Watch the video on Raised-Heel Trusses.
Pre-built roof trusses revolutionized the homebuilding industry when they were introduced to the market in the 1960s. Convenient, readily available, and time-saving to install, pre-built roof trusses moved the industry forward one giant step.
For builders who build energy-efficient homes, there's just one catch: conventional pre-built roof trusses hinder the home's energy saving performance because they fail to leave enough space at the eaves for adequate insulation. It's difficult, if not impossible, to insulate the space where the side walls and the roof of the home intersect. This band or rim around the top of the house can allow heat to easily escape. Not insulating this space is like going outside on a cold winter day without a hat.
The best practice for energy-efficient roof framing is the use of raised heel roof trusses; these offer both structural stability and room for more insulation, which helps to increase a home's energy efficiency. A raised heel truss adds an extension to the top of the exterior wall, allowing for the full depth of insulation to be applied. Installation of this style of roof truss isn't any more difficult than traditional pre-built trusses.
Here's how to do it:
- Raise the truss manually for single-story buildings and when the truss is less than 30 feet wide; otherwise you will have to use a crane and proper rigging (be safe!) to set the truss.
- Keep the truss in an upright position to avoid lateral flexing, which could potentially damage the structural integrity of the truss.
- With the peak of the truss pointing downward, place the heels of the gabled end truss on top of the side walls.
- Rotate the truss to its upright position using two "Y" shaped lifting poles.
- Check the overhang and toenail the bottom chord to the end wall top plate with 16D nails.
- Brace the gabled end truss to the ground.
- Raise and toenail common trusses in sequence until you're finished.
- Be sure to laterally brace the trusses at the top chord with 2"x4"s at 8' intervals.
- Diagonally brace the trusses with a descending 45-degree board from top to bottom chord.
- Remove the temporary bracing as you install the roof sheathing.
- Be sure to maintain the ventilation gap by installing the proper baffles.
Raised heel roof trusses can sometimes be more expensive than traditional roof trusses. Also, because the exterior sheathing wall will have to be extended, additional material will be needed. While this can add a few hundred dollars to the cost of construction, the homeowner will easily recoup this money over the life of the house through reduced energy bills. By building energy efficient homes that lower the homeowner's energy bills, builders can increase satisfaction scores, and gain a strong competitive advantage in today's market.
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