The following stumper is presented in BPI's June Performance Matters e-Newsletter.

 

Thanks to Ken Tohinaka of the Vermont Energy Investment Corporation in Burlington, Vermont for this month's stumper!

A technical school near the Canadian border suffered from massive ice dam problems. Of the six entrances/exits (two along each length, one along each width), only the South side entrance/exit was usable during the winter (it was protected by its own gable roof). The others were too dangerous to use due to falling ice and/or ice from the roof blocking the doors. Students often were deployed to remove the ice above the doors with hatchets. The problem was on all sides, but some thought it was worse on the West and South sides.

The main building was a two-story structure housing classrooms and administrative offices. The one-story shed-roof addition on the West side held an automotive shop and a wood-working shop. There was another wood-working shop on the East side, in another one-story shed-roof addition. The attic spaces above the dropped ceilings in the shops were open to the attic of the primary building due to their shed roofs and high ceilings. The building was considered energy efficient in that it had a Trombe wall (extending past the upper ceiling plane) on the South side. The school energy committee was interested in two questions:

  • Would a bio-mass boiler make the building more efficient?
  • Would more insulation make the building more efficient, and reduce the ice-dam problem?

An investigation by two experienced hands, equipped only with flashlights, showed why there were massive ice dams, and why a bio-mass boiler and more insulation wouldn't make the building more energy efficient.

What's the answer to this trick(y) scenario, and the solution to the ice dams problem?

Tags: BPI, Chump, June, Matters, Performance, Stump, the

Views: 101

Replies to This Discussion

Congratulations to Kevin Hanlon of Horizon RES NH LLC in Concord, NH for providing the correct answer and proper evaluation of last month's stumper! There were a number of great responses, but Kevin's illustrates the most comprehensive understanding of the problem. As a reminder, Ken Tohinaka of the Vermont Energy Investment Corporation provided this tricky scenario (scroll down) and asked readers to evaluate the use of a bio-mass boiler and additional insulation in reducing ice-dams and increasing the building's efficiency.

Kevin suggests that a bio-mass boiler "wouldn't make the building more efficient, it would just be a heating system that would be more efficient at contributing to heat loss and ice dams."

Kevin also notes that additional insulation might not solve the problem. Additional insulation "is not the answer unless the pressure barrier of the ceiling assembly of the additions was fixed first, and proven to be complete and effective."

Finally, Kevin explains that a visual inspection, blower door pressure test across the attic, and a pre and post data logging exercise would be good ways to determine the cause of the ice dams and ultimately determine an appropriate solution.

Ken adds that it is important to recognize "the trombe wall which extends above the attic floor plane, the wood shop vacuum, and the auto shop ventilation systems that depressurize the additions."

"The streaking in the fiberglass batts, particularly at the juncture of the additions, indicates that heated air from the classrooms is being drawn into the main attic by the shop equipment, adding to the heating from the trombe wall extending above the attic floor plane. The air is then pulled into the shops by their mechanical equipment through insulation and dropped ceilings."

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