Are Raised-Heel Trusses Worth the Extra Cost? – GreenBuildingAdvisor

Q&A Spotlight

Raised heels solve an insulation problem at the eaves—but how much is enough?

Conventional roof trusses have a little geometry problem. As the top chord slopes toward the eave, the available space for insulation gets smaller and smaller. Unfortunately, heat doesn’t give you a discount just because you’ve reached the edge of the attic.

That shrinking space can make it difficult to maintain full insulation depth over the exterior walls while still leaving room for ventilation. It can also make air-sealing more difficult. The result is a strip around the perimeter of the house with considerably less insulation—right where you’d rather not have it—and, in cold climates, conditions that can contribute to ice dams.

Raised-heel trusses, also called energy-heel trusses, solve the geometry problem by increasing the distance between the top plate and the top chord. That provides room for full-depth insulation, ventilation baffles, and better air-sealing details. Of course, like many good building details, they come with a catch: Somebody has to pay for them.

That’s what GBA member “FortLivingRoom” is thinking about as he plans a Pretty Good House in Climate Zone 5. His roof design calls for trusses with 22-in. raised heels and R-60 blown cellulose, but his builder is pushing back. Dropping the raised heels would save money, the builder says, and most of the attic would still reach R-60. Only the perimeter would have less insulation.

Fort isn’t convinced. He suspects that the intersection of the trusses and exterior walls may be one of the worst places to skimp on insulation. But how much raised heel is enough—and at what point are you paying for more heel than you really need?

The topic for this Spotlight: Are raised heel trusses worth the extra money?

What the forum had to say

Some responses seem to agree wholeheartedly with keeping the raised heels,…