# Removing blown-in fiberglass insulation attic replacing just foam board



## professorj (Nov 16, 2015)

I like to remove all my blown in insulation and utilize foam board (4 inch) with silver side facing shingles or towards the sky).

* can I leave the foam side (NOT foiled) without drywall or other covering?
and or do I need to get double foiled like silverglow.

Installed: done horizontal to rafter (perpendicular) and all seams sealed.
still allowing air movment through soffits.

Location: tampa, florida 

Roof: hip style

Upon removal I will also seal any air leaks, pipes, recessed cans (with app. fire retardent foam) etc etc.

I DONT want to put the fiberglass insulation back.

In other words creating conditioned attic.

Anyone do this with success, see signficant heat reduction, in high humid florida.


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## gregzoll (Dec 25, 2006)

If you remove all of that insulation, you are going to lose a lot of heat from the house into the attic. Placing that Foam board on the backside of the roof sheathing, will just cause the Shingles to bake to an early death.

You cannot create a conditioned attic space in what you want to do. You have to leave the Blown in insulation in. There is no in between.


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## professorj (Nov 16, 2015)

gregzoll said:


> If you remove all of that insulation, you are going to lose a lot of heat from the house into the attic. Placing that Foam board on the backside of the roof sheathing, will just cause the Shingles to bake to an early death.
> 
> You cannot create a conditioned attic space in what you want to do. You have to leave the Blown in insulation in. There is no in between.


First restate: I DONT WANT HEAT- i live in FL. (over 15 yrs). I deal with too much heat and humidity in attic.


a.) using rigid board with reflective coating so -question your logic of "baking the shingles" due to IM currently backing the shingles now by not getting the heat out * yes I do have ridge vents.

I like to hear from someone that has placed ridge board in an attic in FLORIDA. 

I might test the attached garage attic portion first with ridgid board as this has NO insulation and where the air handler is located. Yes in the attic typical florida stupid building.
Addtionally I dont want fiberglass insulation batt, blown etc in the garage portion since this is our storage * we dont and cant have basements in FL.
In addtion looking into whole house fan.


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## professorj (Nov 16, 2015)

to add some more information (not cause debates ).
This is a vented attic system on a hip roof. 
soffit continuous around home.
1991 home.
2nd roof 2006.
Shingles are sandstone brown- lighter in color that back in 1992

4 ft. 26-Gauge Galvanized Steel Weather Vent in 2006 (like a ridge vent put not a typical ridge vent strip where rafters met.
6 total on * except there is NOT one on the garage roof (hips).

There is different applications I am aware on how a house breaths in a vented, unvented, semi conditioned, conditioned and unconditioned etc etc... 

lets get down the verbage correctly- many different approaches -which one determines the content.

My content is I have a very hot roof attic space over the garage. I DO NOT WANT TO 
CUT ANOTHER hole into the attic for ventilation article:
My air handler in in the roof GARAGE attic portion: I like to get the temps down.

I believe my ventilation is good for the house roof square footage.
http://www.fsec.ucf.edu/en/publications/pdf/FSEC-CR-1496-05.pdf

What I like to do is radiate the temp back out away from the roof NOT in !
Ridge foam board with foil is a radiant barrier from all the manuf. I have read.


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## gregzoll (Dec 25, 2006)

Regardless what you want to do. A properly ventilated and insulated attic space will not get that hot. What you are going to do will cause more problems then it is worth. You are going to bake the shingles to death, along with making the house hotter, including the attic, because that space has no way to vent any heat, once you close it off.

A finished attic with hvac supplies and returns is what is considered a conditioned space. What you are dreaming of, is as I have stated twice. Attics are supposed to be warm during the Summer to a degree if properly ventilated.


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## beenthere (Oct 11, 2008)

Usually what you want to accomplish is done with spray foam. I don't know how well foam board will work.

But you will need to find out if your local building code will permit the foam board to be exposed. Which will probably depend on its flame spread rating.


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## professorj (Nov 16, 2015)

Once again not looking for a debate what I am looking for is someone (especially in FL) that has applies a radiant barrier or ridge board that has a radiant barrier.

Skip the removal of insulation comment in my orginal post- thats throwing in the wrong tone.

Heres a video of the debunk of the shingles baking out there not 7 -10 more degrees on the shingles is sufficient and wont kill the life of the shingle.





Theres lots of videos showing that radiant heat barriers wont :bake roof.

Whats baking now is my garage attic stuff- melting the wheels on my suitcases one example and 2. the effects of the air handler dealing with unnecessary.

Again you can have a EFFECTIVE VENTED OR UNVENTED HOME!!!!! people use these words even builders without knowledge what the heck there talking about in context. YOU CAN HAVE A SEALED HOME (UNVENTED) but it better be sealed correctly. I dont have that type of home.

Again looking for someone who as applied a radiant barrier or ridge board with radiant barrier on it and what where the measures of success.
Keep in context Im in SOUTHEAST (FL) high humidity all 4 seasons pretty much- its Nov. humidity is still 65-75% .

Trying to stay away from the high cost of foam.
Radiant barriers i.e atticfoil.com are in my budget and price range.


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## professorj (Nov 16, 2015)

GREGZOLL: No offense (maybe offense) midwesterns (grew up in midwest) usually have no clue of how insulation is done or not done in the south. Not saying you don't know insulation saying you dont know insulation in the south.
Example, just had a Michigan builder (so called certified GC) that visited me on a project; wheres your furnace? he said- "we dont have furnances in FL". Typically we have heat pumps. Whats that said the GC. how do you get heat from a heat pump?- with a chuckle I said oh you have a lot to learn about HVAC systems.

http://www.joelstiburek.com/topten/south.htm


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## professorj (Nov 16, 2015)

here is one of the radiant barrier products looking at http://www.homedepot.com/p/Reach-Ba...lation-Roll-with-Single-Air-SS48125/204476670

Not a home depot fan yet amazon other places sell similiar i.e. atticfoil.com


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## professorj (Nov 16, 2015)

Another reason I like a SOUTHERN to answer question:

*By Jane Friedmann*
*APRIL 29, 2013 — 9:41AM*


TEXT SIZE



*7*



EMAIL

PRINT

MORE

As Larry Stopa ate a free steak at an Oshkosh, Wis., restaurant, he listened to a sales pitch for “radiant barrier” insulation that was supposed to save him a bundle.
Stopa was skeptical of claims that a thin blanket of aluminum-clad insulation laid over existing attic insulation could significantly reduce heating and cooling costs.
Stopa later researched the product and concluded that the radiant barrier seller was “scamming the seniors,” who made up the the majority of the audience that day.
The Minnesota Department of Commerce is concerned, as well. For the second time in as many years, the department has warned consumers to think twice about installing radiant barriers, because of their questionable benefit in northern climes.
*“Radiant barriers in attics may be valid for homes in Southern states*,” said Commerce Commissioner Mike Rothman, “but they save very little energy in Minnesota homes.”



​


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## gregzoll (Dec 25, 2006)

Modern attics are not meant to be used for storage. Again, what you want to do, cannot be done. You are going to cause problems. Also you cannot open the Garage attic space into the Living space, because it allows for Carbon Monoxide to enter into the living space. Also if there is a fire in the garage and you have that foam board up there, it will give fuel for a fire.

Leave it a lone, purge some stuff or build some closets in the garage and get rid of some stuff that you have not used for a long time.

A properly ventilated attic during the hottest day of the Summer, should get no hotter then around 115. As for that Turbine, it is counterproductive of what the passive vents are supposed to do.

The last thing is that if you put in a whole house fan and have the garage attic space open to the Living space, again Carbon Monoxide.

Use your energy to build some closets and purge out stuff that you have not used for years.


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## Bud9051 (Nov 11, 2015)

Hi Professorj,
I'm way up in Maine but do read Joe's many articles and have read some of Danny Parker's work on shingle temps in Florida. 

Most of the solar energy that hits a roof is re-radiated into space or blown away by winds or convection, thus what enters our attics is only a smaller portion of that total energy. If we block it with either a hot rood design or a radiant barrier it does increase the shingle temperature, but that extra heat is easily blown or radiated away resulting in a minimal increase in shingle temperature. 

Note before I forget, if you do use some foil faced rigid foam board, Dow Thermax is the only one I know of that has been approved to be left uncovered.

In addition to foil faced rigid foam board or the foil bubble foil from HD, there are rolls of radiant barrier material that can be installed below the rafters. But your hip structure would not provide good air flow. If you installed strapping and then the radiant barrier, then the air would have a path.

I have avoided delving into Florida construction due to the many special requirements, radiant barriers among them.

What may help would be to search for information on insulating a cathedral ceiling. 

Going too long so I will stop.

Bud


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## Tally Wacher (Nov 17, 2015)

I think for the OP's situation, radiant barrier is reasonable so long as it is part of a system that consists of air sealing, good ventilation, and quality insulation suitable for his location R-38, I think). Is you FG nasty with animal droppings and you want to remove it? If not just blow on top to reach your target R value.


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## Windows on Wash (Aug 30, 2011)

How about some pictures?

Is the roof currently vented? Soffits open? How is the venting on the top side?


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## professorj (Nov 16, 2015)

Dow Thermax is the only one I know of that has been approved to be left uncovered.

a.) yes this is something looking into. OR
b.) might abandon FOAM/aka ridge board all together.

whats a prob. on these forums is you have northerns no little about the south usually vica versa.
**The building codes in FL have changed 4 times in last decade does not include county.

Repeat myself again on these questions:
How about some pictures? of what? its an attached garage with hip roof no insulation over the garage: air handler in attic located between wall off garage and first wall of home- that will make sense if you familiar with how FL builders put air handlers (which there really called inside coils not air handlers or evaps anymore).



Is the roof currently vented? Yes read thread 

Soffits open? Yes read thread

How is the venting on the top side? Read thread response below:vs_OMG:


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## Windows on Wash (Aug 30, 2011)

You ever heard of the saying that you catch more flies with honey....? 

I read your first post and scanned through the rest. I did not see where the mention of the soffits and vented design until the second read through. 

You can put rigid foam in the rafter bays if you want. Despite the fact that you posted up a video from a retailer of radiant barriers (not a usually unbiased source of information), the fact is that sealed attics do not result in a dramatic spike in peak shingle temperatures over the same roof in a well vented design. Most records show a 6-15 degree spike and well within the range of safety for the plywood and shingles. 

Most (more than 95%) of the shingle cooling happens to outside. 

Feel free to rigid foam it up but I would either cover it with drywall or have the foil facing the attic side. The radiant barrier aspect won't be helping on the roof facing side without an air gap and some air movement. 

As Greg mentioned, I would be very cautious about the communication between the garage and the now conditioned attic space.

You are going to spend a bunch in foam and time to make this work and get it sealed properly if you do it correctly. If you are worried about the handler and working inside of those conditions, why not build an enclosure around the handler to back that with rigid foam. Probably have 1/10th the foam and materials and time.


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## Gary in WA (Mar 11, 2009)

Rigid (not ridge- too confusing) foam board-- the Dow as mentioned should be checked with local AHJ as it is approved in MOST areas without an ignition barrier due to the facings. You could apply RB up the rafter faces and level at the top 1/4 to maximize full venting of the turtle vents as exhaust. Leave a few inches open to attic at bottom, with vents at top in the umbrella portion to vent the main attic area. If you could restate your questions again, for me, I will try to help... RB is perfect for your location with AH in attic and min, R-19 on ceiling; http://www.fsec.ucf.edu/en/consumer/buildings/homes/faq.htm

Another, with more examples/results; http://www.fsec.ucf.edu/en/publications/html/FSEC-CR-1231-01/

Pretty bad to lose 1/3 of your A/C before it even reaches the room; http://www.fsec.ucf.edu/en/research/buildings/zero_energy/lakeland/construction.htm

Gary


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