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Furnace Mold & Moisture Issues

Project Report > Inspection for Mold in HVAC System

Crawlspace - no ducts

Reason for inspection:

  • The client has noted condensation and minor mold growth around windows and doors in the home.

Summary of concerns:

  • Inadequate ventilation has led to the buildup of excess occupant generated moisture and subsequent condensation-based mold growth.


Imporper Ducting

  • The home is heated primarily by a ductless heat pump.
  • No system for whole-house ventilation or fresh-air intake has been installed in the home.
  • Inadequate ventilation has caused the buildup of moisture and subsequent condensation-based damage.
  • To achieve the recommended air exchange rate it is necessary to move 37-75CFM constant air exchange.
  • Options for improving ventilation:


  1. Set existing fan in bathroom to run for 4 hours per day.
  2. Install a ducted Heat Recovery Ventilator in the hall closet with all ducting passing through the attic space and all registers mounted in the ceiling.  The appropriate model for this application is the Venmar Constructo 1.0.

Project Report > Mold Inspection for HVAC System

Work #: 106003

Furnace / HVAC

  • Homes must have special care taken to ensure appropriate ventilation, and prevent the buildup of humidity and other pollutants.
  • Current standards recommend 0.35 to 0.7 air changes per hour, this may be attained by installation of a ducted heat recovery ventilator or upgrading mechanical exhaust ventilation to function on a continuous flow (the recommended units for this method is a Panasonic Whisper Green exhaust fan).
  • The estimated square footage of this home is 1,164.ft.
  • The necessary flow rate to establish 0.35-0.7 ACH for this home is 61-122CFM. 


  • Cavity under jetted tub shows obvious signs of water intrusion.
  • Obvious significant mold growth noted on sheetrock along exterior wall in jetted tub cavity.
  • Increased moisture content noted in accessible portions of contaminated sheetrock.
  • Tub surround is composed of slab granite.
  • No access to affected sheetrock is possible without removal of jetted tub.
  • Home owner reports that the water intrusion is due to a leaking exterior planter.
  • RH: 58.5%     Temp: 67.6F     CO2 = 773ppm     CO = 0ppm

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