HVAC

Published on August 14th, 2013 | by Henri

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Insulating an attic that is cooled with a fan

Q.    I currently have a 3 bedroom colonial, with walk-up attic. In the attic (aside from storage), is the air handler for the central air conditioner. The roof of the attic is/was insulated with standard in-between the rafters insulation strips.

Some of the insulation is falling down, and I am considering removing it all entirely. The attic has a 36-inch attic fan with metal louvers; the attic is hot in summer and cold in the winter.

Would it be wise to re-insulate the attic roof completely even though the metal louvers for the fan permit air to flow either way? The floor of the attic is also insulated. Thank you for any advice you can give me.

A.    I assume that the attic fan is on a gable and not on the attic’s floor (as a means of cooling the whole house) since you have central air conditioning. You haven’t told me where you are located, but you may want to consider the following:

Since the attic floor is insulated (and if the insulation can easily be improved, do so), there is no need to have insulation between the rafters. It was probably put there to keep the attic somewhat cooler in summer but this has limited value. A better strategy, usually only recommended in hot climates where air-conditioning is greater than heating, is to have a reflective foil barrier stapled to the bottom of the rafters, its purpose being to reflect the summer’s sun heat back out and thus to keep the attic cooler. This will reduce the strain on the air handler, keep any air-conditioning ducts cooler and cut down on your energy bill.

Is the attic fan controlled by a reverse thermostat that turns it on when the temperature rises above a certain chosen temp? That would cool the attic in the summer and relieve the stress on the air handler.

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