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Q & A with Anthony DeMiglio, President at AMD Environmental Consultants: How Do Ventilation Imbalances Cause Moisture Imbalances?

Q & A with Anthony DeMiglio, President at AMD Environmental Consultants: How Do Ventilation Imbalances Cause Moisture Imbalances?

AMD Environmental professionals encounter many problems in homes caused by ventilation imbalances.

A question that is often asked is:

How do ventilation imbalances cause moisture problems?

Anthony DeMiglio, President at AMD Environmental, answers questions about proper ventilation and moisture control.

Q: What are ventilation imbalances?

A: Ventilation imbalances have the potential to create a lot of problems in your home. This means the air pressure in the house is not evenly distributed, temperatures vary from room to room, or moisture is evident.

We see this mainly when people renovate homes older than 30 years old. The energy efficiency of materials and building products has changed, but the home’s structure may not be able to handle energy-efficient upgrades without accounting for proper ventilation. On the one hand, you are increasing the efficiency of your home and potentially saving money. On the other hand, this could create problems with moisture – ultimately leading to mold growth.


Q: When are ventilation imbalances caused?

A: We typically see ventilation imbalances after people renovate older homes, particularly when making the house more energy efficient. This includes installing a new furnace, new windows, or a change to the roof ventilation. These energy-efficient upgrades can change the pressure and relative humidity inside a home, increasing moisture or the potential for moisture buildup.

Q: Will installing a gas fireplace affect the moisture in my home?

A: Yes. A gas fireplace releases a lot of moisture and increases the relative humidity inside a home. Wall units especially kick out a lot of moisture, trapping the moist air inside the house. Proper ventilation needs to be accounted for to avoid giving mold opportunities to grow.

Q: How do energy-efficient upgrades cause ventilation imbalances?

A: Older homes, in particular, are not airtight. Houses let air stack through the roof from the basement. Moisture may not have been a concern because of a drafty roof, cracks, or openings in older windows or doors. Once you change the structure to be airtight, the moisture cannot dissipate or escape as it once did. This is when homeowners start seeing an increase in relative humidity with possible mold growth or unusual odors.

Q: How will I know if moisture is a problem in my home?

A: Some problems are easier to detect than others. For example, if you have new windows installed without considering other ventilation measures, you may see “sweaty windows.” The relative humidity increases in a home, causing condensation inside the windows. This is because moisture can’t leave the house as it once did.

Moisture problems may also present themselves in the form of “ghosting.” This occurs when an unvented gas fireplace (wall unit) kicks out carbon, staining your walls black.

Bathrooms are another source of moisture if not adequately ventilated. Since bathrooms are the wettest spaces in the home, you will want to ensure your fan is relative to the bathroom’s square footage and adequately vented to the roof. An easy way to fully air out the space is to run the vent for about 20 minutes after a shower. If you are one of those people who shower and jet out the door, consider a fan with an automatic humidity sensor or an adjustable timer. The convenience is that the fan automatically kicks on and off when the humidity levels are too high.

Q: What can I do to prevent ventilation imbalances?

A: The first thing you should do is be aware of the problems that can occur before renovating an older home. If you renovate a space or install new windows, contact a roofer or contractor to see how you can increase venting in the attic based on cubic footing.

Q: Can I build a house that is “too tight?” 

A: People ask this question a lot! The answer is no. Tight is good, but underventilated is terrible! Tight construction can reduce a significant issue called ice dams. Ice damming occurs when hot air moves into the attic, and the house can’t get rid of the heat. The ice builds up on the eave of a slanted roof because the snow underneath melts. The meltwater flows down the roof until it reaches a point where there is no longer heat from the inside. The meltwater freezes and forms a dam. This can cause structural damage to the roof and leak inside the house. So sealing up air leaks into the attic is an excellent way to prevent ice dams from building up. Remember, tight is good – underventilated is bad.

Q: How can AMD Environmental Consultants help me with ventilation imbalances in my home?

AMD Environmental Consultants has been advising homeowners for over twenty years. Collectively, our experts have decades of experience dealing with structural issues, ventilation imbalances, and other factors contributing to toxic mold growth. Contact (716) 833-0043, follow us on Facebook and LinkedIn or visit