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Old 06-09-2011, 12:15 PM   #1
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Attic ventilation


Hi, first post here.

My attic is extremely hot and i am sure the A/C unit is working overtime to overcome the ambient temperature effect on the ducting. It is nearly impossible to get the rooms upstairs below 80F on a 90F+ day. The installer came to the house at my request and put more refrigerant in the unit. It seems to me that adding refrigerant means there is a leak or the unit wasn't charged properly to begin with. $200 later, i still have the problem. Oh, he replaced my filter free of charge. LOL.
The ducting is the flexible tube type and is secured to each vent and the returns with plastic strapping. All the metal ducting is wrapped with foil insulation. However, the air handler is leaking some cold air around the sheet metal that makes up the outside of the unit. I will get some HVAC tape and seal that up so that should help.

I have a baffled ridge vent installed, 30 ft in length over an attic that measures 36X20. There are gable vents at each end of the house. However, at one end, the attic A/C unit installed during my last remodel is blocking 75% of the vent. Why they did that is beyond me. Didn't notice it until i went up in the attic recently.

I want to bring the temp down in the attic and i am thinking of either an electric or solar exhaust fan in the roof. Do i need to worry about how much air flow can pass thru the gables? Should i consider putting a couple of passive vents in the roof to allow more air flow to the fan?

There is 12" of fiberglass insulation in the attic floor but none inthe rafters. And the roof has no soffit venting due to the gambrel style. No overhang.

If is 12:30 PM EST and the outside temp is 85F and the attic is 99F

Any suggestions would be much appreciated.

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Old 06-09-2011, 02:40 PM   #2
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Attic ventilation


While i am no expert, from what you said it appears obvious you could benefit from additional venting. If you don't want to take away from the style of that roof with something like a whirlybird, what you may want to look into is a 'roof ridge vent'. Seems like that would suit your purpose nicely.

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Old 06-09-2011, 03:59 PM   #3
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Attic ventilation


Hey tmaher,

It sounds like you have several challenges and opportunities to make your upstairs more comfortable. Unfortunately, there are no simple fixes including installing the attic fan which will help a little.

The real problem is two-fold.

Your AC equipment in your attic is probably insulated to an R6 level which means a lot of cold air is turning into warm air before it reaches your living spaces.

The second part of the problem is warm air is flowing from the attic through the fiberglass insulation and into your living spaces. If you have an attic hatch or stairs that are not air sealed and insulated...start there. This opening is typically the size of a large window. Hot air from the attic flows right through it.

When it comes to the HVAC unit...
Sealing up all of the joints around the air handler and AC unit with HVAC metal foil tape will help a little. Burying the ductwork with cellulose insulation will increase the R-value surrounding the ductwork. Which will make the air flowing into your rooms colder.

Before you start working, you should really air seal the entire attic space. You'll need to move the fiberglass insulation around or get rid of it completely and replace it.

Air sealing your attic will keep the intense attic heat from flowing through holes, gaps and cracks in your ceiling into your bedrooms.

The good news is that if you go through with the insulation and air sealing upgrades, your overall energy bills will be lower and your house more comfortable.
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Old 06-09-2011, 04:47 PM   #4
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Attic ventilation


i agee that your biggest issue is inadaquate attic insulation. the insulation on the ductwork is prolly sufficient (could be better). you sould blow in new insulation into the attic. this will keep it from seeping into the upstairs rooms and reduce you heat load.
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Old 06-09-2011, 07:38 PM   #5
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Attic ventilation


Might want to look into installing radiant barrier.
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Old 06-09-2011, 10:54 PM   #6
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Attic ventilation


If you have gabel vents and a ridge vent, you may want do a couple different things. One you can seal both gabel vents and allow you ridge vent to pull the hot air out but you have to make sure that your soffit vents are not blocked so that air can flow through the attic. (depends on the pitch of your roof as well) Or you can put a power vent on one of your gabel vents to pull air out. ( There should be a 2 inch opening in your ridge vent for air to escape) Like the other people were saying insulate your opening going into your attic)

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