As LEED APs, material efficient framing is incorporated into every project we work on, regardless of if the project is seeking LEED (Leadership in Energy and Environmental Design) certification or not. It is not only good for the environment, but it is also good for the budget. Material efficient framing is typically defined as the following:
Precut framing packages
Open-web floor trusses
Structural insulated panel (SIP) walls
SIP roof, SIP floors
Stud spacing greater than 16” o.c.
Floor joist spacing greater than 16” o.c.
Roof rafter spacing greater than 16” o.c.
Implement 2 of the following:
Size headers for actual loads
Use ladder blocking or drywall clips
Use 2-stud corners
One of the key factors to being efficient is limiting waste. In order to meet LEED prerequisite requirements, the framing waste factor must be 10% or less. Waste factor is defined as the percentage of framing material ordered in excess of the estimated material needed for construction. In order to achieve this, we do framing plans and elevations showing each stud, joist, etc. That way we each member can be counted, instead of the contractor having to make an estimate. Of course, there are always changes in the field and studs that aren't perfect, but we try and limit the excess amount ordered to 5% - on materials. (I'll discuss additional efforts in future blog posts.) Typically, we specify that the exterior and interior walls of the home are framed with studs 24" on center instead of 16" on center. This is typical of commercial construction and not only cuts back on the amount of wood used in the project up to 40%, but it also allows for more insulation in the walls, which increases the energy efficiency of the home. Additionally, floor joists, ceiling joists and roof rafters are also placed 24" on center and 2-stud or "California" corners are used instead of 3 stud corners.
We also prefer the use of "Finger Joint Studs" over standard solid wood studs on our projects. Finger joint studs are engineered studs that make use of what would normally be considered scrap lumber. Some don't like the way these studs look, but they are typically more cost effective, better for the environment and up to 85% stronger vertically than conventional studs. Finger joint studs are also engineered to be straighter and stay straighter through the construction process. Straight flat walls result in fewer drywall cracks and allow for a smoother finish.
Most modern homes have interior walls with a smooth flat finish. A framer with an eye for detail is the first step in making sure these walls look smooth. If one stud sticks out past the others at any point it will cause the gypsum board (commonly called Sheetrock) to bow when installed. You may not see it at first, but when the wall is painted with a paint that has any sort of sheen, that sheen will highlight every imperfection. As you can imagine, bowing of the gypsum board also causes cracks to form over time. Therefore, extremely straight studs and a framer with an eye for detail can make a big difference on not only the interior finish of the home, but also the longevity of that finish.
The design of the home should also always take into account standard lumber sizes. This is important to not only use as little waste as possible, but also to cut back on labor and minimize error. The fewer cuts that have to be made, the less work the framers have to do and it also means the less chance there is for error. This is why use full height studs whenever possible. The same can be said for sheathing materials and gypsum board, which I'll discuss more in a future post. Below are drawings and images from the ARROhouse construction. While we did not file for official certification on this home, it meets and potentially exceeds LEED Gold standards.
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