Attic Venting

June 21, 2017  •  Leave a Comment

Most people do not think much about attic space in their home.  In the old houses of yester-year that we often work on, the attic space typically has a floor of some kind and maybe a stairway that is narrow and steep. In these older homes the builders did not typically use insulation or think about energy efficiency, so any make-shift space in the rafters was not much different from the rest of the house. Today these attics are accessed through what we in the trade call a scuttle-hole. This may be located in a closet or hallway in your home.    

This may be located in a closet or hallway in your home.  Most new homes have attic spaces; however in most cases the space is unusable for anything but insulation. 

Most people think the only thing that matters in a typical attic is having a lot of insulation. This is true but the most important thing is ventilation.  Question: Should your attic space be warm or cold in the winter? The answer is cold if you have good attic ventilation.  In the wintertime, the attic should be close to the temperature outside.  Why?  This means your house is properly insulated and sealed. Also, a cold, ventilated attic will not grow mold.  Lastly, a well-ventilated attic will keep your roof from creating ice dams and/or icicles on eaves which are hazards to a home.

In the summertime, a well-ventilated attic keeps the house cool inside.  A poorly ventilated attic can easily reach temperatures over 160 degrees while a well-ventilated attic may only reach 100 degrees.  Once a home is built, obtaining proper ventilation can be difficult.  The best ventilation schemes involve bringing air in low at the eaves and releasing the warmth out high in the attic. I wrote an article on soffit venting in the Journal of Light Construction, Three Ways to Vent a Soffit.

One thing that improves an attic in the summertime is installing a power vent.  This is basically a fan on a thermostat. When the temperature increases to a pre-set setting, the fan will kick on and draw air into the attic.  Oftentimes on a hot day an attic power vent will keep running possibly until 3 a.m. when the air temperature finally cools below say, ninety degrees. The drawback to these fans is that depending upon the conditions of your attic, a slight hum can be heard from within the house when the unit is running.  Also, you can expect to get less than ten years before the motor needs replacing on one of these units.


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