Commercial Roof Insulation: R-Values, Types, and FL Code (2026)
Everything Pinellas County building owners need to know about commercial roof insulation, from Florida energy code requirements to choosing between polyiso, EPS, and XPS for your next roofing project.
Commercial roof insulation does two jobs at once. It controls energy costs by reducing heat transfer through the roof assembly, and it creates the slope needed for proper drainage. In Pinellas County, FL, where cooling costs dominate energy budgets and 50+ inches of annual rainfall demand effective drainage, insulation is not an afterthought. It is a core component of every commercial roofing system.
The 2023 Florida Energy Conservation Code (based on IECC 2021 with Florida amendments) sets minimum insulation requirements that apply to new construction and major reroofing projects across Pinellas County. Meeting these requirements while managing moisture, maintaining drainage slope, and controlling costs requires understanding the three primary insulation types and how each performs in Florida's subtropical climate.
This guide walks through everything you need to make informed insulation decisions for your Pinellas County commercial building in 2026.
Florida Energy Code Requirements for Commercial Roof Insulation
Pinellas County falls within IECC Climate Zone 2A (hot-humid), which sets specific insulation minimums for commercial buildings. Understanding these requirements is the starting point for any insulation decision.
For low-slope commercial roofs (the most common configuration for offices, retail, warehouses, and industrial buildings), the Florida Energy Conservation Code requires:
- R-20 continuous insulation (ci) for insulation entirely above the roof deck
- R-19 for metal building roofs with filled cavity insulation
- R-30 for attic and other air spaces (wood-framed roofs with attic cavities)
The "continuous insulation" requirement is important. It means the insulation must be uninterrupted across the roof surface, without thermal bridging from fasteners, supports, or structural elements. This eliminates traditional batt insulation between purlins as a standalone solution for commercial flat roofs.
These requirements apply when installing a new roof system on new construction, performing a complete tear-off and replacement, or adding a recover board and new membrane over existing insulation (in some cases). Simple roof coating applications and repairs that do not involve removing or adding insulation layers generally do not trigger energy code upgrades.
It is worth noting that these are minimums. Many Pinellas County building owners choose to exceed code requirements because the energy savings from additional insulation pay for themselves within a few years given Florida's intense cooling loads.
Three Types of Commercial Roof Insulation
Commercial roofing in Pinellas County uses three primary rigid foam insulation types. Each has distinct properties that affect performance, cost, and suitability for Florida conditions.
Polyisocyanurate (Polyiso)
Polyiso is the dominant insulation choice for commercial roofing in Florida and across the United States. It delivers the highest R-value per inch of any commonly used rigid foam insulation, making it the most space-efficient option for meeting code requirements.
A standard 2-inch polyiso board provides an aged R-value of approximately R-11.4, using the LTTR (Long-Term Thermal Resistance) method that accounts for performance over the insulation's expected life. At this rating, just 3.5 inches of polyiso meets the R-20 code requirement.
Polyiso boards are manufactured with glass fiber facers on both sides, which provide dimensional stability, adhesion surfaces for membrane attachment, and some moisture resistance. The boards are available in thicknesses from 1/2 inch to 4 inches, with multiple layers stacked to achieve higher R-values.
The primary concern with polyiso is its performance at low temperatures. The blowing agent used in polyiso manufacturing can condense within the foam cells at temperatures below approximately 50 degrees Fahrenheit, temporarily reducing R-value. However, this is largely irrelevant in Pinellas County, where temperatures below 50 degrees are rare and short-lived. Polyiso performs at or above its rated value for the vast majority of the year in Florida's climate.
Polyiso is also available in tapered configurations, making it the standard choice for creating drainage slope on flat commercial roofs. Tapered polyiso systems include crickets, saddles, and valleys that direct water toward drain locations while providing thermal performance.
Expanded Polystyrene (EPS)
EPS is the most cost-effective rigid foam insulation for commercial roofing. It is manufactured by expanding polystyrene beads with steam and pressing them into boards of various densities and thicknesses.
Standard EPS (Type I, 1 lb/ft3 density) provides an R-value of approximately R-3.85 per inch. Higher density EPS (Type II at 1.5 lb/ft3 or Type IX at 2.0 lb/ft3) provides slightly higher R-values and better compressive strength but at increased cost.
EPS has a key advantage in Florida: its R-value does not decrease at low temperatures. While this matters less in Pinellas County than in northern climates, it means EPS delivers consistent thermal performance year-round without the temperature-dependent fluctuations that affect polyiso.
EPS also handles moisture better than polyiso in certain conditions. While no insulation should be exposed to standing water long-term, EPS absorbs less moisture than polyiso and dries out more readily when minor moisture intrusion occurs. This can be an advantage on commercial roofs where drainage issues or membrane leaks introduce occasional moisture.
The main drawback of EPS is its lower R-value per inch. Meeting the R-20 code requirement with EPS alone requires approximately 5.2 inches of thickness, compared to 3.5 inches for polyiso. This additional thickness can create challenges with flashing heights, door thresholds, and equipment curb heights.
Extruded Polystyrene (XPS)
XPS falls between polyiso and EPS in both R-value and cost. It provides approximately R-5.0 per inch and is manufactured in a continuous extrusion process that creates a closed-cell structure with uniform density throughout the board.
XPS is recognizable by its color: blue (Dow), pink (Owens Corning), or green (Kingspan). It offers excellent moisture resistance and high compressive strength, making it popular for applications where the insulation may be exposed to water or heavy loads.
In commercial roofing, XPS is commonly used in Protected Membrane Roof (PMR) or inverted roof assemblies where insulation sits above the waterproofing membrane. In this configuration, the insulation protects the membrane from UV exposure, temperature extremes, and physical damage, while water drains between the insulation boards and over the membrane surface below.
XPS has faced environmental scrutiny because its manufacturing process historically used high-GWP (Global Warming Potential) blowing agents. Major manufacturers have transitioned to lower-GWP alternatives, but this remains a consideration for projects pursuing green building certifications.
For most conventional commercial roofing projects in Pinellas County, XPS is less common than polyiso or EPS due to its higher cost relative to EPS without the R-value advantage of polyiso. Its sweet spot is PMR assemblies and below-grade applications where moisture resistance is the primary concern.
Insulation Type Comparison
| Property | Polyiso | EPS | XPS |
|---|---|---|---|
| R-Value Per Inch | R-5.7 (aged LTTR) | R-3.85 (Type I) | R-5.0 |
| Thickness for R-20 | 3.5 inches | 5.2 inches | 4.0 inches |
| Cost Per Sq Ft (R-20) | $1.60 to $2.60 | $1.20 to $2.00 | $2.00 to $3.20 |
| Moisture Resistance | Moderate | Good | Excellent |
| Cold Temp Performance | Reduced below 50F | Stable at all temps | Stable at all temps |
| Compressive Strength | 20 to 25 PSI | 10 to 60 PSI (by density) | 25 to 60 PSI |
| Tapered Available | Yes (standard) | Yes (limited) | No |
| FL Suitability | Excellent | Good | Good (niche use) |
Tapered Insulation for Drainage
On commercial flat roofs in Pinellas County, insulation does double duty. In addition to thermal performance, it creates the slope necessary to move water toward roof drains and prevent ponding.
Tapered insulation systems use boards manufactured with a built-in slope, most commonly 1/4 inch per foot or 1/2 inch per foot. These boards are arranged in a cricket-and-valley pattern across the roof, creating ridges that direct water toward drain locations like a series of shallow channels.
The tapered system design starts with a layout drawing that maps every board position, accounting for drain locations, equipment curbs, penetrations, and edge conditions. A typical tapered system on a 20,000 square foot commercial roof in Pinellas County might include 15 to 20 different board configurations, each with a specific thickness at its high and low ends.
Tapered polyiso is the standard because it is the only insulation type widely available in pre-manufactured tapered configurations. EPS can be factory-tapered for specific projects but requires longer lead times. XPS is not commonly available in tapered formats.
The cost of a tapered insulation system typically runs $1.50 to $3.50 per square foot more than flat insulation of the same average thickness. This premium covers the engineering design, the varied board thicknesses, and the additional material at the high points of the crickets. Given that proper drainage is essential for roof longevity in Florida, this is one of the most worthwhile investments in any commercial roofing project.
Above-Deck vs. Below-Deck Insulation
Commercial roof insulation can be installed above the structural deck (the standard approach) or below the deck (within the building interior). Each approach has implications for thermal performance, moisture management, and cost.
Above-Deck Insulation (Standard)
Above-deck insulation sits on top of the structural roof deck, directly beneath the roofing membrane. This is the most common configuration for commercial roofs in Pinellas County and offers several advantages.
Placing insulation above the deck keeps the entire roof structure within the building's thermal envelope. The deck, steel framing, and fasteners all remain at or near interior temperature, which eliminates condensation risk on structural components and provides a more consistent thermal barrier.
Above-deck insulation also provides the surface for tapered drainage systems and supports direct membrane attachment through adhesive or mechanical fasteners. The vast majority of commercial roofing systems are designed for above-deck insulation.
Below-Deck Insulation
Below-deck insulation is installed on the underside of the roof deck or within the structural cavity below. This approach is common in metal building systems where fiberglass batt or spray foam insulation fills the space between purlins.
Below-deck insulation has a significant disadvantage in Florida: it places the roof deck outside the thermal envelope. The deck temperature can exceed 160 degrees Fahrenheit on summer afternoons, then drop overnight. This cycling creates condensation risk, especially in Pinellas County's humid climate where dew points regularly exceed 70 degrees.
For this reason, the Florida Energy Conservation Code requires continuous insulation above the deck for most commercial roof types. Below-deck insulation alone does not satisfy the "ci" (continuous insulation) requirement because thermal bridging occurs at every purlin and fastener location.
Many metal building retrofits in Pinellas County combine existing below-deck batt insulation with a new above-deck rigid foam layer to achieve code compliance and improve overall thermal performance.
Moisture Considerations in Florida
Moisture is the enemy of roof insulation, and Florida's climate puts insulation at higher risk than most regions. Understanding how moisture enters and affects insulation systems helps Pinellas County building owners protect their investment.
Moisture enters commercial roof insulation through three primary paths:
- Roof leaks: Even small membrane breaches allow rainwater to reach the insulation layer. In Florida, where 50+ inches of rain falls annually, a pinhole leak can saturate significant insulation area over a single wet season.
- Vapor drive: In air-conditioned buildings (nearly every commercial building in Pinellas County), cool interior air creates a vapor pressure differential that can draw moisture through the roof assembly from the warm, humid exterior. Proper vapor retarder placement is critical.
- Construction moisture: Insulation installed during Florida's rainy season can absorb moisture before the membrane is completed. Staging and protection protocols are essential for summer roofing projects.
Wet insulation loses thermal performance dramatically. Water conducts heat approximately 23 times more efficiently than still air, so even a modest moisture content can reduce R-value by 40% or more. Wet insulation also adds weight to the roof structure, promotes mold growth, and accelerates corrosion of metal decks and fasteners.
Moisture detection should be part of every commercial roof assessment in Pinellas County. Infrared (IR) thermography, nuclear moisture scanning, and capacitance metering can identify wet insulation beneath an intact membrane without destructive testing. This information is critical when deciding whether to recover (overlay) an existing roof or perform a complete tear-off and replacement.
Recover Boards: When and Why
A recover board (also called a cover board or overlay board) is a thin, high-density board installed over existing insulation or a new insulation layer to provide a smooth, stable surface for membrane attachment. Recover boards serve multiple functions that make them a standard component on most commercial roofing projects in Pinellas County.
Common recover board types include:
- High-density polyiso (HD polyiso): 1/4 inch to 1/2 inch, provides additional R-value along with surface protection
- Gypsum fiber board: 1/4 inch to 5/8 inch, provides fire resistance and impact resistance, commonly required by FM Global and insurance carriers
- Perlite board: Lightweight, fire-resistant, provides a smooth substrate for membrane attachment
- High-density wood fiber: Provides excellent adhesion surface for hot-applied systems
Recover boards protect the primary insulation from foot traffic damage, provide enhanced fire resistance (important for insurance ratings), and create a dimensionally stable surface that prevents insulation joint patterns from telegraphing through the membrane. On recover (overlay) projects, they bridge minor imperfections in the existing roof surface.
Most membrane manufacturers require or recommend recover boards as part of their warranty specifications. Omitting the recover board to save costs can void the manufacturer warranty and reduce long-term roof performance.
When to Add Insulation vs. Replace It
One of the most important decisions in any commercial reroofing project is whether to add new insulation over the existing (a recover) or tear off the old roof system and start fresh. This decision has major cost implications and depends on the condition of the existing insulation.
Add Insulation (Recover/Overlay) When:
- Moisture testing confirms the existing insulation is dry (less than 5% moisture by weight)
- The existing insulation has adequate compressive strength to support the additional layers
- The total number of roof layers does not exceed code limits (typically two membrane layers maximum)
- The existing roof structure can support the additional weight
- You need to bring insulation up to current energy code R-values
Replace Insulation (Full Tear-Off) When:
- Moisture testing reveals widespread wet insulation
- The existing insulation is crushed or compressed from foot traffic or equipment
- Two roof layers already exist (code limit in most jurisdictions)
- The existing roof deck needs inspection or repair
- The drainage slope needs to be redesigned with new tapered insulation
- Mold or biological contamination is present in the existing insulation
In Pinellas County, the high humidity and intense rainfall make moisture testing especially critical. A recover over wet insulation traps moisture in the assembly, accelerating deterioration of the deck, fasteners, and new insulation layers. Always invest in a comprehensive moisture survey before committing to a recover approach.
The cost difference is significant. A recover with additional insulation typically costs $3 to $5 per square foot for the insulation and recover board, while a full tear-off adds $1.50 to $3.00 per square foot in removal and disposal costs before any new material is installed. On a 20,000 square foot building, that is $30,000 to $60,000 in additional cost for a tear-off versus a recover.
Cost Per R-Value: Making Smart Insulation Investments
When comparing insulation options, cost per R-value per square foot provides the clearest picture of value. This metric normalizes the comparison across different insulation types and thicknesses.
| Insulation Type | Cost Per Sq Ft (2-inch) | R-Value (2-inch) | Cost Per R-Value |
|---|---|---|---|
| Polyiso | $0.90 to $1.50 | R-11.4 | $0.08 to $0.13 |
| EPS Type I | $0.60 to $1.00 | R-7.7 | $0.08 to $0.13 |
| EPS Type II | $0.80 to $1.30 | R-8.3 | $0.10 to $0.16 |
| XPS | $1.10 to $1.80 | R-10.0 | $0.11 to $0.18 |
On a cost-per-R-value basis, polyiso and EPS Type I are comparable and represent the best value for most commercial roofing projects in Pinellas County. Polyiso wins on space efficiency (fewer inches needed), while EPS wins on raw material cost and moisture tolerance. XPS costs more per R-value but earns its premium in applications requiring superior moisture resistance.
Insulation and Your Commercial Roof System
Insulation does not exist in isolation. It is part of an integrated roof assembly that includes the structural deck, vapor retarder, insulation layers, recover board, and waterproofing membrane. Each component must be compatible with the others and appropriate for Florida conditions.
For TPO roofing systems, polyiso insulation with a gypsum fiber recover board is the standard assembly. The TPO membrane is mechanically attached or adhered to the recover board, creating a complete system that meets Florida wind uplift requirements.
For EPDM roofing systems, similar assemblies apply, with polyiso or EPS insulation and an appropriate recover board for adhesive attachment.
For metal roofing retrofits, above-deck rigid insulation can be added over existing metal panels with a new membrane system, creating a metal building re-cover that significantly improves energy performance.
Your roofing contractor and insulation supplier should provide a complete system specification that addresses thermal performance, drainage slope, wind uplift resistance, fire rating, and manufacturer warranty requirements. In Pinellas County, this specification must also account for the Florida Building Code's enhanced wind speed requirements and the high-humidity environment.
Frequently Asked Questions
What R-value is required for commercial roofs in Florida?
The Florida Energy Conservation Code requires a minimum R-20 continuous insulation (ci) for low-slope commercial roofs in Climate Zone 2, which includes Pinellas County. For metal building roofs, the requirement is R-19. These minimums apply to new construction and major reroofing projects that trigger energy code compliance.
What is the best insulation for commercial roofs in Florida?
Polyisocyanurate (polyiso) is the most commonly used insulation for commercial roofs in Florida because it provides the highest R-value per inch (approximately R-5.7 at the aged value) and is available in tapered configurations for drainage. EPS foam is a cost-effective alternative that maintains its R-value better in high humidity. The best choice depends on your budget, moisture exposure, and whether you need tapered insulation for drainage.
How much does commercial roof insulation cost per square foot?
Commercial roof insulation costs range from $0.80 to $3.50 per square foot depending on the type and thickness. Polyiso insulation costs approximately $0.90 to $1.50 per square foot for a 2-inch board (R-11.4). EPS costs $0.60 to $1.00 per square foot for equivalent thickness. Tapered insulation systems add $1.50 to $3.50 per square foot including the cricket design and additional material.
What is tapered insulation and why does my commercial roof need it?
Tapered insulation is manufactured with a built-in slope, typically 1/4 inch per foot, that creates positive drainage on flat commercial roofs. It directs water toward drains while providing thermal insulation value. The Florida Building Code requires minimum 1/4 inch per foot slope on low-slope roofs, and tapered insulation is the standard way to achieve this on flat structural decks.
Should I add insulation over existing insulation or replace it?
If existing insulation is dry and structurally sound, adding new insulation on top (a recover or overlay) is often more cost-effective than full replacement. However, if moisture testing reveals wet or degraded insulation, it must be removed and replaced. In Pinellas County, moisture scans should always be performed before deciding to overlay, as Florida's humidity and heavy rainfall increase the likelihood of trapped moisture.
Does polyiso insulation lose R-value in cold weather?
Yes, polyiso R-value decreases at temperatures below 50 degrees Fahrenheit due to the blowing agent condensing within the foam cells. However, this is rarely a concern in Pinellas County, FL, where winter temperatures rarely drop below 40 degrees. Polyiso performs at or above its rated R-value for the vast majority of the year in Florida's climate, making it an excellent choice for the region.
Making the Right Insulation Decision
Commercial roof insulation is a long-term investment that affects energy costs, roof longevity, and building comfort for 20 to 30 years or more. In Pinellas County, where cooling represents the largest portion of commercial energy costs and intense rainfall demands effective drainage, getting the insulation right is critical.
Whether you are planning a new commercial roof, evaluating a recover versus tear-off, or simply trying to reduce energy costs in an existing building, understanding your insulation options puts you in a stronger position to make decisions that pay dividends for decades.
Start with a professional roof assessment that includes moisture testing, energy analysis, and a clear comparison of insulation options for your specific building. The right insulation system will pay for itself through energy savings while protecting your roof investment for the long term.