Hello: If you have double-stud walls about 12" thick, did you enlarge the interior window openings to allow more light to enter, or, is this really not necessary? Thanks, Rob

our present client asked us not to, but it does help eliminate the tunnel effect. We have an 1812 three story brick house in town with deep sills, where the interior opening is wider, so it's not a new idea, but again,it is a nice feature.

My walls are double stud, with 12" inside cavity, and except for two bathroom windows and a rather wide kitchen window with cabinets to either side we did flared out jambs, about 20 degrees from straight. The effect is nice, overall, and I'm glad we did it.

Thanks Bob & Dick. :)
I have read where people flare out the jambs 45 degrees.
Is the amount of 'flare' just a personal choice or is there a formula or rule of thumb for its' determination?
Thanks,
Rob.

Robert, I just measured mine, and the as-built angle is more like 24 degrees (5" to the side of straight out over 11 inches straight out sill width). As far as admitting more liight with a wider angle, I doubt the perceived increase would be dramatic, especially if the jamb extensions are drywall with light-colored paint. Mine happen to be stained maple veneer. For me, the light admittance improvement is fine, and I notice more the much improved outward viewing angle as the bigger gain. As I sit here, looking out through two of these windows, I'm trying to envision the look of a wider angle, especially out to 45 degrees. While I do like the look of what I have, I'm inclined to think that anything at all close to 45 degrees would look downright funny, but that may be just my being so used to seeing what I have. Given a tossup as to narrower vs very wide angle out from straight, from aesthetic point of view, I'd opt for the narrower angle, as the thermal impact on that R40 wall is less.

Thanks Dick, I appreciate your time. My wife and I are fighting about straight or flared. I'd go with flared. I 'built' a window wall in Sketchup with 30, 25, 20 degree flares and straight - the jury is still out. Your point of 'outward viewing angle' is well taken - I hadn't really considered that.

I'm doing flared windows in our ICF home. I went 45 degrees. If we don't like it, I can always reduce or eliminate the flare. I only have about 8" of depth inside of the window frame. Time will tell.

I did one for my mom back in 93 with flared openings. Everyone loves it. It even won a home building award in N.S. back then.

Mike, how does one attach pictures to a post here? I don't see anything to click on.

Posted By DickRussell on 03 Feb 2013 06:31 PM
Mike, how does one attach pictures to a post here? I don't see anything to click on.

I had to type something, then post, then go into edit. If I just hit reply... all the buttons at the top wouldn't show up

To insert images, you need to click the (+ Add Reply) button just below and to the left of the last post on the page, not the (Quick Reply) box at the very bottom of the page.  Once the (Reply To Topic) page pops up, go to the bottom and click the arrow next to (Attachments).  Then click (Browse) and find the file on your computer that you want to upload.  Photo and pdf size limits are pretty restrictive on this site - 100k if I remember correctly.  After you reduce the size of the file below the limits, then click (Upload).  Then you have to put your cursor where you want to insert the image and click (Add File to Post) next to it.

My solution, not built yet but FWIW.
Put the windows near the middle of the wall. Centered windows have the lowest possible heat loss, up to 20% less heat loss than either innie or outie. With a 12 inch wall 4" outside recess, 4" window frame 4" inside recess. The look is very close to typical 2x6 with foam outie from the inside. The outside recess is really close to what a typical brick veneer adds & hardly noticed. No need for flares which will be tricky to air seal and compromise thermal performance.

Liebler, good call. To build a enegy efficient wall then attach the windows on the outside of the insulated shell is crazy. I tell my customers to forget the nail flange and install the windows inside the opening. This helps with trim and it helps to lose the tunnel effect without spending alot of time on special carpentry.

Thanks people! :)
Liebier:
I think your idea is great! Now, if I can only convince my wife...
Rob.

Your viewing angle is not improved by moving the window. This does not solve the original question. And it does create a waterproofing problem, or at least some extra precautions needed to keep water out of the wall. I would even say the location of the window has no effect on energy use in most climates, your either exposing interior insulation to the outside or vice versa.

NFC,
If someone is building an r40 wall, they obviously are concerned with heat loss and in a climate where such concern is economically justified. Thorsten Chlupp, who successfully builds passive houses in the permafrost zones of Alaska, has done extensive thermal modeling of window placement within a wall. His results clearly show significant reduction of heat loss with centered windows. You are absolutely right in asserting that attention to waterproofing details is even more important with centered windows. You are also correct in asserting that viewing angle is not improved BUT the viewing angle in the case of a 12" wall, with centered windows,l is not significantly different than what we are used to seeing in a typical 2x6 wall with brick veneer. If angled viewing is really important wider windows may be needed.

Somehow until the late 70's windows were installed without nailing flnages and were weather tight, so I'm not buying the waterproofing angle. We had this discussion on the window thread a few years ago and a rep. from one of the fiberglass window companies agreed that it was true. If you look at a new construction window that is installed on the outside of a wall the top sash is outside of the wall. The first area that is hit by the wind is that top sash. Move the window into the wall and wind has a harder time hitting it at the same velocity. Look at any product that is placed in a wind tunnel. Look at any window and they are designed to force air to change direction from a straight line. Reduce straight line force and you reduce air infiltration.

I'm not talking about the window, but the new exterior window ledge that exposes your interior portion of the wall by putting the window inside the wall instead of flush with the outside.

If your talking about the exterior sill that is installed first and extends under the window and past the exterior material whatever you choose for siding, plus tradioinally this is always sloped to the exterior

NFC,
If you can make an exterior corner water tight, why would it matter if that corner is at the jam of a window. Yes a sloped sill is a good idea and head flashing that slopes down and out is as well. Typically double stud walls are connected to each other with plywood around window openings. For a centered window some blocking may be needed to assure a robust window mounting.