric.	$0.88	$0.00	$0.88	1.10
	NO HPWH	1BR: ≤ 500 kWh/yr; electric. \| 2BR: ≤ 550 kWh/yr; electric.	$0.91	$0.00	$0.91	1.10
Dishwasher	HPWH	≤ 269 kWh/yr; electric.	$0.47	$0.00	$0.47	1.10
	NO HPWH	≤ 269 kWh/yr; electric.	$0.47	$0.00	$0.47	1.10
Clothes Washer	HPWH	IMEF 1.0; ≤ 141 kWh/yr; electric.	$0.49	$0.00	$0.49	1.10
	NO HPWH	IMEF 1.0; ≤ 141 kWh/yr; electric.	$0.49	$0.00	$0.49	1.10
Clothes Dryer	HPWH	Standard electric dryer; vented; CEF 3.93.	$0.61	$0.00	$0.61	1.00
	NO HPWH	Standard electric dryer; vented; CEF 3.93.	$0.61	$0.00	$0.61	1.00
Stove / Oven	HPWH	Electric range.	$0.63	$0.00	$0.63	1.05
	NO HPWH	Electric range.	$0.63	$0.00	$0.63	1.05

Path Comparison - Electrical

Item	Path	Detailed Specifications	Cost $/sf	Incentive $/sf	Net $/sf	OpEx
Lighting	HPWH	100% high-efficacy (LED).	$4.00	$0.00	$4.00	0.85
	NO HPWH	100% high-efficacy (LED).	$4.00	$0.00	$4.00	0.85
Solar Ready	HPWH	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
	NO HPWH	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	HPWH	At least 20% of parking spaces wired EV-ready (40-amp, 240-volt Level II).	$0.30	$0.00	$0.30	1.00
	NO HPWH	At least 20% of parking spaces wired EV-ready (40-amp, 240-volt Level II).	$0.30	$0.00	$0.30	1.00
HPWH Ready	HPWH	N/A	$0.00	$0.00	$0.00	1.00
	NO HPWH	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	HPWH	HERS/ERI energy model to the required rating, energy-code compliance documentation, and incentive paperwork.	$0.83	$0.00	$0.83	1.00
	NO HPWH	HERS/ERI energy model to the required rating, energy-code compliance documentation, and incentive paperwork.	$0.83	$0.00	$0.83	1.00
Testing & Verification	HPWH	Blower-door, duct-leakage, and ventilation-airflow testing, with pre-drywall and final inspections.	$0.00	$0.00	$0.00	1.00
	NO HPWH	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

Exterior-Wall Continuous Insulation: Adding a layer of continuous insulation outboard of the 2x6 R-30 cavity walls was weighed and cut, since both paths pass without it and the furring, longer fasteners, and reworked window and cladding details across two 3-story buildings buy no compliance benefit. On the recommended path the added insulation also counts against the embodied carbon the R406.5.2 credit is measured on, and that credit is what allows the HERS 48 ceiling.
Triple-Pane Windows: Triple-pane glazing was considered and set aside. The specified U-0.24 / SHGC 0.24 windows already carry both paths to compliance, at HERS 44 against the 45 all-electric ceiling and HERS 48 against the R406.5.2 carbon-credit ceiling, so the triple-pane premium across 36 units is cost the developer absorbs with no rating benefit.
Ground-Source (Geothermal) Heat Pumps: A geothermal loop field was compared against the ducted air-source heat pumps both paths carry. The air-source equipment already holds the target rating and earns the same DOER Alternative Energy Credits, while drilling and the well field cost well beyond what those credits return, so geothermal was not justified.
Central Water Heating Plant: Serving all 36 apartments from a central water heating plant in each residential building was reviewed against in-unit tanks. A central plant adds mechanical room space, long distribution runs, and a recirculation loop that gives up heat around the clock, so it costs more to build and works against the modeled rating.
Heat-Pump Clothes Dryers: A ventless heat-pump dryer in every unit was considered and cut. The standard vented electric dryer at CEF 3.93 already keeps each apartment all-electric and holds the target rating, so the per-unit premium across 36 units stays in the construction budget.
HVAC Installation Grading: Grading the ducted heat pump installations under the RESNET protocol earns a modeling credit for verified airflow, fan watt draw, and refrigerant charge. Both paths comply without it, and grading would add a field test at all 36 units plus contractor rework whenever a system misses its grade, so it stays out of scope.
Rooftop Solar PV: Installing rooftop solar during construction was reviewed on top of the solar-ready provisions each path already carries. Both paths clear their ceilings without on-site generation, at HERS 44 and HERS 48, so the reserved roof zone, conduit pathway, and panel space keep solar open for a later ownership decision instead.
Mixed-Fuel Design With Gas Heating and Water Heating: A gas-fired heating and water heating design was ruled out early. No gas utility serves the site, so the project would pay to bring service in, the Stretch Code would hold the building to HERS 42 instead of the 45 allowed all-electric, and the SELCO heat pump and DOER Alternative Energy Credit incentives would fall away with the heat pump equipment.
ENERGY STAR Multifamily New Construction Certification: Certifying to ENERGY STAR MFNC above the code rating was considered and set aside. Certification adds program fees, a design review, and added field verification, and Shrewsbury is served by SELCO, a municipal utility outside the Mass Save new construction programs that normally pay for that work, so the project holds at code compliance.