Ventilation Requirements for your Home

March 24, 2014 | Filed under: Metal Roofing,News,Ventilation

Homes need to breath.  Modern homes are made to be airtight.  Good insulation, energy efficient windows and doors all keep air from coming into your home.  However, your attic needs some amount of airflow.  This is called ventilation.  Many homes, especially newer homes, do not have proper ventilation.

What is ventilation?

Ventilation is the movement of fresh airflow, coming in from the bottom (eave) of the roof assembly and leaving through the top (ridge) of the roof assembly.  Proper ventilation moves air along the underside the roof deck.  Ventilation should be balanced. This means the right amount of airflow should be entering and leaving your attic space.  Imbalanced ventilation leads to a host of problems which we discuss below.

Roof Ventilation

A properly ventilated home channels airflow through the bottom of the roof toward the top.

Why does an attic need ventilated?

In the summer, radiant heat builds up inside the attic.  Without proper ventilation, heat gets trapped.  The inside temperature of the home rises causing an increase in cooling costs.  In addition, the roof surface becomes too hot, reducing the life of your asphalt roof by as much as half.

In the winter, moisture produced from inside the home rises into the attic.  An improperly ventilated home traps the moisture, causing condensation.  Condensation allows mold and mildew to develop on the underside the roof surface, reducing air quality in the home.  Additionally, trapped moisture in an attic causes the underside the roof deck to rot and could ruin attic insulation.  Improper ventilation is one major cause of harmful ice-damming.

Many asphalt shingle warranties become void in the absence of proper ventilation.  If your shingles begin to curl (as seen in the picture below) it may be due to improper ventilation.  The 30-year shingle warranty which helped convince you on your choice of roofing product could not be honored if your home is deemed to have improper ventilation.

An improperly ventilated attic could void your shingle warranty!

An improperly ventilated attic could void your shingle warranty!

How do I know if my home has improper ventilation?

Look for problems.  In the winter, look at the underside of your roofing surface.  If you notice condensation, mold, or mildew buildup, you have ventilation problems.  Also, look at your attic insulation.  If it shows signs of moisture damage, then you may have ventilation problems.  If you have trouble keeping your house cool in the summer, it could be a ventilation issue.  

How do I know if I have enough ventilation?

There is a simple way to check.  Our rule of thumb is this: for every square foot of attic floor space, you should have 1 square inch of ventilation, half from the intake, the other half from exhaust.  It’s a simple 1-to-1 ratio.  One square foot of attic floor space needs 1 square inch of ventilation.  To find out if your home has enough ventilation, do the math.  Figure your attic floor space in square feet.  Then measure your ridge vent, box vent, pipe vents.  Add that number to the number of inches of intake ventilation you have, usually along the soffits, and compare.

If your home does not have overhang at the eave, you may need to add eave ventilation.  There are a number of products on the market and our attic ventilation specialists would be glad to show you a few.

How to fix attic ventilation problems.

There are some DIY tricks out there.  However, we recommend you have a roofing and ventilation specialist inspect your home.  At Schroer & Sons, we offer free attic inspections and roofing consultations.  Fill out the form below and schedule an appointment with one of our roofing and ventilation specialists.