Cathedral Ceiling Attic Ventilation

Research has shown that the amount of airflow in the vent channels of low slope roofs is very limited for roofs with less than a 3 12 pitch.

Cathedral ceiling attic ventilation.

When renovating an older home whose roof rafters are only 2x6 really 5 1 2 x 1 5 in dimension the available space for insulation and ventilation is limited therefore limiting the options for a combination of good under roof ventilation and high insulation r values in the cathedral ceiling. You ll want a tight ceiling air barrier with no air leakage into the cathedral ceiling a critical detail for all cathedral ceiling designs. Attic ventilation for cathedral and vaulted ceilings require attic baffle vents. With v baffe s design you can quickly and easily retrofit cathedral and vaulted ceilings that would otherwise have been next to impossible.

Sometimes they included flimsy proper vents between the fiberglass and the roof sheathing but often they just specified thin batts to ensure that there would be an air space above the batts for ventilation. Bliss points out in the original q a on cathedral ceiling ventilation the risk of forming a vapor barrier sandwich around fiberglass ceiling insulation foil faced insulation above and poly vapor barrier below is that any moisture entering the insulation will be trapped risking future mold or rot problems. Proper ventilation is necessary in order to address water vapor that cannot be blocked to allow it to escape rather than allowing it to accumulate until it causes problems. The cathedral ceilings of the 1970s and 1980s were thermal disasters.

Although there is no separate attic to vent air circulation is still necessary to. If your cathedral ceiling ventilation ports space between the decking and the top surface of insulation resting on the ceiling drywall is visible from an accessible attic and there are no obstructions any type of properly installed attic vent will do as long as it provides adequate output. Federal housing authority recommends a minimum of at least 1 square foot of attic ventilation evenly split between intake and exhaust for every 300 square feet of attic floor space. A vaulted roof offers open living space directly below the rafters because there are no horizontal ceiling joists.

Proper attic ventilation consists of a balance between air intake at your eaves soffits or fascias and air exhaust at or near your roof ridge. Even with the attic bypasses sealed and effective vapor retarders installed proper ventilation is essential to prevent moisture problems in cathedral ceilings.