Attic venting from garage stairs

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Old 04-16-19, 11:38 AM
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Attic venting from garage stairs

My attic is accessed by drop down folding stairs in my garage ceiling. Whenever I climb into the attic I feel a great cool breeze coming from the open garage door and being drawn up the attic stair opening. Especially in the summer when the attic is 100+ degrees. I have soffit vents that are open on three sides of the home and one gable wall vent about two square feet. I can easily see daylight through all these vents. There is a limited amount of ridge vent due to roof design so there is also a powered vent in the roof.

I have read on this forum not to worry about attic temps under 120 degrees. But I still wonder if leaving the attic stairs and one garage door partially open wouldn’t help cool the attic? The 20 year old house has only about R30 or so ceiling insulation. Plus the minimally insulated HVAC ducts are in this attic. Would leaving this stair opening do any good toward making the A/C any more effective?
 
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Old 04-16-19, 03:45 PM
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Leaving it open will help cool the attic. Will you ever notice a difference... probably not.
 
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Old 04-16-19, 04:11 PM
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Also, 120F is nothing. Dont know where you heard that. Focusing on attic temps will drive you crazy. Some people add attic fans thinking thats a good idea but whether or not the electricity use of the attic fans actually offsets the use of your AC is debatable.

In many parts of the country, is not out of the ordinary for attics to reach 150-160F during the heat of the summer. Much has to do with the color of roofing. It's one reason why insulation is needed- to slow the radiation of that heat into the home.
 
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Old 04-16-19, 04:29 PM
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20 year old house has only about R30 or so ceiling insulation
Want to help the AC and heat efficiency, more insulation!!!

Don't know where you are located but R30 ceiling insulation is wholly inadequate.

Min is R38 in southern states and R48 in northern states.
 
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Old 04-16-19, 04:54 PM
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In addition, see this Energy Star brochure for more details and tips.

https://www.energystar.gov/sites/def...Guide_2016.pdf
 
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Old 04-17-19, 06:57 AM
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It is the A/C I am concerned about

I understand sealing air leaks is the most important, in the attic, the crawl space and the ducting. Then insulation. My concern are the cooling ducts and the A/C evaporator unit in the attic. Would dropping the attic temp increase the effectiveness of the unit sitting in the attic. Or is that not a concern?
 
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