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alex bondrea Posted: May 15, 2015 08:00 PM	attic Hi I have attic to spray foam Right now is fiber glass insulation on the celling ,ventilated attic whit electric fan whit thermostat incorporated Today I was in attic and was hot and I her the fan running outside temp 75-80 What is the best idea to spray foam between rafters make it unventilated or on the ceiling? and leave ventilated attic Should I leave the exhaust fan there? I'm midwest area
james keegan Posted: May 16, 2015 10:22 AM	Hey Cata are you saying that in the attic there is insulation on the ceiling? Or floor of the attic most likely. If that's the case you can spray the underside of the roof decking and seal off the ventilation it would no longer be needed. The attic space would then be considered conditioned and no ventilation, or fan required. You could pull the batts out and put a proper floor in the attic and use for storage. You will need 5" of Foam ( code in Canada not sure of US) to properly insulate. Hope this helps. Jk @ greenedge
alex bondrea Posted: May 16, 2015 10:48 AM	The fibre glass insulation in on the floor of attic on the top of drywall Ceiling of the house
mason Posted: May 16, 2015 12:11 PM	Yes, you need to remove the insulation on the floor of the attic, seal off the vents and fan and spray foam to the underside of the attic. However, it is not always advantageous to spray an unvented attic. It is beneficial if you have any of the following: 1. There are HVAC units and/or ventilation ducts in the attic and you can effectively seal off the air leaks (to the outside) in the attic 2. Or, You intend to make portions of the space inhabited in the future. But, if you have no AC/furnace or ductwork in the attic and/or don't intend to make it inhabited space in the future then it is cheaper and more energy efficient to spray foam to the floor of the attic and leave the attic vented. For more information on vented attics go to spray foam.org and download SPFA's technical documents on unvented attics assemblies, Also go to buildingscience.com to read up on their articles on unvented attics. I also have written a few articles you may wish to have on the subject. email me at masonknowles@aol.com In the midwest it can get both very hot in the summer and very cold in the winter, so it pays to have a good amount of insulation I agree with the previous comment of 5-6 inches of closed cell and if using open cell I would go with 10-12 inches. Of course your building codes may dictate more than that, check with the code official for their requirements. The most important thing is to get a good contractor, check out his references, call each one. Ask a number of suppliers who does the best work in your area, if the same name pops up, it is a good sign. Make sure they are in good shape financially, ask how their guys are trained. SPFA has a certication program that is excellent. Applicators carry cards with their photo on it. Most suppliers certify their contractors, check out the suppliers background as well.
mason Posted: May 16, 2015 12:24 PM	I just re-read your post and guess that you are a spray foam contractor, so never mind the selecting the contractor bit. But, definitely check with the local building code official on how much foam they require.
mark moyer Posted: May 19, 2015 07:20 AM	leave the insulation in the subfloor there... should be obvious it is not working well thermally,,, and it will make a wonderful sound deadening media in that subfloor. if you add the $$$for the removal to the $$for the foam insall you are reaching consumer freakout level "for insulation".... leave it there,,,get the job... it will cause no untoward effect,,, ...i drove my foamrig of the bridge,,, i dont care,,,uh huh,,i dont care
alex bondrea Posted: May 21, 2015 04:28 PM	Close cell or open ? Some people told me close cell is not good only open because if is any problems whir roof can't see it whit close cell and the wood can rod out
mason Posted: May 24, 2015 07:51 PM	Nope that is a myth. Read a few of my articles on it at masonknowles.com or email at masonknowles@aol.com and I will send the articles.
John Shockney Posted: May 29, 2015 08:34 PM	you can use open or closed cell foam on the underside of the roof as Mason says! But from an installers point of view I find that open cell is a better choice for an existing attic. open cell foam expands 120 times its liquid volume and does a better and easier job of sealing down at the rafter tails. you can spray open cell with up to a 10 inch lift. And most closed cell foams recommend no more than a 2 inch lift making it harder to fill those hard to reach places. hope this is helpful Airpro
John Shockney Posted: May 29, 2015 08:48 PM	Oh, I forgot to say foamdude is right leave the fiberglass as long as the new foam is equal or greater than that of the fiberglass it will pose not problems. Airpro
mason Posted: May 31, 2015 09:06 AM	Have to disagree with leaving fiberglass on the floor of the attic. It just works against the energy efficiency of foam on the underside of the roof deck, also can have lots of dirt, dust and other crud trapped in it, plus it can absorb odors that linger longer than it should. Never a good idea. Check out SPFA's technical info on the subject at spray foam.org or contact Rick Duncan at SPFA for more specific information
james keegan Posted: Jun 06, 2015 12:18 PM	Hey Cata u would also recommend getting rid of the old insulation. It can have all sorts of contaminates from critters droppings to dust to dirt. This potentially impacts the indoor air quality. It can be expensive to pull out the old not to mention a pain!! Do your customer a favor and remove it though unless it's not practical to remove. Now you have bare substrate you can spray against and seal properly. Better seal...better performance.

Author

Comments

alex bondrea

Posted: May 15, 2015 08:00 PM

attic

Hi
I have attic to spray foam Right now is fiber glass insulation on the celling ,ventilated attic whit electric fan whit thermostat incorporated Today I was in attic and was hot and I her the fan running outside temp 75-80
What is the best idea to spray foam between rafters make it unventilated or on the ceiling? and leave ventilated attic
Should I leave the exhaust fan there?

I'm midwest area

james keegan

Posted: May 16, 2015 10:22 AM

Hey Cata are you saying that in the attic there is insulation on the ceiling? Or floor of the attic most likely. If that's the case you can spray the underside of the roof decking and seal off the ventilation it would no longer be needed. The attic space would then be considered conditioned and no ventilation, or fan required. You could pull the batts out and put a proper floor in the attic and use for storage. You will need 5" of Foam ( code in Canada not sure of US) to properly insulate. Hope this helps. Jk @ greenedge

alex bondrea

Posted: May 16, 2015 10:48 AM

The fibre glass insulation in on the floor of attic on the top of drywall
Ceiling of the house

mason

Posted: May 16, 2015 12:11 PM

Yes, you need to remove the insulation on the floor of the attic, seal off the vents and fan and spray foam to the underside of the attic. However, it is not always advantageous to spray an unvented attic. It is beneficial if you have any of the following:
1. There are HVAC units and/or ventilation ducts in the attic
and you can effectively seal off the air leaks (to the outside) in the attic
2. Or, You intend to make portions of the space inhabited in the future.

But, if you have no AC/furnace or ductwork in the attic and/or don't intend to make it inhabited space in the future then it is cheaper and more energy efficient to spray foam to the floor of the attic and leave the attic vented.

For more information on vented attics go to spray foam.org and download SPFA's technical documents on unvented attics assemblies, Also go to buildingscience.com to read up on their articles on unvented attics. I also have written a few articles you may wish to have on the subject. email me at masonknowles@aol.com

In the midwest it can get both very hot in the summer and very cold in the winter, so it pays to have a good amount of insulation I agree with the previous comment of 5-6 inches of closed cell and if using open cell I would go with 10-12 inches. Of course your building codes may dictate more than that, check with the code official for their requirements.

The most important thing is to get a good contractor, check out his references, call each one. Ask a number of suppliers who does the best work in your area, if the same name pops up, it is a good sign. Make sure they are in good shape financially, ask how their guys are trained. SPFA has a certication program that is excellent. Applicators carry cards with their photo on it. Most suppliers certify their contractors, check out the suppliers background as well.

mason

Posted: May 16, 2015 12:24 PM

I just re-read your post and guess that you are a spray foam contractor, so never mind the selecting the contractor bit. But, definitely check with the local building code official on how much foam they require.

mark moyer

Posted: May 19, 2015 07:20 AM

leave the insulation in the subfloor there...
should be obvious it is not working well thermally,,,
and it will make a wonderful sound deadening media in that subfloor.
if you add the $$$for the removal to the $$for the foam insall you are reaching consumer freakout level "for insulation"....
leave it there,,,get the job...
it will cause no untoward effect,,,

...i drove my foamrig of the bridge,,,
i dont care,,,uh huh,,i dont care

alex bondrea

Posted: May 21, 2015 04:28 PM

Close cell or open ?
Some people told me close cell is not good only open because if is any problems whir roof can't see it whit close cell and the wood can rod out

mason

Posted: May 24, 2015 07:51 PM

Nope that is a myth. Read a few of my articles on it at masonknowles.com or email at masonknowles@aol.com and I will send the articles.

John Shockney

Posted: May 29, 2015 08:34 PM

you can use open or closed cell foam on the underside of the roof as Mason says!

But from an installers point of view I find that open cell is a better choice for an existing attic. open cell foam expands 120 times its liquid volume and does a better and easier job of sealing down at the rafter tails. you can spray open cell with up to a 10 inch lift. And most closed cell foams recommend no more than a 2 inch lift making it harder to fill those hard to reach places.

hope this is helpful

Airpro

John Shockney

Posted: May 29, 2015 08:48 PM

Oh, I forgot to say foamdude is right leave the fiberglass as long as the new foam is equal or greater than that of the fiberglass it will pose not problems.

Airpro

mason

Posted: May 31, 2015 09:06 AM

Have to disagree with leaving fiberglass on the floor of the attic. It just works against the energy efficiency of foam on the underside of the roof deck, also can have lots of dirt, dust and other crud trapped in it, plus it can absorb odors that linger longer than it should. Never a good idea.

Check out SPFA's technical info on the subject at spray foam.org or contact Rick Duncan at SPFA for more specific information

james keegan

Posted: Jun 06, 2015 12:18 PM

Hey Cata u would also recommend getting rid of the old insulation. It can have all sorts of contaminates from critters droppings to dust to dirt. This potentially impacts the indoor air quality. It can be expensive to pull out the old not to mention a pain!! Do your customer a favor and remove it though unless it's not practical to remove. Now you have bare substrate you can spray against and seal properly. Better seal...better performance.

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