attic ventilation

[stevie]

In 1997 I had vinyl siding installed on my house, which is mostly brick. The siding covers the soffit and fascia boards. When the siding was installed, the 4x8 plywood soffit vents were removed, but the holes were left of course. The vinyl siding has vented sections (2 ft wide) about every 5 feet. The original plywood vents were 8-10 ft apart.

My concern is that the attic is not adequately ventilated. I'm not sure that enough air is getting through the siding vents, then through the plywood 4x8 holes. There is about 1/2 to 1 inch gap between siding and original plywood soffit. I want to make sure the airflow is good enough to ventilate the attic and help lower my energy bills.

The attic insulation is OK-I plan on adding some more.

What I am thinking about doing is removing the ventilated siding panels (maybe not all of them), then cutting out more sections of the original plywood soffit directly above the siding vent. Hopefully, this would allow more airflow through the attic. The roof has 4 wind powered turbines, and I may add 2 more.

Removing and re-installing the siding sections should not be a problem. The house is about 2300 sq ft living area and was built in mid 70s.

I just wanted to get some opinions on whether the additional soffit vents in the plywood would increase the attic airflow.

[trader4]

Without seeing it, it's impossible to give an answer. For one thing, you only state that there are ventilated section of soffit every 5 feet, but not how long the ventilated sections are. We have no way of knowing the amount of air intake in square inchs. What makes you think there isn't adequate air flow?

[stevie]

thanks trader- the vent sections are 2 ft wide, soffit is about 3 ft overhang. actually, i don't know if there is adequate airflow or not. it was pointed out by an insulation contractor that i probably was not getting enough with the siding. his suggestion was to remove the entire siding along each side, then remove the plywood underneath the siding. but this sounds pretty extreme.

i live in texas-gets really hot in summer. attic temp gets to 140-150.

[Don Phillipson]

Consult your municipal building office. It ought to be able to tell you how many square inches of ventilation each type of attic needs for 100 cubic feet of volume. Minima are probably prescribed in the building code (for new construction.)

[mm]

140 is hot enough to burn the hair off a dogie.

Maybe you need a roof fan.

Remove NOPSAM to email me. Please let me know if you have posted also.

[hallerb]

Attic at 140 degrees is way too hot. I would do what the original poster had in mind and add at least 2 electrical powered roof vents.

with your roof so hot it will fail sooner....

[Gntry]

[barry]

My house, in SW CT, originally had no access to the attic; clearly a stairwell was cut later. Upper ends of rafters are blackened, apparently from the temps. (Only a couple of passive vents, at opposite eaves.) One side of roof has three courses of 3-tabs (honest), seemingly indicating a temperature problem, besides incompetence.

Installing powered exhaust fan, with thermostatic switch, really keeps the temp under control up there now in August. For the OP, I'd suggest that he give up on the passive turbines, since they are obviously not working. They can probable be replaced by "mushroom"-looking powered exhaust fans, with t-stat switch.

Expert advice might be needed, for sizing of fans and air-entry passages.

HTH, J

[Chub]

it would be easy to use a circular saw and cut out the plywood eave a section where the holes in the vinyl are then put back.

[trader4]

"Installing powered exhaust fan, with thermostatic switch, really keeps

the temp under control up there now in August. For the OP, I'd suggest that he give up on the passive turbines, since they are obviously not working. They can probable be replaced by "mushroom"-looking powered exhaust fans, with t-stat switch. "

Since he's concerned about air intake under the soffits, I wouldn't jump to the conclusion that the ventilation at the top of the attic needs to be fixed. Proper ventilation requires both intake and exhaust. Unless he figures out how much intake he has and verifies that it's sufficient, adding power vents is likely to do little to help and could actually make things worse, by sucking cool air from the living space, through outlets, gaps, etc.

I'm also not a big fan of powered vents period. A good ridge vent with soffit intakes is widely recognized as the best solution. And it doesn;t take any energy to run.

[bud smith]

One thing I did at my previous house that really helped with the attic temperature was to install something to block the heat from coming into the attic space. I bought these rolls of quilted aluminum foil that had kraft paper on the back. I stapled this stuff against the rafters (shiny side down to keep dust from settling on the aluminum and decreasing the reflectivity). It really helped.