New windows and a thicker wall

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Pointedstick
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New windows and a thicker wall

#1 Post by Pointedstick »

I've got a house in the Albuquerque, NM area that needs new windows. The ones it has are old aluminum double-paned ones that don't seem to perform very well. They are leaky, cold to the touch in cold weather and many don't open well. One large picture window seems to have a single-pane-only center lite! :?

At some point, I plan to beef up the insulation by adding two inches of EPS foam to the exterior and applying stucco, effectively increasing the wall thickness. How would this interact with the windows? Should I have the windows done first, thicken the walls around them, and leave them in indentations in the wall? Or would you recommend doing the wall and windows at the same time, and putting the new windows flush with the new cladding? If so, how would this interact with the drainage plane? Would such a project necessitate thickening or re-doing the window rough openings and allow the use of new construction windows?

This is a climate that gets less than 10 inches of rain a year so it'll probably be fairly forgiving of sloppy moisture management practices, but I still want it done right the first time.

Additionally, do any of the pros here know of any really good windows and installers in the Albuquerque area?

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Windows on Washington
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Re: New windows and a thicker wall

#2 Post by Windows on Washington »

Less important that you do them exactly right as you mentioned with the lack of moisture you get.

You can set the windows where you want them and just do the re-trimming when you start the new wall modifications.

Drip caps over the trim and behind the stucco. :D

Pointedstick
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Re: New windows and a thicker wall

#3 Post by Pointedstick »

Thanks WoW. I asked a similar question on greenBuildingTalk a few months ago and was strongly cautioned to keep the drainage plane between the sheathing and the new foam insulation sheeting, and to keep the windows co-planar with the drainage plane:

http://www.greenbuildingtalk.com/Forums ... fault.aspx

Is this just overthinking things? I don't even have a clue what the current drainage plane is. For all I know, the plywood sheathing doesn't even have a housewrap-type coating at all (it's a 1972 house).

Pointedstick
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Re: New windows and a thicker wall

#4 Post by Pointedstick »

Thinking about this more, I think I need to keep the water-resistive barrier over the plywood sheathing. If I add foam insulation, then the plywood will be the first cold surface that any water that penetrates the stucco and gets vaporized by the heat of the sunlight will condense on. If I put the WRB over the foam and co-planar with outie windows, then vaporized water will permeate through it and condense on the plywood.

Next question: This strongly implies that I need innie windows so that the windows remain a part of the drainage plane. If I really want outie windows instead, can I add a second WRB over the foam? This may be the wrong forum to ask such a question, and if so I apologize.

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Windows on Washington
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Re: New windows and a thicker wall

#5 Post by Windows on Washington »

There are valid arguments for both. I do like the inside set but they do require more trimming out.

Pointedstick
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Re: New windows and a thicker wall

#6 Post by Pointedstick »

Thinking about this even more (I think too much), there's no way the plywood sheathing will be cold enough to be a condensation plane with two or more inches of foam (R-8+) protecting it from the exterior cold in winter, and R-13 fiberglass batts protecting it from interior cold in the summer. Given that EPS foam is code-approved for use as a water-resistive barrier if installed properly, I'm going to use as that, and beef up the foam thickness to at least 3" to make sure it's at least R-12 or so.

I found this awesome document that details window flashing against foam: http://www.nrel.gov/docs/fy05osti/37583.pdf

For any window installation experts here, does that look sane? I especially like the use of taped, regletted head flashing.

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Windows on Washington
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Re: New windows and a thicker wall

#7 Post by Windows on Washington »

Little overkill with the two layers of jamb flashing if you ask me and they should just spec a rigid sill pan if they want it done without a corner or use Tyvek FlexWrap.

The reglet drip cap is right but it needs to be cut at an upward angle.

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Re: New windows and a thicker wall

#8 Post by Guy »

Installing a new window over insulation board is very tricky to say the least. I've done it numerous times with complications on each job. The biggest issue is getting your fasteners to hit something rigid enough to secure the window. If your going to use a three inch insulation board you might as well use framing nails to lock the window in place. The other big issue is not over pounding your fasteners. The foam board dimples and causes the fin to pucker. Just straight up crazy to use any window with a nail fin application.
My last one of these jobs went really well. I used a vinyl Lincoln window with their attached Brickmould on all four sides. This Brickmould has a removable cap that pops off to reveal a fastener channel. We back caulk the Brickmould, slap it up plumb and square, then fasten with galvanized screws threw the Brickmould and into the stud. Install the snap on cover and your done outside. The rigid Brickmould won't pucker or waiver. On the inside you adjust the Jamb Jacks, shim, then screw. You can install these with the jamb screws only if need be. I pre-order each window with a new Jamb Box, painted or stained to the customers request. These are full frame replacements. Four good installers can hammer out 30-40 of these in a good day. Only if there's no complications. We did 35 in one day. That was a good day! Good Luck!!!

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