WallDew: Wall Dew Point Check
Stack your wall layers, see where condensation forms inside — before you build.
Download on the App StoreFeatures
Layer-by-layer wall builder
Add plasterboard, insulation, plywood, cladding and more from 32 built-in materials, in the order they sit in your wall.
Temperature and dew point overlay
See the temperature gradient and dew point line drawn across the wall cross-section as you build it.
Interstitial condensation, highlighted
The layer where the dew point line crosses the temperature line is marked in red, so you can see exactly where moisture would condense.
U-value and R-value, calculated automatically
No manual formulas. Stack the layers and the thermal values update instantly.
Reverse-calculated fix estimate
If condensation shows up, WallDew estimates how many extra millimetres of outer insulation would move the crossing point away — shown as a starting estimate, not a guarantee.
No account, no ads, no network
One-time purchase. Every calculation runs on your device. Nothing is sent anywhere.
Will this wall condense inside? WallDew overlays temperature and dew point on a cross-section of your wall, layer by layer — and turns the crossing layer red.
U-value and R-value are calculated automatically as you stack materials. No separate formula to look up.
If a layer crosses the dew point, WallDew works backward to estimate how many more millimetres of outer insulation would clear it.
Most U-value calculators stop at the number. WallDew goes one step further and shows where inside the wall the risk actually sits.
WHAT IT DOES
• Build a wall from the inside out: plasterboard, insulation, sheathing, cladding — any order, any thickness
• See temperature and dew point curves drawn across the section; the layer where they cross is highlighted
• U-value and R-value update instantly as you edit
• Get a reverse-calculated estimate: how much more insulation on the outside would remove the crossing
• Pick from 30+ built-in materials with thermal conductivity (λ) values, or enter your own measured value
• Save multiple wall assemblies, duplicate one and change only the thickness to compare options
• Switch between SI and Imperial units
WHAT IT DOESN'T DO
WallDew is an estimation tool for a single, one-dimensional steady-state calculation. It does not model thermal bridges (studs, beams, fasteners), airtightness, ventilation, or moisture from rain. It does not certify against any national building code. Real-world condensation often starts at a thermal bridge before it starts within a layer, and actual behavior can differ from this estimate.
This app does not replace a qualified architect, engineer, or building professional. Always consult one for actual design and construction decisions. The developer is not responsible for outcomes based on the app's estimates.
No account, no ads, no network access — everything runs and stays on your device. One-time purchase.