Venting a hip roof with limited exhaust due to reduced ridge vent area.

Venting a hip (pyramid) style roof with standard ridge vent and soffit venting is a bit more of a challenge than a standard gable end roof. Assuming you actually need more ventilation.

Hip roofs are limited in the length of the topmost horizontal ridge making it less likely that a simple installation of ridge vent will be sufficient to supply enough ventilation exhaust area for the attic.

Example

Your attic measures 30’x 40’ for a total of 1200 sq. ft. of attic floor space. According to generally accepted ventilation standards, you would need about 32-42 lineal ft. (approximately 576-756 square inches of net free area) of good ridge vent for the exhaust. And 64-84 lineal feet(approximately 576-756 square inches of net free area) of continuous soffit vent at the eave. On a hip roof your top ridge length may only be 10 feet long. A 10 foot long ridge vent will only net you 180 square inches of exhaust. You would be short 22-32 feet of ridge vent or 396 sq. inches of exhaust area.

There are a few ways to make up for this shortage.

• If you have a capable roofer, ridge vents can also be installed along the sloping hip ridges. Adding an extra 6 – 8 feet of ridge vent to the other hip ridges will gain you that extra ventilation capacity .
  Extra care needs to be paid to the installation and flashing of ridge vent along these angled hips. There is a greater possibility of wind blown rain making its way under the ridge vent and into the attic.

• You can also add large static/passive roof louvers to the hip ends for additional exhaust.
• Or if you need more exhaust, say in the warmer climates, a powered attic roof ventilator might be in order.

Make sure there is proper soffit venting installed. More is better. If possible install continuous soffit vents around the entire perimeter of the house.

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