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Old 04-14-2014, 09:15 AM   #1
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How is attic converted to non-vented?


My home is 1400sq ft, single level, constructed of concrete block with a trussed roof and a semi vaulted ceiling over about 50% of the living space. The home is 30 years old and has the original blown-in fiberglass insulation in the attic. The walls have no insulation against the concrete block.

I had new energy efficient windows and sliding doors installed last year. I'm considering having closed-cell spray foam insulation installed in the attic and removing the old blown-in fiberglass.

My question is; how is the attic converted to a non-vented configuration? The existing soffit is perforated. Does the sofitting need to be replaced with a solid materiel?

How is the existing ridge vent addressed?

Thanks.

Tipsy

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Old 04-14-2014, 11:22 AM   #2
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How is attic converted to non-vented?


Hi, I recently did some drafting for a house here in south Florida and it sounds similar. I am NOT an expert BUT here is what we did: First the foam is sprayed under the roof sheathing. This covers the trusses top cord and the back of the roof plywood. They put panels (seemed like foam board?) in to block where the overhang joined to keep foam from going out into the overhang, and we never sealed the sofit vents. I don't know if this is correct or not though. Also I was told to take pictures of the beck of the roof plywood at a few spots so I could latter show that the correct grade stamps were on the plywood, etc. Then 2 - 6" round vents were installed in a hallway below at opposite ends to allow some cool air to eventually mirgrate into the attic space, where after a few months it became a reasonable temperature compared to the oven it used to be. Also (I think) your duct work is now considered to be in a conditioned space now? Should reduce your cooling load, etc. OH as far as the ridge vent we didn't have one. They seem not to use them on tile (concrete) roofs here in South Florida.

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Old 04-15-2014, 06:10 AM   #3
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How is attic converted to non-vented?


Tipsy,

Is there HVAC in the attic?

If not, why bother with the conversion.
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Old 04-15-2014, 07:51 AM   #4
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How is attic converted to non-vented?


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Tipsy,

Is there HVAC in the attic?.
Yes, there is.

Tipsy
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Old 04-15-2014, 08:18 AM   #5
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How is attic converted to non-vented?


Putting SPF on the duct work would be far cheaper than converting the whole attic.

If it is just for the HVAC system, spray the duct lines if they are rigid and put R-50 on the floor after you do the top plates.

Why would you want to condition the entire attic if you aren't using it?
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Old 04-15-2014, 08:21 AM   #6
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How is attic converted to non-vented?


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Putting SPF on the duct work would be far cheaper than converting the whole attic.

If it is just for the HVAC system, spray the duct lines if they are rigid and put R-50 on the floor after you do the top plates.

Why would you want to condition the entire attic if you aren't using it?
I'm trying to effectively insulate an otherwise very poorly insulated house.

Tipsy
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Old 04-15-2014, 08:37 AM   #7
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How is attic converted to non-vented?


Tipsy,

Putting SPF across the roof deck is not the most cost effective way to insulate a poorly insulated home.

Conditioned attics do work but in this case is a very expensive band-aid for a poorly insulated attic.

Please search around on Air Sealing and Insulation.

A quick sealing of all the top plates in the attic along with sealing of the duct work connections would keep the conditioned air in the home and solve the air loss issue. At that point, a loose fill insulation blown up to R-50 would more that insulate the home.
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Old 04-15-2014, 08:43 AM   #8
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How is attic converted to non-vented?


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At that point, a loose fill insulation blown up to R-50 would more that insulate the home.
I have other motivations. The house has been replumbed through the attic. Blown in insulation buries all of the plumping, making it difficult to locate.

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Old 04-16-2014, 08:35 AM   #9
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How is attic converted to non-vented?


Why would you need to locate the plumbing once it is done?

If it is leaking, insulation will only minutely slow down the locating of the leak.
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Old 04-16-2014, 07:32 PM   #10
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How is attic converted to non-vented?


Sounds like you know what you are doing, Tipsy. Is R-30 required per energy code? http://energycode.pnl.gov/EnergyCode...?state=Florida

R-10 of that requires cc/oc SPF to meet code and prevent condensation; http://www.buildingscience.com/docum...rchterm=attic+

Why- as you know already; http://www.buildingscience.com/docum...r-all-climates

Whoever removes the FG will seal the soffit vents at the exterior wall-line from the attic. The holes/slots may still allow air in the soffit area only, outside the thermal/air barrier that SPF creates.

Same with the ridge vent, plastic/building paper (30#) cover, then the SPF. They may have better options locally, ask them. Reminds me of the old Perry Mason shows, "badgering the witness, your honor..."

Gary
PS. with all that new storage now, you can stop renting a locker, lol.
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Old 04-16-2014, 09:26 PM   #11
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How is attic converted to non-vented?


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Sounds like you know what you are doing, Tipsy. Is R-30 required per energy code? http://energycode.pnl.gov/EnergyCode...?state=Florida
With all due respect to you Gary (and you know that I very much value your opinion)...and to you Tipsy as well...but why is foam a good idea here still?

You want to seal up the home and insulate the roof buy spraying a bunch of foam on the roof and largely seal up the home in a potential chemical bath.

http://www.greenbuildingadvisor.com/...oisonous-fumes

They jury on SPF is still way out and even more-so as it pertains to application and installer error.

I love SPF in certain applications but this is not one of them.
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Old 04-17-2014, 10:49 PM   #12
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How is attic converted to non-vented?


We could discuss this all day and use links to back our opinions, but in the end, they are just opinions. It would not be fair to Tipsy as he/she has already addressed your concerns, with much patience, I might add. If you were at my door, it would have shut on you after post #4. Start a new thread of your own (surprised a mod hasn't sent you a warning already or am I the only one that feels this way)? Any other concerns, Tipsy?

Gary
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Old 04-17-2014, 11:08 PM   #13
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How is attic converted to non-vented?


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Originally Posted by Gary in WA
We could discuss this all day and use links to back our opinions, but in the end, they are just opinions. It would not be fair to Tipsy as he/she has already addressed your concerns, with much patience, I might add. If you were at my door, it would have shut on you after post #4. Start a new thread of your own (surprised a mod hasn't sent you a warning already or am I the only one that feels this way)? Any other concerns, Tipsy? Gary
I must have missed the memo where providing a poster with advice that might be contrary to their plans was banned.

If that is the case, your post count is really going to take a hit Gary.

My advice was not aimed at being contrarian but to challenge Tipsy's rationale and perhaps save him or her some money in the process.

There are plenty of contractors out there spraying foam that have no business doing it so make sure that you really vet your contractor and plan on being out of the home for at least a day for the air to clean up.
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Old 04-17-2014, 11:15 PM   #14
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How is attic converted to non-vented?


To help out Tipsy then.

- soffits don't require replacing
- how old and what kind of roof is on the home
- how is the sheathing
- once you spray to it, you can't change it as readily at re-roof time
- any past leaks
- they would close up the ridge just like they would block off the overhang prior to application
- be sure to ask the installer as to what lifts he will be applying
- have an HVAC pro balance the system and supply some supply and return air

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