Okay, you've got a classic condensation and mold situation, and you're right to address it before installing the new vent hood. Here's a breakdown of what's likely happening and how to tackle it

Understanding the Problem
Condensation is Key

You're correct. The "grease" is almost certainly condensation. Hot, humid air from outside entering a cooler vent (cooled by your AC) will cause water to condense.

Mold Loves Dampness

Add organic material (dust, grease residue), darkness, and time, and you've got the perfect breeding ground for mold.

Taping Made it Worse

The tape likely sealed the vent opening well enough to trap the humid air and slow down evaporation, exacerbating the condensation and mold growth.

Immediate Actions & Safety Protective Gear

Before you do anything with the moldy area, wear a mask (N-95 or better), gloves, and eye protection. Mold spores can be irritating and harmful.

Isolate the Area

If possible, seal off the kitchen area from the rest of the house with plastic sheeting and tape to prevent spores from spreading during cleaning.

Stop the Source

Remove the wet paper towels and dispose of them in a sealed bag.

Cleaning Up (or Determining if you need a professional)1. Assess the Extent of the Mold

How far has the mold spread? Is it just on the surface, or does it appear to have penetrated the wallboard (drywall)? If it's extensive or seems deep within the wall, consider calling a mold remediation specialist.2.

If you decide to clean it up yourself (for small surface areas only)



Mold Removal Solution

Mix a solution of either: 1 part bleach to 10 parts water. (Open windows and use a fan when using bleach) OR a mold-killing cleaner specifically designed for porous surfaces (available at hardware stores).

Scrub Gently

Use a sponge or brush to gently scrub the affected area. Avoid aggressive scrubbing, which can spread spores.

Dry Thoroughly

Once cleaned, thoroughly dry the area with a clean cloth and a fan. Moisture is mold's best friend.

Monitor

Keep an eye on the area for a few days to see if the mold returns.

Preventing Future Condensation and Mold

This is the most important part! Here's a multi-pronged approach:1. Seal the Exterior Vent

This is crucial.

Inspect the Flapper/Damper

The exterior vent hood should have a damper (a flap) that closes when the fan is off. Make sure it's in good working order, seals properly, and isn't damaged.

Seal Around the Vent

Use exterior-grade caulk to seal around the perimeter of the vent where it meets the exterior wall. This prevents air infiltration.

Consider an Insulated Vent Cap

Some vent caps are insulated, which can further reduce condensation.2.

Address the Interior Vent Opening



Install the New Vent Hood Promptly

The new hood will help direct airflow and reduce the chance of condensation.

Proper Ducting

Ensure the ductwork connecting the hood to the exterior vent is properly installed, insulated (especially in unconditioned spaces like attics or crawl spaces), and sealed to prevent leaks. Use foil tape, not duct tape, to seal duct joints.

Backdraft Damper

Most vent hoods have a built-in backdraft damper, but it's wise to double-check.3.

Ventilation Practices



Use the Vent Hood

Run the vent hood whenever you're cooking, especially when boiling water or doing anything that creates a lot of steam.

Run it for a few minutes after cooking

This helps to remove residual moisture and odors.

Who to Call



HVAC Technician

An HVAC tech is a good choice to inspect your entire ventilation system, especially the ductwork. They can ensure it's properly sized, insulated, and sealed. They can also help diagnose any underlying issues with airflow or moisture control.

Mold Remediation Specialist

If the mold is extensive or you're uncomfortable dealing with it yourself, a mold remediation specialist can properly assess the problem and remove the mold safely and effectively.

Handyman/General Contractor

For smaller tasks like sealing the exterior vent or installing a backdraft damper, a handyman or general contractor may be sufficient.

Important Considerations



Local Codes

Check your local building codes regarding kitchen ventilation. There may be specific requirements for duct size, vent type, etc.*

Duct Length and Bends

Long duct runs and sharp bends can reduce the effectiveness of your vent hood. Minimize these if possible.

In summary: Focus on sealing the exterior vent, properly installing and maintaining your vent hood, and ensuring good ventilation practices. If you're unsure about any of these steps, don't hesitate to consult with a qualified professional. Good luck! Flag for review