EN 15026 Benchmark Test Report

Software Version: Better Building with EnergyPlus v25.1 I Date of Testing: xxxx - 1xxxx I Report Version: 1.0 I Prepared by Darren 'Dea

1. Purpose

This report documents the results of running the EN 15026 benchmark test against [Software Name]. The benchmark verifies that the software correctly simulates coupled heat and moisture transport in a semi-infinite homogeneous specimen subjected to a step change in boundary conditions. Pass criteria: simulated temperature and moisture profiles at 7, 30, and 365 days must not deviate from the EN 15026 analytical reference solution by more than 2.5%.

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2. Test Scenario Summary

The benchmark simulates a specimen initially in equilibrium with a constant climate, then exposed to a sudden step change:

Parameter	Initial Condition	Boundary Condition (t > 0)
Temperature	20°C	30°C
Relative Humidity	50%	95%

The specimen is treated as semi-infinite and homogeneous. No surface transfer resistances are applied at the exposed (left) surface. The right surface is assumed at infinite distance from the boundary. Profiles are evaluated at t = 7 days, t = 30 days, and t = 365 days.

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3. Material Properties Used

This section records how the EN 15026 benchmark material was defined within [Software Name]. Note any conversions or approximations required to express the standard's analytical functions in the format the software accepts.

3.1 Basic Properties

Property	EN 15026 Specification	Value Entered	Notes
Volumetric heat capacity (ρ₀·c₀)	1.824 × 10⁶ J/m³K
Bulk density (ρ₀)	Derived	kg/m³	Arbitrary factoring of ρ₀·c₀
Specific heat capacity (c₀)	Derived	J/(kg·K)
Porosity	0.146		Based on u_f = 146 kg/m³

3.2 Thermal Conductivity

Thermal conductivity varies linearly with water content: λ = 1.5 + (15.8/1000)·w

Water Content (kg/m³)	λ (W/mK)	Notes
0	1.5
146	3.8068

Interpolation method used: [Linear / Other — specify if other]

Conversion notes: [Describe any adjustments needed for software input format]

3.3 Moisture Storage Function

The EN 15026 moisture storage function (as a function of relative humidity at T = 293.15 K):

$$w = \frac{146}{\left(1 + \left(-8 \cdot 10^{-8} \cdot R_{H_2O} \cdot T \cdot \rho_w \cdot \ln(\varphi)\right)^{1.6}\right)^{0.375}}$$

RH (–)	w (kg/m³)	RH (–)	w (kg/m³)
[value]	[value]	[value]	[value]

(Reproduce the tabulation used as software input. Sufficient points must be included to keep tabulation error below an acceptable threshold, particularly in the 50–95% RH range relevant to this benchmark.)

Maximum tabulation error (full range): [value] kg/m³ Maximum tabulation error (50–95% RH): [value] kg/m³

3.4 Vapour Diffusion Resistance Factor (µ)

The EN 15026 standard specifies δ_p directly. Conversion to µ was performed using representative conditions of ϑ = 25°C and P = 101,325 Pa:

$$\mu = \frac{1.968 \cdot 10^{-7} \cdot (25 + 273)^{0.81}}{101325 \cdot \delta_p}$$

Tabulation was limited to the 0–95% RH range (µ → ∞ at free saturation; humidities above 95% do not occur in this benchmark).

RH (–)	µ (–)	RH (–)	µ (–)
[value]	[value]	[value]	[value]

Maximum relative tabulation error (0–95% RH): [value] %

Conversion notes: [Describe how the software handles δ vs. µ vs. δ_p, and any residual discrepancy between the software's internal δ_p evaluation and the standard's specification]

3.5 Liquid Transport Coefficient (D_w)

The EN 15026 liquid conductivity K(w) was converted to D_w via:

$$D_w = -K \cdot \frac{\partial p_{suc}}{\partial w}$$

If the software applies a viscosity correction factor (temperature-dependent liquid transport), the input values must be pre-divided by the correction factor applicable at the dominant transport temperature. For this benchmark, the dominant temperature is 30°C.

Correction applied	[Yes / No]
Viscosity correction factor at 30°C	[value, expected ~1.26]
Input values pre-divided by correction factor	[Yes / No]

Tabulation was limited to the moisture range 40–130 kg/m³ (corresponding to 50–95% RH).

w (kg/m³)	D_w (m²/s)	w (kg/m³)	D_w (m²/s)
[value]	[value]	[value]	[value]

Maximum relative tabulation error of log(D_w) (40–130 kg/m³): [value] %

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4. Model Configuration

4.1 Initial Conditions

Parameter	Value
Initial temperature (uniform)	20°C
Initial relative humidity (uniform)	50%

4.2 Boundary Conditions

Surface	Heat Transfer Resistance	Vapour Resistance (s_d)	T (°C)	RH (%)
Left (exposed)	0 m²K/W	0 m	30	95
Right (far field)	[high value]	[high value]	—	—

Boundary conditions are constant throughout the calculation period (step change applied at t = 0).

4.3 Geometry and Numerical Grid

Parameter	Value	Notes
Component thickness	[value] m	Must be sufficient that right surface is unaffected
Temperature rise at right surface (365 days)	[value] °C	Should be negligible
Moisture penetration depth (365 days)	[value] m	Expected ~0.2 m
Total grid elements	[value]
Grid refinement strategy	[description]	Fine grid near exposed surface; coarse toward far field

(Describe sub-grid regions, element counts, and expansion factors if applicable.)

4.4 Calculation Period

Parameter	Value
Start date	[DD.MM.YYYY]
End date	[DD.MM.YYYY] (at least 365 days after start)
Profile output dates	Day 7, Day 30, Day 365
Time step	[value] h

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5. Results

5.1 Moisture Profiles

Comparison of simulated water content w(x) against EN 15026 analytical reference at t = 7, 30, and 365 days.

[Insert Figure: Moisture distribution at 7, 30, and 365 days. Plot both simulated and reference curves. Include the ±2.5% permissible error band.]

Time	Max. deviation from reference	Pass / Fail
7 days	[value] %
30 days	[value] %
365 days	[value] %

5.2 Temperature Profiles

Comparison of simulated temperature T(x) against EN 15026 analytical reference at t = 7, 30, and 365 days.

[Insert Figure: Temperature distribution at 7, 30, and 365 days. Plot both simulated and reference curves. Include the ±2.5% permissible error band.]

Time	Max. deviation from reference	Pass / Fail
7 days	[value] %
30 days	[value] %
365 days	[value] %

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6. Deviations and Known Limitations

This section documents any systematic differences between the software's internal transport model and the exact formulation used by EN 15026. These are not errors; they are model characteristics that affect how the benchmark material properties must be prepared.

Issue	EN 15026 Assumption	Software Behaviour	Workaround Applied
Temperature dependence of liquid transport	Temperature-independent K(w)	Automatic viscosity correction applied	Pre-divide D_w by correction factor
δ_p formulation	Explicit δ_p(w) function	Internal µ-based model, auto-computes δ	Convert δ_p → µ at representative T and P
Moisture storage function	Temperature-dependent (T in formula)	Temperature-independent	Use reference T = 293.15 K as fixed value
[Other software-specific issue]	[Standard assumption]	[Software behaviour]	[Action taken]

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7. Overall Compliance

Criterion	Result
All moisture profiles within 2.5% of reference	[Pass / Fail]
All temperature profiles within 2.5% of reference	[Pass / Fail]
General requirements of EN 15026 met	[Pass / Fail]

Overall verdict: [PASS / FAIL]

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8. Notes and Observations

Use this section for anything worth flagging: numerical instabilities observed during testing, sensitivity to grid refinement, tabulation resolution effects, or anything that required more than one attempt to get right (there's usually something).

[Free text]

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9. Document Control

Revision History:

Version	Date	Author	Changes
1.0	xxxxx	DOD	Initial release

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Appendix A: Material Property Tables (Full Tabulations)

Reproduce the complete input tables used for moisture storage function, µ-value, and D_w as submitted to the software.

A.1 Moisture Storage Function Table

RH (–)	w (kg/m³)

A.2 µ-Value Table

RH (–)	µ (–)

A.3 Liquid Transport Coefficient Table

w (kg/m³)	D_w (m²/s)