Ken's E-Tip: Fresh Air Year-Round
As winter approaches, energy consciences members will be sealing up their homes to make them air-tight. Stale air and a buildup of pollutants are common problems associated with super insulated houses.
Poor indoor air quality symptoms include irritation of the eyes, nose, throat, headaches, dizziness and fatigue. The answer to the problem is simply bringing in fresh air. To do this properly, fresh air must replace stagnate air at the same volume level. The fresh air will also dilute pollutants inside our homes such as molds, allergens and cooking odors.
Heat Recovery Ventilation (HRV) Systems
HRV (heat recovery ventilation) system is the most efficient (but most expensive)way to accomplish fresh air introduction without sacrificing energy efficiency. They typically cost between $1,000 and $2,000. During winter, heat from the stale outgoing warm air is transferred to the incoming cold fresh air. During summer, the stale, outgoing cold air precools the incoming hot, outdoor fresh air.
An HVR is a simple system with a heat exchanger inside a cabinet and two separate blowers, one for incoming air and one for outgoing air. It has its own duct system drawing the stale indoor air usually from bathrooms and the kitchen. The incoming fresh air ducts often lead to the living room and hallway for distribution.
This balanced system uses a combination of ducted supply and exhaust-only systems. It will not cause back drafting of gas appliances.
Energy Recovery Ventilation (ERV) System
An ERV system goes a little further than the HRV unit, as this type of system also captures some of the humidity in the air to keep it on the same side of the thermal wall that it came from. So in winter, the system transfers the humidity from the air being extracted to the incoming fresh (and dry) air to help keep the surrounding humidity level at a reasonable value (between 40 and 60%) at all times.
In summer, the humidity transfer reverses and the humidity in outside air is removed before it is injected into the home. This saves energy by reducing the load on your air conditioning system and/or dehumidifier. A high efficiency of humidity transfer would be around 70 percent, but this value depends on the actual humidity on either side of the envelope.
How To Choose
The best option between a HRV and a ERV system depends on your climate and specific needs. If your house is too humid in winter (above 60% RH) then an HRV is the better choice, as it would surely get rid of excess humidity while an ERV would tend to keep it at a high level.
If the opposite is true and your house is too dry in winter, then an ERV would be a better choice as it helps retain humidity, eliminating the need (and cost) for you to generate it through other means.
In summer time, the use of an HRV will usually increase the humidity level inside your home, so an ERV is better in hot and humid zones. But a dedicated dehumidifier will likely do the trick much better. At the very least, the ERV will lower the load on the air conditioning system, even if it can't keep up with the high humidity level on the outside.
So in the end, there is not one right choice. It depends on your climate, your lifestyle and your home. In a perfect world we would have one of each, short of that we are left to make a choice.
One thing is for certain though, whichever you choose, an airtight home with an ERV or HRV is an energy efficient leap beyond the leaky houses of the 20th century, so if you are building or have a reasonably airtight house, don't lose sleep over which one to get - just get one.
MEMBER SATISFACTION SURVEY
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Visit www.central.coop and the survey will be accessible through a red button in the top right corner of our home page.
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CEC thanks members for the opportunity to learn how to serve them better and reminds members that specific answers will be completely anonymous.
Earn $50 Bill Credit
Let CEC install a load control device on your own electric water heater and earn a $50 one-time bill credit and a monthly $2.50 bill credit. Call 800-521-0570 x2195 to learn more. Members having a water heater installed by the cooperative are not eligible for the credits.
Twitter and Load Control
Participants in our load control program for electric heat and water heaters can find out when and how long control periods are predicted by logging onto www.central.coop and clicking our Twitter logo. Please remember these are only predictions and actual times may vary.