Dimensional Stability of XPS at Temperature and Humidity

10 June 2026

All PNP XPS boards carry the declared dimensional stability class DS(70,90), meaning they meet the EN 13164 requirement for linear dimensional change tested at 70 °C and 90 % relative humidity. Combined with a continuous service temperature range of −70 °C to +75 °C, this confirms that PNP XPS boards maintain their shape under the thermal and moisture conditions typical of building envelopes in Central and Eastern Europe.

What DS(70,90) Means

Dimensional stability of thermal insulation boards is declared under EN 13164:2012+A1:2015 using the code DS(T,RH), where T is the test temperature in °C and RH is the relative humidity in %. The class DS(70,90) means the board was conditioned at 70 °C and 90 % relative humidity and the resulting linear dimensional change remained within the limit defined by that class.

All PNP XPS products for which technical data are published carry the DS(70,90) declaration. This is the standard class used for boards intended for building construction, covering the most demanding combination of heat and moisture that insulation is likely to encounter behind cladding, beneath a screed, or in a flat-roof assembly.

Why Dimensional Stability Matters in Practice

An insulation board that creeps, warps, or shrinks after installation can open joints between boards, create point loads on membranes, and shift the thermal resistance of the assembly. Three scenarios in Central and Eastern European construction are particularly sensitive:

Flat and inverted roofs — boards are exposed to summer surface temperatures well above ambient; board-to-board joints that open allow moisture ingress beneath the membrane.
ETICS facades — render and mesh are bonded directly to the board face; any board movement transfers stress into the reinforcing layer.
Sub-screed floors — trapped moisture and elevated temperatures from underfloor heating act simultaneously; a board that swells or settles unevenly causes screed cracking.

The DS(70,90) class, tested under the combined worst-case condition, supports confidence that boards will not cause these problems under in-service conditions.

Service Temperature Range

In addition to the DS(70,90) class, all published PNP XPS products state an operating temperature range of −70 °C to +75 °C. This covers cold-store floor insulation at one extreme and exposed summer roof conditions at the other.

Note that the upper continuous service temperature of +75 °C is a material property limit, not a design target. Where surface temperatures may exceed this — for example, directly beneath dark membrane on a south-facing roof in a continental climate — a qualified designer should verify the assembly. The TDS and DoP for each product should be consulted for the relevant declared values.

Dimensional Stability Across the PNP XPS Range

The table below lists the DS class and operating temperature range for every PNP XPS product for which data are available.

Product	DS class	Operating temperature
XPS 150	DS(70,90)	−70 … +75 °C
XPS 150 MG	DS(70,90)	−70 … +75 °C
XPS 150 W X-Grip	DS(70,90)	−70 … +75 °C
XPS 200	DS(70,90)	−70 … +75 °C
XPS 200 MG	DS(70,90)	−70 … +75 °C
XPS 200 W	DS(70,90)	−70 … +75 °C
XPS 300	DS(70,90)	−70 … +75 °C
XPS 300 MG	DS(70,90)	−70 … +75 °C
XPS 300 W	DS(70,90)	−70 … +75 °C
XPS 400	DS(70,90)	−70 … +75 °C
XPS 500	DS(70,90)	−70 … +75 °C
XPS 700	DS(70,90)	−70 … +75 °C

Dimensional stability data for XPS 300 SLOPE and XPS 150 SLOPE are not included in the data available for this article; see the current TDS for those products.

Relationship to Other Declared Properties

Dimensional stability interacts with two other declared properties on higher-grade boards:

Compressive creep CC(2/1,5/50) — declared on XPS 300, XPS 300 W, XPS 300 MG, XPS 500, and XPS 700 — quantifies long-term thickness reduction under sustained load. DS(70,90) addresses planar (in-plane) stability; CC addresses thickness under compression. Both are needed for structural floor and roof design.
Freeze–thaw resistance FTCD — declared on XPS 200, XPS 200 MG, XPS 200 W, XPS 300, XPS 300 W, XPS 300 MG, XPS 500, and XPS 700 — confirms that the board retains its dimensions and absorption class after repeated freeze–thaw cycling. This is particularly relevant for inverted roofs and sub-grade applications in frost climates.

Where a design requires verification of all three properties together — dimensional stability, creep, and freeze–thaw — a qualified structural or façade engineer should review the full DoP and TDS for the selected product.

Sources

EN 13164:2012+A1:2015 — Thermal insulation products for buildings — Factory made products of extruded polystyrene foam (XPS)
TDS pnp_xps300-300TB_600x1250_techcard_en(20.07.2026).pdf (updated 2026-07-22)
TDS pnp_xps300W-300WTB_600x1250_techcard_en(20.07.2026).pdf (updated 2026-07-22)
TDS pnp_xps500-500TB_600x1250_techcard_en(20.07.2026).pdf (updated 2026-07-22)
TDS pnp_xps700_600x1250_techcard_en (21.07.2023).pdf (updated 2025-03-17)
TDS pnp_xps150-150TB_600x1250_techcard_en(20.07.2026).pdf (updated 2026-07-22)
TDS pnp_xpsX-Grip_X-GripTB_600x1250_techcard_en(19.06.2026).pdf (updated 2026-07-22)
TDS pnp_xps200-200TB_600x1250_techcard_en(20.07.2026).pdf (updated 2026-07-22)
TDS pnp_xps200W-200WTB_600x1250_techcard_en(05.08.2025).pdf (updated 2026-07-22)
TDS pnp_xps400-400TB_600x1250_techcard_en(20.07.2026).pdf (updated 2026-07-22)
TDS pnp_xps150MG_600x1250_techcard_en (21.07.2023).pdf (updated 2025-03-17)
TDS pnp_xps200MG_600x1250_techcard_en (21.07.2023).pdf (updated 2025-03-17)
TDS pnp_xps300MG_600x1250_techcard_en (21.07.2023).pdf (updated 2025-03-17)
DoP PNP XPS 300 EMI_en (U).pdf (updated 2025-10-14)
DoP PNP XPS 500_en (U).pdf (updated 2025-07-22)
DoP PNP XPS 700_eng.pdf (updated 2025-03-17)

Frequently asked questions

What does DS(70,90) mean on a PNP XPS product label?

DS(70,90) is the EN 13164 dimensional stability class. It declares that the board was tested at 70 °C and 90 % relative humidity, and the measured linear dimensional change remained within the class limit. All published PNP XPS boards carry this class.

Does XPS absorb moisture and swell over time?

PNP XPS boards have a homogeneous closed-cell structure. Long-term water absorption by total immersion (WL(T)) is declared at ≤ 0.7 Vol.-% for smooth and waffled boards, and ≤ 3.0 Vol.-% for milled-and-grooved (MG) boards. The DS(70,90) class was achieved under high-humidity conditions, this supports confidence that in-service moisture exposure within the declared operating range does not cause significant dimensional change.

Can PNP XPS be used in underfloor heating assemblies?

PNP XPS boards are rated for continuous use up to +75 °C and carry compressive creep declarations (CC class) on the 300, 500, and 700 series, which supports use under heated screeds. The suitability of a specific board for a given underfloor heating design — including screed temperature, load, and thickness — requires verification by a qualified designer using the current TDS and DoP.

Is dimensional stability the same as compressive creep?

No. DS(70,90) measures in-plane (length and width) dimensional change under heat and humidity. Compressive creep (CC class) measures thickness reduction under a sustained compressive load over time. For structural floor and roof applications, both properties are relevant and are declared separately in the DoP.

Which PNP XPS products also carry a freeze–thaw declaration?

Freeze–thaw resistance (FTCD 1, ≤ 1 Vol.-%) is declared on XPS 200, XPS 200 MG, XPS 200 W, XPS 300, XPS 300 W, XPS 300 MG, XPS 500, and XPS 700. This is relevant for inverted roofs, sub-grade walls, and foundations in frost-prone climates where the board is exposed to repeated wetting and freezing cycles.

Where can I find the exact limit values for DS(70,90) for a specific product?

The precise numerical limit for the DS(70,90) class is defined in EN 13164:2012+A1:2015. The declared class for each product is listed in the current TDS and DoP, available at pnpinsulation.com/documentation/ or by contacting sales@pnpinsulation.com.