Attic condensation

[KevinMalone]

I had additional attic insulation blown in a few years ago and didn't realize condensation became an issue until I saw water staining on our ceiling. There were no other changes since then so I assume the blown in insulation was blocking the soffit vents. At this point I also realized another contractor did not reinstall any vapor barrier on the ceiling drywall that was removed during a past renovation. Seems like everything I do to this house introduces another issue and I am learning to leave well enough alone.

I ended up using a 10' extension kit with a leaf blower to hopefully blow out any insulation blocking the vents. I will have no idea if it worked until next winter as the attic has very limited access (low sloping roof and the attic is 3' high at the highest point).

 

[Number_35]

You will want to add barriers of some sort to the studs to keep the insulation from blocking the soffit vents. Premade cardboard ones are available for 16" and 24" rafter spacing. Of course plywood works well too.

Do you have a ridge vent or sufficient roof vents? I think the guideline is 1 ft^2 of ventilation for 300 ft^2 of attic floor area (w/ vapour barrier), or 150 ft^2 (w/o vapour barrier).

It sounds like you have loose-fill (blown-in cellulose) insulation, correct?

You can add a vapour barrier from the attic. Alternatively, you can paint the attic side of the ceiling drywall with vapour-barrier paint.

 

[KevinMalone]

You will want to add barriers of some sort to the studs to keep the insulation from blocking the soffit vents. Premade cardboard ones are available for 16" and 24" rafter spacing. Of course plywood works well too.

Do you have a ridge vent or sufficient roof vents? I think the guideline is 1 ft^2 of ventilation for 300 ft^2 of attic floor area (w/ vapour barrier), or 150 ft^2 (w/o vapour barrier).

It sounds like you have loose-fill (blown-in cellulose) insulation, correct?

You can add a vapour barrier from the attic. Alternatively, you can paint the attic side of the ceiling drywall with vapour-barrier paint.

I had fiberglass blown in on top of existing fiberglass batts. Ceiling joists are 2x8 so I assume the batts are R25 at best and the insulation contractors claimed to add R30 worth of blown in fiberglass. The contractors couldn't use the baffles because of limited access, but said they would be able to avoid the soffit vents. I was doubtful and I guess I was right.

There are six roof vents which seems in line with the 300sqft floor area guideline. There is also an unused range hood roof vent that is open; it is located half way between the roof edge and ridge. I wonder if this presents any airflow "short cutting" issues? I read that powered or whirlybird vents are no longer recommended as they end up drawing air from other static roof vents rather than the soffit vents.

Unfortunately there really isn't enough space in the attic to do anything, and access is even worse now with the blown in insulation. I really regret doing it as it'll be a huge pain if I ever need to go in the attic

 

[CarLuver]

sounds like you have an air leak somewhere that is putting humid air form the house into the attic. see if you can find borrow buy an infrared camera and look for any cold spots

 

[scoot]

Make sure your bathroom vent is stable , no air leaking out etc . Many contractors use the wrong venting material or run it incorrectly.

 

[Number_35]

I had fiberglass blown in on top of existing fiberglass batts. Ceiling joists are 2x8 so I assume the batts are R25 at best and the insulation contractors claimed to add R30 worth of blown in fiberglass. The contractors couldn't use the baffles because of limited access, but said they would be able to avoid the soffit vents. I was doubtful and I guess I was right.

There are six roof vents which seems in line with the 300sqft floor area guideline. There is also an unused range hood roof vent that is open; it is located half way between the roof edge and ridge. I wonder if this presents any airflow "short cutting" issues? I read that powered or whirlybird vents are no longer recommended as they end up drawing air from other static roof vents rather than the soffit vents.

Unfortunately there really isn't enough space in the attic to do anything, and access is even worse now with the blown in insulation. I really regret doing it as it'll be a huge pain if I ever need to go in the attic

A roofer friend says that turbine vents are pretty much useless.

Our old house, built in 1912, had no vapour barrier (naturally enough), and originally the attic was insulated with wood shavings. At some point, someone had blown in a few inches of grey cellulose insulation.

I went up a ladder and opened the hatch one winter - the roofing nails coming through the roof deck from above bristled with hoarfrost.

When spring came, we could hear it raining in the attic.

Over the summer and fall, I hauled out about 200 green garbage bags of sodden cellulose insulation.

I put down a 6 mil poly vapour barrier, rewired the 2nd floor, and installed pink fibreglass bats - R12 between the joists, and then two overlapping layers of R20 over that.

I also added some soffit vents.

I feel exhausted just thinking about it now. I guess I had more energy and ambition 35 years ago.

 

[KevinMalone]

Revisiting this to see what options there are to improve attic venting in the future. The roof (low slope) was replaced in 2013 and the installers used what appears to be 8x8" gooseneck vents:

https://www.menzies-metal.com/steep-roofing/gooseneck-8-x-8-professional-vent/

Not sure if there are designs that offer increased ventilation? Also, what happens when the roof is covered in snow and the vents are blocked?

 

[JimPghPA]

Usually the outside air is much dryer than inside air. People think about attic moisture as coming from outside the the house. But almost always it comes from the much more moist air inside the house getting into the cold attic and then moisture in that air condenser out as water.

Look for EVERY small air crack for air to get from the house into the attic. People often thing a hole here, or a small gap there is no big deal. But it is. You have to seal up EVERY small crack, like around access place from house to attic, and everything else.

 

[KevinMalone]

Something I've noticed in this summer heat is that the temperature difference between our upstairs and downstairs living areas are not as drastic as before, and the AC doesn't seem to be cycling as much. Previously, our downstairs (ground floor, not basement) was ice cold from the AC constantly blasting while our upstairs was barely comfortable. This year, both are very similar in feel with no changes other than clearing the soffit vents.

I'm hopeful that this is an indicator that that the attic is venting. I'm assuming it is not getting as hot and is therefore less of a thermal battery on the upstairs living areas.

 

[repairman54]

Your spot on. Air flow has returned and now heat is now venting out. I'm the opposite, just put gable vents my new to me place after dealing with ice dams last winter. Ridge vents are useless in a snow zone, house should have had gable vents from day one.

 

[Rob_Roy]

I had additional attic insulation blown in a few years ago and didn't realize condensation became an issue until I saw water staining on our ceiling. There were no other changes since then so I assume the blown in insulation was blocking the soffit vents. At this point I also realized another contractor did not reinstall any vapor barrier on the ceiling drywall that was removed during a past renovation. Seems like everything I do to this house introduces another issue and I am learning to leave well enough alone.

I ended up using a 10' extension kit with a leaf blower to hopefully blow out any insulation blocking the vents. I will have no idea if it worked until next winter as the attic has very limited access (low sloping roof and the attic is 3' high at the highest point).

Do you have any gable vents?

 

[Donald]

One issue at my home with venting the attic was given the design of the roof there was not enough linear feet for the proper amount of ridge vent. So they added a fan powered roof vent.

But it's one or the other. With both the fan will pull air from the ridge vent. There will be no draw of air from the soffit vents.

My new roof has no ridge vent in that area. Just a roof fan.

Mine is not the only house in the 20 year old development with this issue, unknown to probably every homeowners.

 

[BMWTurboDzl]

Deleted