Attic Ventilation: What Most People Don’t Know

Most individuals believe that the more ventilation, the better when it comes to the attic, and others wonder why they even have to ventilate the attic. The truth to all this is that it varies between regions of the country and systems that you see installed every day may not actually be functioning the way they were intended.

In the north, attic ventilation is used to prevent ice damming. This is when the snow on the roof melts at the higher regions of the roof and then refreezes at the gutters. This can lead to water damage in the home. In the south, the attic ventilation is used to reduce the temperature in the attic to help with the cooling load on the home. The main idea that needs to be taken from this is that with traditional construction the attic needs to be vented no matter where you are located.

Building code will typically requires a certain ratio of net free ventilation area (NFVA). Depending on where you live, this can be anywhere from 1 to 300 to 1 to 150. There are several methods of venting the attic, but the most common methods that I see are ridge and soffit vents, gable vents, and powered attic fans or ventilators. Each of these systems are used as standalone systems, and at times they are used in conjunction with each other.

As with almost any system in the home, there are some issues that you should be aware of when evaluating your attic ventilation or looking to modify it:

1. Soffit and Ridge vents must not be used with gable vents.
This comes directly from the Cor-A-Vent installation instruction. “COR-A-VENT ridge vents should always be installed with soffit/eave/intake vents of equal or greater area. All other vent openings (except soffits) should be closed off. The air passageway, or “Ventilation Chute,” between the inlet (soffit/eave/intake) and the outlet (ridge) vent must not be blocked or restricted.”

2. Powered ventilators may not save you money and can cause problems.
A study conducted by the Bureau of Standards found that the cost of operating power ventilators did not outweigh the minimum savings in cooling cost due to the decrease in the attic temperature. The use of solar-powered ventilators may correct this issue, but then you must weigh the cost of the unit vs. the savings in cooling cost. Powered ventilators have other issues that include depressurization of the home. This can cause backdrafting and moisture problems in the home if there is not enough ventilation in the attic to accommodate the fan or if the ceiling in the home is not tight. Even if the fan is not powerful enough to depressurize the home, it can still pull conditioned air out of the house through leaks in the ceiling and therefore cost you more money to cool the home. Powered ventilators must be used with caution, and I do not recommend them except in extreme situations.

Ventilation is important if you intend to stay with a vented attic. Shingle manufacturers may void warranties, and you can cause damage to the roof sheeting if the ventilation is not sufficient. The important item with any system you install is to make sure that it is installed per manufacturers instruction and local building codes. As mentioned before, a good source of information regarding natural ventilation and the various types of vents is the manufacturer Cor-A-Vent. The Energy Star Website and Advanced Energy also have resources regarding attic ventilation.

Insulate Your Water Heater

Many people will argue on this subject for various reasons, but the most common two arguments are that the water heater doesn’t feel warm and the water heater is in the home and therefore doesn’t need a blanket. The truth is that at 120 degrees Fahrenheit, your 75 degree home looks really good to the heat in the tank. No matter where the tank is, it will lose heat. As for the argument that it doesn’t feel hot to the touch, the truth is that tanks are becoming more efficient with their insulation, but they will still lose some heat. If you don’t believe this, put some towels on the top of the tank, come back after a day, and put your hand under them to see if they are warm.

A water heater with R-7 insulation at 130 degrees Fahrenheit can potentially save $33.10 a year based on a $0.10 kWh electric rate. This is not a bad return on a $15 blanket!

If you are going to wrap with a blanket, make sure you do it right and follow any instructions from the manufacturer. If your tank is fueled by gas, there are additional measures you need to be aware of, so make sure you take the time to learn how to install the blanket safely on your system, or have someone experienced install it for you.

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