Archive for month: February, 2013

In several regions of the United States, powered attic ventilators enjoy the pleasures of a positive reputation. They are promoted by builders, shingle manufactures, roofers, HVAC contractors, utilities, weekender material retailers, ventilation manufactures, consultants and others. Extending shingle life, protecting shingle warrantee, removing moisture from attics and reducing the air conditioning load by the removal of attic heat are their believed benefits. These regional cultures accept and sometimes expect the use of powered attic ventilators. Cash flow in their regional economic systems is saturated with their use. Those who manufacture sell or install powered attic ventilators in these regional cultures could experience financial hardships should it be suggested that powered roof ventilators should not be used. However, that is our central theme as a result of our measurements of some of their unplanned impacts on houses.

A review of some of the important issues Attic Ventilator’s & the problems they can cause in your home includes the following:

1. Ventilators can cause negative pressures in combustion appliance zones. By themselves or in conjunction with other negative pressures they can cause backdrafting.
2. Ventilators run during electric utilities peak demand period and can become a peak demand problem.
3. Ventilators can draw conditioned air out of houses and cause the air conditioner to run more.
   1. They can cause increased latent load that air conditioners must remove.
   2. They can increase the cost for air conditioning for the homeowner.
   3. They can cause temperature discomfort, hot areas, which homeowners try to solve by increasing cooling through closing some supply registers which can cause additional problems.
4. Ventilators can be an unexpected and undocumented source of increased infiltration rates in houses.
5. If a powered ventilator is used, more energy will be consumed by the motor than will be saved on the air conditioning bill.
6. It has been proven that when attic ventilation was increased it did not necessarily reduce the transfer of heat across the ceiling insulation into the house.
7. It was proven by research and field testing that by running Attic Ventilator’s in climates with seasonal environments changes; that when the outside humidity (moisture) & temperature is high you introducing moisture back into your home, attic areas and crawlspaces.
8. Ventilators can cause your home to draw into negative pressures, increasing your overall energy usage.

What really happens is that when that power attic ventilator runs, it’s going to pull air from wherever it can find it. Since air takes the path of least resistance, some of it will most likely be coming from the conditioned space in your home. So basically what you’re doing is air conditioning your attic. The longer the fan runs the more conditioned air it pulls into the attic.

If you have a perfectly air-sealed ceiling, you’re not going to have this problem, of course. The reality, however, is that few ceilings are leak-free. Since air needs only a pressure difference and a pathway to move, and your ceiling probably has plenty of pathways, it’s best not to enhance any pressure differences that will increase air movement into or out of your home. Air sealing & tighten is key along with changing the overall environmental conditions. With properly sized dehumidifiers you can remove the moisture and condition your space keeping it nice and dry without bringing high humid air moisture back in.

In other words, don’t install that power attic ventilator. If you have some installed already, disable them so they never run.

Power attic ventilators can cause problems even without air conditioning. One potential problem would be sucking moist, moldy air up from the crawl space into the house.

Another would be backdrafting a water heater and putting carbon monoxide in the house. These are real problems from real houses that have really happened.

The first step before investing in an Attic Ventilator is to have your home properly assisted by a certified Home Energy Auditor to see at a minimum, if you are a good candidate. Don’t be fooled by fast talking salesman that hide the truth when it comes to the negative issues attic ventilators can cause to your home.  It is Key that you have the whole house approach before jumping to this so called quick fix. Having a Home Energy Audit, Blower door Test & Duct Testing can be some methods to properly examine & resolve your homes infiltration issues. By locating infiltration and improving the tightness in your home you can increase your comfort and save on your overall energy consumption.  It is recommended that if a powered attic ventilator is chosen as part of an attic ventilation strategy, the following guidelines should be provided. Make sure you are a good candidate. The installer should provide a good air barrier between the house and the attic and adequate, net free, vent area should be provided. Confirmation of safe operation is provided by measuring not by ignoring, guessing, or hoping.

Please Call Air Concept Solutions, LLC Today to learn more and schedule a free assessment.