ventilate roof or insulate at membrane?

[rob]

Calling all roofing opinions-I have a small area of flat roof (to be modified bitumin) with a dropped ceiling below with insulation laid above the ceiling. I think the insulation in the walls goes to the underside of the roof. Is it better to drill air holes in my fascia board to allow air to circulate and reduce moisture or (since I am about to add a new layer of roof)is it better to lay insulation boards down and then roofing and skip the ventilation holes? The space below this small roof is a bathroom and the ceiling drywall is moisture resistant drywall plus we have an exhaust fan when we remember to use it.... Also, we have had roof leaks and I am afraid mold may have started growing-ventilation holes may help that?????

any suggestions would be appreciated.

[Robert Allison]

Your second plan is the best. Insulation panels on the roof, then a new roof over that. Don't put fascia vents in, this will not be good.

If you are worried about trapped moisture, take out the drop ceiling tiles and run a dehumidifier and a fan for a day or so.

[tbasc]

Take a look at the Building Science Corporation web site. This is researched information on issues like yours.

I would agree witn Mr. Allison. His comments about treating the potentially dead air space is critical. TB

[rob]

Fascia ventilation is not good because....water may blow in through the holes? Why do you think it is not good in this case? I would like to get above the ceiling and see if there is mold, but the ceiling is drywall and would involve some demo to the newly renovated space (double ouch). Any thoughts on how to dry out the space? The area above the ceiling of the bathroom actually is open to the space above the ceiling in the rest of the house and given that this is a 100 plus year old house there is natural ventilation of sorts already going on. If I were to add ventilation holes I would have to somehow close this opening up. I don't really get the whole ventilation of roof thing....Just rambling now... Thanks for your thoughts.

[Robert Allison]

Well, I am confused now. In your first post you said you had a drop ceiling. (I had to reread your original post). Then you said that you had a drywall ceiling. Which is it?

If you have a drywall ceiling, then you could put in some soffit vents preferably, or if no soffit, then a few fascia vents.

If you have a drop ceiling, then it would not be good to put in vents as drop ceilings are notorious about leaking air which would increase your heating/cooling costs. If it is a drop ceiling, it is better to remove the drop ceiling tiles and air it out that way, then replace the ceiling tiles.

[rob]

[rob]

critical.