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Discussion Starter · #1 ·
Hello all! New home-owner and first time poster!

So I was going to link an article but I can't apparently. It says I need one post which I did... Go to Google and search "Insulation Man - To vent or not to vent"
Anyway...
I planned on having 2" of spray foam throughout the attic floor of my house. I like what I read about how it stops air infiltration etc. Then I would blow cellulose on top of that to increase the R value.
My roof is less than 3 months old and is vented up high and the soffits are vented as well.
This part of the article concerns me if I go the sprayed route:
"Installing roof ventilating in a foam roof can lead to limited moisture problems because there will be days in spring and fall when snow is on the roof, but it is relatively high humidity outside with outside temperatures in the high 30’s to low 50’s. that air gets pulled into the roof vent space and condenses because the roof vent space is much colder due to the snow cover. The water runs out roof the vents and forms icicles in the soffit and/or it runs between the exterior finish and the wall sheathing. If it is trapped in the soffit or between the sheathing and finish, it can cause rot in those areas. Since the ventilation is not necessary either by code or science, and it can cause this rot phenomenon, we recommend you do not vent a foam roof."

Any recommendations or insight of what route to go? Is it ok to spray the attic floor as long as the it is vented high and low?

I don't want the cold air being 'sucked' into my attic and condensing and rotting away slowly.

Thanks in advance!
 

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When they are talking about a foam roof, they are referring to the insulation layer being the same plane as the roof deck.

You aren't doing that here.

Where is the home located first off?

Second, spraying 2" of foam over the entire attic floor is a waste of money and resourced in my opinion. You can get all the same performance by spot sealing the top plates, penetrations, and other envelope bypasses. You will still likely be using foam there, but to cover the entire attic floor wastes all that product in those areas where the air seal is not improved with foam (i.e. across the open spans of unbroken drywall).

Loose fill cellulose is a bunch cheaper and just as good and insulator.

I would spot seal (air seal), make sure you have baffles at the eaves to ensure the unbroken ventilation, and then blow in a combined R-50 of loose fill cellulose.
 

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Discussion Starter · #3 ·
Thanks for the clarification on the foam room thing.

I am located in Northern IL near the WI border(Coulda sworn i filled that out during registration).

Okay that makes sense. What sort of foam do you use on those spots...Great Stuff?
Will that stuff be good enough to spray directly against boiler chimney bricks, duct work for kitchen/bathroom vents etc?

My house was built in 1951 the walls and ceilings are plaster. There are a few cracks in the ceiling and walls that I have used spackling paste in to paint over. They were all 'cosmetic' cracks in my opinion all under 1/8" wide.
Would the hairline cracks be on the same playing field as 'broken drywall'?

I will have to read up on installing baffles.
Is cellulose blown directly over the batts without any plastic barrier? My logic says yes because Cellulose is basically the texture of shredded newspaper.

Thanks for the reply! Being a young engineer and this is my first house I am focused on ROI and effectiveness so I wasn't pleased with the spray foam price.
 

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I'm new here, but $700 two-part spray foam is diving into the deep end for your first air sealing adventure.

A super-cheap alternative is to just buy the disposable cans of Great Stuff. They're single-use and come with a built-in straw.

A better alternative is to buy the professional cans of Great Stuff with a professional gun. This is still single-part foam, but REUSABLE.

I use the Foamnseal FNS 500 because it's cheap and well rated (http://www.amazon.com/Foamnseal-Polyurethane-Foam-Dispensing-Tool/dp/B00F2ZGTJE/). But Great Stuff makes their own guns as well.

I have a second gun, 30" version, for accessing hard to reach places, like wall top-plates where the roof rafters meet the floor.

Then, once you have a professional spray gun, you just buy simple $12 cans of reusable Great Stuff at any box store. http://www.amazon.com/Dow-Great-Stuff-Gaps-Cracks/dp/B0044UYJXG You can leave this on your gun for a month or more.

So, for $30 plus $12/can you can seal any gaps/cracks directly, rather than spray your whole floor, which isn't an efficient use of foam, as Windows on Wash pointed out.

Plus, with single-part foam, you don't need to mix the foam, shake the two cans, keep them at 70 degrees, keep a stock of disposable tips, nor wear a hazmat suit and breathing apparatus. Single-part foam is way way simpler for just sealing top plates and other gaps.

An example of sealing a plumbing chase with 2" rigid foam, plus the Great Stuff I mentioned.

 

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Discussion Starter · #8 ·
I appreciate your input Alketi! Since my last post I have researched further and found a pro gun similar to one you purchased. I also had decided single foam would be easier for me.

I may be starting this endeavor the first of the year! (my heat bills have doubled and the avg temp only decreased 8 degrees F)
 

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The one part spray foam cans are definitely the more regular choice for DIY applications.

Definitely spend the money on getting a proper foam gun in this case.

You will save quite a bit of money going with the one part spray foam versus the two-part froth kits. That being said, we have tested homes both in and out using each application and have found that the two-part spray yielded better overall air seal.
 

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Discussion Starter · #10 ·
I have no doubt that the two part spray yields better results, that is why most (if not all) professionals use it.
I am already trying something new (insulating an attic) and adding the learning curve of properly applying/mixing 2 part foam is something I don't think I want to deal with.
 

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I may be starting this endeavor the first of the year! (my heat bills have doubled and the avg temp only decreased 8 degrees F)
Start with by looking around your plumbing vent pipes, which are often run up a double-wall leaving a large gap in the attic floor (as was my case). And your chimney, if you have one. Sealing the chimney chase requires metal flashing and fire rated caulking, not Great Stuff foam. Look for the big gaps first and get all the wall top plates and electrical penetrations along the way. Good luck!
 

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I have no doubt that the two part spray yields better results, that is why most (if not all) professionals use it.
I am already trying something new (insulating an attic) and adding the learning curve of properly applying/mixing 2 part foam is something I don't think I want to deal with.
If you aren't doing 2-Part foam because you are worried about the skill required, don't. It is as simple as it gets. Most of the videos are quite clear and comprehensive.

When it comes to the nozzles...when in doubt...swap it out.
 

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