Installing Attic Ventilation Fans

A Cooler House With a Vented Attic

Introduction: Proper attic ventilation is critical to maintain a balanced environment inside your home and prevent roof damage due to excessive heat and moisture. Unlike most of the house, we want the attic to be as cool as possible and that includes during the winter.

A properly ventilated attic will prevent moisture from building up that can cause all sorts of damages to your home. Excessive moisture can lead to roof rot and the formation of ice at the soffit edge and icicles to hang from the eaves during winter. Neither of these situations is good for your home. Excessive heat in the attic during the summer will increase the cost of energy for air conditioning and cause excessive drying of roof rafters and roof sheathing.

Insulation in the attic slows down the migration of heat from your living space to the outside and keeps your home warm or cool regardless of the attic temperature.

Sufficient ventilation helps to keep attic temperature and moisture at their optimum levels year around. In winter the perfect attic temperature is the same as the outside temperature, very cold and dry.  In summer there must be a lot of air movement so the attic is as cool as possible. This may require attic fans if there is insufficient venting.

Proper attic ventilation has year around benefits. The obvious benefit of increased ventilation in the warmer months is to lower the attic temperature which can decrease cooling costs in the home.   During the summer months attic insulation can actually cause an increase in temperature inside the home as the insulation holds the heat long after the sun sets and continuing to transfer the heat slowly through the ceilings into your living space.   

In the hot months lowering the attic temperature increases roof shingle life.   Though asphalt shingles are designed to take the abuse of the sun for many years, they are subjected to greater temperatures when the roof is allowed to overheat in an under ventilated attic.

During the cooler months moisture is a serious concern.  Even with the use of vapor barriers to keep moisture from entering the attic there are air leaks around ceiling light fixtures, bathroom exhaust fans, access panels and attic stairways that allow moisture into the attic.  

Moisture condensing on the structural members often leads to the growth of mold, mildew and rot framing. To check your attic for excessive moisture check the exposed roof nails, if they are rusty or if the wood around them is black or stained, there is a moisture problem.   

Even though you have adequate attic vents (ridge, soffit, and gable) there still can be hot spots of overheated stagnant air. Installing an attic fan may be the best solution to increase attic venting.

Attic fans will force hot air out of the attic and draw cool air in during the summer. A cool attic can reduce air conditioning energy cost by as much as 25% and increase your shingle life by keeping the roof cool. During the winter it will help keep the attic temperature close to the outside temperature, preventing ice build up on the soffit edge.

Installing attic ventilation fans is a relatively easy DIY task. In most cases it is installed on the gable end either behind or in place of the gable vent. A solar powered attic ventilation fan is much easier to install because you do not have to run an electrical circuit to the attic.

Related articles:  

Installing Solar Powered Attic Fans

Proper Attic Ventilation

More Heating and Cooling Projects

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