School me on the ventilation gap in a vaulted ceiling
730d
| Posted in General Questions on
I have never used more than one inch. I don’t understand suggestions of two or three inches. Is there science behind this ? I typically use 1 inch bead board with rips on edges to hold it down. Should the edges be sealed ?
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Mike,
There ar two rationals for deeper gaps:
Some codes call for three inches because they do not require a separation (baffles) between the insulation and gap, and are worried about keeping it clear.
A larger volume allows both more area for moisture to dissipate in, and less friction allowing greater air-movement, much as you find in duct design.
Sealing the edges keeps the insulation below free of wind-washing.
Hi Mike.
I believe the International Residential Code only calls for a 1 inch space. Some think more is better; others think venting a roof is altogether nonsense (other than for some drying potential of the sheathing).
I agree with Malcolm about the worthiness of sealing the site-made baffles. Just as important, make sure the ceiling is airtight, or your ventilation may do more harm than good. Have you read this: How to Build an Insulated Cathedral Ceiling
Thanks guys. Just wondering. You don't know what you don't know. Never had a condensation issue in an attic or vault. Allways build with ventilation. Always seal them tight and always worry about wind wash. I think a big ventilation space does nothing but reduce room for insulation.