CS37 Energy Code Feasibility Study in Boston, Massachusetts
Energy code feasibility study for a 2-unit Multifamily in Massachusetts. Compares multiple design paths. Recommended: Airtight. View full study.
- Study Type
- Energy Code Feasibility Study
- State
- Massachusetts
- Units
- 2
- Building Type
- Multifamily
- Fuel Type
- All-Electric
- Recommended Path
- Airtight
Goal
To find the most cost-effective compliance path, this report isolates energy code related costs from total construction. We use real MA bid data from vendors & clients to create a reliable framework for aligning incentives and design, with all recommendations confirmed by detailed energy modeling.
Project
- Boston, MA 02130
- 12 Townomes | 63,689 sqft
- 2 stories | 2 residential over basement | 2-unit building (x6) | Side-by-side units
- New Construction | Specialized Opt-In Code | HERS ≤ 45 or HERS ≤ 48 (GWP) | All Electric
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.
Airtight (Recommended): The Airtight path targets ENERGY STAR certification to reach the highest available performance tier. Key design changes include tightening the building envelope to an ACH50 of 1.5 using AeroBarrier, upgrading from one to two ERVs to manage the increased mechanical ventilation requirements, and specifying double-pane windows with a U-factor of 0.25 and an SHGC of 0.30 to 0.40. This path is the most cost-effective option because the significant savings from downgrading from triple-pane to double-pane windows easily offset the cost of the AeroBarrier application and the second ERV, all while unlocking the premium $15,000 per unit incentive instead of the base $7,500. This is our highly recommended path because it maximizes financial incentives and delivers a superior, highly controlled building envelope at the lowest overall cost.
Balanced: The Balanced path is designed to comfortably achieve the base incentive tier without relying on extreme, labor-intensive air-sealing measures. Key design changes include targeting a standard ACH50 of 3.0, installing a Heat Pump Water Heater (HPWH), and upgrading to triple-pane windows with a U-factor of 0.15 and an SHGC of 0.20 to 0.30. While this approach successfully secures base-level incentives, it does increase the overall budget by relying on expensive triple-pane glazing to compensate for a standard air leakage rate. This path is only recommended as a runner-up if the client believes they cannot reliably achieve the stringent air-sealing targets of the Airtight path, provided they are comfortable paying the premium for triple-pane windows.
GWP: The GWP path pursues the Embodied Carbon Credit under the Massachusetts code to secure a 3-point buffer on the final HERS score. Key design changes include utilizing carbon-storing insulation throughout the assemblies, installing a Heat Pump Water Heater (HPWH), targeting an ACH50 of 3.0, and using a strategic mix of double and triple-pane windows to achieve an average U-factor of 0.22 with an SHGC of 0.30 to 0.40. Despite providing a compliance buffer for the energy model, this approach is almost tied for the most expensive to build and adds significant administrative complexity by requiring specialized carbon credit paperwork to be submitted during both the permitting and Certificate of Occupancy phases. Consequently, this path is not recommended due to its high overall costs and the added bureaucratic hurdles it introduces to the project.
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
Airtight: $186,600 - $201,000
- MassSave Single-Family ENERGY STAR Certification ($180,000): You get this rebate for having each townhome ENERGY STAR NextGen certified. Certification typically occurs at the end of construction around when certificate of occupancy is received. This rebate comes in the form of a check within 4 months of the certification paperwork being provided to MassSave.
- MassSave Single-Family Induction Cooktop Adder ($3,000): You get this rebate for installing an induction cooktop in each townhome. This is a bonus adder to the ENERGY STAR program and follows the same timelines for submission & receipt of rebate. This rebate comes in the form of a check within 4 months of the ENERGY STAR certification paperwork being provided to MassSave.
- DOER Alternative Energy Credits ($3,600-18,000): This rebate is received for installing APS eligible air source heat pumps. 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.
Recommended Design - Units
Item | Detailed Specifications |
|---|---|
Exterior Walls | 2" Zip R9 Continuous Insulation (R-9) installed on the outside of 2x6 wood-framed walls with R-23 Batt Insulation. OR 2.5" Zip R12 Continuous Insulation (R-12) installed on the outside of 2x6 wood-framed walls with R-21 Batt Insulation. |
Garage Wall | R-21 Batt Insulation. |
Below Grade Walls | 3" R-15 XPS continuous insulation installed on the exterior side of the below grade wall and connecting with the below grade slab insulation. OR 2.5" R-15 Below grade rated polyiso continuous insulation installed on the exterior side of the below grade wall and connecting with the below grade slab insulation. |
Below Grade Slab | 3" R-15 XPS Insulation installed fully underneath the slab and connecting with the below grade wall insulation. OR 2.5" R-15 Below grade rated polyiso continuous insulation installed fully underneath the slab and connecting with the below grade wall insulation. |
Floor Over Unconditioned Space | R-38 Batt Insulation In Cavity. |
Rim Joists | Seal interior rim cavity with minimum 4" closed-cell spray foam (R-28) for air sealing and thermal performance. 2" Zip R9 Continuous Insulation (R-9) shall continue over floor transitions without interruption. |
Roof | For Attics: 16.5" Blown Cellulose Loose Fill (R-60 Total): Fills 9.5" truss cavity plus a 7" continuous layer above. For Flat Sealed Roofs: 9.5" Closed-Cell Spray Foam (R-66.5). |
Windows | U-0.25 / SHGC 0.30-0.40; Double Pane Windows; |
Doors | Glazed: U-0.25 / SHGC 0.30-0.40; Opaque: U-0.17 (R-5.88); |
Air Sealing | Units: ≤ ACH50 1.5; (Air sealing protocol) (Additional Air Sealing) |
HVAC | A1: Ducted; split cold climate heat pump; SEER2 17; EER2 12.2; HSPF2 10; (Product Rec) A2: Ducted; split cold climate heat pump; SEER2 17; EER2 12.2; HSPF2 10; (x2) |
Duct Sealing | Total duct leakage shall not exceed 8 CFM25 per 100 sqft of served floor area. (Duct Sealing Protocol - If You Swap To Ducted Systems) |
HVAC Grading | Fan Flow Test: N/A Watt Draw Test: N/A Refrigerant Charge: N/A |
Mechanical Ventilation | A1: 132 CFM, 87% rated recovery; Use 2 ERVs each set to 66 cfm; (Product Ref) A2: 150 CFM, 85% rated recovery; Use 2 ERVs each set to 75 cfm; |
Local Mechanical Exhaust | Bathroom(s): ≥ 50 CFM intermittent & ≤ 3.0 sones OR ≥ 20 CFM continuous & ≤ 2.0 sones, Kitchen (s): ≥ 100 CFM intermittent & ≤ 3.0 sones OR continuous, ≥ 5 ACH Based on kitchen volume & ≤ 1.0 sone. Both: Exhaust directly outdoors, ENERGY STAR certified, can utilize ERV to meet these requirements. |
Thermostats | Programmable Thermostat (Option 1) (Option 2) (Option 3) |
DHW | HPWH In Garage (UEF ≥3.88; 80 Gal) (Product Rec) |
DHW Piping | Supply piping insulated to R-3 minimum; Hot water pipe runs optimized to the following lengths: A1 Max Hot Water Pipe Length: 83.2 ft A2 Max Hot Water Pipe Length: 87.8 ft |
Water Fixtures | Watersense Certified Fixtures (Lavatory: ≤1.2 GPM, Shower: ≤2.0 GPM) |
Refrigerator | All: ≤ 700 kWh annual usage; ENERGY STAR; Electric; (Option 1) (Option 2) (Option 3) (Option 4) |
Dishwasher | All: ≤ 240 kWh annual usage; ENERGY STAR; Electric; (Product Rec) |
Clothes Washer | ≤ 141 kWh annual usage; ≥ 1.84 IMEF; ≥ 5 cubic ft capacity; ENERGY STAR; Electric; (Product Rec) |
Clothes Dryer | ≥ 3.93 CEF; ENERGY STAR; Electric; (Product Rec) |
Stove / Oven | Induction Stovetop & Convection Oven; Electric; (Product Ref) |
Lighting | 100% high-efficacy (LED) |
Solar Ready | Applicability: The requirements apply if the townhome has at least 600 sqft of roof area oriented between 110 degrees and 270 degrees of true north. Minimum Area: The total solar-ready zone area must be not less than 300 sqft. Zone Dimensions: The solar-ready zone can be composed of multiple smaller areas, but each area must be at least 5 feet wide and not less than 80 sqft. Obstructions & Setbacks: The 300 sqft zone must be entirely exclusive of any mandatory access or setback areas required by the Massachusetts Fire Code. It must also be completely free from obstructions, including vents, chimneys, and roof-mounted equipment. Design & Infrastructure: The structural design loads must be confirmed to support a future solar system. Electrical interconnection pathways must be provided. Reserved panel space must be designated in the electrical panel for the future system. Documentation: The solar-ready zone must be clearly indicated on the construction documents. A permanent construction documentation certificate, which indicates the solar-ready zone and its accommodated system size, must be posted near the electrical distribution panel or in another conspicuous location. |
EV Ready | Minimum Circuit Requirement: You must provide at least one 50-amp branch circuit per dwelling unit to allow for AC Level II charging. Termination and Receptacle: The circuit must terminate within 6 feet (1828 mm) of the EV ready parking space. The termination must be a NEMA receptacle or a Society of Automotive Engineers (SAE) standard electrical connector, specifically SAE J1772 or SAE J3400 (which includes the NACS/Tesla standard). Labeling: The dedicated branch circuit must be clearly identified as "EV READY" in the service panel or subpanel directory. Additionally, the actual termination location at the parking space must also be marked "EV READY". Conductor Sizing: Conductors and outlets for the Electric Vehicle Supply Equipment (EVSE) must be sized and installed in accordance with the Massachusetts Electrical Code (527 CMR 12.00). |
HPWH Ready | N/A |
Paperwork & Modeling | ERI Energy model, 2021 IECC checklists, ENERGY STAR SFNH checklists, and incentive documentation. |
Testing & Verification | Unit Blower Door Test, Mechanical Ventilation Testing, Fan Flow, Watt Draw, Refrigerant Charge, Room Balancing, Slab, Predrywall & Final Inspection. |
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
Airtight: $186,600 - $201,000
- MassSave Single-Family ENERGY STAR Certification ($180,000): You get this rebate for having each townhome ENERGY STAR NextGen certified. Certification typically occurs at the end of construction around when certificate of occupancy is received. This rebate comes in the form of a check within 4 months of the certification paperwork being provided to MassSave.
- MassSave Single-Family Induction Cooktop Adder ($3,000): You get this rebate for installing an induction cooktop in each townhome. This is a bonus adder to the ENERGY STAR program and follows the same timelines for submission & receipt of rebate. This rebate comes in the form of a check within 4 months of the ENERGY STAR certification paperwork being provided to MassSave.
- DOER Alternative Energy Credits ($3,600-18,000): This rebate is received for installing APS eligible air source heat pumps. 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.
Balanced: $97,800 - $112,200
- MassSave Single-Family Base Program ($90,000): You get this rebate for having each townhome ENERGY STAR NextGen certified. Certification typically occurs at the end of construction around when certificate of occupancy is received. This rebate comes in the form of a check within 4 months of the certification paperwork being provided to MassSave.
- MassSave Single-Family Induction Cooktop Adder ($3,000): You get this rebate for installing an induction cooktop in each townhome. This is a bonus adder to the Base program and follows the same timelines for submission & receipt of rebate. This rebate comes in the form of a check within 4 months of the HERS certification paperwork being provided to MassSave.
- MassSave Single-Family WIFI enabled Thermostat Adder ($1,200): You get this rebate for installing a WIFI enabled thermostat in each townhome. This is a bonus adder to the Base program and follows the same timelines for submission & receipt of rebate. This rebate comes in the form of a check within 4 months of the HERS certification paperwork being provided to MassSave.
- DOER Alternative Energy Credits ($3,600-18,000): This rebate is received for installing APS eligible air source heat pumps. 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.
Balanced: $97,800 - $112,200
- MassSave Single-Family Base Program ($90,000): You get this rebate for having each townhome ENERGY STAR NextGen certified. Certification typically occurs at the end of construction around when certificate of occupancy is received. This rebate comes in the form of a check within 4 months of the certification paperwork being provided to MassSave.
- MassSave Single-Family Induction Cooktop Adder ($3,000): You get this rebate for installing an induction cooktop in each townhome. This is a bonus adder to the Base program and follows the same timelines for submission & receipt of rebate. This rebate comes in the form of a check within 4 months of the HERS certification paperwork being provided to MassSave.
- MassSave Single-Family WIFI enabled Thermostat Adder ($1,200): You get this rebate for installing a WIFI enabled thermostat in each townhome. This is a bonus adder to the Base program and follows the same timelines for submission & receipt of rebate. This rebate comes in the form of a check within 4 months of the HERS certification paperwork being provided to MassSave.
- DOER Alternative Energy Credits ($3,600-18,000): This rebate is received for installing APS eligible air source heat pumps. 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.
Path Comparison - Net Cost Summary
Path | Total Cost $/sf | Total Incentives $/sf | Net $/sf |
|---|---|---|---|
Airtight | $139.83 | $2.92 | $136.91 |
Balanced | $147.33 | $1.53 | $145.80 |
GWP | $146.52 | $1.53 | $144.99 |
Path Comparison - Envelope
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf |
|---|---|---|---|---|---|
Exterior Walls | Airtight | 2" Zip R9 Continuous Insulation (R-9) installed on the outside of 2x6 wood-framed walls with R-23 Batt Insulation. OR 2.5" Zip R12 Continuous Insulation (R-12) installed on the outside of 2x6 wood-framed walls with R-21 Batt Insulation. | $16.00 | $0.00 | $16.00 |
Balanced | 2" Zip R9 Continuous Insulation (R-9) installed on the outside of 2x6 wood-framed walls with R-23 Batt Insulation. OR 2.5" Zip R12 Continuous Insulation (R-12) installed on the outside of 2x6 wood-framed walls with R-21 Batt Insulation. | $16.00 | $0.00 | $16.00 | |
GWP | 2" Zip R9 Continuous Insulation (R-9) installed on the outside of 2x6 wood-framed walls with R-23 Densepack Cellulose (or R-23 Wood Fiber Batt). (Cellulose) (Zip System). | $16.50 | $0.00 | $16.50 | |
Garage Wall | Airtight | R-21 Batt Insulation. | $1.41 | $0.00 | $1.41 |
Balanced | R-21 Batt Insulation. | $1.41 | $0.00 | $1.41 | |
GWP | R-21 Densepack Cellulose (or R-21 Wood Fiber Batt) (Cellulose). | $1.55 | $0.00 | $1.55 | |
Below Grade Walls | Airtight | 3" R-15 XPS continuous insulation installed on the exterior side of the below grade wall and connecting with the below grade slab insulation. OR 2.5" R-15 Below grade rated polyiso continuous insulation installed on the exterior side of the below grade wall and connecting with the below grade slab insulation. | $19.00 | $0.00 | $19.00 |
Balanced | 3" R-15 XPS continuous insulation installed on the exterior side of the below grade wall and connecting with the below grade slab insulation. OR 2.5" R-15 Below grade rated polyiso continuous insulation installed on the exterior side of the below grade wall and connecting with the below grade slab insulation. | $19.00 | $0.00 | $19.00 | |
GWP | 2.5" R-15 Below grade rated polyiso continuous insulation installed on the exterior side of the below grade wall and connecting with the below grade slab insulation. (Product Rec) | $19.00 | $0.00 | $19.00 | |
Below Grade Slab | Airtight | 3" R-15 XPS Insulation installed fully underneath the slab and connecting with the below grade wall insulation. OR 2.5" R-15 Below grade rated polyiso continuous insulation installed fully underneath the slab and connecting with the below grade wall insulation. | $9.50 | $0.00 | $9.50 |
Balanced | 3" R-15 XPS Insulation installed fully underneath the slab and connecting with the below grade wall insulation. OR 2.5" R-15 Below grade rated polyiso continuous insulation installed fully underneath the slab and connecting with the below grade wall insulation. | $9.50 | $0.00 | $9.50 | |
GWP | 2.5" R-15 Below grade rated polyiso continuous insulation installed fully underneath the slab and connecting with the below grade wall insulation. (Product Rec) | $9.50 | $0.00 | $9.50 | |
Floor Over Unconditioned Space | Airtight | R-38 Batt Insulation In Cavity. | $13.00 | $0.00 | $13.00 |
Balanced | R-38 Batt Insulation In Cavity. | $13.00 | $0.00 | $13.00 | |
GWP | R-38 Densepack Cellulose (or R-38 Wood Fiber Batt) (Cellulose). | $14.00 | $0.00 | $14.00 | |
Rim Joists | Airtight | Seal interior rim cavity with minimum 4" closed-cell spray foam (R-28) for air sealing and thermal performance. 2" Zip R9 Continuous Insulation (R-9) shall continue over floor transitions without interruption. | $1.00 | $0.00 | $1.00 |
Balanced | Seal interior rim cavity with minimum 4" closed-cell spray foam (R-28) for air sealing and thermal performance. 2" Zip R9 Continuous Insulation (R-9) shall continue over floor transitions without interruption. | $1.00 | $0.00 | $1.00 | |
GWP | Fill interior rim cavity with R-23 Densepack Cellulose (or R-23 Wood Fiber Batt). 2" Zip R9 Continuous Insulation (R-9) shall continue over floor transitions without interruption. (Cellulose) (Zip System). | $0.80 | $0.00 | $0.80 | |
Roof | Airtight | For Attics: 16.5" Blown Cellulose Loose Fill (R-60 Total): Fills 9.5" truss cavity plus a 7" continuous layer above. For Flat Sealed Roofs: 9.5" Closed-Cell Spray Foam (R-66.5). | $15.00 | $0.00 | $15.00 |
Balanced | For Attics: 16.5" Blown Cellulose Loose Fill (R-60 Total): Fills 9.5" truss cavity plus a 7" continuous layer above. For Flat Sealed Roofs: 9.5" Closed-Cell Spray Foam (R-66.5). | $15.00 | $0.00 | $15.00 | |
GWP | For Attics: 16.5" Blown Cellulose Loose Fill (R-60 Total): Fills 9.5" truss cavity plus a 7" continuous layer above. (Cellulose) For Flat Sealed Roofs: 9.5" R-35 Densepack Cellulose + 5.5" R-19 North American Wood Fiber board continuous insulation at roof deck. (Cellulose) (Wood Fiber Board). | $18.00 | $0.00 | $18.00 | |
Windows | Airtight | U-0.25 / SHGC 0.30-0.40; Double Pane Windows; | $35.00 | $0.00 | $35.00 |
Balanced | Glazed: U-0.15 / SHGC 0.20-0.25; Triple Pane Windows; | $45.00 | $0.00 | $45.00 | |
GWP | Glazed: U-0.22 / SHGC 0.30-0.40; Mix of Double Pane & Triple Pane Windows; | $40.00 | $0.00 | $40.00 | |
Doors | Airtight | Glazed: U-0.25 / SHGC 0.30-0.40; Opaque: U-0.17 (R-5.88); | $2.00 | $0.00 | $2.00 |
Balanced | Glazed: U-0.15 / SHGC 0.20-0.25; Opaque: U-0.17 (R-5.88); | $2.50 | $0.00 | $2.50 | |
GWP | Glazed: U-0.22 / SHGC 0.30-0.40; Opaque: U-0.17 (R-5.88); | $2.25 | $0.00 | $2.25 | |
Air Sealing | Airtight | Units: ≤ ACH50 1.5; (Air sealing protocol) (Additional Air Sealing) | $2.25 | $0.00 | $2.25 |
Balanced | Units: ≤ ACH50 3.0; (Air sealing protocol) (Backup plan) | $0.75 | $0.00 | $0.75 | |
GWP | Units: ≤ ACH50 3.0; (Air sealing protocol) (Backup plan) | $0.75 | $0.00 | $0.75 |
Path Comparison - Mechanical
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf |
|---|---|---|---|---|---|
HVAC | Airtight | A1: Ducted; split cold climate heat pump; SEER2 17; EER2 12.2; HSPF2 10; (Product Rec) A2: Ducted; split cold climate heat pump; SEER2 17; EER2 12.2; HSPF2 10; (x2) | $7.00 | $0.09 | $6.91 |
Balanced | A1: Ducted; split cold climate heat pump; SEER2 17; EER2 12.2; HSPF2 10; (Product Rec) A2: Ducted; split cold climate heat pump; SEER2 17; EER2 12.2; HSPF2 10; (x2) | $7.00 | $0.09 | $6.91 | |
GWP | A1: Ducted; split cold climate heat pump; SEER2 17; EER2 12.2; HSPF2 10; (Product Rec) A2: Ducted; split cold climate heat pump; SEER2 17; EER2 12.2; HSPF2 10; (x2) | $7.00 | $0.09 | $6.91 | |
Duct Sealing | Airtight | Total duct leakage shall not exceed 8 CFM25 per 100 sqft of served floor area. (Duct Sealing Protocol - If You Swap To Ducted Systems) | $0.50 | $0.00 | $0.50 |
Balanced | Total duct leakage shall not exceed 8 CFM25 per 100 sqft of served floor area. (Duct Sealing Protocol - If You Swap To Ducted Systems) | $0.50 | $0.00 | $0.50 | |
GWP | Total duct leakage shall not exceed 8 CFM25 per 100 sqft of served floor area. (Duct Sealing Protocol - If You Swap To Ducted Systems) | $0.50 | $0.00 | $0.50 | |
HVAC Grading | Airtight | Fan Flow Test: N/A Watt Draw Test: N/A Refrigerant Charge: N/A | $0.00 | $0.00 | $0.00 |
Balanced | Fan Flow Test: N/A Watt Draw Test: N/A Refrigerant Charge: N/A | $0.00 | $0.00 | $0.00 | |
GWP | Fan Flow Test: N/A Watt Draw Test: N/A Refrigerant Charge: N/A | $0.00 | $0.00 | $0.00 | |
Mechanical Ventilation | Airtight | A1: 132 CFM, 87% rated recovery; Use 2 ERVs each set to 66 cfm; (Product Ref) A2: 150 CFM, 85% rated recovery; Use 2 ERVs each set to 75 cfm; | $5.50 | $0.00 | $5.50 |
Balanced | A1: 83 CFM, 84% rated recovery; (Product Ref) A2: 92 CFM, 83% rated recovery; | $4.00 | $0.00 | $4.00 | |
GWP | A1: 83 CFM, 84% rated recovery; (Product Ref) A2: 92 CFM, 83% rated recovery; | $4.00 | $0.00 | $4.00 | |
Local Mechanical Exhaust | Airtight | Bathroom(s): ≥ 50 CFM intermittent & ≤ 3.0 sones OR ≥ 20 CFM continuous & ≤ 2.0 sones, Kitchen (s): ≥ 100 CFM intermittent & ≤ 3.0 sones OR continuous, ≥ 5 ACH Based on kitchen volume & ≤ 1.0 sone. Both: Exhaust directly outdoors, ENERGY STAR certified, can utilize ERV to meet these requirements. | $0.50 | $0.00 | $0.50 |
Balanced | Bathroom(s): ≥ 50 CFM intermittent & ≤ 3.0 sones OR ≥ 20 CFM continuous & ≤ 2.0 sones, Kitchen (s): ≥ 100 CFM intermittent & ≤ 3.0 sones OR continuous, ≥ 5 ACH Based on kitchen volume & ≤ 1.0 sone. Both: Exhaust directly outdoors, ENERGY STAR certified, can utilize ERV to meet these requirements. | $0.50 | $0.00 | $0.50 | |
GWP | Bathroom(s): ≥ 50 CFM intermittent & ≤ 3.0 sones OR ≥ 20 CFM continuous & ≤ 2.0 sones, Kitchen (s): ≥ 100 CFM intermittent & ≤ 3.0 sones OR continuous, ≥ 5 ACH Based on kitchen volume & ≤ 1.0 sone. Both: Exhaust directly outdoors, ENERGY STAR certified, can utilize ERV to meet these requirements. | $0.50 | $0.00 | $0.50 | |
Thermostats | Airtight | Programmable Thermostat (Option 1) (Option 2) (Option 3) | $0.15 | $0.00 | $0.15 |
Balanced | Programmable Thermostat (Option 1) (Option 2) (Option 3) | $0.15 | $0.02 | $0.13 | |
GWP | Programmable Thermostat (Option 1) (Option 2) (Option 3) | $0.15 | $0.02 | $0.13 |
Path Comparison - Plumbing & Appliances
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf |
|---|---|---|---|---|---|
DHW | Airtight | HPWH In Garage (UEF ≥3.88; 80 Gal) (Product Rec) | $3.25 | $0.00 | $3.25 |
Balanced | HPWH In Garage (UEF ≥3.88; 80 Gal) (Product Rec) | $3.25 | $0.00 | $3.25 | |
GWP | HPWH In Garage (UEF ≥3.88; 80 Gal) (Product Rec) | $3.25 | $0.00 | $3.25 | |
DHW Piping | Airtight | Supply piping insulated to R-3 minimum; Hot water pipe runs optimized to the following lengths: A1 Max Hot Water Pipe Length: 83.2 ft A2 Max Hot Water Pipe Length: 87.8 ft | $1.00 | $0.00 | $1.00 |
Balanced | Supply piping insulated to R-3 minimum; Hot water pipe runs optimized to the following lengths: A1 Max Hot Water Pipe Length: 83.2 ft A2 Max Hot Water Pipe Length: 87.8 ft | $1.00 | $0.00 | $1.00 | |
GWP | Supply piping insulated to R-3 minimum; Hot water pipe runs optimized to the following lengths: A1 Max Hot Water Pipe Length: 83.2 ft A2 Max Hot Water Pipe Length: 87.8 ft | $1.00 | $0.00 | $1.00 | |
Water Fixtures | Airtight | Watersense Certified Fixtures (Lavatory: ≤1.2 GPM, Shower: ≤2.0 GPM) | $0.18 | $0.00 | $0.18 |
Balanced | Watersense Certified Fixtures (Lavatory: ≤1.2 GPM, Shower: ≤2.0 GPM) | $0.18 | $0.00 | $0.18 | |
GWP | Watersense Certified Fixtures (Lavatory: ≤1.2 GPM, Shower: ≤2.0 GPM) | $0.18 | $0.00 | $0.18 | |
Refrigerator | Airtight | All: ≤ 700 kWh annual usage; ENERGY STAR; Electric; (Option 1) (Option 2) (Option 3) (Option 4) | $1.20 | $0.00 | $1.20 |
Balanced | All: ≤ 700 kWh annual usage; ENERGY STAR; Electric; (Option 1) (Option 2) (Option 3) (Option 4) | $1.20 | $0.00 | $1.20 | |
GWP | All: ≤ 700 kWh annual usage; ENERGY STAR; Electric; (Option 1) (Option 2) (Option 3) (Option 4) | $1.20 | $0.00 | $1.20 | |
Dishwasher | Airtight | All: ≤ 240 kWh annual usage; ENERGY STAR; Electric; (Product Rec) | $0.60 | $0.00 | $0.60 |
Balanced | All: ≤ 240 kWh annual usage; ENERGY STAR; Electric; (Product Rec) | $0.60 | $0.00 | $0.60 | |
GWP | All: ≤ 240 kWh annual usage; ENERGY STAR; Electric; (Product Rec) | $0.60 | $0.00 | $0.60 | |
Clothes Washer | Airtight | ≤ 141 kWh annual usage; ≥ 1.84 IMEF; ≥ 5 cubic ft capacity; ENERGY STAR; Electric; (Product Rec) | $0.80 | $0.00 | $0.80 |
Balanced | ≤ 141 kWh annual usage; ≥ 1.84 IMEF; ≥ 5 cubic ft capacity; ENERGY STAR; Electric; (Product Rec) | $0.80 | $0.00 | $0.80 | |
GWP | ≤ 141 kWh annual usage; ≥ 1.84 IMEF; ≥ 5 cubic ft capacity; ENERGY STAR; Electric; (Product Rec) | $0.80 | $0.00 | $0.80 | |
Clothes Dryer | Airtight | ≥ 3.93 CEF; ENERGY STAR; Electric; (Product Rec) | $0.80 | $0.00 | $0.80 |
Balanced | ≥ 3.93 CEF; ENERGY STAR; Electric; (Product Rec) | $0.80 | $0.00 | $0.80 | |
GWP | ≥ 3.93 CEF; ENERGY STAR; Electric; (Product Rec) | $0.80 | $0.00 | $0.80 | |
Stove / Oven | Airtight | Induction Stovetop & Convection Oven; Electric; (Product Ref) | $1.50 | $0.00 | $1.50 |
Balanced | Induction Stovetop & Convection Oven; Electric; (Product Ref) | $1.50 | $0.00 | $1.50 | |
GWP | Induction Stovetop & Convection Oven; Electric; (Product Ref) | $1.50 | $0.00 | $1.50 |
Path Comparison - Electrical
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf |
|---|---|---|---|---|---|
Lighting | Airtight | 100% high-efficacy (LED) | $1.05 | $0.00 | $1.05 |
Balanced | 100% high-efficacy (LED) | $1.05 | $0.00 | $1.05 | |
GWP | 100% high-efficacy (LED) | $1.05 | $0.00 | $1.05 | |
Solar Ready | Airtight | Applicability: The requirements apply if the townhome has at least 600 sqft of roof area oriented between 110 degrees and 270 degrees of true north. Minimum Area: The total solar-ready zone area must be not less than 300 sqft. Zone Dimensions: The solar-ready zone can be composed of multiple smaller areas, but each area must be at least 5 feet wide and not less than 80 sqft. Obstructions & Setbacks: The 300 sqft zone must be entirely exclusive of any mandatory access or setback areas required by the Massachusetts Fire Code. It must also be completely free from obstructions, including vents, chimneys, and roof-mounted equipment. Design & Infrastructure: The structural design loads must be confirmed to support a future solar system. Electrical interconnection pathways must be provided. Reserved panel space must be designated in the electrical panel for the future system. Documentation: The solar-ready zone must be clearly indicated on the construction documents. A permanent construction documentation certificate, which indicates the solar-ready zone and its accommodated system size, must be posted near the electrical distribution panel or in another conspicuous location. | $0.25 | $0.00 | $0.25 |
Balanced | Applicability: The requirements apply if the townhome has at least 600 sqft of roof area oriented between 110 degrees and 270 degrees of true north. Minimum Area: The total solar-ready zone area must be not less than 300 sqft. Zone Dimensions: The solar-ready zone can be composed of multiple smaller areas, but each area must be at least 5 feet wide and not less than 80 sqft. Obstructions & Setbacks: The 300 sqft zone must be entirely exclusive of any mandatory access or setback areas required by the Massachusetts Fire Code. It must also be completely free from obstructions, including vents, chimneys, and roof-mounted equipment. Design & Infrastructure: The structural design loads must be confirmed to support a future solar system. Electrical interconnection pathways must be provided. Reserved panel space must be designated in the electrical panel for the future system. Documentation: The solar-ready zone must be clearly indicated on the construction documents. A permanent construction documentation certificate, which indicates the solar-ready zone and its accommodated system size, must be posted near the electrical distribution panel or in another conspicuous location. | $0.25 | $0.00 | $0.25 | |
GWP | Applicability: The requirements apply if the townhome has at least 600 sqft of roof area oriented between 110 degrees and 270 degrees of true north. Minimum Area: The total solar-ready zone area must be not less than 300 sqft. Zone Dimensions: The solar-ready zone can be composed of multiple smaller areas, but each area must be at least 5 feet wide and not less than 80 sqft. Obstructions & Setbacks: The 300 sqft zone must be entirely exclusive of any mandatory access or setback areas required by the Massachusetts Fire Code. It must also be completely free from obstructions, including vents, chimneys, and roof-mounted equipment. Design & Infrastructure: The structural design loads must be confirmed to support a future solar system. Electrical interconnection pathways must be provided. Reserved panel space must be designated in the electrical panel for the future system. Documentation: The solar-ready zone must be clearly indicated on the construction documents. A permanent construction documentation certificate, which indicates the solar-ready zone and its accommodated system size, must be posted near the electrical distribution panel or in another conspicuous location. | $0.25 | $0.00 | $0.25 | |
EV Ready | Airtight | Minimum Circuit Requirement: You must provide at least one 50-amp branch circuit per dwelling unit to allow for AC Level II charging. Termination and Receptacle: The circuit must terminate within 6 feet (1828 mm) of the EV ready parking space. The termination must be a NEMA receptacle or a Society of Automotive Engineers (SAE) standard electrical connector, specifically SAE J1772 or SAE J3400 (which includes the NACS/Tesla standard). Labeling: The dedicated branch circuit must be clearly identified as "EV READY" in the service panel or subpanel directory. Additionally, the actual termination location at the parking space must also be marked "EV READY". Conductor Sizing: Conductors and outlets for the Electric Vehicle Supply Equipment (EVSE) must be sized and installed in accordance with the Massachusetts Electrical Code (527 CMR 12.00). | $0.35 | $0.00 | $0.35 |
Balanced | Minimum Circuit Requirement: You must provide at least one 50-amp branch circuit per dwelling unit to allow for AC Level II charging. Termination and Receptacle: The circuit must terminate within 6 feet (1828 mm) of the EV ready parking space. The termination must be a NEMA receptacle or a Society of Automotive Engineers (SAE) standard electrical connector, specifically SAE J1772 or SAE J3400 (which includes the NACS/Tesla standard). Labeling: The dedicated branch circuit must be clearly identified as "EV READY" in the service panel or subpanel directory. Additionally, the actual termination location at the parking space must also be marked "EV READY". Conductor Sizing: Conductors and outlets for the Electric Vehicle Supply Equipment (EVSE) must be sized and installed in accordance with the Massachusetts Electrical Code (527 CMR 12.00). | $0.35 | $0.00 | $0.35 | |
GWP | Minimum Circuit Requirement: You must provide at least one 50-amp branch circuit per dwelling unit to allow for AC Level II charging. Termination and Receptacle: The circuit must terminate within 6 feet (1828 mm) of the EV ready parking space. The termination must be a NEMA receptacle or a Society of Automotive Engineers (SAE) standard electrical connector, specifically SAE J1772 or SAE J3400 (which includes the NACS/Tesla standard). Labeling: The dedicated branch circuit must be clearly identified as "EV READY" in the service panel or subpanel directory. Additionally, the actual termination location at the parking space must also be marked "EV READY". Conductor Sizing: Conductors and outlets for the Electric Vehicle Supply Equipment (EVSE) must be sized and installed in accordance with the Massachusetts Electrical Code (527 CMR 12.00). | $0.35 | $0.00 | $0.35 | |
HPWH Ready | Airtight | N/A | $0.00 | $0.00 | $0.00 |
Balanced | N/A | $0.00 | $0.00 | $0.00 | |
GWP | N/A | $0.00 | $0.00 | $0.00 |
Path Comparison - Soft Costs
Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf |
|---|---|---|---|---|---|
Paperwork & Modeling | Airtight | ERI Energy model, 2021 IECC checklists, ENERGY STAR SFNH checklists, and incentive documentation. | $1.04 | $2.83 | -$1.79 |
Balanced | ERI Energy model, 2021 IECC checklists, and incentive documentation. | $1.04 | $1.41 | -$0.38 | |
GWP | ERI Energy model, 2021 IECC checklists, and incentive documentation. | $1.04 | $1.41 | -$0.38 | |
Testing & Verification | Airtight | Unit Blower Door Test, Mechanical Ventilation Testing, Fan Flow, Watt Draw, Refrigerant Charge, Room Balancing, Slab, Predrywall & Final Inspection. | $0.00 | $0.00 | $0.00 |
Balanced | Unit Blower Door Test, Mechanical Ventilation Testing, Slab, Predrywall & Final Inspection. | $0.00 | $0.00 | $0.00 | |
GWP | Unit Blower Door Test, Mechanical Ventilation Testing, Slab, Predrywall & Final Inspection. | $0.00 | $0.00 | $0.00 |
Additional Design Considerations Not Represented In This Study
- Net Zero Path: To eliminate the heat pump water heaters we considered pursuing the Net Zero Path by installing a solar system capable of lowering the HERS score to 0. Unfortunately there was not enough roof space to make this possible.
- Ventless Heat Pump Dryers: Typically this lowers the HERS score 1-2 points, but in this case it had little to no impact on the score. Unless this is preferred I don’t recommend this.
- Electric Resistance Water Heaters: This would be much cheaper than the heat pump water heaters, but comes at the cost of 2-3 HERS points. While I tried to make this possible, code requires a water heater with a UEF of 2.0 or higher, which can only be achieved with a heat pump water heater.
- Hot Water Recirculators: This typically takes 2-3 points off the energy model, but in this case it had little to no impact. I don’t recommend this unless it’s preferred.
- Drain Water Heat Recovery: This typically takes 2-3 points off the energy model, but in this case it had little to no impact. I don’t recommend this unless it’s preferred.