CS49 Energy Code Feasibility Study in Lexington, Massachusetts
Energy code feasibility study for a 40-unit 3 Story Multifamily Building Over Underground Podium Parking in Massachusetts. Compares multiple design paths. Recommended: ZIP System. View full study.
- Study Type
- Energy Code Feasibility Study
- State
- Massachusetts
- Units
- 40
- Building Type
- 3 Story Multifamily Building Over Underground Podium Parking
- Fuel Type
- All-Electric
- Recommended Path
- ZIP System
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
- Lexington, MA 02421
- 40 Units | 64,905 sqft
- New Construction | 3 Story Multifamily Building Over Underground Podium Parking
- All-Electric | Specialized Opt-In | PHIUS CORE 2024 | ESTAR MFNC v1.2
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
Path A: Same PHIUS certification and ENERGY STAR MFNC path as Path B, with the same R-60 polyiso roof, in-unit electric tank water heaters, and ducted split heat pumps (SEER2 17-17.5 / HSPF2 9). Uses 3" ROCKWOOL Comfortboard 80 continuous insulation secured with Technoform thermal isolator clips plus R-21 batt in the cavity, and Henry Blueskin VP100 self-adhered membrane as the primary wall air barrier. This combination runs roughly $0.35/sf higher on the wall and requires the separate VP100 membrane and Technoform clip installation that Path B eliminates. Not recommended due to higher construction cost with no incentive or performance advantage over Path B. Net cost: $44.06/sf.
Path B (Recommended): PHIUS certification and ENERGY STAR MFNC path using 2.5" ZIP System R-Sheathing (R-12.6 integrated into the sheathing panel) plus R-21 batt in the cavity, R-60 polyiso roof, in-unit electric tank water heaters, and ducted split heat pumps. ZIP tape serves as the primary air barrier across the wall field, eliminating both the Technoform thermal isolator clips and the separate Henry Blueskin VP100 membrane required on Paths A and C. This reduces wall cost by roughly $0.35/sf versus Path A and simplifies the air barrier scope. All $175,000 in MassSave Passive House incentives are available. Recommended as the lowest net cost path at $42.22/sf.
Path C: Same PHIUS certification and ENERGY STAR MFNC path, with the same ROCKWOOL Comfortboard CI wall, VP100 air barrier, and ducted split heat pumps as Path A. Removes the R-21 batt from the wall cavity, swaps the R-60 roof for a thinner R-50 polyiso roof (9" instead of 11"), and replaces the in-unit electric tank water heaters with heat pump water heaters (UEF ≥3.45). The reduced envelope is offset by the higher-efficiency HPWHs, keeping the project in compliance. Not recommended because the HPWH cost premium ($3.40/sf vs. $1.15/sf) more than offsets the envelope savings, and the higher HPWH operating load adversely affects the PHIUS energy balance. Net cost: $46.17/sf.
Code Path
Recommended Design - Incentives
Available Incentives: $175,000 (All Paths)
- MassSave Passive House Feasibility Study ($5,000): Rebate for completing a PHIUS feasibility study and a 1-hour charette with the design team and MassSave representative before construction is complete. Paid as a check within 4 months of the charette. IMPORTANT: Capped at 100% of the applicable service charge.
- MassSave Passive House Energy Model ($20,000): Rebate for completing a PHIUS energy model and a 1-hour charette with the design team and MassSave representative before construction is complete. Paid as a check within 4 months of the meeting. IMPORTANT: Capped at 75% of the applicable service charge.
- MassSave Passive House Pre-Certification ($30,000): Rebate for achieving PHIUS pre-certification toward the end of the pre-construction phase. Paid as a check within 4 months of pre-certification paperwork being provided to MassSave.
- MassSave Passive House Certification ($120,000): Rebate for achieving PHIUS certification at the end of construction around certificate of occupancy. Paid as a check within 4 months of certification paperwork being provided to MassSave.
- DOER Alternative Energy Credits (N/A - Ducted Systems Do Not Qualify): This rebate is received for installing APS eligible air source heat pumps. Ducted systems on this project do not qualify. IMPORTANT: Although an estimate is provided where applicable, this incentive can vary widely between $300-1,500 per heat pump based on expected kWh usage and market value of alternative energy credits when sold.
Recommended Design Specifications (Path B)
| Item | Detailed Specifications |
|---|---|
| Exterior Walls | R-12.6 - 2.5" ZIP System Insulated R-Sheathing & R-21 batt insulation in cavity |
| Floor Over Garage | Steel Frame Slab: R-38 batt insulation resting on drop ceiling (must use thermally broken ceiling system). Post Tensioned Slab: R-30 continuous insulation on either side of the slab. Note: Either of these options work. |
| Rim Joists | Seal interior rim cavity with minimum 3" closed-cell spray foam for air sealing and thermal performance. Continuous Insulation shall continue over floor transitions without interruption. |
| Roof | 11" Rigid Polyiso Continuous Insulation (R-60) installed in multiple layers with staggered joints on the roof deck. |
| Windows | Weighted Avg: U-0.15 / SHGC 0.20 |
| Doors | Glazed: U-0.15 / SHGC 0.20; Opaque: U-0.21 (R-4.75) |
| Air Sealing | Units: ≤0.30 CFM50/sqft; Whole Building: ≤0.06 CFM50/sqft. ZIP tape serves as the primary air barrier across the wall field. Henry Air-Bloc fluid-applied air barrier at the underside of the concrete podium slab and all penetrations. Continue ZIP tape up and over the parapet, transitioning to Blueskin PE200HT high-temperature roof membrane at the roof level. |
| HVAC | 1 Bed: Ducted split heat pump; SEER2 17.5; HSPF2 9. 2 Bed: Ducted split heat pump; SEER2 17; HSPF2 9. |
| Duct Sealing | The greater of 8 CFM/100 ft² conditioned floor area or 80 CFM |
| HVAC Grading | Fan Flow Test: N/A; Watt Draw Test: N/A; Refrigerant Charge: N/A |
| Mechanical Ventilation | ERV; 84-90% rated recovery; Any Climate |
| 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 & ≤1.0 sone. Both: Exhaust directly outdoors, ENERGY STAR certified, utilize ERV to meet these requirements. |
| Thermostats | Programmable Thermostat |
| DHW | Electric tank heater in unit (UEF ≥0.93) |
| DHW Piping | Supply piping insulated to R-3 minimum; Max 1.8 gallons stored volume per run; Modeled pipe runs are optimized to 1/3 program default lengths. |
| Water Fixtures | WaterSense Certified Fixtures (Lavatory: ≤1.2 GPM, Shower: ≤2.0 GPM) |
| Refrigerator | 1 Bed: ≤422 kWh/yr; ENERGY STAR; Electric. 2 Bed: ≤489 kWh/yr; ENERGY STAR; Electric. |
| Dishwasher | All: ≤240 kWh annual usage; ENERGY STAR; Electric |
| Clothes Washer | IMEF 2.92; 105 kWh/yr; 4.5 cu ft; front-load; ENERGY STAR |
| Clothes Dryer | Electric standard vented dryer; CEF 3.94; moisture sensing |
| Stove / Oven | Induction Stovetop & Convection Oven; Electric |
| Lighting | 100% high-efficacy (LED) |
| Solar Ready | Designated Solar Zone ≥40% of total horizontal roof area; free of all obstructions; minimum 5 ft width; engineered for future 5 PSF collateral dead load; conduit pathways from roof to electrical service; labeled breaker space reserved in main panel. |
| EV Ready | EV Ready infrastructure for ≥20% of total parking. ≥10% with Active Level 2 EVSE (≥6.2 kVA / 30A at 208/240V per space). Remaining required spaces as Level 2 Ready branch circuits. EMS option: 2.1 kVA per space. |
| HPWH Ready | N/A |
| Paperwork & Modeling | WUFI & HERS/ERI Energy model, 2021 IECC checklists, ENERGY STAR MFNC checklists, PHIUS checklists, PHIUS Feasibility Study, and incentive documentation. |
| Testing & Verification | Whole Building & Unit Blower Door Test, Mechanical Ventilation Testing, Room Balancing, Slab, Predrywall & Final Inspection. |
Exterior Wall Assembly
Rim Joist
Roof
Podium Option 1
Podium Option 2
Path Comparison - Incentives
All Paths: $175,000
- MassSave Passive House Feasibility Study ($5,000): Rebate for completing a PHIUS feasibility study and a 1-hour charette with the design team and MassSave representative before construction is complete. Paid as a check within 4 months of the charette. IMPORTANT: Capped at 100% of the applicable service charge.
- MassSave Passive House Energy Model ($20,000): Rebate for completing a PHIUS energy model and a 1-hour charette with the design team and MassSave representative before construction is complete. Paid as a check within 4 months of the meeting. IMPORTANT: Capped at 75% of the applicable service charge.
- MassSave Passive House Pre-Certification ($30,000): Rebate for achieving PHIUS pre-certification toward the end of the pre-construction phase. Paid as a check within 4 months of pre-certification paperwork being provided to MassSave.
- MassSave Passive House Certification ($120,000): Rebate for achieving PHIUS certification at the end of construction around certificate of occupancy. Paid as a check within 4 months of certification paperwork being provided to MassSave.
- DOER Alternative Energy Credits (N/A - Ducted Systems Do Not Qualify): IMPORTANT: Although an estimate is provided where applicable, this incentive can vary widely between $300-1,500 per heat pump based on expected kWh usage and market value of alternative energy credits when sold.
Path Comparison - Net Cost Summary
| Path | Total Cost $/sf | Total Incentives $/sf | Net $/sf | OpEx Factor |
|---|---|---|---|---|
| Path A | $45.57 | $2.70 | $44.06 | 1.03 |
| Path B (Recommended) | $43.27 | $2.70 | $42.22 | 1.04 |
| Path C | $46.78 | $2.70 | $46.17 | 1.05 |
Path Comparison - Envelope
| Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx Factor |
|---|---|---|---|---|---|---|
| Exterior Walls | Path A | R-12.6 - 3" ROCKWOOL Comfortboard 80 CI secured with Technoform Thermal Isolator Clips & R-21 batt in cavity | $3.85 | $0.00 | $3.85 | 0.85 |
| Exterior Walls | Path B | R-12.6 - 2.5" ZIP System Insulated R-Sheathing & R-21 batt in cavity | $3.50 | $0.00 | $3.50 | 0.95 |
| Exterior Walls | Path C | R-12.6 - 3" ROCKWOOL Comfortboard 80 CI secured with Technoform Thermal Isolator Clips (no cavity batt) | $3.40 | $0.00 | $3.40 | 0.85 |
| Floor Over Garage | Path A | Steel Frame Slab: R-38 batt on thermally broken drop ceiling; Post Tensioned Slab: R-30 CI on either side of slab. | $3.45 | $0.00 | $3.45 | 0.90 |
| Floor Over Garage | Path B | Same as Path A | $3.45 | $0.00 | $3.45 | 0.90 |
| Floor Over Garage | Path C | Same as Path A | $3.45 | $0.00 | $3.45 | 0.90 |
| Rim Joists | Path A | Minimum 3" closed-cell spray foam; CI continues over floor transitions without interruption. | $0.10 | $0.00 | $0.10 | 0.85 |
| Rim Joists | Path B | Same as Path A | $0.10 | $0.00 | $0.10 | 0.85 |
| Rim Joists | Path C | Same as Path A | $0.10 | $0.00 | $0.10 | 0.85 |
| Roof | Path A | 11" Rigid Polyiso CI (R-60) in multiple layers with staggered joints | $4.40 | $0.00 | $4.40 | 0.95 |
| Roof | Path B | Same as Path A | $4.40 | $0.00 | $4.40 | 0.95 |
| Roof | Path C | 9" Rigid Polyiso CI (R-50) in multiple layers with staggered joints | $3.85 | $0.00 | $3.85 | 0.98 |
| Windows | Path A | Weighted Avg: U-0.15 / SHGC 0.20 | $6.25 | $0.00 | $6.25 | 1.05 |
| Windows | Path B | Same as Path A | $6.25 | $0.00 | $6.25 | 1.05 |
| Windows | Path C | Same as Path A | $6.25 | $0.00 | $6.25 | 1.05 |
| Doors | Path A | Glazed: U-0.15 / SHGC 0.20; Opaque: U-0.21 (R-4.75) | $0.95 | $0.00 | $0.95 | 1.00 |
| Doors | Path B | Same as Path A | $0.95 | $0.00 | $0.95 | 1.00 |
| Doors | Path C | Same as Path A | $0.95 | $0.00 | $0.95 | 1.00 |
| Air Sealing | Path A | Units: ≤0.30 CFM50/ft²; Whole Building: ≤0.06 CFM50/ft². Henry Blueskin VP100 self-adhered membrane across full exterior wall surface; Henry Air-Bloc fluid-applied at podium slab; VP100 sill pans and jamb wraps at windows/doors. | $5.80 | $0.00 | $5.80 | 0.85 |
| Air Sealing | Path B | Units: ≤0.30 CFM50/sqft; Whole Building: ≤0.06 CFM50/sqft. Henry Air-Bloc at podium slab; ZIP tape as primary wall air barrier; Blueskin PE200HT at roof; VP100 sill pans and jamb wraps at windows/doors. | $3.85 | $0.00 | $3.85 | 1.05 |
| Air Sealing | Path C | Same as Path A (VP100 wall air barrier) | $5.80 | $0.00 | $5.80 | 0.85 |
Path Comparison - Mechanical
| Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx Factor |
|---|---|---|---|---|---|---|
| HVAC | Path A | 1 Bed: Ducted split heat pump; SEER2 17.5; HSPF2 9. 2 Bed: Ducted split heat pump; SEER2 17; HSPF2 9. | $6.60 | $0.00 | $6.60 | 1.10 |
| HVAC | Path B | Same as Path A | $6.60 | $0.00 | $6.60 | 1.15 |
| HVAC | Path C | Same as Path A | $6.60 | $0.00 | $6.60 | 1.15 |
| Duct Sealing | Path A | The greater of 8 CFM/100 ft² conditioned floor area or 80 CFM | $0.35 | $0.00 | $0.35 | 0.95 |
| Duct Sealing | Path B | Same as Path A | $0.35 | $0.00 | $0.35 | 0.95 |
| Duct Sealing | Path C | Same as Path A | $0.35 | $0.00 | $0.35 | 0.95 |
| HVAC Grading | Path A | Fan Flow Test: N/A; Watt Draw Test: N/A; Refrigerant Charge: N/A | $0.00 | $0.00 | $0.00 | 1.00 |
| HVAC Grading | Path B | Same as Path A | $0.00 | $0.00 | $0.00 | 1.00 |
| HVAC Grading | Path C | Same as Path A | $0.00 | $0.00 | $0.00 | 1.00 |
| Mechanical Ventilation | Path A | ERV; 84-90% rated recovery; Any Climate | $4.40 | $0.00 | $4.40 | 1.30 |
| Mechanical Ventilation | Path B | Same as Path A | $4.40 | $0.00 | $4.40 | 1.30 |
| Mechanical Ventilation | Path C | Same as Path A | $4.40 | $0.00 | $4.40 | 1.30 |
| Local Mechanical Exhaust | Path A | 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 & ≤1.0 sone. Both: Exhaust directly outdoors, ENERGY STAR certified, utilize ERV. | $0.30 | $0.00 | $0.30 | 1.10 |
| Local Mechanical Exhaust | Path B | Same as Path A | $0.30 | $0.00 | $0.30 | 1.10 |
| Local Mechanical Exhaust | Path C | Same as Path A | $0.30 | $0.00 | $0.30 | 1.10 |
| Thermostats | Path A | Programmable Thermostat | $0.09 | $0.00 | $0.09 | 1.05 |
| Thermostats | Path B | Same as Path A | $0.09 | $0.00 | $0.09 | 1.05 |
| Thermostats | Path C | Same as Path A | $0.09 | $0.00 | $0.09 | 1.05 |
Path Comparison - Plumbing & Appliances
| Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx Factor |
|---|---|---|---|---|---|---|
| DHW | Path A | Electric tank heater in unit (UEF ≥0.93) | $1.15 | $0.00 | $1.15 | 0.90 |
| DHW | Path B | Same as Path A | $1.15 | $0.00 | $1.15 | 0.90 |
| DHW | Path C | 1 Bed: HPWH In Unit OR Corridor (UEF ≥3.45; 50 Gal). 2 Bed: HPWH In Unit OR Corridor (UEF ≥3.45; 66 Gal). | $3.40 | $0.00 | $3.40 | 1.35 |
| DHW Piping | Path A | Supply piping insulated to R-3 minimum; Max 1.8 gallons stored volume per run; Modeled pipe runs at 1/3 program default lengths. | $1.50 | $0.00 | $1.50 | 0.95 |
| DHW Piping | Path B | Same as Path A | $1.50 | $0.00 | $1.50 | 0.95 |
| DHW Piping | Path C | Same as Path A | $1.50 | $0.00 | $1.50 | 0.95 |
| Water Fixtures | Path A | WaterSense Certified (Lavatory: ≤1.2 GPM, Shower: ≤2.0 GPM) | $0.18 | $0.00 | $0.18 | 1.05 |
| Water Fixtures | Path B | Same as Path A | $0.18 | $0.00 | $0.18 | 1.05 |
| Water Fixtures | Path C | Same as Path A | $0.18 | $0.00 | $0.18 | 1.05 |
| Refrigerator | Path A | 1 Bed: ≤422 kWh/yr; ENERGY STAR; Electric. 2 Bed: ≤489 kWh/yr; ENERGY STAR; Electric. | $0.49 | $0.00 | $0.49 | 1.00 |
| Refrigerator | Path B | Same as Path A | $0.49 | $0.00 | $0.49 | 1.00 |
| Refrigerator | Path C | All: ≤550 kWh/yr; ENERGY STAR; Electric. | $0.45 | $0.00 | $0.45 | 1.00 |
| Dishwasher | Path A | All: ≤240 kWh/yr; ENERGY STAR; Electric | $0.31 | $0.00 | $0.31 | 1.00 |
| Dishwasher | Path B | Same as Path A | $0.31 | $0.00 | $0.31 | 1.00 |
| Dishwasher | Path C | Same as Path A | $0.31 | $0.00 | $0.31 | 1.00 |
| Clothes Washer | Path A | IMEF 2.92; 105 kWh/yr; 4.5 cu ft; front-load; ENERGY STAR | $0.43 | $0.00 | $0.43 | 1.15 |
| Clothes Washer | Path B | Same as Path A | $0.43 | $0.00 | $0.43 | 1.15 |
| Clothes Washer | Path C | Same as Path A | $0.43 | $0.00 | $0.43 | 1.15 |
| Clothes Dryer | Path A | Electric standard vented dryer; CEF 3.94; moisture sensing | $0.37 | $0.00 | $0.37 | 1.40 |
| Clothes Dryer | Path B | Same as Path A | $0.37 | $0.00 | $0.37 | 1.40 |
| Clothes Dryer | Path C | Same as Path A | $0.37 | $0.00 | $0.37 | 1.40 |
| Stove / Oven | Path A | Induction Stovetop & Convection Oven; Electric | $0.62 | $0.00 | $0.62 | 1.25 |
| Stove / Oven | Path B | Same as Path A | $0.62 | $0.00 | $0.62 | 1.25 |
| Stove / Oven | Path C | Same as Path A | $0.62 | $0.00 | $0.62 | 1.25 |
Path Comparison - Electrical
| Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx Factor |
|---|---|---|---|---|---|---|
| Lighting | Path A | 100% high-efficacy (LED) | $1.05 | $0.00 | $1.05 | 0.80 |
| Lighting | Path B | Same as Path A | $1.05 | $0.00 | $1.05 | 0.80 |
| Lighting | Path C | Same as Path A | $1.05 | $0.00 | $1.05 | 0.80 |
| Solar Ready | Path A | Contiguous zone ≥40% of total horizontal roof area; free of obstructions; minimum 5 ft width; engineered for 5 PSF future dead load; conduit pathways from roof to electrical service; labeled breaker space reserved. | $0.15 | $0.00 | $0.15 | 1.00 |
| Solar Ready | Path B | Same as Path A | $0.15 | $0.00 | $0.15 | 1.00 |
| Solar Ready | Path C | Same as Path A | $0.15 | $0.00 | $0.15 | 1.00 |
| EV Ready | Path A | EV Ready for ≥20% of parking; ≥10% with Active Level 2 EVSE (≥6.2 kVA per space); remaining spaces as Level 2 Ready branch circuits; EMS option at 2.1 kVA per space. | $0.31 | $0.00 | $0.31 | 1.30 |
| EV Ready | Path B | Same as Path A | $0.31 | $0.00 | $0.31 | 1.30 |
| EV Ready | Path C | Same as Path A | $0.31 | $0.00 | $0.31 | 1.30 |
| HPWH Ready | Path A | N/A | $0.00 | $0.00 | $0.00 | 1.00 |
| HPWH Ready | Path B | Same as Path A | $0.00 | $0.00 | $0.00 | 1.00 |
| HPWH Ready | Path C | Same as Path A | $0.00 | $0.00 | $0.00 | 1.00 |
Path Comparison - Soft Costs
| Item | Path | Detailed Specifications | Cost $/sf | Incentive $/sf | Net $/sf | OpEx Factor |
|---|---|---|---|---|---|---|
| Paperwork & Modeling | Path A | WUFI & HERS/ERI Energy model, 2021 IECC checklists, ENERGY STAR MFNC checklists, PHIUS checklists, PHIUS Feasibility Study, and incentive documentation. | $1.69 | $0.85 | $0.85 | 1.00 |
| Paperwork & Modeling | Path B | Same as Path A | $1.69 | $0.85 | $0.85 | 1.00 |
| Paperwork & Modeling | Path C | Same as Path A | $1.69 | $0.85 | $0.85 | 1.00 |
| Testing & Verification | Path A | Whole Building & Unit Blower Door Test, Mechanical Ventilation Testing, Room Balancing, Slab, Predrywall & Final Inspection. | $0.77 | $1.85 | -$1.08 | 1.00 |
| Testing & Verification | Path B | Same as Path A | $0.77 | $1.85 | -$1.08 | 1.00 |
| Testing & Verification | Path C | Same as Path A | $0.77 | $1.85 | -$1.08 | 1.00 |
Additional Design Considerations Not Represented In This Study
N/A
