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Old 12-27-2011, 12:22 AM   #1
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Removing Insulation from Soffit Vents


While looking around my attic, I'm noticing that a previous owner seems to have shoved/blew insulation into the soffits, blocking the vents (I can't see any daylight when looking between the beams).

I have a hip roof with a low slope and 24 inch overhangs with vinyl soffits. There is no way I can get in there to clean them out from the attic without having a nail in my head.

I'm also concerned I may not have enough ventilation to begin with...it seems like I have two sets of two vents on each straight gutter run (the house is 60 years old and the previous homeowner would have installed the vinyl soffits himself).

Luckily, I'll be having gutters and shingles replaced next year...however I have a different contractor doing each. I want to make sure with the new roof that I don't screw it all up with poor ventilation.

My thinking would be to have the gutter guy assess whether I have enough ventilation and maybe add some soffit vents as well as make sure the existing ones are cleaned out and add some baffles from the outside to keep them clean.

What do you guys think? Is the gutter guy the right person? What kind of additional effort would it be for one of these guys to take care of this - it would seem to me he may have the soffit panels freed anyway, or if not, he could pull them out with very little effort?

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Old 12-27-2011, 05:24 AM   #2
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Removing Insulation from Soffit Vents


Your going to need to pull it back and add foam baffles to prevent them from getting blocked up again.
One way to pull it back is with a hoe, another is a big shop vac with a piece of PVC duck taped to the hose.
If this is a real gutter company and not a contractor that owns a gutter machine then he's not the one to use.
Same for the roofer. If that's all they do most liky there not even going to mess with it.

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Old 12-27-2011, 08:37 AM   #3
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Removing Insulation from Soffit Vents


I had the same problem with our house. Also a hip roof. Builder or original owner had stuffed rolls of insulation right into the soffit all around. I got up there with a short-handled, narrow garden rake that fit between the roof members, and a hockey stick and hauled it all out of there.

Took several hours of low-crawling around, but I got all of it except for about 6-8 feet leading into one corner, where, because of some cross-members fastened across the tops of the ceiling joists, I could not get in there.

You'll want a couple of sheets of plywood or particle board to lay on. Those ceiling joists get uncomfortable real quick And wear a dust mask.

If your home is old enough they thought sealing the attic crawl like that was a Good Idea, odds are you have insufficient roof vents, too. Ours did. I had my roofer add a couple. When we had the house re-sided a few years later, I had additional soffit vents added, too.

I still need to add another 8" or so of insulation. Maybe next year...

Jim
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Old 12-27-2011, 10:42 AM   #4
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Removing Insulation from Soffit Vents


So here's the full story....I found out about this because I'm up there adding insulation now and have 1/3 of the job done (tool me 3-4 hours to get this far). My attic is a pain due to the low slope, ductless air conditioning running all over, my size, etc. So now I've got a layer of R-30 running across most of the joists. I made sure not to block the soffits with any of the R-30 but from the previous homeowner's work, right now there is both blown insulation and R-15 batts down the soffits.

My roofer claims to do roofs, gutters and masonry (I don't know if he subs out the gutters) and my gutter guy is a subcontractor for a number of roofers but all he does is gutters and to be honest, he's probably more like a guy with a gutter machine. My roofer comes with a number of recommendations from a number of sources - both friends who have used them and Angie's List.

I think I'd rather pay someone else to deal with the problem - due to a number of projects this year, I've already spent too much time laying on plywood and cramming myself into small spaces. So I take it if I want to take care of it from the outside (which would be ideal because I could also add more venting) I'd need to call a siding person. I take it if I wanted to take care of it from the inside I wouldn't need anyone with any specific skills...just anyone hungry for work, however nasty it will be.

Are there any other solutions? Could the roofers add some venting somehow? It doesn't seem like it because of the hip roof, but I'm reaching for anything here :-)

Then also, what if I choose to do nothing but add insulation? It seems to me the extra insulation would help the issue because it would keep heat out of the attic and allow less opportunity for the attic to suck A/C out of the house. The house has survived years with no ice damming or moisture issues...if my only risk is potential extra A/C costs I may just choose to live with it.
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Old 12-27-2011, 10:56 AM   #5
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Removing Insulation from Soffit Vents


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Originally Posted by cpfoutz View Post
Then also, what if I choose to do nothing but add insulation? It seems to me the extra insulation would help the issue because it would keep heat out of the attic and allow less opportunity for the attic to suck A/C out of the house.
Besides energy efficiency, the attic crawl not being able to breath creates two problems, both resulting from trapped air: 1. It allows increased heat build-up in the summertime, shortening the life of the shingles. 2. It prevents moist air from leaving. As the space cools you get condensate on the wood, which will eventually destroy it.
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Old 12-27-2011, 08:11 PM   #6
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Removing Insulation from Soffit Vents


Hip roofs are more difficult to vent.

You need intake venting at the soffits and exhaust venting as close to the top of the roof as possible.

The way to figure out how much is "enough" ventilation is with a calculation called Net Free Ventilating Area (NFVA).

Here is the short version: You want one square inch of ventilation for every two square feet of attic floor space. Split the square inches of ventilation between intake and exhaust.

For example, if you have a 1200 square foot ranch with hip roof, you need 600 square inches of ventilation total, 300 of that as intake and 300 as exhaust. At the soffit, you need roughly six 5"x10" rectangular openings cut in (six times 50 square inches). For exhaust, you need six standard "pod" vents which are rated at 50 sq inches each (8" diameter circular opening x 3.14 (pi, y'all).

If your roofer can't do these calculations, you need a new roofer.

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Old 12-28-2011, 04:34 AM   #7
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Removing Insulation from Soffit Vents


I might be good on my amount of ventilation then...

I have an 1800 square foot split level with two equally sized attics. Each attic has 8 vents at the soffit that are at least 5"x10" and a powered exhaust fan at the top of each attic (then the question is, does one powered exhaust fan = 3 passive pod vents)

I got an insulation guy coming out to give an estimate on cleaning out soffits and I'll also talk to the gutter guy then the roofer about pulling it out from the outside and see what the most efficient solution is.
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Old 12-28-2011, 10:12 AM   #8
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Removing Insulation from Soffit Vents


You can't do it from the outside. All the insulation has to be pulled back, the baffle installed, and the insulation packed back in there over the wall plate below. This area is especially vulnerable to heat loss because there's a large seam in the drywall at the ceiling corner, and with the low sloped roof above there is not enough height to get even 1/2 the recommended R value worth of fiberglass in there.
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Old 12-28-2011, 10:57 AM   #9
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Removing Insulation from Soffit Vents


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I might be good on my amount of ventilation then...

I have an 1800 square foot split level with two equally sized attics. Each attic has 8 vents at the soffit that are at least 5"x10" and a powered exhaust fan at the top of each attic (then the question is, does one powered exhaust fan = 3 passive pod vents)

I got an insulation guy coming out to give an estimate on cleaning out soffits and I'll also talk to the gutter guy then the roofer about pulling it out from the outside and see what the most efficient solution is.
OK, so that is an application where power vents are sometimes useful ... as long as you block up any other exhaust venting.

You want your power vent to have both a thermostat and a humidistat.

You want to know the CFM rating for the power fans. There are technical specs that you want to understand if you want to be sure that it is doing the job you want it to.

As long as you are certain that the vents from the soffits (probably the 8 x 16 louvered variety, I'm guessing) are unblocked and the air can get from them to the power fan, that's what you want.

With two attics about 900 sf each, you want 450 sq inches of ventilation, split between soffit and exhaust. So, if you didn't have the power vent, you would want 5 of the 8" diameter exhaust vents on each roof (250 sq inches of exhaust ventilation) with the same or more ventilation at the soffit.
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Old 12-28-2011, 02:42 PM   #10
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Removing Insulation from Soffit Vents


So the insulation guy came out today and said the insulation is fine...which was still surprising because I see the batts between the joists, but after reading jmiller's comment it makes sense. The batts are loosely in there, so i can see where air could still flow from the soffits over them yet still providing insulation for the wall plate. The right way to do it would be to add baffles and shove the insultation underneath, but I'm thinking it's probably good enough. I'm not looking for perfection.

The reason I'm not seeing any daylight through the vents is because whoever did the soffits put vinyl soffits over plywood, but didn't cut the plywood holes any bigger. So while my vents may look big, they are functionally pretty small.
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Old 12-28-2011, 03:17 PM   #11
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Removing Insulation from Soffit Vents


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The reason I'm not seeing any daylight through the vents is because whoever did the soffits put vinyl soffits over plywood, but didn't cut the plywood holes any bigger. So while my vents may look big, they are functionally pretty small.
It's amazing to me the things some contractors will/won't do, when one would think common sense and a drive to do things right would seem to dictate otherwise. Witness what you've found, and the person who started the thread about the roofer who didn't cut the underlayment back for a ridge vent, resulting in a ridge vent that doesn't vent.

The contractor who put our replacement siding up actually asked me if I wanted the underlaying plywood holes made bigger to match the soffit grill size in the new siding material. I also had him add one or two.

Jim
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Old 12-28-2011, 05:03 PM   #12
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Removing Insulation from Soffit Vents


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With two attics about 900 sf each, you want 450 sq inches of ventilation, split between soffit and exhaust. So, if you didn't have the power vent, you would want 5 of the 8" diameter exhaust vents on each roof (250 sq inches of exhaust ventilation) with the same or more ventilation at the soffit.
But he does have the power vent, so that formula isn't applicable. Lets say he has the Air Vent power vent with the humidistat. It exhausts 1,500 CFM, and Air Vent suggests dividing that number by 300, and using that number as the square footage of intake needed. In this case that means provide 720 square inches of intake.

What they don't mention is that having less intake is not a matter of being slightly less than perfect, but probably worse than inadequate passive ventilation because you're just pulling conditioned air from the living space to make up for lack of soffit intake.

I say either lose the power vents and install five box vents, or strive for intake perfection at the eave.
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Old 12-29-2011, 07:53 AM   #13
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Removing Insulation from Soffit Vents


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But he does have the power vent, so that formula isn't applicable. Lets say he has the Air Vent power vent with the humidistat. It exhausts 1,500 CFM, and Air Vent suggests dividing that number by 300, and using that number as the square footage of intake needed. In this case that means provide 720 square inches of intake.

What they don't mention is that having less intake is not a matter of being slightly less than perfect, but probably worse than inadequate passive ventilation because you're just pulling conditioned air from the living space to make up for lack of soffit intake.

I say either lose the power vents and install five box vents, or strive for intake perfection at the eave.
+1

Well said.
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Old 12-29-2011, 08:34 AM   #14
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Removing Insulation from Soffit Vents


I have the easiest, fastest, cheapest and cleanest solution for you: install roof vents near the bottom of your roof (the kind that normally go near the ridge).

A couple of friends have asked me in the past to look at a way of clearing the blown-in insulation from their blocked soffit vents in their shallow attics (just like yours). After taking a quick look, I said to myself: "Am I going to get myself into that sh_t? Hell, no." So I installed a few roof vents near the bottom of their roofs, about a foot above the top of the insulation. I installed them properly, so they haven't leaked and never will.

Granted that it is not the best solution as far as aesthetics go, but they don't look that bad either, and if they are in the back or the sides of the house, who cares? (It doesn't sound from your description that your house looks like a palace anyway.)
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Old 12-29-2011, 10:07 AM   #15
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(It doesn't sound from your description that your house looks like a palace anyway.)
Ouch!

Even if that's the case, box vents at the eave would look ridiculous. I feel sorry for your friends.

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