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 Post subject: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Tue Apr 12, 2011 2:32 pm 

Joined: Thu Aug 07, 2008 11:35 pm
Posts: 134
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Hello everyone:

Many of you were very helpful towards steering me towards selecting the Simonton 5500 sliders. They are now all installed and I am happy with them. I followed a new construction style approach (nail fin flange) and had siding replaced, so I followed the DuPont instructions for first putting up new Tyvek house wrap, then inserting the windows through the cut-out in the Tyvek (with Tyvek flaps on each vertical side), then DuPont flex-wrap for the sill membrane, then the window went in followed by proper flashing on the sides and head with straight-flash.

All I have done on the interior is to run a bead of caulk between bottom of window frame and the FlexWrap sill membrane. This is in accordance with DuPont instructions to form the back-dam feature. I also ran the caulk over the cedar shims that were used in some locations to shim up the window from the sill. I assume the trim carpenter will snap off any excess.

Now I need to know how to properly seal the interior. I have attached a picture. On most of the windows, there is enough clearance on the sides to insert either the Great Stuff straw (disposable can), or the tip of the Pro guns they make. However, with some of the windows, there is so little clearance, I don't think it will be possible to insert the straw or tip. I was thinking for these locations perhaps I could insert backer rod just to the point it clears the window frame and then caulk between the side of the Tyvek flap and the window frame. However, in these spots, obviously the air seal would be made more on the interior of the window, rather than back against the other side of the nail fin flange. Is backer rod/caulk ever used in this manner and is it proper to make the seal on this side of the window? (Hope that makes sense)

So, my questions would be:
1. do I even need foam or backer rod/caulk considering I have followed new construction window installation thoroughly and with all Tyvek, flashing, siding, etc., is this something to really worry about?
2. Should I use a combination of backer rod/caulk and foam - ie, backer rod/caulk in locations with little clearance and foam where I can insert the straw or gun?

Advice is appreciated. I need to get this done this weekend so my trim carpenter can trim out the windows for me.

Attachment:
window 2.JPG [215.91 KiB]
Downloaded 328 times


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Wed Apr 13, 2011 7:13 am 
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Joined: Wed Apr 04, 2007 11:21 pm
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Location: DC Metropolitan Area-Maryland/Virginia/DC
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If you can't get the foam straw in there, just caulk and you should not really need backer rod on that small a gap.


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Wed Apr 13, 2011 8:54 am 
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Joined: Tue Feb 16, 2010 6:14 pm
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Location: Milwaukee, Madison areas
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+1 to wow... Foam where you can, caulk where you can't.


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Wed Apr 13, 2011 12:14 pm 

Joined: Thu Aug 07, 2008 11:35 pm
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Thank you.

For areas where I can't insert the foam gun or straw, do I just caulk between the Tyvek flap and the window frame? In other words, the caulk bead seal will be on the interior side of the window, briding the Tyvek flap to the frame, as opposed to back up against the back side of the nail fin flange where foam would seal.

Also, I notice the DuPont instructions for window installation in conjunction with Tyvek, recommends Todol or Selena foam. Is the Dow Great Stuff window and door foam on par with these brands they mention?


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Wed Apr 13, 2011 2:23 pm 
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Location: DC Metropolitan Area-Maryland/Virginia/DC
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Window and Door specific foams are very similar. You should be fine with either.


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Wed Apr 13, 2011 9:22 pm 

Joined: Thu Aug 07, 2008 11:35 pm
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Thanks everyone:

For areas where I can't insert the foam gun or straw, do I just caulk between the Tyvek flap and the window frame? In other words, the caulk bead seal will be on the interior side of the window, bridging the Tyvek flap to the frame, as opposed to back up against the back side of the nail fin flange where foam would seal. Is that correct?


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Fri Apr 15, 2011 8:21 am 

Joined: Mon Mar 17, 2008 7:55 am
Posts: 100
Location: scranton pa
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IMO
Foam straw can be squeezed/hammered to fit into smaller voids
To avoid snapping straw at nozzle drag straw along with other hand
Wear gloves as the foam is hard to remove from skin
Put foam in sparingly, start at bottom work up (gravity)
I prefer two beads one back towards the fin and then wait 20 minutes or so and apply the second bead if needed
be careful if it gets on carpet etc.
lock the windows and don't put too much in to avoid bowing mainframe
If straw still doesn't fit then caulk it
I back up interior gap with caulk too not so much that it interferes with extension jambs


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Fri Apr 15, 2011 12:34 pm 

Joined: Thu Aug 07, 2008 11:35 pm
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Thanks:

For tight spaces along the vertical sides, is closed cell or soft, open cell better? I talked with some folks that make backer rod and was told soft cell (which in reality has a closed cell skin and soft cell interior) is better for variable gaps because you can compress it better than closed cell. Is one better than another in regards to any other features?


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Fri Apr 15, 2011 2:44 pm 
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Location: DC Metropolitan Area-Maryland/Virginia/DC
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Closed cell injection foam trumps all other comparisons when applied properly.


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Fri Apr 15, 2011 10:17 pm 

Joined: Thu Aug 07, 2008 11:35 pm
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Thanks everyone.

WOW.. by closed cell injection foam, you are talking low expansion foam from a cannister, right? Does Great Stuff window and door Pro fall in this category? I bought one of their Pro guns to use with the cannisters.

What I will do is used the Great Stuff pro in spots I can insert the gun nozzle or plastic straw extension, and in areas too tight to fit the nozzle, I will use closed cell backer rod and caulk, or just a bead of caulk, between the Tyvek flap and the window frame. I assume for the low expansion foam, I should try to lay down the bead of foam as far back in the rough opening as possible -basically along the backside of the nail fin flange, right?

Am I on the right track here folks? Is Great Stuff Pro decent material?


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Sat Apr 16, 2011 2:09 am 
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Location: DC Metropolitan Area-Maryland/Virginia/DC
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Yes.

You are right on track.


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Mon Jun 06, 2011 11:20 am 

Joined: Mon Jun 06, 2011 11:15 am
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Hi,

Just installed a 4' X 3' vinyl reno window and insulated with low expansion foam around the perimeter. I had previously installed a smaller bathroom window using the same technique with no issues. However this time, the larger window bowed significantly on the sides. Perhaps I used too much foam, but I think what happens is that the foam cures on the surface and sticks to the framing and the window frame and the inside of the foam continues to expand, pushing out like a man in a narrow hallway pushing against both walls with outstretched arms! The larger window yielded to these forces because it had a relatively more flexible frame than the small one.

Anyway - if this happens to you, you can cut slashes in the foam to release the pressure, re adjust your screws to re-align things, and stuff the gaps with fibreglass insulation. I will just use fibreglass next time. BTW - A local installer/director of a window manufacturer near here told me afterwards that he never uses expanding foam - only fibreglass...

Good luck with your installation.

Regards,
Chris


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Mon Jun 06, 2011 2:31 pm 

Joined: Sat Feb 10, 2007 11:51 pm
Posts: 1579
Location: Northern,Virginia
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This is the reason we advise homeowners that using foam is not critical. You are much better off having your windows installed by an experienced installer who uses fiberglass than to let someone not experienced with using foam, experiment on your home. The advantages of using foam are way overblown considering the potential problem from using it incorrectly, as your post rightfully points out.


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 Post subject: Re: Dow Great Stuff foam or backer rod/caulk?
PostPosted: Mon Jun 06, 2011 10:30 pm 
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Joined: Tue Feb 16, 2010 6:14 pm
Posts: 1753
Location: Milwaukee, Madison areas
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crbennett wrote:
Hi,

Just installed a 4' X 3' vinyl reno window and insulated with low expansion foam around the perimeter. I had previously installed a smaller bathroom window using the same technique with no issues. However this time, the larger window bowed significantly on the sides. Perhaps I used too much foam, but I think what happens is that the foam cures on the surface and sticks to the framing and the window frame and the inside of the foam continues to expand, pushing out like a man in a narrow hallway pushing against both walls with outstretched arms! The larger window yielded to these forces because it had a relatively more flexible frame than the small one.

Anyway - if this happens to you, you can cut slashes in the foam to release the pressure, re adjust your screws to re-align things, and stuff the gaps with fibreglass insulation. I will just use fibreglass next time. BTW - A local installer/director of a window manufacturer near here told me afterwards that he never uses expanding foam - only fibreglass...

Good luck with your installation.

Regards,
Chris

Wrong type of foam, poor installation technique... Foam is superior in every way. I prefer not to install an "air-filter" (fiberglass) around the opening of my clients' new windows... That being said, fg is definitely more user friendly for diy's, as are other inferior products and procedures.... I dont mean to discourage diy's, but if there was little or no difference between a diy installation and a professional one, we wouldn't have much business. :mrgreen:


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