Avoid The Carbon Rebound

Avoid The Carbon Rebound

On California’s Net Zero goals, embodied carbon of materials, and the Smart Enclosure System

In the fight to mitigate Climate change in California, the term Net Zero may be getting a makeover.  Policy makers still view Net Zero buildings as a fundamental tool to reach climate mitigation goals; however, the carbon elephant in the room forces us to realize that not all net zero is created equal.

In the newly proposed 2019 update to California’s Title 24 Energy Code, Bronwyn Barry, of Passive House California and the North American Passive House Network, points out on LinkedIn that the growing focus of California is on carbon.  And with the focus on carbon reduction, looking forward, the State says, “...the most important energy characteristic for a building will be that it produces and consumes energy at times that are appropriate and responds to the needs of the grid, which reduces the building’s emissions.”  In other words, Net Zero is no longer an end in itself, but one of many factors that can help deliver a lower carbon grid. Barry notes that the code focus also includes greater efficiency and electrification.

Carbon Rebound

But what’s not addressed in the proposed California code update is the effect of embodied energy and carbon emissions on our goals.  Recent data shows that the embodied carbon from harvesting, processing, and manufacturing materials likely far outweigh the benefit of operational savings. The research of Chris Magwood of Trent University in Ontario, Canada - presented here - spells out the stark reality:  First, that new, energy efficient, high-performance buildings, made today of high impact materials like spray foam have a much higher lifecycle carbon impact than conventional code buildings, and so actually make the problem worse!

The unavoidable conclusion is that, in combination with electrification, energy efficiency and a new Net Zero tuned to the grid, there is a fundamental need to also dramatically shift toward low carbon and carbon negative materials in the construction of our buildings - like Gutex wood fiberboard and Havelock Wool insulations.

Stop the Rebound and Go Negative

Incremental carbon savings can get complicated but by following just 6 simple rules we can easily solve the majority of the carbon impact of our homes. The recipe for a good, very low carbon building is simple.
  1. Follow the principles of the Passive House approach to deliver energy efficiency by modeling airtightness and insulation levels to accurately predict load.
  2. Make a durable building with robust enclosure airtightness and moisture control systems, providing maximum drying potential, and supported by high-efficiency ventilation.
  3. Choose wood-based materials with low embodied energy for structure, insulations, and finishes. These act as a carbon sink - locking carbon in place for generations.
  4. Choose non-wood building materials that also have low embodied energy - like sheep's wool insulation. 
  5. Complete high-efficiency electrification of systems with heat pumps for space conditioning and water heating, LED lighting and induction cooktops.  
  6. Install PV and battery storage that can be responsive to the needs of the utility grid.  

The Smart Enclosure System Supports a Carbon Negative Future

To simplify the process of implementing low embodied energy or carbon negative strategies, 475 has developed a Passive House and Living Building Challenge compliant enclosure system that meets the most stringent low carbon, health, durability, comfort, and efficiency goals, called the Smart Enclosure System (SES). The SES and ZNE will soon be best friends. You could even say they were designed to be together.

The Smart Enclosure System is a return to fundamental principles of building science.  We leverage the basics of natural principles with highly selective technological innovation and manufacturing – working in harmony with nature, not in opposition. The SES is a range of approaches, that lowers the embodied energy, uses less toxic and more natural materials - with less stuff - resulting in optimized performance and durability.

The Smart Enclosure System is plug-and-play for standard 2x6 framing, double stud walls, mass timber, and enclosure systems using only exterior insulation. The first step in a successful carbon-negative project is to design a truly good and durable enclosure system - So let’s dig into some SES details.

The Smart Enclosure System Assemblies

The SES assemblies below can be used in almost any climate (except hot humid), but they can be adapted to fit almost any design. Please contact us - we are happy to help!

Unvented Gable Roof System (R-63):

  • Finish roof of choice (typ metal or comp shingle)
  • Proper roof underlayment
  • ½” plywood
  • Ventilation channel (typ 1x4 battens)
  • Gutex ULTRATHERM/MULTIPLEX TOP or Pro Clima SOLITEX membrane for vapor open airtightness and waterproofing (typ Pro Clima SOLITEX MENTO 3000 with Gutex THERMOSAFE WD 80 as continuous exterior insulation
  • Diagonal strapping or plywood sheathing.
  • Rafter system with Havelock Wool loose-fill insulation or Gutex THERMOFIBER wood insulation.  (typ engineered truss or 11 7/8” I-joist)
  • Pro Clima INTELLO PLUS membrane system as the primary air barrier, smart vapor control layer, and insulation netting with TESCON VANA taped seams.
  • Optional: include a service cavity to minimize penetrations through INTELLO PLUS and provide space for lighting, ductwork, etc
  • Interior finish of choice

Vented Roof System (R-51):

  • Finish roof of choice
  • Proper roof underlayment
  • Plywood sheathing with high and low ventilation (vented to ridge and eaves)
  • 12” deep layer of Havelock Wool loose-fill on attic floor (bury and ductwork or plumbing)
  • Ceiling joists with INTELLO PLUS system stapled to the warm side to provide the primary air barrier, smart vapor control, and insulation netting
  • Optional: include a service cavity to minimize penetrations through Intello and provide space for lighting, ductwork, etc
  • Interior finish of choice

Wall System (R-30):

  • Exterior cladding of choice
  • Ventilation cavity (typ 1x4 battens)
  • Gutex MULTITHERM or Pro Clima SOLITEX WRB (MENTO 1000 for closed joint cladding and FRONTA QUATTRO for open joint cladding) with Gutex THERMOSAFE WD 40 continuous exterior insulation
  • Diagonal strapping or Plywood sheathing
  • 2x6 stud wall filled with Havelock Wool loose fill or Gutex THERMOFIBER wood insulation
  • Pro Clima INTELLO PLUS membrane system as the primary air barrier, smart vapor control, and insulation netting
  • Optional: include a 2x4 service cavity to minimize penetrations through INTELLO PLUS and provide easy runs for plumbing and electrical
  • Interior finish of choice

WUI Zone Wall System (R-30):

  • Gutex THERMOWALL 40 continuous exterior insulation with an integrated vapor open stucco finish
  • Plywood sheathing
  • 2x6 stud wall filled with Havelock Wool loose fill or Gutex THERMOFIBER insulation
  • Pro Clima INTELLO PLUS membrane system as the primary air barrier, smart vapor control, and insulation netting
  • Optional: include a 2x4 service cavity to minimize penetrations through INTELLO PLUS and provide easy runs for plumbing and electrical
  • Interior finish of choice

Slab on Grade Floor System (R-20):

  • Native soils with insulated footings
  • Glavel recycled glass structural fill and insulation below slab (R-20 would be standard, which is roughly 15” of depth before ~30% compression for a final depth of roughly 11.2”)
  • Stego sub-slab vapor barrier (any durable vapor closed vapor barrier works) with Pro Clima COMPEGO tape
  • 4-6” thick concrete slab

Raised Floor System (from bottom side up, R-40):

  • Vapor barrier over soils, seams taped with Pro Clima COMPEGO, and connected to foundation walls with CONTEGA MULTIBOND.
  • Pro Clima SOLITEX MENTO PLUS membrane (waterproof, airtight, vapor open, and insulation netting), seams taped with TESCON VANA, connected to foundations walls with CONTEGA MULTIBOND
  • 2x10 floor joists with Havelock Wool loose-fill or Gutex THERMOFIBER for R-40 (MENTO PLUS as the netting)
    • Alt: Havelock Wool batts (one layer of 2x6 and one layer of 2x4 results in R-33)
  • Plywood subfloor seams taped with TESCON VANA.
  • Finish floor system of choice

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