svetz
Works in theory! Practice? That's something else
As we have members from all walks of life, thought I'd post this to see if anyone had knowledge on it....
Discovered the mother-in-law's house has mold in the attic. We had it tested and it's all benign. But, obviously want to do something about it before some strain takes root that requires a hazmat team to get rid of.
To make things more complicated, the front and back have vaulted ceilings (they have 1" vents too, so assuming not filled). Of the 1280 sqft, there's only 275 sqft of actual attic space which is where the AC ducting lies. There is no ridge vent.
I would have thought "cold AC ducting" = sweating = mold, but the visible mold is on the drywall 3' away. The ducting is insulated, but one part looks damaged and needs more investigation.
Currently the inside roof panels have fiberglass batting stapled to them between the rafters, the attic is only slightly warm (approximately outside temperature) so the attic is being cooled by the AC, which is wrong for a vented attic as far as I know. The floor of the attic is plywood, I doubt there is insulation under the plywood but need to check.
While trying to figure this out, I came across a 2005 a paper that was submitted to the FBC (Florida building Commission) saying that:
Questions
Discovered the mother-in-law's house has mold in the attic. We had it tested and it's all benign. But, obviously want to do something about it before some strain takes root that requires a hazmat team to get rid of.
The rules are 1 sqft of ventilation per 300 sqft or 150 sqft if no vapor barrier or ridge cap. The idea being that good air circulation will prevent condensation as the temperature drops. The house in question has a 1" diameter vent (a few of which are coated with paint) every rafter (24") for a total of 52, totaling 0.28 sqft. By the rules above she should have 4 or 8 sqft of ventilation space (house was built in the 90's). |
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To make things more complicated, the front and back have vaulted ceilings (they have 1" vents too, so assuming not filled). Of the 1280 sqft, there's only 275 sqft of actual attic space which is where the AC ducting lies. There is no ridge vent.
I would have thought "cold AC ducting" = sweating = mold, but the visible mold is on the drywall 3' away. The ducting is insulated, but one part looks damaged and needs more investigation.
Currently the inside roof panels have fiberglass batting stapled to them between the rafters, the attic is only slightly warm (approximately outside temperature) so the attic is being cooled by the AC, which is wrong for a vented attic as far as I know. The floor of the attic is plywood, I doubt there is insulation under the plywood but need to check.
While trying to figure this out, I came across a 2005 a paper that was submitted to the FBC (Florida building Commission) saying that:
M1. Although the rationale for attic ventilation is for moisture control, this was historically based on needs in cold climates and to prevent ice dams. The justification for attic ventilation for moisture control in hot humid climates is not scientifically defensible.
M2. Ventilated attics can introduce additional moisture loads into Florida homes by allowing moisture laden air in the attic that may communicate with the indoors.
Questions
- Regardless of code, should it be sealed? (still trying to figure out what the actual codes are) Update: Sealed is legal
- Currently the asphalt shingle roof needs replacing. A metal roof cools faster, would it need more ventilation? Update: not if not in roof contact
- If it should be vented, would adding a ridge cap count towards opening space, or do you still need 4 or 8 sqft in the soffit? Update: 4 sqft with ridge cap, 8 without
- Does soffit ventilation contribute to roof uplifting in a hurricane? Worried if I put in 4" diameter vent caps it'll weaken the soffit. Update: Yes
- I saw where some metal roofs were installed with insulation sandwiched between the metal and the roof panels, is that a good idea? Update: yes, also helps to deaden noise.
- If the attic part is sealed, what to do with the vaulted ceiling, should the vent size be increased?
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