Solid vs Insulated Window Headers
Hello all.
I am looking for opinions about solid versus insulated window headers. The house is in SE Michigan. The exterior is wood siding. Windows constitute most of the wall area of 3 exterior walls of a sun room.
The builder is contending that solid wood framing with 1 LVL beam on a 2×6 exterior wall is fine (a solid wood header). The span of each window is about 48″, but since there are so many windows, this “tripled combination” will run continuously around 3 walls of the room.
My contention is that there is no thermal break in these headers and that a “cool band” will exist at that level on the 3 walls. Since these windows take up most of the area on the 3 walls, the only part of the walls that has open stud spaces is below the window openings. These stud spaces will be filled with spray-in foam.
Any opinions on the matter would be greatly appreciated. Thanks in advance.
Eric
Replies
What is the U factor of the windows?
What is the header thickness? A short span should allow you to foam the interior side of lvl as the lvl should not be as thick as two by six wall.
In my house I used spray in foam but we used 2x6's. With a double 2x10 header I still get 2.5" of foam at the header. With a double LVL you would still get 2".
We have a lot of windows and like you I couldn't stand the thought of all those headers either not getting insulated or only getting 1/2" foam board if the studs had been 2x4.
You have a 5.5" wide LVL beam?
These are easy to use. Just cut to length. http://www.trusjoist.com/PDFFiles/2070.pdf
With that many windows, even of the best R-value (or u, whatever the corresponding insulating # for windows is called) you are wasting your time, IMHO, worrying about an insulated vs. non-insulated header. It's like the guy driving a Hummer 3 blocks worrying if his tires are 2 pounds under-inflated!
An uninsulated header is going to have a higher R value than just about any window you put in. With that much glass, it no longer matters whether the header is insulated or not.
>> The builder is contending that solid wood framing with 1 LVL beam on a 2x6 exterior wall is fine (a solid wood header). <<
Are the lvl's 5-1/2" wide?
sounds like you are wasting your money on LVLs. 3 LVLs for a 48" opening?! Is there another story or 2 or 3 above? Even with 1 LVL and an air space I wouldn't worry about R value with all of those windows.
I agree that the loss at the header being a soild LVL is nothing when you look at the loss thru the glass.
I didn't bat an eye on mine. I wanted rock solid and got it.
Do you have the option to raise your headers into the rim joist on the ceiling above? We do this whenever possible. You can insulate the rim joist out into the ceiling space as much as you like and you have a cripple wall over the window and can even drop back to a single trimmer if you get engineering on it and it doesn't present a trim nailing problem. It sure looks wierd though.
I'm sure I'll catch major grief for suggesting this but my structural engineer signed off on it for this house and said that since the trees hit the fascia first during a hurricane reinforcing the band at the edge of the attic actually makes the house more resistant to hurricane damage due to flying trees. We Energy Star certified at HERS 92.3 (61.5% better than old code) on this house with spray foam and a Variable Speed Zoned-Bypass HVAC.
All you traditionalists can tear into me at your pleasure.
Michael
I also like to put the header in the rim if possible.
Beer was created so carpenters wouldn't rule the world.
I have done the same thing on some projects. Works well and while I have had to explain to some inspectors just how it works they all signed off on it without question, no engineers needed .
But then I used to frame gable roofed garages that had the garage door in the gable end without a large garage door header too.
Just ordered a bearing truss with infill nailers for the gable end. Can't do that any more here because of the "Portal Frame" code requirements.
I really like these insulated headers:
http://www.swi-joist.com/p_04.htm
I didn't read everyone's replies, so perhaps this was said...from a structural engineering standpoint you are throwing away a lot of money on LVLs. For a 48" opening in bearing walls use 3 2x6s (on edge) with a layer of rigid insulation between each to make up your wall width. Make sure you use a 16d nail to get adequate penetration. On non-loadbearing walls like a gable end you can even use a horizontal plate like you would on an interior wall and really cut down on cold spots.
Regards.
Edit, these days you can get EPS cheaper than plywood anyway, and it's easier to cut your spacers with a utility knife than ripping plywood or OSB spacers.
Edited 2/2/2007 11:51 am ET by tuolumne
Here is one by Trusjoist:
http://www.ilevel.com/walls/w_TJ_insulatedheaders.aspx
I usually put a layer of 1" dow board on the inside face of a triple header.