Green framing focuses on building walls that use less wood but are still structurally sound. This technique is called the Advanced Framing Techniques, or more specifically Optimum Value Engineering (OVE). As a New York green contractor we are not concerned so much about exterior stud walls since most of our jobs are in brownstones where the exterior walls are brick.
But on the interior we do have a lot of framing and OVE is very much part of our process. We salvage all our studs and have yet to buy any new wood, something we are very proud of. But we still conserve wood as much as we can because wood is wood and deserves to be valued.
The basics of OVE are:
- Walls are framed with 2x6s on 24-in centers rather than 2x4s on 16-in. center
- Corners are made from two studs rather than four
- Headers are sized according to the load they actually carry
- Roofs are built with trusses rather than framed conventionally
- Floors are framed with I-joists rather than sawn lumber
- Insulating sheathing replaces conventional plywood or oriented strand board
Some important aspects of this are:
In most cases code allows studs to be laid out every 24″ instead of every 16″.
End Walls, Corners etc.
It is often possible to reduce the corner wall to only two studs like the image below:
Check out the next image comparison between the right way and the old way. The main places where you can remove studs are cripple studs below windows, places where studs and door/windows fall at the same place, header plates, and double stud window/door openings.
Below is another example of old and new. The main difference between the comparison below is that the doorway and window on the “new” method still have a jack stud and a king stud. I am presuming that some people feel that removing the jack stud (the smaller inner stud) compromises the strength of the opening too much. I am still on the fence.
Another purpose of green framing is to reduce the amount of heat transfer between the inside and outside of the house. This is done in two ways. One is to reduce the connections, aka thermal bridges. So framing is built in a way that the inside and outside have very little routes to take along the framing. Often the walls are framed so that insulation cuts through any path between the outside and inside. This is done in many ways. One example is to decouple interior walls from exterior walls like in the image below:
The second method of stopping heat transfer is by reducing the amount of wood and increasing the amount of air space in the walls, which can then be filled with insulation. Typically this is done with 2″x6″ lumber spaced 20″ on center instead of 2×4 lumber spaced 16 on center.
Here is another example. Notice the doors and windows have been alligned to take advantage of the natural 24″OC stud spacing. It is important to realize that green framing starts with good green design. By placing the doors, windows and walls in the right places you can double up on studs and save wood while staying strong.
And in case you missed all that here it is again: