Humidity Problem in the Under Home Space

Humidity problems in the under-home space, whether it's a crawl space, basement, or subfloor area, can lead to serious issues like:

Mold and mildew

Wood rot or termite infestation

Musty odors rising into the home

Damaged insulation or rusted ducts

Higher indoor humidity levels

Controlling indoor humidity in an ideal range is important for people who live or work in the area.

 

Signs You Have a Humidity Problem

Symptom:	What It Indicates:
Musty smell inside the home	Mold/mildew in the crawl space
Visible mold on floor joists	High humidity or poor air circulation
Condensation on ducts/pipes	Humid air + cool surfaces = condensation
Buckled flooring above	Moisture rising into the subfloor
High indoor humidity (over 60%)	Crawl/basement air affecting the house

 

Target Humidity Levels

Ideal RH for under-home areas: 45% to 55% RH

Above 60% RH = mold risk

Above 70% RH = high risk for rot, pests, poor air quality

 

Dehumidification Solutions Based on Problem Severity

1. Mild Humidity / Seasonal Moisture

Install a vapor barrier (6–20 mil plastic sheeting) over the soil or floor.

Ensure vents are unblocked (for ventilated crawl spaces).

Seal gaps in foundation walls or access doors.

Add a humidity sensor (hygrometer) to monitor changes.

 

 2. Moderate to High Humidity

Use an under home dehumidifier (70-150 pints/day) with:

Continuous drainage hose to sump pit or outside

Auto-humidistat

Built for low-clearance spaces

Recommended Units:

Preair HD70 (70 PPD/ducted/direct drainage)

Preair HD103 (103 PPD/ducted/direct drainage)

Preair WH70 (70 PPD/MERV8/remote control)

Preair WH95 (95 PPD/MERV8/remote control)

Preair WH103 (103 PPD/MERV8/remote control)

Home dehumidifiers often don't work well in unconditioned, cooler spaces.

 

3. Severe Humidity or Mold, or Standing Water

Add a sump pump if water collects on the ground.

Fully encapsulate the crawl space:

Seal vents, insulate walls, and install a heavy-duty vapor barrier

Use a permanent dehumidifier with drainage

Consider a French drain or external grading fix to move water away from the foundation.

 

Smart Approaches to Humidity Control

Solution:	Benefit:
Smart Wi-Fi humidity sensor	Get alerts on your phone
Ducted dehumidifier setup	Can dry both the crawl space & the inside home
Insulate pipes/ducts	Prevents condensation in humid air
Add an exhaust fan (optional)	Helps exchange stale air (vented spaces)

 

Maintenance Tips for Dehumidification Equipment

Users need to check dehumidifier filters every 2–3 months.

Users need to clean the vapor barrier surface yearly (if accessible).

Users need to monitor humidity in both the crawl space AND inside the home.

It is better to watch for seasonal spikes (rainy season, monsoon, snowmelt).