Thermal transmittance: how insulating is your roller shutter really?
Everything you need to know about Pracal’s active shading systems—made of insulated aluminum and PVC, including roller shutters—to qualify for the 2026 tax credits and improve comfort and lower your energy bills thanks to optimal thermal transmittance levels.
The thermal transmittance (U-value) measures the amount of heat that passes through 1 m² of material when the temperature difference is 1 °C (W/m²K). The lower the number, the less heat “escapes”: in practical terms, this means greater comfort in the home, lower utility bills, and a reduced risk of condensation and mold. In 2026, the limits and inspections for building envelopes were updated, and the management of shading systems (roller shutters, blinds) is increasingly factored into the calculation of overall efficiency.
What is thermal transmittance (U-value) and why it is so important
Thermal transmittance measures how much energy (heat) passes through a material or structure.
The lower the transmittance value (expressed in W/m²K), the better the insulation.
An element with low transmittance limits heat loss in winter and heat ingress in summer: result, stable comfort and lower utility bills.
In the case of shutters, the U value depends not only on the material of the slat, but also on:
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Type of internal insulation,
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profile thickness,
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Possible presence of air or polyurethane foam between the layers,
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Matching with the window frame and shutter box.
In summary: the shutter is not an accessory, but a technical component of the window system.
What is a good thermal transmittance?
In 2026, according to the Minimum Requirements Decree (Ministerial Decree of June 26, 2015), updated to reflect the parameters for tax deductions, the reference values for Italian climate zones range from:
| Climate zone | Maximum transmittance for window frames (Uw) |
|---|---|
| A and B (South and islands) | ≤ 2.60 W/m²K |
| C | ≤ 2.00 W/m²K |
| D | ≤ 1.80 W/m²K |
| E | ≤ 1.40 W/m²K |
| F (mountainous north) | ≤ 1.00 W/m²K |
These limits refer to the complete window, but the contribution of the shutter, especially if made of insulated aluminum, can significantly improve the overall value of the window.
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A and B → warmer areas (South and islands)
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C and D → intermediate zones (Central Italy and Tyrrhenian/Adriatic coasts)
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E and F → cold or mountainous areas (North and Apennines)
PVC or aluminum insulated roller shutters? The difference in thermal transmittance
Online you will often find it written that PVC shutters have good thermal transmittance due to the natural low conductivity of the plastic material.
This is true, but only partially. PVC insulates, yes, but:
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Is less mechanically stable,
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Deforms with heat,
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And tends to fade over time.
Pracal insulated aluminum shutters, on the other hand, combine the strength of aluminum with internal polyurethane foam, which acts as a thermal and acoustic barrier.
This means:
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Lower transmittance than bare aluminum,
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greater durability over time,
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Better indoor comfort in both summer and winter.
Most importantly: better performance-to-weight ratio, thus less stress on motors and lifting mechanisms.
The thermal transmittance of garage doors.
Shutters also fall under the logic of energy efficiency, especially when they demarcate heated rooms.
Laboratory tests show how:
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a C19 steel damper has an intermediate transmittance around 5.2 W/m²K,
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while an insulated L19 aluminum damper also falls below 3.5 W/m²K, thanks to internal insulation.
The lower the value, the lower the dispersion: a difference that translates into tens of kWh saved per year.
Thermal transmittance and incentives for 2026: what you need to know
Those who carry out energy-efficiency upgrades or window replacements in 2026 may still be eligible for tax credits (the Home Bonus or Eco-Bonus), provided that:
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the new window frames meet the transmittance limits above;
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certifications are provided (manufacturer's declaration + data sheet + ENEA affidavit).
Insulated shutters can be included in the calculation if they are installed at the same time as the window frames and contribute to the overall energy improvement.
Comparative table: materials and average thermal transmittance
| Roller shutter material | Type of insulation | Average transmittance (W/m²K) | Technical Notes |
|---|---|---|---|
| PVC | None | 4,0 - 5,5 | Insulating but less mechanically stable |
| Uninsulated aluminum | None | 6,0 - 7,0 | High thermal conductivity |
| Insulated aluminum | Polyurethane foam | 2,8 - 3,5 | Excellent balance between resistance and insulation |
| Insulated steel | Polyurethane foam | 3,5 - 4,0 | Greater strength, slightly heavier |
How to choose the roller shutter with the right transmittance
If you live in cold or mountainous areas, the priority isthermal insulation: choose insulated aluminum profiles with high foam density.
In warmer areas, on the other hand, sun protection and color stability matter more, where Pracal coatings provide durability and UV resistance.
Pracal insulated aluminum roller shutters are created to provide insulation, convenience and design in one active blackout system.
Pracal is practical.
And also efficient, quiet, sustainable.