Calculator Inputs
Enter project conditions to estimate drying time, equilibrium moisture, and exposure risk for wood framing under site conditions.
Drying Trend Graph
The graph compares modeled moisture reduction against the requested target, estimated equilibrium moisture, and the 20% caution threshold.
Example Data Table
| Scenario | Initial MC | Target MC | Temperature | RH | Thickness | Estimated Days |
|---|---|---|---|---|---|---|
| Interior wall framing after delivery | 24% | 16% | 23°C | 50% | 38 mm | 18.0 |
| Roof truss members after light rain | 30% | 18% | 20°C | 65% | 89 mm | 49.0 |
| Open framed deck joists with airflow | 22% | 16% | 26°C | 45% | 38 mm | 11.5 |
| Dense framing in enclosed wet shell | 32% | 16% | 18°C | 78% | 89 mm | 82.0 |
Formula Used
EMC = clamp(2 + 0.18 × RH − 0.05 × (T − 20), 5, 22)
Daily Rate = clamp((0.45 × Temp Factor × RH Factor × Airflow Factor × Exposure Factor) ÷ Resistance Factor, 0.10, 2.50)
Resistance Factor = (Thickness ÷ 38) × Species Factor × Surface Factor × Wetting Factor
Climate-Limited Target = max(User Target, EMC + Safety Margin)
Drying Days = max(0, Initial MC − Climate-Limited Target) ÷ Daily Rate
This model is a field planning estimate. It does not replace meter readings, species-specific lab data, enclosure review, or professional judgment.
How to Use This Calculator
- Enter the wood member’s starting moisture content.
- Set the desired target moisture content for your project stage.
- Input air temperature, relative humidity, and local air velocity.
- Select thickness and adjustment factors that match site conditions.
- Choose a safety margin if finishes require drier framing.
- Click the calculate button to view drying time and risk.
- Review the graph, interpretation notes, and climate-limited target.
- Download the summary as CSV or PDF if needed.
FAQs
1) What does this calculator estimate?
It estimates how quickly wood framing may dry under the entered site conditions. It also shows an equilibrium moisture estimate, a climate-limited target, and a drying risk score for planning work sequencing.
2) Why can the climate-limited target be higher than my target?
Wood generally will not dry below the surrounding equilibrium level unless site conditions improve. If humidity remains high, the model raises the practical target to reflect likely field behavior.
3) How should I choose the species factor?
Use lower values for faster-drying softwoods and higher values for denser or slower-drying stock. If you are unsure, the typical framing lumber option is a reasonable starting assumption.
4) Does thickness really change drying time that much?
Yes. Thicker members usually dry more slowly because moisture travels farther to the surface. The model increases resistance as thickness rises, which lengthens the estimated drying period.
5) Why is 20% moisture highlighted on the graph?
Many field teams track 20% moisture as a practical caution point. Remaining above that level can increase mold exposure, delay finishes, and raise the need for closer monitoring.
6) Should I rely on this estimate for final signoff?
No. Use it for planning, not final acceptance. Final decisions should be based on calibrated moisture meter readings, project specifications, enclosure status, and the judgment of qualified professionals.
7) What increases drying speed the most?
Lower humidity, better airflow, warmer air, thinner members, and fewer blocked surfaces usually help most. Preventing repeated wetting is also important because rewetting can erase earlier drying progress.
8) Why include a safety margin above EMC?
The margin gives a more conservative planning target. It helps teams avoid scheduling finishes too close to the equilibrium level when daily weather swings or short wetting events could reverse progress.