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Old 07-28-2014, 01:38 PM   #1
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Very Confused - Should I Insulate Attic floor?


My home is currently insulated with Closed Cell Insulation including the roof ^.
The temperature is currently 77 Degrees and 48% humidity inside the living space, while the empty attic is 84 degrees and 74% humidity.

Outside Temperature is currently 94 degrees.

My question is seeing the attic will never be finished, would it be cost effective to insulate the attic floor? Is my forced hot air system running constantly because I am battling keeping an empty attic cool? The electric bill is $400 per month and system is running contantly.

Thnx

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Old 07-28-2014, 03:59 PM   #2
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Very Confused - Should I Insulate Attic floor?


It won't hurt but the roof is the insulation layer and the attic is therefore being treated as conditioned space.

Do you have forced air going into the attic?

How much do you have against the roof and where do you think the humidity is coming from?

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Old 07-29-2014, 08:43 AM   #3
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Very Confused - Should I Insulate Attic floor?


Thanks for helping me with my issue.

There is no forced air going to the attic- no vents, no duct work, no nothing. We will never use the attic as liveable space.

The roof is insulated just like the rest of the house- closed cell foam insulation.

I think the humidity is coming in from the vents in the attic ( soffit vents I think they are called). It's Really humid in South Carolina right now with 95 degree temperatures and daily thunderstorms.

I am thinking to get quotes from companies to blow in the newspaper insulation in the attic. This way it will seal up the attic and the Forced air system will no longer have to battle to work to cool/heat the attic space. Does this make sense?

Thanks
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Old 07-29-2014, 10:50 AM   #4
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Very Confused - Should I Insulate Attic floor?


Quote:
Originally Posted by foodeefish View Post
My home is currently insulated with Closed Cell Insulation including the roof ^.
The temperature is currently 77 Degrees and 48% humidity inside the living space, while the empty attic is 84 degrees and 74% humidity.

Outside Temperature is currently 94 degrees.

I am battling keeping an empty attic cool? The electric bill is $400 per month and system is running contantly.

Thnx
Let me guess.. Your home is in full sun, is a darker color brick or siding and has a dark color roof...

Do you have lots of windows where the sunlight can enter and heat things up? Check the rooms on the sunny side and see how much warmer they are than the rooms on the shade side of the home.

Also, when you say the system is running constantly, are you talking about air conditioning? If so, have you verified the air conditioner is working properly? You should check your household air temperature and compare that with the temperature coming out of the vents.. Also, go outside and check the air temperature blowing off the condenser fan..

One other big maintenance issue that a lot of folks miss is to clean the refrigerant coil inside your forced air system.. It can be difficult to get to but they can plug up with lint and dust and drastically reduce the efficiency of the blower fan..

The reason I am look at things other than insulation is because it sounds like you have the spray in insulation and that stuff is really good.. once you have that, you don't need much else.
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Old 07-29-2014, 11:16 AM   #5
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Very Confused - Should I Insulate Attic floor?


Thanks PaulBob and I will try and answer your questions.

Yes, house is in full sun.
The shingles are dark gray
Siding is beige cement fiberboard
Many windows as the house is on a lake and yes the sun beats down through them all day

The air conditioning unit is a Carrier high end unit and is only 2 years old and was recently seviced. I have it serviced every 6 months per my annual contract. All the duct work was just resealed to be sure there were no leaks in the Ductwork and it did make the air coming through the vents colder and more efficient.

Is there any way to tell if the foam insulation is keeping the hot air out of the attic and if I will be wasting money insulating the attic Floor?

My home is 2600 Sqr Feet, the electric bill is $420 a month and I have a Tankless Water Heater.
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Old 07-29-2014, 01:48 PM   #6
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Very Confused - Should I Insulate Attic floor?


Insulation is probably not your issue..

Your large "lake front" type windows are acting as giant solar collectors.

What I think you need are some light filtering or reflecting shades on the EXTERIOR of the home..

It sounds to me like your air conditioner is basically at war with the sun coming through your windows. You need to find a way to shade them from the sun.. Either an awning over the top or tinted exterior shading, or something that suits your fancy..

I'd bet that if you figure out a way to stop the sun from shining on those windows and you'll probably drop your air conditioning bill by 75% or more..

Do an experiment for a day by shading the windows from the sun and see what happens.
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Old 07-30-2014, 02:57 PM   #7
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Very Confused - Should I Insulate Attic floor?


Quote:
Originally Posted by foodeefish View Post
The roof is insulated just like the rest of the house- closed cell foam insulation.

I think the humidity is coming in from the vents in the attic ( soffit vents I think they are called). Thanks
Wouldn't spray foaming the underside of the roof with a closed cell insulation make the attic area part of the conditioned space? If so, wouldn't the soffet vents act as an open window, raising both the temp and humidity?

Sorry to the op, if wrong.
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Old 07-30-2014, 03:23 PM   #8
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Very Confused - Should I Insulate Attic floor?


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Originally Posted by 47_47 View Post
Wouldn't spray foaming the underside of the roof with a closed cell insulation make the attic area part of the conditioned space? If so, wouldn't the soffet vents act as an open window, raising both the temp and humidity?

Sorry to the op, if wrong.
The soffits would have been sealed off at the same time and the attic would therefore be part of the conditioned space (and should be getting conditioned).

If they are not sealed off, this job was incorrect from the start.
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Old 07-30-2014, 03:40 PM   #9
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Very Confused - Should I Insulate Attic floor?


Does he need HVAC ducts or is air leakage from the house into the attic enough?

Again, sorry to the op
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Old 07-30-2014, 03:59 PM   #10
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Most times there is enough duct leakage to condition the space.
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Old 08-03-2014, 12:05 PM   #11
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Very Confused - Should I Insulate Attic floor?


If your conditioned attic has open soffits, that is incorrect and they need to be sealed up. As 47_47 pointed out, soffit vents in a conditioned attic are basically open windows. Wrong!

Since you already have closed cell foam on the underside of your roof deck, and yet your attic is a higher temperature than the rest of the house, clearly you don't have enough insulation, since the roof/attic is a major source of heat gain in a hot and sunny climate. Because the foam that's already there is closed cell (= moisture barrier) you can get away with spraying much cheaper open-cell foam for the additional insulation I'm recommending.

The closed cell foam is probably R-6 to R-7 per inch. 4 inches of it (typical; this stuff is expensive) means your roof is insulated to R-24 through R-28. That's not very good. You should have double that amount. In addition, you should make sure the rafters or upper truss chords are completely encased in foam. If they're not, they're just big thermal bridges. They heat up and radiate that heat right into the attic.

As other people point out, your windows are likely a huge part of the problem; they're acting as solar collectors, but that heat can't escape except for your air conditioner dumping it outside. Better windows with low solar heat gain coefficients can help a lot. Shading them can help a lot too. Plant some nice trees. If you have a lake view, the water is probably hurting you by bouncing sunlight into your windows that would otherwise be absorbed if there was just bare earth there. All the more reason to get better windows with super low SHGC values.

You can also replace your roof with a light-colored metal one the next time your shingles need replacement.
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Old 08-03-2014, 01:44 PM   #12
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Very Confused - Should I Insulate Attic floor?


Most roof insulation jobs where clients aren't happy with the results are a result of poor sealing.

You absolutely need to do a blower door on the home and make sure the envelope is tight.

R-38 of foam is plenty in the roof and code compliant.

Open Cell SPF works just fine in roof assemblies and will more than control the moisture from the exterior. Where we worry about OC vs. CC is when we have moisture from the interior side of the home and it can percolate through the foam and condense on the cold underside of the sheathing.

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