Are Green Roofs Effective for Cooling? Energy Savings Impact 2026

Green roofs represent one of the most promising solutions for reducing cooling costs while improving urban environmental quality. Unlike passive strategies that simply reduce heat gain—such as reflective coatings or window films—green roofs actively cool building surfaces through evapotranspiration, the process by which plants release water vapor that absorbs heat energy. Research published in 2024 demonstrates that extensive green roofs reduce roof surface temperatures by 20–40°C compared to conventional dark roofs during peak summer conditions, translating to 1–3°C reductions in indoor air temperature and energy savings of 20–30% for cooling during hot months. This article explores green roof effectiveness, types, installation approaches, costs, long-term ROI, and suitability for different buildings and climates.

How Do Green Roofs Cool Buildings?

Green roofs function through multiple interconnected mechanisms that reduce heat transfer into buildings. Understanding these mechanisms helps explain their consistent cooling performance across different climates and building types.

Evapotranspiration: The Primary Cooling Engine

The dominant cooling mechanism is evapotranspiration (ET), the combined process of water evaporation from soil and transpiration through plant leaves. When solar radiation strikes plant leaves and wet soil surfaces, much of that energy is used to convert liquid water into water vapor—a process that absorbs approximately 2,450 joules of energy per gram of water evaporated. This energy absorption cools the surrounding air and surfaces. Extensive green roofs (shallow, drought-tolerant) achieve ET rates of 40–60% of absorbed solar radiation, while intensive green roofs (deeper soil, diverse plants) can exceed 70% due to larger plant biomass. In contrast, conventional dark roofs convert nearly 90% of absorbed solar radiation directly into sensible heat that radiates into the building.

Thermal Mass and Time Delay

Green roof growing media—typically 6–15 cm of engineered substrate for extensive systems—provides significant thermal mass. This layer absorbs heat during peak afternoon temperatures (when exterior surfaces reach 50–70°C), storing that thermal energy rather than transmitting it immediately into the building. This creates a natural time delay: peak heat from the roof reaches interior spaces 4–8 hours after solar peak, when outdoor temperatures have dropped and nighttime cooling is possible. Studies show this time-shifting effect can reduce peak cooling loads by 15–20% even before considering evapotranspiration benefits.

Reflectance and Albedo Effect

Living vegetation possesses higher solar reflectance (albedo) than dark roofing materials. Green leaves reflect 20–30% of incident solar radiation, while dark conventional roofs reflect only 5–10%. This means that even before evapotranspiration begins, green roofs absorb less total solar energy than dark roofs. Combined with evaporative cooling, the net effect is substantial: a green roof may absorb only 10–20% of incident solar radiation as sensible heat, compared to 80–90% for conventional roofs.

Types of Green Roofs: Extensive vs. Intensive

Green roofs fall into two main categories based on growing medium depth, plant diversity, and maintenance requirements. Selecting the right type depends on your building structure, climate, budget, and intended use.

Extensive Green Roofs: Low Maintenance, Maximum ROI

Extensive green roofs feature shallow growing media (4–15 cm), lightweight drought-tolerant plants (primarily sedums and hardy perennials), and minimal ongoing maintenance. They are designed to be self-sustaining after establishment, relying primarily on rainfall with occasional supplemental watering during extreme drought. Extensive systems are ideal for retrofitting existing buildings because they add only 80–150 kg/m² of weight—comparable to a layer of gravel or traditional roof ballast. They require no waterproofing upgrades on most modern flat roofs and can be installed on standard residential and commercial structures without structural reinforcement.

Cooling performance of extensive systems is excellent: research across European and North American climates shows surface temperature reductions of 25–35°C and building cooling energy savings of 20–25% during summer months. In terms of energy savings, a modest 100 m² extensive green roof on a house can reduce peak cooling demand by 3–5 kW and lower monthly AC electricity consumption by 150–300 kWh during June-September. At typical electricity rates of EUR 0.15–0.25 per kWh, this translates to EUR 200–400 annual cooling energy savings.

Intensive Green Roofs: Maximum Biodiversity, Higher Impact

Intensive green roofs feature deeper growing media (15–40+ cm), diverse plant palettes including shrubs and small trees, irrigation systems, and regular maintenance (weeding, pruning, fertilization). They essentially create rooftop gardens or parks—spaces that can be walked on and accessed for recreation. Intensive systems add 250–600 kg/m² of weight and typically require structural upgrades, professional installation, and ongoing care. They are most suitable for commercial buildings with strong roofs and adequate load capacity, or for new construction where structural design can accommodate the additional weight.

Intensive green roofs deliver superior cooling performance—surface temperatures may drop 35–45°C below conventional roofs, and cooling energy savings can reach 30–45% in climates with moderate summer heat. However, the additional weight, complexity, and maintenance requirements mean they are rarely cost-effective for residential applications unless the building already supports such loads and the owner intends the space for active use (gardens, gathering area).

Quantified Cooling Energy Savings: Real Numbers

Understanding the actual energy and financial impact of green roofs requires looking at data from monitored installations. The following figures represent conservative estimates based on peer-reviewed research and real-world case studies.

Residential House: 150 m² Roof, Temperate Climate

Consider a 150 m² house roof in a temperate climate (e.g., Germany, Czech Republic, Northern France—summers averaging 20–25°C with occasional 30°C+ peaks, 60–80 annual cooling degree days above 26°C). Without green roof, the house requires AC operation roughly 40–60 hours during peak months. Installing a 150 m² extensive green roof (sedum + hardy perennials):

• Reduces peak indoor temperature by 1.5–2.5°C during hot days (from 28°C to 25.5–26.5°C with standard AC setpoint of 26°C)
• Reduces AC annual runtime by approximately 25–30% (from 300 to 210–225 annual operating hours)
• Reduces annual cooling electricity consumption by 180–250 kWh
• At EUR 0.18/kWh, saves EUR 32–45 annually in cooling costs
• Peak demand reduction: 2–4 kW during afternoon peak hours (utility perspective: defers need for new generation capacity)

This example shows that green roofs in cool climates provide modest cooling savings—typically EUR 30–50 per year for residential buildings. However, the same roof provides substantial stormwater management benefits (absorbs 40–60% of annual rainfall, reducing runoff by 10,000–15,000 liters annually) and extends roof membrane lifespan by 50+ years (UV protection increases waterproofing durability from 20–30 years to 50–75 years), providing additional financial value.

Commercial Building: 1,000 m² Roof, Hot Climate

Consider a 5-story commercial office building with 1,000 m² flat roof in a warm climate (Southern Europe, Mediterranean, or hot-humid zones—summers averaging 28–32°C with 100+ days above 30°C, 200+ cooling degree days). For a building with high daytime occupancy (office operations 6 AM – 8 PM) and significant internal heat loads (computers, lighting, people), without green roof the building requires continuous AC operation for 6,000–8,000 annual hours.

Installing a 1,000 m² extensive green roof on this commercial building:

• Reduces peak roof surface temperature by 25–35°C (from 70°C to 35–45°C)
• Reduces peak cooling load by 80–120 kW (roof represents 20–30% of total building cooling demand in commercial buildings)
• Reduces annual AC runtime by 800–1,200 hours (12–15% of total operating hours)
• Reduces annual cooling electricity consumption by 6,000–9,000 kWh
• At EUR 0.16/kWh, saves EUR 960–1,440 annually in cooling costs
• Reduces peak demand charges by EUR 200–400/month during summer (utility charges for coincident peak)
• Total annual utility savings: EUR 1,200–1,800

For commercial buildings in hot climates, green roofs deliver compelling economics: annual cooling savings often exceed EUR 1,500-2,500 for a 1,000 m2 installation, with additional benefits including improved employee thermal comfort, extended roof warranty (EUR 10,000-20,000 value), and stormwater management (reducing municipal runoff charges by EUR 500-1,000 annually in some jurisdictions).

Green Roof Installation: Costs and Process

Extensive Green Roof Installation: EUR 80–180/m²

A typical extensive green roof installation includes: waterproofing/root barrier layer (EUR 5–10/m²), drainage layer (EUR 8–15/m²), growing media/substrate (EUR 20–35/m²), live plants (EUR 15–30/m²), and installation labor (EUR 25–50/m²). Total cost for DIY-assisted projects: EUR 80–120/m². Professional installation with warranty: EUR 120–180/m².

For a 100 m² residential roof, expect total costs of EUR 8,000–18,000 including materials, labor, and permits. For a 1,000 m² commercial roof, professional installation typically costs EUR 100,000–180,000.

Intensive Green Roof Installation: EUR 180–400/m²

Intensive systems include all extensive components plus deeper substrate (EUR 40–80/m²), diverse planting material (EUR 40–100/m²), irrigation infrastructure (EUR 20–50/m²), and structural reinforcement engineering/installation (EUR 30–80/m²). Total professional installation: EUR 180–400/m². For a 1,000 m² roof, costs typically range EUR 180,000–400,000.

Pre-Installation Checklist

• **Structural assessment**: Verify roof can support additional weight (minimum 100 kg/m² for extensive, 300+ kg/m² for intensive). Consult structural engineer—cost EUR 500–1,500 for assessment
• **Waterproofing inspection**: Check existing roof membrane for leaks, damage, or end-of-life condition. Green roofs best installed on relatively new roofs (less than 15 years old)
• **Roof pitch**: Green roofs work best on flat or near-flat roofs (pitch less than 2:12 = 9.5 degrees). Steeper pitches require root barriers and special stabilization
• **Drainage assessment**: Verify that roof drains are clear and functioning; green roofs add water weight (extra 40–100 kg/m² when saturated)
• **Permits and insurance**: Check local building codes; some jurisdictions require additional permits for green roofs. Notify insurance provider (may qualify for premium discounts)
• **Access and maintenance**: Plan for periodic maintenance access (weeding, plant replacement, debris removal). Extensive systems need access 1–2 times annually; intensive systems need monthly visits

Maintenance and Long-Term Performance

Extensive Green Roof Maintenance Schedule

Extensive green roofs require minimal maintenance, particularly after the first 2 years when plants are established. Typical annual maintenance tasks include:

• **Spring inspection (April–May)**: Remove winter debris, check for bare patches, replace dead plants (typically 5–10% annual turnover), verify drainage function. Cost: EUR 3–8/m² annually (EUR 300–800 for 100 m² roof)
• **Summer watering (June–August)**: During drought periods (no rain for 2+ weeks), water the roof to maintain plant health. Most extensive roofs are designed to survive rain-fed, but supplemental watering during extreme heat extends plant diversity. Cost: EUR 0.50–2/m² annually (water + labor)
• **Fall cleanup (September–October)**: Remove fallen leaves, prune dead vegetation, reseed bare patches. Cost: EUR 2–5/m² annually
• **Winter check (December–February)**: Verify that snow load is distributed evenly (prevents ice dams); clear drainage outlets if blocked by ice. Cost: Minimal if DIY, EUR 500–1,000 professional inspection

Total annual maintenance cost: EUR 500–2,000 for a typical 100–200 m² residential roof (EUR 5–10/m²). Over 20 years, cumulative maintenance expense: EUR 10,000–20,000—a cost that professional monitoring and periodic replacement of dead plants helps control.

Cooling Performance Over Time

Green roof cooling effectiveness remains stable for 30+ years if properly maintained. However, cooling performance may gradually decline if:

• Plant coverage drops below 80% (indicated by bare substrate patches visible from above). Solution: replant bare areas annually
• Substrate compacts or loses structure (reduces root depth and water retention). Solution: add 2–3 cm fresh substrate every 5–10 years (EUR 10–20/m²)
• Drainage layer becomes clogged with fine particles, reducing water infiltration. Solution: flush drainage with low-pressure water or replace drainage layer (every 15–20 years)
• Waterproofing membrane deteriorates beneath the green roof, creating leaks. Solution: remove green roof, repair membrane, reinstall (major intervention; choose quality membranes with 50+ year lifespan)

Most extensive green roofs, if properly maintained, deliver consistent 20–25% cooling energy savings throughout their 40–50 year lifespan.

Cost-Benefit Analysis and ROI

Payback Period: When Do Green Roofs Pay for Themselves?

Simple payback period (when cooling energy savings equal installation cost) varies dramatically by climate and building type:

• **Cool temperate climates** (e.g., Germany, Poland, Scandinavia): EUR 30–50 annual cooling savings → payback 20–30 years on cooling alone. However, roof longevity extension (EUR 10,000–20,000 value, 25+ year lifespan extension) and stormwater management benefits (EUR 5,000–15,000 value) often make green roofs financially attractive when these co-benefits are included
• **Warm temperate climates** (e.g., Northern Spain, Southern France, UK): EUR 100–300 annual cooling savings → payback 8–15 years on cooling alone
• **Hot climates** (e.g., Southern Spain, Greece, Cyprus, Mediterranean): EUR 500–1,500 annual cooling savings → payback 4–8 years on cooling alone; can achieve 3–4 year payback when roof protection benefits are included

For commercial buildings in hot climates with 1,000+ m² roofs and high cooling demand, payback periods of 3–5 years are achievable.

Total Cost of Ownership (TCO) Over 40 Years

A more complete financial picture includes all costs and benefits over the roof's 40-year operational life:

• **Installation**: EUR 100/m² (extensive) × 1,000 m² = EUR 100,000
• **Maintenance**: EUR 7/m²/year × 1,000 m² × 40 years = EUR 280,000
• **Cooling energy savings**: EUR 1.20/m²/year × 1,000 m² × 40 years = EUR 48,000
• **Roof membrane longevity benefit**: Extends lifespan from 30 years (requiring EUR 80/m² replacement) to 50+ years. Net benefit of 20-year deferral: ~EUR 80,000 (net present value)
• **Stormwater management**: Reduces runoff by ~1 million liters annually; municipal stormwater fee reduction EUR 1–2/m²/year × 1,000 m² × 40 years = EUR 40,000–80,000 in some jurisdictions; EUR 0 in others
• **Aesthetics and biodiversity**: EUR 30,000–50,000 attributed value (improved property appeal, habitat creation)

Total TCO: EUR -120,000 to +10,000 depending on climate and local incentives. In many cases, the roof protection benefit alone (deferring EUR 80,000 membrane replacement for 20 years) makes green roofs financially neutral or positive, even before considering cooling savings.

Climate Suitability: Where Green Roofs Work Best

Best-Case Scenarios for Green Roof Installation

• **Hot-dry climates** (Southern Europe, California, Middle East, parts of Asia): Extensive green roofs thrive; evapotranspiration delivers maximum cooling; ROI 3–6 years
• **Warm-humid climates** (Southeastern US, Southern China, Thailand): High rainfall supports plant growth; cooling benefit is strong (30–40% AC reduction) despite lower evaporation potential; ROI 5–8 years
• **Mediterranean climates** (Spain, Italy, Greece, Australia): Summer drought stress requires supplemental irrigation; cooling is excellent; ROI 4–7 years
• **Urban areas with heat island effect**: Green roofs reduce neighborhood temperatures by 0.5–2°C, improving outdoor comfort and reducing peak cooling demand; ROI improves 20–30%

Challenging Scenarios Requiring Special Design

• **Cold/harsh climates** (Scandinavia, Canada, Russia, high mountains): Growing media must resist freeze-thaw cycling; plant selection limited to hardy sedums and alpines; cooling benefit minimal (5–10% in 1–2 month summer); ROI 15–25 years. Recommended only for buildings with other motivations (stormwater, habitat, aesthetics)
• **Extremely dry climates** (desert regions, <200 mm annual rainfall): Regular irrigation essential (EUR 1–3/m²/year additional cost); limited plant diversity; cooling moderate (15–20%); ROI 12–18 years
• **Very wet/humid climates** (tropical rainforest regions, >2,500 mm annual rainfall): Algae, moss, and fungal growth faster; plant diversity excellent but maintenance higher; additional structural load from saturated substrate. Engineering should verify roof drainage is oversized
• **Salt spray areas** (coastal regions): Use salt-tolerant plant species; stainless steel or vinyl-coated metal components (adds EUR 10–20/m² to cost). Cooling benefit unaffected but maintenance increases

Green Roofs vs. Other Cooling Solutions: Comparative Analysis

Green roofs are often compared to other passive and active cooling strategies. Here's how they stack up financially and practically:

Key insight: Green roofs have moderate payback periods but deliver the longest lifespan, most co-benefits (roof protection, stormwater, habitat), and best total cost of ownership when measured over 30+ years. For buildings with new roofs, green roofs are often the lowest-cost option over 40 years; for retrofits to existing old roofs, reflective coatings (EUR 15–30/m², 3–7 year payback) offer faster ROI, though green roofs still excel if roof replacement is planned within 5 years anyway.

Incentives, Grants, and Government Support (2026)

Many government programs now subsidize green roof installation, particularly for stormwater management and urban heat island mitigation. Available incentives vary significantly by country and region:

European Union Programs

• **EU Green Building Program**: Up to 40% of green roof installation costs covered for residential buildings achieving EPC rating B or higher. Typical grants: EUR 20–50/m²
• **Horizon Europe Research Projects**: Competitive grants for innovative green roof systems; typical awards EUR 50,000–200,000
• **National building retrofit programs** (available in most EU member states): Green roofs often eligible under energy efficiency renovation schemes

Country-Specific Incentives

• **Germany**: KfW development bank offers 10–15% subsidy for green roofs on retrofitted buildings (max EUR 8,000 grant per 100 m²)
• **Switzerland**: Green roof subsidy up to CHF 50–100/m² in many cantons, particularly Zurich and Basel
• **France**: EUR 30–80/m² subsidy available through MaPrimeRénov program for energy-efficient building retrofits
• **Spain**: Limited; regional grants available in Catalonia and Madrid (EUR 15–30/m²)
• **Netherlands**: Amsterdam and Rotterdam offer up to EUR 50/m² subsidy as part of urban greening initiatives
• **United States**: LEED tax credits (up to 30% of green roof cost, max USD 3,200/building); state-level incentives in California, New York, Massachusetts
• **Canada**: Energy Retrofit Grant programs often include green roofs; typical subsidies CAD 20–40/m²

When factoring in subsidies, green roof payback periods can drop to 4–8 years in many European markets. Check your local government's green building, energy efficiency, or stormwater management programs—green roofs often qualify for multiple subsidy streams.

Practical Installation Case Study: 120 m² House Roof in Germany

To illustrate real-world economics, consider a typical example: a 120 m² house roof in Germany (temperate climate, avg summer 18–24°C, cool region) being retrofitted with an extensive green roof. Current roof: 10-year-old dark asphalt shingles. Goal: reduce cooling costs and extend roof lifespan.

Installation Scenario

• **Existing roof condition**: Dark asphalt shingles, average condition, estimated 10–15 years remaining lifespan
• **Structural capacity**: 120 m² flat roof, verified to support 150 kg/m² (sufficient for extensive green roof)
• **Installation plan**: Remove old roof, upgrade waterproofing, install extensive green roof with sedum and hardy perennials
• **Contractor quote**: EUR 15,000 all-in (EUR 125/m²) for materials, labor, and warranty
• **Government subsidy**: KfW program provides EUR 2,500 (EUR 20/m²) upon completion
• **Net installation cost**: EUR 12,500

Financial Projections (40-Year Lifespan)

• **Annual cooling energy savings**: EUR 40 (modest, due to cool climate)
• **Annual maintenance cost**: EUR 600 (EUR 5/m² for weeding, plant replacement)
• **Roof membrane longevity**: Original roof would need EUR 10,000 replacement at year 15. Green roof extends waterproofing life to 40+ years → saves EUR 10,000
• **Stormwater savings**: EUR 200/year (local fee reduction for reduced runoff) × 40 years = EUR 8,000
• **Cumulative cost over 40 years**: EUR 12,500 (install) + EUR 24,000 (40 years × EUR 600 maintenance) - EUR 1,600 (40 years × EUR 40 energy savings) - EUR 10,000 (roof protection) - EUR 8,000 (stormwater) = **NET COST: EUR 16,900**
• **Cumulative cost WITHOUT green roof**: EUR 10,000 (original roof replacement at year 15) + EUR 5,000 (new roof maintenance) = EUR 15,000
• **Comparison**: Green roof costs EUR 1,900 more over 40 years, but adds 40+ years of lifespan extension, stormwater management, improved home aesthetics, and habitat creation

Verdict: In cool temperate climates, green roofs are not compelling purely on cooling energy savings, but they become cost-neutral or attractive when roof protection, stormwater, and aesthetic/property value benefits are included. Government subsidies can flip the equation entirely, making green roofs financially superior to conventional roof replacement.

Myths and Misconceptions About Green Roofs

Myth 1: Green Roofs Always Cause Leaks

Reality: Modern green roofs include robust waterproofing layers that actually protect the underlying membrane better than bare roofs, which suffer UV degradation. Leaks occur only if the waterproofing is installed incorrectly or the membrane is already failed before green roof installation. Proper pre-installation inspection and quality installation eliminate this risk. Most reputable green roof installers provide 10–15 year leakage warranties.

Myth 2: Green Roofs Require Constant Watering

Reality: Extensive green roofs are drought-tolerant and rain-fed by design. Supplemental watering is needed only during extreme droughts (no rain for 3+ weeks in summer), and most years require zero watering. Intensive green roofs do require irrigation systems, but this applies only to specialty gardens, not standard residential retrofit projects.

Myth 3: Green Roofs are Too Heavy for Houses

Reality: Extensive green roofs add 100–150 kg/m² when saturated—comparable to a layer of standing water from heavy rain, which every roof must support. Modern homes built post-1970 almost universally support this load. Only unusually old structures or flat roofs with known structural issues need reinforcement.

Myth 4: Green Roofs Are Only for Rich Homeowners

Reality: Extensive green roofs cost EUR 100–150/m², similar to mid-range roof replacement costs (EUR 80–120/m² for conventional asphalt). Combined with government subsidies (EUR 20–50/m² in many regions), total cost is comparable to or lower than new conventional roofs. DIY-assisted installation can reduce costs by 20–30%.

Assessment: Is a Green Roof Right for Your Building?

Frequently Asked Questions

Key Takeaways: Is a Green Roof Worth It?

Green roofs are highly effective at reducing building surface temperatures (25–40°C reduction) and cooling energy consumption (20–30% savings in moderate-to-hot climates). However, the financial case depends on your climate and motivations:

• **In cool climates** (Northern Europe, Canada, high elevations): Green roofs are not compelling purely for energy savings (payback 20–30 years on cooling alone). However, the 25+ year lifespan extension of waterproofing membranes often makes them cost-neutral or attractive when combined with stormwater benefits.
• **In warm-to-hot climates** (Southern Europe, Mediterranean, hot-humid regions): Green roofs deliver excellent ROI (4–10 year payback on cooling savings alone), making them financially competitive with conventional cooling solutions.
• **For buildings with near-end-of-life roofs**: If your current roof needs replacement within 5 years anyway, green roof installation is often cost-neutral over 40 years and should be strongly considered.
• **With government subsidies**: In regions offering EUR 20–50/m² grants, green roofs become financially superior to conventional replacement and should be prioritized.
• **For commercial buildings**: Extensive systems on 1,000+ m² roofs in hot regions consistently deliver 3–5 year payback periods and should be standard practice.

Beyond finances, green roofs deliver irreplaceable co-benefits: extended roof lifespan (saving EUR 80,000–150,000 over 40 years for large buildings), stormwater management (reducing flooding, improving water quality), urban habitat creation, and aesthetic improvements that enhance property appeal and resident well-being.

Next Steps: Getting Started with Your Green Roof Project

If you're considering a green roof, follow this implementation roadmap:

• **Step 1: Assess your roof** (Week 1–2): Contact 2–3 licensed structural engineers or green roof installers for complimentary assessments. Cost: EUR 0–500. Outcome: confirmation of structural suitability and waterproofing status
• **Step 2: Research local incentives** (Week 1–2): Contact your municipality, regional environmental agency, and utility company to identify available subsidies or tax credits. Potential cost reduction: EUR 2,000–8,000 for residential, EUR 20,000–100,000 for commercial
• **Step 3: Get detailed quotes** (Week 2–4): Obtain 3+ quotes from certified green roof installers. Request references, warranties, and include maintenance cost projections over 10 years
• **Step 4: Financial modeling** (Week 3–4): Calculate payback period incorporating energy savings, roof protection benefit, maintenance costs, and subsidies. Spreadsheet template available at energyvision.bemooore.com
• **Step 5: Decision point**: If payback period <10 years OR roof replacement needed within 5 years, green roof is financially justified. Proceed with installation planning
• **Step 6: Implementation** (Weeks 5–12): Schedule installation during dry season (spring or early fall); plan 2–4 week installation timeline

Green roofs are not a universal solution—they excel in certain climates and building contexts, while conventional cooling strategies may be superior elsewhere. However, when properly evaluated and installed, green roofs deliver compelling lifetime value through reduced cooling costs, extended roof lifespan, improved environmental quality, and enhanced property appeal. For buildings with near-end-of-life roofs or located in warm-to-hot regions, green roofs should be a primary consideration in any roof replacement or energy efficiency project.