Are your windows trying to tell you something?
Have you noticed condensation on your windows lately? What does this mean? If you see condensation, you likely have high humidity levels in your home. Condensation can accumulate particularly in the kitchen, laundry room, bathrooms, or in bedrooms with adjoining bathroom. The cause? Insufficient ventilation. It’s important to address high humidity or those subtle warning signs of condensation can turn into expensive repairs. Condensation can damage windowsills and framing, while indoor humidity can create mold patches on ceilings and walls and eventually penetrate the sheetrock, deteriorating wood framing and reducing the effectiveness and integrity of insulation.
The major sources of humidity in a home include cooking, dishwashers, clothes dryers, and bathing. Let’s look at three important ways to control these sources.
Kitchens exhaust fans
Check to see if your kitchen vent fan is actually a vent fan. If you see a metal duct running up and out through the wall above the stove, your fan is vented to the outdoors. This is good. If there is no metal duct, chances are you have a circulation fan, which does absolutely nothing for removing contaminants and moisture created by cooking and washing dishes. Install a proper vent fan that ducts to the outdoors with a hard metal duct.
Dryer exhaust vents
A full load of laundry can contain as much as 5 pounds of water after the wash cycle, or about 0.6 gallons. Leaky dryer vents will dump that hot humid air right into your house. Check to see that the ductwork is tightly sealed. And, since we are on the topic of dryer exhaust vents, be sure to clean the exhaust port on the exterior of the house regularly to prevent lint fires.
Bathroom exhaust fans
During our Whole-Home Assessments, we check the flow rate of bathroom fans and often measure flows of 20-30 cubic feet per minute (CFM). (For reference, one CFM is about the volume of a basketball.) We find that this is insufficient to properly ventilate and manage moisture. We prefer to see flow rates between 50-60 CFM, which ENERGY STAR uses as their benchmark.
What affects bathroom exhaust flow rate?
- Quality of the fan: Some fans simply don’t pull enough air. Be sure to check the rated flow rate before purchasing. You’ll want to select a fan with a 50 CMF rating at least. E3 recommends the Panasonic Whisper Green Select ventilation fan, which allows users to customizes and automate the controls. This fan has three flow rate settings (50, 80, and 110 CMF) and can automatically turn on when it senses occupancy or humidity.
- Ducting: Hard metal piping is the best option because its smooth surface reduces turbulence created with flexible ductwork. Turbulent flow will decrease the flow rate of the fan.
- Duct design: Air moves easily when the ductwork is straight, so avoid sharp angles and bends. A straight run from the fan to the roof is optimal.
- Dirty fan grates: We recommend removing the dust and lint from the fan grate periodically to ensure maximized airflow.
Now, before you install a new kitchen exhaust and a couple new bathroom fans, call us first! If you suddenly add 300+ CMF of ventilation without first determining the leakiness of the building shell, you could introduce a lot of unwanted unconditioned outdoor air, which can increase energy use and introduce unwanted air pollutants (and humidity in the summer). It is important to address air-leakage, if it is indeed an issue, before installing additional ventilation.
Call E3 INNOVATE to get the scoop on how your house is performing. Our team of experts will complete a Whole-Home Assessment – which includes testing fan flow rates and building leakage rates – and provide you with a report of findings, photo documentation, and a customized set of recommendations. Learn more about our Whole-Home Assessments here.