Shop Programming Meeting: Envelope and Mechanical, October 6, 2015

The third meeting in the Phase 1a Shop Building Programming Meeting series, held on October 6, 2015, focused on envelope and mechanical systems. Similar to the first two meetings, it was facilitated by Rob Bast and Mac Rood of Bast & Rood Architects and attended by staff, faculty, interns and friends of Yestermorrow.

The meeting stayed fairly focused on mechanical issues related to shop functions.

Performance Standards:

The shop building will be designed and built to meet Passive House (PH) standards.

Passive building comprises a set of design principles used to attain a quantifiable and rigorous level of energy efficiency within a specific quantifiable comfort level. “Maximize your gains, minimize your losses” summarize the approach. To that end, a passive building is designed and built in accordance with these five building-science principles: 

  • It employs continuous insulation through its entire envelope without any thermal bridging.
  • The building envelope is extremely airtight, preventing infiltration of outside air and loss of conditioned air.
  • It employs high-performance windows (typically triple-paned) and doors
  • It uses some form of balanced heat- and moisture-recovery ventilation and uses a minimal space conditioning system. 
  • Solar gain is managed to exploit the sun's energy for heating purposes and to minimize it in cooling seasons.         

- excerpt from Passive House Institute US (

Read more about the Passive House standard at the Passive House Institute US (PHIUS) website.

The Passive House methodology has been applied to a variety of building types; however, not to the design of a shop building. Several PH design principles, such as the elimination of thermal bridging and maximizing air sealing, may pose an issue in meeting the standard since these design principles do not readily apply to the design of a shop. It will be necessary to approach with the intent to design this shop as a prototype for future shops achieving PH standards. Despite the challenges, it is generally believed that the shop can be designed and operated in a way that will allow for achievement of PH standards.

Doors: A large door is possible for completed projects, and should be built to Passive House standards. Additional human scale doors with an air lock or a double opening would suit people and materials.

Materials: Given the intent of this building to be used as a carpentry shop for tiny houses and other production, the floor will likely be wood. It could potentially include a crawl or storage area below, while also serving as a useful surface for fasteners, jigs, etc.

A discussion related to the use of local wood for siding would allow us to achieve a lower embodied energy goal, although this is not necessarily a requirement of Passive House standards. Local materials would require attention to detail in managing moisture issues and durability.

Roofing: A roofing discussion focused on a sloped versus flat roof. Sloped may be lower in cost and add to architectural effect, while flat could allow for easy maintenance of solar panels.

Mechanicals/HVAC: A more robust air exchange is needed in the shop while less will be needed in the classroom and bathroom. A mini split could serve the needs of the classroom by providing a small point source for heating and cooling over short, dense time periods. Less heat is needed in shop due to the physical activity occurring in the shop. Point source heat could be augmented with solar thermal, while cooling would occur by stack effect only. Additional discussions focused on wood boiler heated by “waste” wood, wood district heating, and biomass.

Toilets: Options for toilets include low-flow fixtures flushed using rain and greywater, waterless urinals, and composting toilets. It was noted that composting toilets could pose a maintenance issue, as it requires the addition of biomass for composting.