Green Building: Advanced Framing
As I started researching advanced framing, or OVE (Optimal Value Engineering), I found a lot of technical data and wasn’t sure how to present it. This opening paragraph of an article at www.buildingscience.com summed it up for me:
The current industry standard wall – a 2×4 frame at 16-inch centers with double top plates, three stud corners, jack studs, cripples and double headers – is being replaced by a 2×6 frame at 24-inch centers with single top plates, two stud corners, no jack studs, no cripples and single headers (and in many cases no headers at all).
It’s more detailed than that, but this was a good place to begin to understand the premise of cutting back on lumber without sacrificing structural quality.
Optimal value engineering history
OVE is not new. In the mid 1800s, it was called in-line framing. Rafters, joists and wall studs were all placed on 24” centers, and they lined up with each other. Somewhere along the line, we started framing walls and floors at 16” centers, which meant double top plates and headers over windows and doors were needed to carry the load.
Going back to 24” centers means the load is transferred from roof rafters to wall studs to floor joists. Only a single top plate is necessary, and headers are needed only in load-bearing walls.
In the 1970s, the National Association of Home Builders Research Foundation studied which framing components were not structural and could be eliminated. OVE was born! It creates an energy efficient building envelope that uses less material, which means less waste in our landfills.
Benefits of optimal value engineering advanced framing
- 5-10% less board feet of lumber
- 30% fewer pieces of lumber
- 60% more wall cavity available for insulation
- reduces thermal bridging saving energy for heating and cooling
- easier to design in multiples of 4
- less work for framers loading, unloading and building
- reduces labor costs
- fewer holes to drill for drywallers, plumbers, HVAC specialists and electricians
Drawbacks to advanced framing
- It may not be suitable for areas prone to high winds (hurricanes) and earthquakes. A structural engineer should be consulted.
- Many windows may not allow for much lumber reduction.
- Framers need to be trained. While they are learning on the job, construction may go slower. As they gain experience, though, work time will return to normal.
- OVE is not seen as sturdy. The public and contractors need to be educated on the building process and benefits of OVE.
Advanced framing and energy efficiency
By framing a wider module, less lumber is needed and more space is opened up for insulation. The more insulation a home has, the more energy efficient it will be. When a wall stud meets the outside wall, there is an opportunity for air movement, letting heat out in winter and in in summer. This is thermal bridging. The fewer studs there are, the less air movement there will be. Insulated sheathing used on the exterior of the building will further reduce thermal bridging and increase energy efficiency.
Headers are only needed in load bearing walls, and they should be insulated with foam board between two pieces of wood for energy efficiency. Cripples are not necessary underneath windows, and window and door openings can be aligned with studs on 24” spacing. Roofs are trussed, not framed, saving on materials and labor. The traditional 3-stud corner is reduced to two studs. Clips or scrap lumber are used for attaching drywall, instead of that third stud.
Advanced framing and floors
Floors can be framed with I-joists for a stiffer, sturdier floor using less material. To reduce lumber further, a home can be built on a poured slab, which eliminates all first floor framing and a wood subfloor.
With less lumber, and fewer nails are used. Reducing the embodied energy of materials saves natural resources and is environmentally friendly. According to energysavers.gov, the approximate savings on materials for a 1200 sq ft house is $500, and $1000 for a 2400 sq ft house.
Better use of natural resources
Saving lumber is synonymous with saving forests. Trees are important globally, because they take CO2 out of the atmosphere and turn it into oxygen. If people realized the major role trees play, they’d be more hesitant to cut them down without replacing them.
I have written about other building methods that use little or no lumber, but sometimes there is no choice. If you need or want to build a stick frame house, please consider advanced framing. Interview contractors to see if they are very familiar with this method. Find out how many houses they have built this way. One source said five would make a builder feel comfortable with it.
Not all aspects of OVE need to be used, though. Parts of it can be implemented while building conventionally at the same time. This is actually a great way for a contractor to break into using OVE. I personally think they should learn it to conserve resources and build energy efficient homes.