CS72 Energy Code Feasibility Study in Andover, Massachusetts
Energy code feasibility study for a 165-unit Multifamily in Massachusetts. Compares multiple design paths. Recommended: Exterior Mineral Wool. View full study.
- Study Type
- Energy Code Feasibility Study
- State
- Massachusetts
- Units
- 165
- Building Type
- Multifamily
- Fuel Type
- All-Electric
- Recommended Path
- Exterior Mineral Wool
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
- Andover, MA
- 2 Buildings | 165 Units | 181,074 SF Conditioned
- New Construction | Multifamily High-Rise | 5 stories, 165 residential units over a Level 1 garage, restaurant and amenity, plus a separate single-story Community Building
- All-Electric | MA Specialized Code | Phius CORE 2024 (C401.2.2.1) | Phius CORE 2024
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 certify the building to Phius CORE 2024 on the Certified Performance route of 225 CMR 23 C401.2.2.1, and all three carry the same 33 line items. Two of those items change between them: the exterior wall and the water heater. Costs below are per square foot of conditioned floor area, net of incentives and weighted by the owner-side operating factor, which is what moves the ranking here. The Mass Save incentives are identical on every path and cannot break the tie.
What Changes Between Paths
- Exterior Walls: Insulated Sheathing puts R-12.6 of continuous insulation in the sheathing panel, R-28.1 effective at 10.0 in. Exterior Mineral Wool hangs 3 in. of semi-rigid wool outboard on thermal-isolator clips and girts, R-27.5 effective at 11.85 in. Double Stud deletes the continuous layer and dense-packs an 11.5 in. cavity across two offset rows, R-38.1 effective at 14.1 in.
- DHW: Insulated Sheathing carries an in-unit integrated heat pump water heater. Exterior Mineral Wool and Double Stud carry in-unit electric resistance water heaters, which cost less to install and far less to maintain, and draw more source energy that the Phius model has to absorb in the envelope.
Everything else is specified once and carried across all three: roof, floor over the garage, slab, glazing, airtightness, space conditioning, ventilation, appliances, lighting and soft costs.
Exterior Mineral Wool: Recommended
$36.57 per square foot net, the lowest of the three. A conventional 2x6 cavity with R-21 mineral wool and 3 in. of semi-rigid wool outboard of the sheathing, carried on thermal-isolator clips and vertical girts so the cladding attachment does not short the thermal break. R-27.5 effective at 11.85 in. Paired with in-unit electric resistance water heaters. It wins on the operating side rather than on first cost: its gross cost is $0.07 above the Insulated Sheathing path, and it still finishes $0.26 ahead once the owner-side maintenance factor is applied, because a resistance element is the least demanding water heater to keep running across 165 units.
Double Stud
$36.61 per square foot net, $0.04 above the recommendation, which on this building is about $7,200 across the whole project. It buys 10.6 more points of effective R than either alternative, R-38.1, by deleting the continuous layer entirely and dense-packing an 11.5 in. cavity across a load-bearing 2x6 inner row and a non-bearing 2x4 outer row set 2.5 in. apart. The rows are offset, so no framing member spans the wall. The trade is 2.25 in. of wall thickness against the recommended path and a floor-line support detail for the outer row that has to be drawn properly or the bridge comes back. For a four-cent-per-foot premium this is the path to take if the Phius model is tight, and it is the one to fall back on if the model does not clear on the recommended wall.
Insulated Sheathing
$36.83 per square foot net, $0.26 above the recommendation, despite having the lowest gross construction cost of the three at $39.75. The wall is a single 2x6 cavity with R-21 mineral wool behind a 2.5 in. structural panel that delivers sheathing, weather barrier and continuous insulation in one layer, R-28.1 effective at 10.0 in., the thinnest wall here. What costs it the ranking is the heat pump water heater: it is a more efficient machine and a more expensive one for the owner to service, and across 165 units that operating premium outweighs the wall saving.
Code Path
High Rise Buildings (Specialized Opt-In)
Multifamily Mid-Rise, 5 stories
MA Specialized Code | Phius CORE 2024 (C401.2.2.1)
Buildings of four or more stories in Group R, and all commercial construction, are governed by 225 CMR 23, the Massachusetts commercial stretch amendments (with the Specialized Appendix CC) to the 2021 IECC. Group R buildings may comply through per-unit HERS ratings (C407.4), keeping the same HERS ceilings as the residential chapter; the alternatives are the Targeted Performance (TEDI) pathway, a full ASHRAE 90.1-2019 Appendix G model, or Passive House certification. The prescriptive path serves nonresidential buildings up to 20,000 sf, and residential buildings over 12,000 sf use a performance or certified pathway. Specialized municipalities additionally apply Appendix CC: new multifamily over 12,000 sf pursues Passive House certification, and mixed-fuel buildings carry on-site solar and full electrification pre-wiring.
Commercial, 1 story
MA Specialized 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 compliance documentation for the selected pathway is submitted: HERS projections with component specifications on the C407.4 route, or the simulation submittals (Attachment B or C) with backstop and thermal-bridge derating calculations for modeled buildings over 20,000 sf; COMcheck certificates on the prescriptive route. On the Certified Performance route of C401.2.2.1, the submittal is the Passive House package instead: evidence of registration with the certifying body, a statement from the Certified Passive House Consultant, and the energy model to the standard's own targets. Certified Performance is not held to the prescriptive tables of C402.1.4, C402.4 and C402.5, to the fifteen additional efficiency credits of C406, or to C408 commissioning; those tables stay on the drawings for the contractor's reference. C401.3 thermal envelope certificate, C402.3 solar readiness and C405.13 electric-vehicle readiness still apply.
At certificate of occupancy, the built work is confirmed: mandatory third-party air-leakage testing (whole-building 0.35 CFM75 per square foot, or per-unit compartmentalization for dwelling units), duct and ventilation verification, final Home Energy Rating Certificates on the HERS route, and commissioning documentation where triggered. On the Certified Performance route, the confirming document is the certificate issued by the certifying body, backed by a whole-building blower-door test against the standard's airtightness limit and the verifier's field quality-assurance record.
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: $693,250 - $891,250
- MassSave Passive House Certification ($495,000) : You get this rebate for having your project PHIUS certified. Certification typically occurs at the end of construction around when certificate of occupancy is received. This rebate comes in the form of a check within 4 months of the certification paperwork being provided to MassSave.
- IMPORTANT: $3,000 per unit with no cap.
- MassSave Passive House Pre-Certification ($123,750) : You get this rebate for having your project PHIUS pre-certified. Pre-Certification typically occurs toward the end of the pre-construction phase. This rebate comes in the form of a check within 4 months of the pre-certification paperwork being provided to MassSave.
- IMPORTANT: $750 per unit with no cap.
- MassSave Passive House Energy Model ($20,000) : You get this rebate for having a PHIUS energy model completed for your project & having a 1 hour charette with the design team and MassSave representative to review that study. This process must be completed before construction is complete. This rebate comes in the form of a check within 4 months of the 1 hour meeting taking place.
- IMPORTANT: The incentive is the lesser of 75% of the applicable service charge and $20,000.
- MassSave Passive House Feasibility Study ($5,000) : You get this rebate for having a PHIUS feasibility study completed for your project & having a 1 hour charette with the design team and MassSave representative to review that study. This process must be completed before construction is complete. This rebate comes in the form of a check within 4 months of the charette taking place.
- IMPORTANT: The incentive is capped at 100% of the applicable service charge.
- DOER Alternative Energy Credits ($49,500 - $247,500) (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-27.5 effective. 2x6 @ 16 in. o.c. with R-21 mineral wool batt, 3 in. semi-rigid mineral wool rated R-12.0 continuous on thermal-isolator clips and girts. 11.85 in. assembly. |
Below Grade Walls | N/A. Garage is outside the certified enclosure. |
Corridor Walls | N/A. Interior partition. |
Slab | R-10 continuous under the full slab plus R-10 vertical at the perimeter, extended 4 ft beyond the face of wall. |
Floor Over Unconditioned Space | N/A. Carried as Floor Over Podium. |
Floor Over Garage | N/A. Carried as Floor Over Podium. |
Floor Over Podium | R-30 closed-cell spray foam at the underside of the deck, intumescent ignition barrier, returned 4 ft past the conditioned boundary. |
Rim Joists | R-21 rim and band insulation at floor transitions, air sealed continuous with the wall. |
Roof | R-51 assembly. R-24 continuous polyisocyanurate at the roof deck with R-27 closed-cell spray foam in the cavity. |
Windows & Glass Doors | Triple pane, uPVC frame. U-0.15 fixed, U-0.17 operable. SHGC 0.32 solar-facing, 0.20 elsewhere. |
Doors | Opaque insulated steel, U-0.21. Balcony doors U-0.20, aluminum entries U-0.25. |
Air Sealing | 0.06 CFM50 per sf of gross enclosure, whole building. 0.25 CFM50 per sf unit compartmentalization. Continuous self-adhered air barrier, foundation to parapet. |
HVAC | Ductless multi-head cold-climate heat pump, SEER2 17 / HSPF2 10. One head per zone. |
Ductwork | N/A. Ductless equipment. |
Duct Sealing | N/A. No ductwork. |
HVAC Grading | Grade I verification: fan flow, watt draw, refrigerant charge. |
Mechanical Ventilation | In-unit balanced ERV, ASRE 89 to 90%, with pre-heater defrost. Continuous rate is the greater of 15 CFM per occupant (bedrooms plus 1, studio counts as 1) and continuous exhaust of 25 CFM kitchen plus 20 CFM per bath: 45 CFM studio and 1BR, 65 CFM 2BR and 3BR at two baths. Supply and exhaust balanced within 10%. |
Local Mechanical Exhaust | Bath 50 CFM intermittent at 3.0 sones or 20 CFM continuous at 2.0 sones. Kitchen 100 CFM intermittent at 3.0 sones or continuous at 5 ACH. Both exhaust direct to exterior. |
Thermostats | Wi-Fi connected programmable thermostat, one per zone. |
DHW | In-unit electric resistance water heater, tank or tankless, UEF 0.93, 240V. |
DHW Piping | Supply piping insulated to R-3 minimum. Longest hot water run 40 ft. |
Water Fixtures | WaterSense certified. Lavatory 1.2 GPM, shower 2.0 GPM, kitchen 2.2 GPM. |
Refrigerator | ENERGY STAR, 550 kWh per year or better. |
Dishwasher | ENERGY STAR, 269 kWh per year or better. |
Clothes Washer | ENERGY STAR front-load, IMEF 2.92. |
Clothes Dryer | Electric dryer, vented, ENERGY STAR. |
Stove / Oven | Electric induction cooktop, convection oven. |
Lighting | 100% high-efficacy LED. Occupancy and daylight controls in common areas. |
Solar Ready | Rooftop solar-ready zone per 225 CMR 23 CC104 and IECC Appendix CB. |
EV Ready | 20% of parking spaces EV-ready. 40 A Level II branch circuit terminating within 6 ft of the space, shared circuits with load management permitted. |
HPWH Ready | N/A. All-electric; no combustion water heater to pre-wire. |
Paperwork & Modeling | WUFI Passive model to the Phius 2024 Criteria Calculator targets, design review, pre-certification and certification submissions, co-requisite program registrations, Phius Certified Rater or Verifier. Phius registration and certification fees are owner-paid. |
Testing & Verification | Phius QA/QC inspections, whole-building and unit air-tightness testing, Certified Rater field work. Inside the ECC fee. |
Recommended Design - Common Areas
Item | Common Areas (Residential Building) |
|---|---|
Envelope | Common-area walls, roofs, floors, windows and doors are inside the certified thermal enclosure and are part of the whole-building Passive House model. Build them to the same assemblies specified for the dwelling units in this study; there is no separate common-area envelope specification. |
HVAC | Heating, cooling and ventilation serving corridors, lobby, laundry, mail, amenity and stair spaces are inside the model and follow the unit specification. Ventilation must be balanced, with measured supply and exhaust within 10 percent of each other or net pressurization under 5 Pa; only continuous ventilation counts toward the balance. |
DHW | Common-area service water heating is inside the model and follows the unit specification. Phius derives domestic hot water use per person, so fixture flow rates and distribution losses feed the source energy result directly. |
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. Certified Performance suspends the prescriptive envelope and mechanical tables, not the lighting power allowance, and the installed wattage also feeds the model's source energy total. |
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. |
A-2 / A-3 (2,960 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. |
Mixed Fuel Equipment | On the Specialized mixed-fuel pathway: combustion space heating 95 AFUE or higher; refrigerant-based cooling as heat pumps (ducted 8.1 HSPF2 / 15.2 SEER2, ductless 8.5 HSPF2 / 16 SEER2); hot water at 82 EF combustion, 2.0 UEF electric, or 0.4 solar fraction. All-electric buildings electrify 100 percent of design heating load with heat pumps. |
On-Site Solar & Pre-Wiring | Specialized mixed-fuel buildings install on-site renewables at 1.5 W/sf of the three largest floors (or 75 percent of the Potential Solar Zone Area) and pre-wire all combustion equipment for future electrification: labeled 30 A 208/240 V circuit and condensate drain at water heaters, 250 V 40 A outlet at ranges, 250 V 30 A outlet at dryers. |
Exterior Wall (Insulated Sheathing)
Exterior Wall (Exterior Mineral Wool)
Exterior Wall (Double Stud)
Roof (All Paths)
Floor Over Podium (All Paths)
Slab on Grade (All Paths)
Rim Joist (All Paths)
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
Exterior Mineral Wool / Double Stud / Insulated Sheathing: $693,250 - $891,250
- MassSave Passive House Certification ($495,000) : You get this rebate for having your project PHIUS certified. Certification typically occurs at the end of construction around when certificate of occupancy is received. This rebate comes in the form of a check within 4 months of the certification paperwork being provided to MassSave.
- IMPORTANT: $3,000 per unit with no cap.
- MassSave Passive House Pre-Certification ($123,750) : You get this rebate for having your project PHIUS pre-certified. Pre-Certification typically occurs toward the end of the pre-construction phase. This rebate comes in the form of a check within 4 months of the pre-certification paperwork being provided to MassSave.
- IMPORTANT: $750 per unit with no cap.
- MassSave Passive House Energy Model ($20,000) : You get this rebate for having a PHIUS energy model completed for your project & having a 1 hour charette with the design team and MassSave representative to review that study. This process must be completed before construction is complete. This rebate comes in the form of a check within 4 months of the 1 hour meeting taking place.
- IMPORTANT: The incentive is the lesser of 75% of the applicable service charge and $20,000.
- MassSave Passive House Feasibility Study ($5,000) : You get this rebate for having a PHIUS feasibility study completed for your project & having a 1 hour charette with the design team and MassSave representative to review that study. This process must be completed before construction is complete. This rebate comes in the form of a check within 4 months of the charette taking place.
- IMPORTANT: The incentive is capped at 100% of the applicable service charge.
- DOER Alternative Energy Credits ($49,500 - $247,500) (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 |
|---|---|---|---|---|
Exterior Mineral Wool | $39.82 | $3.42 | $36.57 | 1.00 |
Double Stud | $39.86 | $3.42 | $36.61 | 1.00 |
Insulated Sheathing | $39.75 | $3.42 | $36.83 | 1.01 |
Path Comparison - Envelope
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
Exterior Walls | Double Stud | R-38.1 effective. Double stud: 2x6 bearing inner row, 2.5 in. gap, 2x4 outer row; 11.5 in. dense-pack cellulose at 3.5 lb/cu ft. No continuous insulation. 14.1 in. assembly. | $5.18 | $0.00 | $5.18 | 0.95 |
Exterior Mineral Wool | R-27.5 effective. 2x6 @ 16 in. o.c. with R-21 mineral wool batt, 3 in. semi-rigid mineral wool rated R-12.0 continuous on thermal-isolator clips and girts. 11.85 in. assembly. | $5.14 | $0.00 | $5.14 | 0.95 | |
Insulated Sheathing | R-28.1 effective. 2x6 @ 16 in. o.c. with R-21 mineral wool batt, 2.5 in. insulated structural sheathing rated R-12.6 continuous. 10.0 in. assembly. | $4.15 | $0.00 | $4.15 | 0.95 | |
Below Grade Walls | Double Stud | N/A. Garage is outside the certified enclosure. | $0.00 | $0.00 | $0.00 | 1.00 |
Exterior Mineral Wool | N/A. Garage is outside the certified enclosure. | $0.00 | $0.00 | $0.00 | 1.00 | |
Insulated Sheathing | N/A. Garage is outside the certified enclosure. | $0.00 | $0.00 | $0.00 | 1.00 | |
Corridor Walls | Double Stud | N/A. Interior partition. | $0.00 | $0.00 | $0.00 | 1.00 |
Exterior Mineral Wool | N/A. Interior partition. | $0.00 | $0.00 | $0.00 | 1.00 | |
Insulated Sheathing | N/A. Interior partition. | $0.00 | $0.00 | $0.00 | 1.00 | |
Slab | Double Stud | R-10 continuous under the full slab plus R-10 vertical at the perimeter, extended 4 ft beyond the face of wall. | $0.15 | $0.00 | $0.15 | 0.90 |
Exterior Mineral Wool | R-10 continuous under the full slab plus R-10 vertical at the perimeter, extended 4 ft beyond the face of wall. | $0.15 | $0.00 | $0.15 | 0.90 | |
Insulated Sheathing | R-10 continuous under the full slab plus R-10 vertical at the perimeter, extended 4 ft beyond the face of wall. | $0.15 | $0.00 | $0.15 | 0.90 | |
Floor Over Unconditioned Space | Double Stud | N/A. Carried as Floor Over Podium. | $0.00 | $0.00 | $0.00 | 1.00 |
Exterior Mineral Wool | N/A. Carried as Floor Over Podium. | $0.00 | $0.00 | $0.00 | 1.00 | |
Insulated Sheathing | N/A. Carried as Floor Over Podium. | $0.00 | $0.00 | $0.00 | 1.00 | |
Floor Over Garage | Double Stud | N/A. Carried as Floor Over Podium. | $0.00 | $0.00 | $0.00 | 1.00 |
Exterior Mineral Wool | N/A. Carried as Floor Over Podium. | $0.00 | $0.00 | $0.00 | 1.00 | |
Insulated Sheathing | N/A. Carried as Floor Over Podium. | $0.00 | $0.00 | $0.00 | 1.00 | |
Floor Over Podium | Double Stud | R-30 closed-cell spray foam at the underside of the deck, intumescent ignition barrier, returned 4 ft past the conditioned boundary. | $0.98 | $0.00 | $0.98 | 0.90 |
Exterior Mineral Wool | R-30 closed-cell spray foam at the underside of the deck, intumescent ignition barrier, returned 4 ft past the conditioned boundary. | $0.98 | $0.00 | $0.98 | 0.90 | |
Insulated Sheathing | R-30 closed-cell spray foam at the underside of the deck, intumescent ignition barrier, returned 4 ft past the conditioned boundary. | $0.98 | $0.00 | $0.98 | 0.90 | |
Rim Joists | Double Stud | R-21 rim and band insulation at floor transitions, air sealed continuous with the wall. | $0.20 | $0.00 | $0.20 | 0.95 |
Exterior Mineral Wool | R-21 rim and band insulation at floor transitions, air sealed continuous with the wall. | $0.20 | $0.00 | $0.20 | 0.95 | |
Insulated Sheathing | R-21 rim and band insulation at floor transitions, air sealed continuous with the wall. | $0.20 | $0.00 | $0.20 | 0.95 | |
Roof | Double Stud | R-51 assembly. R-24 continuous polyisocyanurate at the roof deck with R-27 closed-cell spray foam in the cavity. | $1.46 | $0.00 | $1.46 | 1.05 |
Exterior Mineral Wool | R-51 assembly. R-24 continuous polyisocyanurate at the roof deck with R-27 closed-cell spray foam in the cavity. | $1.46 | $0.00 | $1.46 | 1.05 | |
Insulated Sheathing | R-51 assembly. R-24 continuous polyisocyanurate at the roof deck with R-27 closed-cell spray foam in the cavity. | $1.46 | $0.00 | $1.46 | 1.05 | |
Windows & Glass Doors | Double Stud | Triple pane, uPVC frame. U-0.15 fixed, U-0.17 operable. SHGC 0.32 solar-facing, 0.20 elsewhere. | $4.52 | $0.00 | $4.52 | 1.00 |
Exterior Mineral Wool | Triple pane, uPVC frame. U-0.15 fixed, U-0.17 operable. SHGC 0.32 solar-facing, 0.20 elsewhere. | $4.52 | $0.00 | $4.52 | 1.00 | |
Insulated Sheathing | Triple pane, uPVC frame. U-0.15 fixed, U-0.17 operable. SHGC 0.32 solar-facing, 0.20 elsewhere. | $4.52 | $0.00 | $4.52 | 1.00 | |
Doors | Double Stud | Opaque insulated steel, U-0.21. Balcony doors U-0.20, aluminum entries U-0.25. | $0.35 | $0.00 | $0.35 | 0.95 |
Exterior Mineral Wool | Opaque insulated steel, U-0.21. Balcony doors U-0.20, aluminum entries U-0.25. | $0.35 | $0.00 | $0.35 | 0.95 | |
Insulated Sheathing | Opaque insulated steel, U-0.21. Balcony doors U-0.20, aluminum entries U-0.25. | $0.35 | $0.00 | $0.35 | 0.95 | |
Air Sealing | Double Stud | 0.06 CFM50 per sf of gross enclosure, whole building. 0.25 CFM50 per sf unit compartmentalization. Continuous self-adhered air barrier, foundation to parapet. | $2.40 | $0.00 | $2.40 | 0.95 |
Exterior Mineral Wool | 0.06 CFM50 per sf of gross enclosure, whole building. 0.25 CFM50 per sf unit compartmentalization. Continuous self-adhered air barrier, foundation to parapet. | $2.40 | $0.00 | $2.40 | 0.95 | |
Insulated Sheathing | 0.06 CFM50 per sf of gross enclosure, whole building. 0.25 CFM50 per sf unit compartmentalization. Continuous self-adhered air barrier, foundation to parapet. | $2.40 | $0.00 | $2.40 | 0.95 |
Path Comparison - Mechanical
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
HVAC | Double Stud | Ductless multi-head cold-climate heat pump, SEER2 17 / HSPF2 10. One head per zone. | $9.27 | $0.00 | $9.27 | 1.15 |
Exterior Mineral Wool | Ductless multi-head cold-climate heat pump, SEER2 17 / HSPF2 10. One head per zone. | $9.27 | $0.00 | $9.27 | 1.15 | |
Insulated Sheathing | Ductless multi-head cold-climate heat pump, SEER2 17 / HSPF2 10. One head per zone. | $9.27 | $0.00 | $9.27 | 1.15 | |
Ductwork | Double Stud | N/A. Ductless equipment. | $0.00 | $0.00 | $0.00 | 1.00 |
Exterior Mineral Wool | N/A. Ductless equipment. | $0.00 | $0.00 | $0.00 | 1.00 | |
Insulated Sheathing | N/A. Ductless equipment. | $0.00 | $0.00 | $0.00 | 1.00 | |
Duct Sealing | Double Stud | N/A. No ductwork. | $0.00 | $0.00 | $0.00 | 1.00 |
Exterior Mineral Wool | N/A. No ductwork. | $0.00 | $0.00 | $0.00 | 1.00 | |
Insulated Sheathing | N/A. No ductwork. | $0.00 | $0.00 | $0.00 | 1.00 | |
HVAC Grading | Double Stud | Grade I verification: fan flow, watt draw, refrigerant charge. | $0.00 | $0.00 | $0.00 | 1.00 |
Exterior Mineral Wool | Grade I verification: fan flow, watt draw, refrigerant charge. | $0.00 | $0.00 | $0.00 | 1.00 | |
Insulated Sheathing | Grade I verification: fan flow, watt draw, refrigerant charge. | $0.00 | $0.00 | $0.00 | 1.00 | |
Mechanical Ventilation | Double Stud | In-unit balanced ERV, ASRE 89 to 90%, with pre-heater defrost. Continuous rate is the greater of 15 CFM per occupant (bedrooms plus 1, studio counts as 1) and continuous exhaust of 25 CFM kitchen plus 20 CFM per bath: 45 CFM studio and 1BR, 65 CFM 2BR and 3BR at two baths. Supply and exhaust balanced within 10%. | $2.00 | $0.00 | $2.00 | 1.20 |
Exterior Mineral Wool | In-unit balanced ERV, ASRE 89 to 90%, with pre-heater defrost. Continuous rate is the greater of 15 CFM per occupant (bedrooms plus 1, studio counts as 1) and continuous exhaust of 25 CFM kitchen plus 20 CFM per bath: 45 CFM studio and 1BR, 65 CFM 2BR and 3BR at two baths. Supply and exhaust balanced within 10%. | $2.00 | $0.00 | $2.00 | 1.20 | |
Insulated Sheathing | In-unit balanced ERV, ASRE 89 to 90%, with pre-heater defrost. Continuous rate is the greater of 15 CFM per occupant (bedrooms plus 1, studio counts as 1) and continuous exhaust of 25 CFM kitchen plus 20 CFM per bath: 45 CFM studio and 1BR, 65 CFM 2BR and 3BR at two baths. Supply and exhaust balanced within 10%. | $2.00 | $0.00 | $2.00 | 1.20 | |
Local Mechanical Exhaust | Double Stud | Bath 50 CFM intermittent at 3.0 sones or 20 CFM continuous at 2.0 sones. Kitchen 100 CFM intermittent at 3.0 sones or continuous at 5 ACH. Both exhaust direct to exterior. | $0.92 | $0.00 | $0.92 | 1.05 |
Exterior Mineral Wool | Bath 50 CFM intermittent at 3.0 sones or 20 CFM continuous at 2.0 sones. Kitchen 100 CFM intermittent at 3.0 sones or continuous at 5 ACH. Both exhaust direct to exterior. | $0.92 | $0.00 | $0.92 | 1.05 | |
Insulated Sheathing | Bath 50 CFM intermittent at 3.0 sones or 20 CFM continuous at 2.0 sones. Kitchen 100 CFM intermittent at 3.0 sones or continuous at 5 ACH. Both exhaust direct to exterior. | $0.92 | $0.00 | $0.92 | 1.05 | |
Thermostats | Double Stud | Wi-Fi connected programmable thermostat, one per zone. | $0.11 | $0.00 | $0.11 | 1.05 |
Exterior Mineral Wool | Wi-Fi connected programmable thermostat, one per zone. | $0.11 | $0.00 | $0.11 | 1.05 | |
Insulated Sheathing | Wi-Fi connected programmable thermostat, one per zone. | $0.11 | $0.00 | $0.11 | 1.05 |
Path Comparison - Plumbing & Appliances
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
DHW | Double Stud | In-unit electric resistance water heater, tank or tankless, UEF 0.93, 240V. | $0.81 | $0.00 | $0.81 | 0.90 |
Exterior Mineral Wool | In-unit electric resistance water heater, tank or tankless, UEF 0.93, 240V. | $0.81 | $0.00 | $0.81 | 0.90 | |
Insulated Sheathing | In-unit integrated heat pump water heater, UEF 3.50, 45 gal (2BR) / 36 gal (1BR), 240V, ENERGY STAR. | $1.73 | $0.00 | $1.73 | 1.20 | |
DHW Piping | Double Stud | Supply piping insulated to R-3 minimum. Longest hot water run 40 ft. | $0.65 | $0.00 | $0.65 | 0.95 |
Exterior Mineral Wool | Supply piping insulated to R-3 minimum. Longest hot water run 40 ft. | $0.65 | $0.00 | $0.65 | 0.95 | |
Insulated Sheathing | Supply piping insulated to R-3 minimum. Longest hot water run 40 ft. | $0.65 | $0.00 | $0.65 | 0.95 | |
Water Fixtures | Double Stud | WaterSense certified. Lavatory 1.2 GPM, shower 2.0 GPM, kitchen 2.2 GPM. | $1.62 | $0.00 | $1.62 | 1.00 |
Exterior Mineral Wool | WaterSense certified. Lavatory 1.2 GPM, shower 2.0 GPM, kitchen 2.2 GPM. | $1.62 | $0.00 | $1.62 | 1.00 | |
Insulated Sheathing | WaterSense certified. Lavatory 1.2 GPM, shower 2.0 GPM, kitchen 2.2 GPM. | $1.62 | $0.00 | $1.62 | 1.00 | |
Refrigerator | Double Stud | ENERGY STAR, 550 kWh per year or better. | $0.70 | $0.00 | $0.70 | 1.10 |
Exterior Mineral Wool | ENERGY STAR, 550 kWh per year or better. | $0.70 | $0.00 | $0.70 | 1.10 | |
Insulated Sheathing | ENERGY STAR, 550 kWh per year or better. | $0.70 | $0.00 | $0.70 | 1.10 | |
Dishwasher | Double Stud | ENERGY STAR, 269 kWh per year or better. | $0.38 | $0.00 | $0.38 | 1.10 |
Exterior Mineral Wool | ENERGY STAR, 269 kWh per year or better. | $0.38 | $0.00 | $0.38 | 1.10 | |
Insulated Sheathing | ENERGY STAR, 269 kWh per year or better. | $0.38 | $0.00 | $0.38 | 1.10 | |
Clothes Washer | Double Stud | ENERGY STAR front-load, IMEF 2.92. | $0.54 | $0.00 | $0.54 | 1.10 |
Exterior Mineral Wool | ENERGY STAR front-load, IMEF 2.92. | $0.54 | $0.00 | $0.54 | 1.10 | |
Insulated Sheathing | ENERGY STAR front-load, IMEF 2.92. | $0.54 | $0.00 | $0.54 | 1.10 | |
Clothes Dryer | Double Stud | Electric dryer, vented, ENERGY STAR. | $0.49 | $0.00 | $0.49 | 1.00 |
Exterior Mineral Wool | Electric dryer, vented, ENERGY STAR. | $0.49 | $0.00 | $0.49 | 1.00 | |
Insulated Sheathing | Electric dryer, vented, ENERGY STAR. | $0.49 | $0.00 | $0.49 | 1.00 | |
Stove / Oven | Double Stud | Electric induction cooktop, convection oven. | $0.70 | $0.00 | $0.70 | 1.05 |
Exterior Mineral Wool | Electric induction cooktop, convection oven. | $0.70 | $0.00 | $0.70 | 1.05 | |
Insulated Sheathing | Electric induction cooktop, convection oven. | $0.70 | $0.00 | $0.70 | 1.05 |
Path Comparison - Electrical
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx |
|---|---|---|---|---|---|---|
Lighting | Double Stud | 100% high-efficacy LED. Occupancy and daylight controls in common areas. | $4.00 | $0.00 | $4.00 | 0.85 |
Exterior Mineral Wool | 100% high-efficacy LED. Occupancy and daylight controls in common areas. | $4.00 | $0.00 | $4.00 | 0.85 | |
Insulated Sheathing | 100% high-efficacy LED. Occupancy and daylight controls in common areas. | $4.00 | $0.00 | $4.00 | 0.85 | |
Solar Ready | Double Stud | Rooftop solar-ready zone per 225 CMR 23 CC104 and IECC Appendix CB. | $0.30 | $0.00 | $0.30 | 1.00 |
Exterior Mineral Wool | Rooftop solar-ready zone per 225 CMR 23 CC104 and IECC Appendix CB. | $0.30 | $0.00 | $0.30 | 1.00 | |
Insulated Sheathing | Rooftop solar-ready zone per 225 CMR 23 CC104 and IECC Appendix CB. | $0.30 | $0.00 | $0.30 | 1.00 | |
EV Ready | Double Stud | 20% of parking spaces EV-ready. 40 A Level II branch circuit terminating within 6 ft of the space, shared circuits with load management permitted. | $0.59 | $0.00 | $0.59 | 1.00 |
Exterior Mineral Wool | 20% of parking spaces EV-ready. 40 A Level II branch circuit terminating within 6 ft of the space, shared circuits with load management permitted. | $0.59 | $0.00 | $0.59 | 1.00 | |
Insulated Sheathing | 20% of parking spaces EV-ready. 40 A Level II branch circuit terminating within 6 ft of the space, shared circuits with load management permitted. | $0.59 | $0.00 | $0.59 | 1.00 | |
HPWH Ready | Double Stud | N/A. All-electric; no combustion water heater to pre-wire. | $0.00 | $0.00 | $0.00 | 1.00 |
Exterior Mineral Wool | N/A. All-electric; no combustion water heater to pre-wire. | $0.00 | $0.00 | $0.00 | 1.00 | |
Insulated Sheathing | N/A. All-electric; no combustion water heater to pre-wire. | $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 | Double Stud | WUFI Passive model to the Phius 2024 Criteria Calculator targets, design review, pre-certification and certification submissions, co-requisite program registrations, Phius Certified Rater or Verifier. Phius registration and certification fees are owner-paid. | $1.54 | $3.42 | $-1.88 | 1.00 |
Exterior Mineral Wool | WUFI Passive model to the Phius 2024 Criteria Calculator targets, design review, pre-certification and certification submissions, co-requisite program registrations, Phius Certified Rater or Verifier. Phius registration and certification fees are owner-paid. | $1.54 | $3.42 | $-1.88 | 1.00 | |
Insulated Sheathing | WUFI Passive model to the Phius 2024 Criteria Calculator targets, design review, pre-certification and certification submissions, co-requisite program registrations, Phius Certified Rater or Verifier. Phius registration and certification fees are owner-paid. | $1.54 | $3.42 | $-1.88 | 1.00 | |
Testing & Verification | Double Stud | Phius QA/QC inspections, whole-building and unit air-tightness testing, Certified Rater field work. Inside the ECC fee. | $0.00 | $0.00 | $0.00 | 1.00 |
Exterior Mineral Wool | Phius QA/QC inspections, whole-building and unit air-tightness testing, Certified Rater field work. Inside the ECC fee. | $0.00 | $0.00 | $0.00 | 1.00 | |
Insulated Sheathing | Phius QA/QC inspections, whole-building and unit air-tightness testing, Certified Rater field work. Inside the ECC fee. | $0.00 | $0.00 | $0.00 | 1.00 |
Additional Design Considerations Not Represented In This Study
- 2x10 studs, dense-pack, no continuous insulation: A 9.25 in. cavity holds R-33.3 of dense-pack, close to the double stud's R-41.4. The problem is the stud: a 2x10 is one continuous piece of wood at R-11.6 crossing the wall every 16 inches, so the parallel path lands at R-23.2 effective. That is 4.9 points below the recommended wall at $0.10 per square foot more. More lumber, more insulation, a worse wall. Sheet A0.10 already carries a 2x10 exterior assembly (EWA-5A) for structural reasons; where it appears, treat the depth as structure and hold the thermal design to the path selected here.
- Exterior mineral wool with an empty stud cavity: Moving all the insulation outboard means the exterior layer carries the whole wall. Matching the mineral wool path takes roughly 6.5 in. of exterior wool, double the current detail, on a clip and girt system deep enough to hold it. Buildable, and the thickest and highest-cost option on the list for no gain in performance.
- Exterior-load-bearing double stud: Phius Appendix B gives an exterior-load-bearing double stud wall no prescriptive path to certification. It would need either a WUFI hygrothermal analysis under the Phius Moisture Risk Assessment Protocol, which carries a fee, or a moisture-engineered design stamped by a licensed engineer. Putting the load on the inner row avoids this; Appendix B allows that case in every climate zone.
- Induction cooking and 0.25 CFM50 compartmentalization adders: Mass Save pays $250 per unit for induction cooking and $400 per unit for unit compartmentalization tested at 0.25 CFM50 per square foot. Both are achievable on this design and neither is counted in the incentive total. Together they are worth $107,250 across 165 units if the specification commits to them.
- Quantity takeoff: Gross enclosure area comes directly from sheet A0.03, which publishes 175,147.90 sf and the matching 10,508.87 CFM50 target, so the airtightness target is exact. The split between wall, roof and floor is derived: roof and floor over garage are the Level 5 and Level 2 plates from the life safety plans, and the wall area is the remainder at the 12.0% window-to-wall ratio on the same sheet. A takeoff at permit will refine that split. The per-square-foot comparison between paths holds regardless.
- Owner-paid Phius fees: Phius registration and certification fees are an owner-paid pass-through per Guidebook Table 1.2.0 and sit outside both the costs and the incentives in this study. Co-requisite program registrations are inside ECC's fee.