Condensation
Modern energy-efficient homes are built to be more airtight than homes built even 10 years ago. While this seals in heating and cooling, it also seals in moisture-laden air. Understanding and managing indoor humidity prevents condensation problems.
Condensation on interior window surfaces indicates high indoor humidity, not a window defect. Condensation between window panes (inside the sealed unit) is different and may indicate a broken seal.
How It Works
Condensation forms when warm, moist air contacts cooler surfaces:
- Warm air holds more moisture than cool air
- When air cools (like touching a window), it releases moisture
- Moisture condenses as water droplets on the surface
Outside, we see this as dew. Inside, you may see it as moisture on windows and glass doors, especially during cold weather.
Sources of Indoor Moisture
New construction moisture:
- A typical new home contains approximately 50 gallons of water in materials
- Water is part of lumber, concrete, drywall texture, paint, and caulk
- This moisture evaporates into the air over time
- First-year condensation is common and typically decreases
Daily activities that add moisture:
- Cooking (especially boiling water)
- Laundry
- Baths and showers
- Aquariums
- House plants
- Breathing and perspiration
Routine Maintenance
| Task | Frequency | Time Required |
|---|---|---|
| Run exhaust fans during/after showers | Every use | Duration of activity + 15 min |
| Run kitchen hood when cooking | Every use | Duration of cooking |
| Check dryer vent connection | Seasonally | 5 minutes |
| Monitor humidifier settings | During heating season | Ongoing |
| Air out home | When weather permits | 15 to 30 minutes |
Reducing Indoor Humidity
Use exhaust fans:
- Run bathroom fans during and after showers
- Run kitchen hood when cooking, especially boiling water
- Let fans run 15 to 20 minutes after activity ends
Check dryer vent:
- Ensure it's connected and venting outside
- Clean lint from hose periodically
- Verify damper opens when dryer runs
Humidifier operation:
- Use low to moderate settings in winter
- Lower setting or turn off if condensation appears
- In extreme cold, you may need to turn it off completely
Open windows:
- When weather permits, air out the home briefly
- Fresh air circulation reduces indoor humidity
Troubleshooting
Seeing Condensation? Check This First
- Check your humidifier - Lower the setting or turn it off
- Use exhaust fans - Run bathroom fans during and after showers
- Run kitchen hood - Use when cooking, especially boiling water
- Check dryer vent - Ensure it's connected and venting outside
- Open windows briefly - When weather permits, air out the home
Common Condensation Locations
| Location | Cause | Solution |
|---|---|---|
| Windows | High humidity, cold glass | Reduce humidity, improve air circulation |
| Mirrors | Bathroom humidity | Run exhaust fan longer |
| Exterior walls | Temperature differential | Improve insulation or air flow |
| Closets on exterior walls | Poor air circulation | Leave doors open periodically |
| Behind furniture on exterior walls | Blocked air circulation | Move furniture away from walls |
Window Condensation vs. Seal Failure
Surface condensation (humidity issue):
- Moisture on the interior surface of the glass
- Wiped away easily
- Varies with humidity and temperature
- Not a defect
Between-pane condensation (seal failure):
- Moisture trapped between glass panes
- Cannot be wiped away
- Indicates broken thermal seal
- Covered under warranty for 1 year
What to Avoid
- Don't set thermostat to extreme temperatures - Causes materials to dry too fast, increasing moisture release and shrinkage
- Don't block ventilation - Keep exhaust fans functional and use them
- Don't ignore condensation - Persistent moisture can lead to mold and damage
- Don't over-humidify - If condensation appears, reduce humidifier setting
- Don't seal the home completely - Some fresh air exchange is healthy
Temperature Settings
Avoid setting your thermostat at extreme temperatures:
- Heating your home causes materials to dry out faster, generating more moisture into the air
- Drying materials out too fast increases shrinkage cracks and separations
- Moderate, consistent temperatures help minimize both condensation and material movement
Humidifier Guidelines
If you install a humidifier, closely observe the manufacturer's directions:
- Use low to moderate settings in winter
- Experiment to find the right level for your family's lifestyle
- In periods of extreme cold, you may need to turn the humidifier off
- If condensation develops on windows, lower the setting
Classic Homes does not install humidifiers and is not responsible for damages due to installation or improper usage.
Related Topics
- Air Conditioning - HVAC and humidity control
- Caulking - Preventing moisture infiltration
- Carpet - Humidity effects on flooring
- Cabinets - Humidity effects on wood
Warranty Coverage: See Condensation Standards for coverage details. Condensation is a lifestyle and weather issue, not covered under warranty.