From ZEB feasibility studies to design support, subsidy applications, and performance verification — one-stop support for existing building ZEB retrofits.
Prioritizing ZEB achievement alone — reducing ventilation, undersizing HVAC, dimming lights — degrades comfort, health, and intellectual productivity. We conduct all analyses with health and comfort as prerequisites. Our goal is people-first "comfortable and healthy" spaces, not endurance-based energy savings.
The ZEB retrofit process progresses from building selection through feasibility study, design, construction, and post-completion operations. Click each step to see details.
Assess equipment condition and building usage to select suitable candidates for ZEB retrofit. Buildings with planned HVAC system renewal within 5 years are ideal. Using our Simple Economic Analysis Tool in advance helps facilitate stakeholder discussions.
A detailed investigation of current energy performance and equipment condition to develop a concrete retrofit plan. This is the most critical step, including economic analysis, scheduling, and comfort verification — the first step toward ZEB realization.
* Study details are explained in the sections below.
Reach consensus among all stakeholders and share the plan. Economic analysis comparing ZEB retrofit vs. standard renovation serves as critical evidence for decision-making.
Carry out detailed retrofit design and obtain ZEB certification (BELS). We advise designers on ZEB requirements, calculate primary energy consumption using the Standard Input Method, and verify ZEB compliance through any design changes.
Select contractors and execute construction. We prepare bid documents to ensure energy performance matches the design, and verify ZEB compliance through any construction changes. For occupied-building retrofits, we maximize use of extended breaks such as summer holidays.
Verify ZEB performance is maintained in as-built documentation. Develop proper equipment operation policies and use BEMS-based data analysis to improve indoor comfort and achieve decarbonization.
From feasibility studies to design support, subsidy applications, performance verification, and operations — available as comprehensive or partial services.
Assess current building conditions and propose specific retrofit measures, economic and environmental performance analysis, subsidy utilization, and implementation schedules.
Advise designers on ZEB requirements, calculate primary energy consumption from detailed design to verify ZEB compliance. Handle energy code compliance and BELS applications.
Prepare bid documents to ensure construction achieves the designed energy performance, incorporating special conditions for subsidy programs.
Post-award equipment verification, ZEB performance checks during design changes, and advisory on modifications to maintain ZEB compliance.
End-to-end support from subsidy application to final reporting. We handle programs from the Ministry of Environment, METI, MEXT, and others.
Verify that energy, environmental, and functional performance are achieved as designed. Comprehensive support from BEMS implementation to operational optimization.
ZEB retrofit of existing buildings achieves greater CO₂ reduction than demolition and new construction. New builds generate significant CO₂ from construction and demolition, which retrofit avoids.
A case study comparing WLC (total CO₂ emissions from material manufacturing, construction to demolition). Compare scenarios by average WLC (kg-CO₂/m²/year). Switch building lifetime using the tabs.
Whether over 60 or 80 years, ZEB retrofit achieves dramatically higher CO₂ reduction than new construction. ZEB retrofit is the most effective choice for decarbonization.
Source: Based on J-CAT registered user seminar Session 4 (June 26, 2024). Retrofit construction emissions included in Material Manufacturing & Construction. 80-year figures are estimates.
Comparing simple equipment replacement (standard renovation) with comfort-enhancing ZEB retrofit.
Insulation lasts the building's lifetime, but HVAC, lighting, etc. need renewal every ~15 years. To understand ZEB retrofit's true value, long-term lifecycle cost analysis including equipment renewal is essential. Individual cases vary significantly based on operational conditions, unit costs, and renewal plans.
A study examining the feasibility of ZEB retrofit from both technical and economic perspectives. It clarifies barriers to ZEB realization and increases feasibility.
Document building envelope performance and equipment status with energy consumption data
Develop strategies combining equipment, envelope, and renewable energy to achieve BEI targets
Ensure proper ventilation, HVAC, and lighting performance with occupant comfort as prerequisite
Calculate energy savings, CO₂ reduction, payback period, and cost-effectiveness including subsidies
Assess occupied-retrofit feasibility and organize timeline including subsidy program schedules
⚠ Note: Prioritizing ZEB achievement alone — reducing ventilation, undersizing HVAC, dimming lights — degrades comfort, health, and productivity. This study ensures health and comfort as prerequisites.
Standard flow assuming buildings of 1,000-10,000㎡. Duration varies by building scale and study scope.
0.5 months
Review drawings and energy consumption data
0.5-5 days
Verify equipment status and drawing discrepancies
0.5-1 month
Calculate current BEI
2-4 months
HVAC load, illuminance calculations, ZEB plan development
0.5-1.5 months
Develop standard renovation plan for comparison
1-2 months
Calculate estimated costs for both plans
0.5-1 month
Economic comparison and report compilation
The following deliverables are provided. These are preliminary study-level documents, not finalized specifications for detailed design or construction.
Study report including economic analysis (ZEB retrofit vs. standard renovation comparison)
Current and post-retrofit BEI calculations using Standard Input Method
Editable calculation spreadsheet
Schematic equipment layout, equipment list, estimated piping/duct routes
Heating/cooling load calculations after insulation and total heat exchange ventilation
Illuminance distribution simulation after lighting retrofit
List and comparison of available subsidy programs
Estimated construction costs for ZEB retrofit and standard renovation
Timeline from subsidy application through design and construction
To systematically advance ZEB retrofit, it is essential to thoroughly investigate the building's current energy performance and challenges. A feasibility study identifies energy, cost, and comfort issues in advance, facilitating stakeholder consensus and increasing project success rates.
A high-quality feasibility study is critically important for existing building ZEB retrofit.
Realistic and economical retrofit plans with concrete schedules. Includes economic analysis to support stakeholder consensus.
Unrealistic retrofit plans without economic analysis or schedules. Does not contribute to ZEB realization.
To avoid low-quality results, proposal-based selection is recommended for consultant selection. However, clients also need knowledge to select consultants capable of delivering high-quality results, which is often challenging.
To ensure feasibility studies contribute to ZEB realization, we have developed a comprehensive specification covering all necessary study contents: "Existing Building ZEB Feasibility Study Specification". Faithfully implementing the contents described here is important for increasing ZEB feasibility.Can be used directly as common specifications for proposals.
Selecting appropriate buildings is essential to maximize the effectiveness of feasibility studies.
* Buildings over 10,000㎡ can be evaluated by building use category. ZEB retrofit initial costs are typically higher than standard renovation even with subsidies, but lifecycle costs (LCC) are often lower.
Documents to prepare for study commencement. Consult us even if data is incomplete — site surveys and equipment registries may supplement missing information.
Subsidy programs are available to support feasibility study costs. We provide end-to-end support from application to reporting.
Direct subsidy for studying ZEB feasibility and CO₂ reduction potential. Reports can be used for next year's retrofit subsidy applications.
Key requirements: ZEB Planner involvement / BEI calculation / Disclosure of technical, design, and cost data
Part of the Housing & Building Supply-Demand Integrated Energy Efficiency program. Supports ZEB diagnosis and retrofit planning costs for existing buildings.
Key requirements: ZEB Planner involvement / ZEB plan submission / Data provision and disclosure
* Subsidy rates may change annually. Selection and disbursement are not guaranteed.
SRC (partially steel) / 8F + B1 / Approx. 16,000㎡ / Built 1993
Drawing review, site survey, transient HVAC load calculation, equipment/envelope retrofit strategy, economic/schedule analysis, cost estimation (with/without solar scenarios)
HVAC renewal (GHP, etc.), vacuum glass windows, chamber ceiling insulation, rooftop waterproofing
RC / 3F / Approx. 4,000㎡ / Built 1990
BPI/BEI calculation (Standard Input), ZEB vs standard renovation comparison, HVAC load, illuminance, economics/LCC, subsidy analysis
Vacuum glass, total heat exchange ventilation (CO₂ control), LED with daylight/occupancy sensors
RC+Steel / Approx. 3,000㎡ / Branch office + multipurpose hall, library, etc.
BPI/BEI calculation (Standard Input), multi-plan comparison, cost estimates, funding (subsidies/bonds), schedules, and maintenance
High-efficiency HVAC, total heat exchange ventilation, LED with sensors, insulated windows, solar PV
Steel / Approx. 10,000㎡
BEI/BPI calculation (Standard Input), realistic target setting (ZEB Ready to Nearly), equipment plans, cost estimation
Vacuum glass, central plant to VRF conversion, total heat exchange ventilation, LED with sensors, solar PV
Use these before a formal feasibility study for planning, budgeting, and stakeholder communication.
Enter minimal information (climate zone, floor area, area ratios) to compare standard vs. ZEB retrofit cumulative costs with payback estimates. Fully web-based, no site survey needed.
Use the Tool →Comprehensive standard specification for high-quality feasibility studies. Can be used directly as common specifications for proposals.
Download →Yes. A feasibility study is the first step in determining whether ZEB is viable. Simply share the building use, floor area, and location.
Yes. On-site surveys and equipment registry checks can supplement missing data. Please consult with us regardless.
Yes. We assess occupied-building retrofit feasibility, required closure scope, and phased renovation approaches.
Yes. ZEB Corporation provides comprehensive support including feasibility studies, planning, design, subsidy programs, BELS/ZEB certification, construction-phase performance management, and operations.
Building use, total floor area, location, year of construction, and current equipment status are most helpful for an initial consultation.
A ZEB feasibility study is the first step toward subsidy applications and retrofit planning.
We serve buildings of any size and use.
Study fees are quoted based on floor area, building use, and location.