On a house with a simple gable roof – say 7/12 – is there a difference between a raised heel truss vs an extended bottom cord truss in:
a) energy efficiency (amount of attic insulation)
b) the ‘look’ of the roof house

I suggested a raised heel roof truss to our architect and he said he would rather do an extended bottom cord truss. He was not too familiar with a raised heel in actual use, which is why I think he didn’t want to use it. I’m not really familiar with either, but have read about the raised heel truss and have seen diagrams of it that show how you can get a good bit more of insulation over the exterior walls.

Thanks

If by extended bottom cord he's thinking that the longer the bottom cord extends beyond the wall, the more space you have for insulation, he's right. Whether that distance creates the "look" you want or gives you the insulation you want is another question. First decide how much insulation you want in the attic. If it is, say, 16", then you'll need 18" for the insulation and the vent space, measured vertically from the outside of the exterior wall from the top plate to the roof deck. A raised heel truss will be built with whatever overhang you specify and will not change the look of the house except that the walls may appear higher. At 7/12 pitch with a 4" fascia, an extended bottom cord will give you a 24" deep overhang which is a good size for lots of reasons.

Unless your architect is your builder why would he care what type of truss is used?

a) not really, could be more or less depending on the raised heel height desired. An extended bottom chord truss will have a fixed heel depth based on span, overhang ordered and pitch. I suppose you could spec larger chord lumber to jack the heel height further but you'd increase your fascia height and defeat the purpose of an engineered roof system. Raised heel is built however high you want, it just raises or lowers fascia height and as Bob said makes the wall appear taller the more heel you spec. So you could order a raised heel truss the exact same overhang and heel depth as a long bottom chord truss.

Long bottom chords make blocking off the heel for insulation a pain in the ass versus a raised heel you can just sheet over, and long bottom chords take longer to set because you lose the point of reference a heel provides in the setting process. If you're doing a paneled soffit or really big overhangs long btm chords speeds the framing process for soffit.