When we think of remodeling, building or home improvement, ventilation is probably not the first thought that comes to mind. In fact, for most of us it’s probably an after-thought. Who hasn’t had less than pleasant experiences with noisy, inefficient bath fans and range hoods which have relegated ventilation to the bottom of the priority list? However, proper ventilation is very important for our health and for our homes.
Why, you may ask, is ventilation so important? The first consideration is health. The interiors of our homes are full of pollutants that can cause health problems. Biological pollutants include mold, mildew, pollen, dust mites, pet dander, viruses and bacteria. Chemical pollutants emanate from carpets and furniture in the form of formaldehyde
and Volatile Organic Compounds (VOCs). VOCs are also emitted from paints, lacquers, household cleaning products and solvents, hair sprays, pesticides, etc. The second consideration is the soundness of our homes. Mold and mildew, which build up in bathrooms, laundry rooms and kitchens silently and invisibly compromise the structural integrity of our homes, causing wood rot and ruined insulation. Running a bathroom exhaust fan long enough to clear that foggy mirror isn’t nearly long enough to rid the room of damaging moisture.
We need effective, properly sized and installed ventilation in our homes. Mechanical ventilation is used to remove stale, moist, polluted air and replace it with fresh outside air. There are two types of ventilation: continuous and intermittent.
Continuous ventilation is a whole-house system connected to the primary duct work using either a Heat Recovery Ventilator (HRV) or an Energy Recovery Ventilator (ERV). HRVs reclaim energy from exhausted stale indoor air to temper incoming fresh air. Heat is retained during cool seasons and removed during warm seasons. ERVs do the same thing as HRVs, but with the addition of humidity control. They are not humidifiers, but they add humidity to the home in the dry, winter months, and remove it in the warm, humid months. If you’re building a home, take to heart the industry adage: “Build tight, ventilate right!” You should most certainly include whole-house, continuous ventilation. You should also consider a whole-house HEPA filtration system, especially if there are family members who are asthmatic or sensitive to allergens. If you’d like to add continuous ventilation in an existing home, take heart: as I learned while attending the recent International Builders’ Show, there are good, easy and affordable options for adding
Intermittent ventilation is also referred to as “spot” or local ventilation which captures and removes pollutants quickly at the source. The obvious areas are bathrooms and kitchens where excessive moisture and pollutants build up. Other areas are laundry rooms and utility rooms. And a special note on garages: if you have an attached garage, strongly consider adding an exhaust fan to remove gas fumes emitted when you drive in or out. Choose one which either runs continuously or one with a motion sensor that will run for a set period of time depending upon the size of the space. Intermittent ventilation in all these areas of concentrated pollution is essential and effective in maintaining good indoor air quality.
Size the ventilation appropriately
This is not as simple a task as you may think. Intermittent exhaust fans and range hoods have a CFM rating right on the package. This means the Cubic Feet per Minute as a measurement of air flow rate. If you buy an 80CFM fan, that tells you the fan will move 80 cubic feet of air per minute. Then you have to know how many air changes per hour (ACH) you need to properly ventilate the room. The Home Ventilating Institute (HVI) recommends the following:
Bathrooms – 8 ACH or 1 CFM/sq ft
Kitchens – 15 ACH, or 2 CFM/sq fit
Other Rooms – 6 ACH or .75 CFM/sq ft
So, if your bathroom is 80 square feet, an 80CFM fan would be appropriate. Easy, right? Except for one other thing: the ducting. The ability of the 80CFM fan to actually achieve that rate of air flow will be diminished by the resistance to that air by the grille, the duct length, whether there are elbows, and the diameter of the ducting. This resistance is called static pressure. Fortunately, the ventilation industry has formulas for figuring this out so that we homeowners don’t have to study up on the physics of air flow. The caution here is to be aware of all these factors so that you choose the appropriately-sized fan for the room, both in its size and function.
Choose a quiet fan and let it run!
I’ll bet just about every one of us has turned off a bathroom exhaust fan because it’s so darned noisy! Or not used the range hood exhaust because we can’t have a conversation in the kitchen with it on. Really quiet fans are going to cost a bit more, but there’s no point in having an exhaust fan if it annoys you too much to run it! Look for the “sones”, the measurement of sound output. The smaller the number, the more quiet the fan. According to HVI, one sone is equivalent to the sound of a quiet refrigerator. At the trade show I just attended, I saw the Broan/NuTone Ultra Series ventilation fans. They are great for retro-fits and they operate at less than .3 sones. That’s less than 1/3 of a sone. It was barely audible!
Now that you have a quiet fan, you need to run it! The best fan you can buy for bathrooms is one with a humidity sensor. Quality fans are very sensitive and will continue to run as long as there is any moisture in the air. You can shower, dress, have breakfast and leave the house and your fan will run until the bathroom is dry. Really dry, which is what is necessary. Another option is to install a motion sensor or a push-button timer which allows the fan to run for a pre-set amount of time depending upon the use and size of the room (see HVI guidelines above). The important consideration is fresh air and dry surfaces.
In-line ventilation fans are very effective and easy to install. You’ll need access to the duct in an attic or basement. The benefit is that you can install a powerful fan which is remote so there is virtually no sound.
Most attics get very hot in the summer and very cold in the winter. This has an impact on your energy bills because that air will seep into the house and create additional strain on heating and cooling systems. Insulating the attic floor is a smart thing to do. Ventilating the attic is too because it protects the structure and reduces energy costs. And one of the smartest, no-brainer solutions I’ve ever seen is a solar-powered attic ventilation system! Talk about a “green solution” to a common problem!! It removes heat during the hot summer months and removes moisture that can cause mold and mildew in the winter. Obviously, it runs at peak efficiency when the sun is shining, but it will run on cloudy days as well.
There are clear advantages to a solar-powered fan over a traditional, electrically powered thermostat-controlled attic fan. The solar fan starts running at first light, before the heat of the day. By starting early, heat-gain in the attic is all but eliminated. A thermostat-controlled fan won’t start running until the attic starts to heat up. By that time, the fan has to run almost continuously to overcome the heat gain, costing even more because it’s running during “peak” rate periods. Another advantage of the solar alternative is that the early start of the solar fan draws humidity out of the attic which may have built up during the night, reducing the potential for mold and mildew build-up. By the time the thermostat-controlled fan starts running, that moisture has already been heated up, creating a hospitable environment for mold and mildew.
Solar-powered attic ventilation is more costly initially than standard powered ventilation. But there is a 30% federal tax credit on both materials and installation which makes the costs about the same. Then there is the deal clincher and real cost benefit: It costs absolutely nothing to run! Not one cent!
I was surprised by the number of companies exhibiting at the recent builders’ show who are now offering solar- powered attic fans. There were three companies in particular that had pretty impressive products. All of them will cost between $900-1400, depending on the size of the unit for materials and installation. But remember to subtract 30% for the tax credit. You might want to check out Solaro Energy’s product, Solaro Aire. Their website is www.SolaroEnergy.com. Solar Breeze, www.SolarBreezeFan.com and Broan at www.Broan.com also seemed to be excellent options.
Mechanical ventilation, both continuous and intermittent is best left to a mechanical contractor. You can buy a $65.00 exhaust fan at your local hardware store and install it yourself, but that could be a waste of time and money if the fan is not appropriate for the conditions of the room and ducting. But whether you have the ability to research and install appropriate products, or need help from a professional, the important thing
is to take a good look at your home, determine your needs, and then act on
that careful evaluation.
Fresh air. Here’s to your health and home!
(Author’s note: I collected more information at the recent trade show than I could possibly include here. I’m happy to share it with anyone who would like to know more.
My email address is firstname.lastname@example.org.)