Super Insulated Building Envelope

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What is It?

The Super Insulated Building Envelope is:

A passive strategy to reduce energy use by making the building airtight and using more insulation with higher R-values than a conventional building. Super insulated buildings require less heating and cooling, therefore they can use smaller HVAC systems than conventional buildings. The super insulated building envelope includes the roof, walls, floor, doors and windows, and consideration of thermal bridging and infiltration. Super insulated buildings have a low need for heating and cooling and make a net-zero energy design possible.

  • Also known as: super insulated, super insulation

Why is it Important?

A super insulated building is important because:

  • Connects building occupants to the earth with views and access to the outdoors.
  • Significantly reduces energy use by keeping heat inside the building in the winter and keeping heat outside the building in the summer.
  • Helps restore the planet's eco-systems by burning less fossil fuel for heating and cooling the building.
  • Keeps the fresh air and comfortable temperatures inside no matter what the outside conditions are.
  • Maintains proper humidity levels while allowing moisture control.

When to Use It?

Super Insulated Building Envelopes:

  • Climates with extremes of hot or cold.
  • To add extra insulation to the exterior or the interior during major renovation or new construction.
  • Cost-effective in warmer or cooler climates.
  • Before building or renovation is completed.

Things to Remember:

  • The amount of glazing, type, and orientation of the glazing are other important considerations.

Green Garage Use of Super Insulated Building Envelope

Sustainability Goals
  • Maintain a high level of indoor air quality.
  • Keep air-changes per hour to less than 0.10 throughout the building envelope.
  • Minimize thermal bridging.
  • Reduce energy use of existing building by at least 70%.
  • Provide daylight to the interior without compromising energy conservation goals.
  • Use hybrid ventilation system to ventilate the building.
  • Use envelope and insulation materials that do not harm building occupants or the environment.
  • Use envelope and insulation materials that are existing, recycled, and/or local materials wherever possible.
  • Control moisture and humidity within the envelope components and the building.
Strategy and Conceptual Design

Envelope Strategy

The major elements of our super insulated building envelope strategy are:

    • Roof
    • Walls
    • Floor
    • Windows and Doors
    • Thermal Bridging and Infiltration

Things to remember:

  • Choose insulating materials with the highest R-values, least environmental impact, and best indoor air quality properties.
  • Simulate the building envelope using energy modeling tools to determine how materials, door and window penetrations, and equipment choices would affect building energy use.
  • Eliminate or minimize thermal bridging and infiltration sources by design wherever possible.
  • Test components at each stage of construction to verify that they meet performance goals and fine tune as needed.

Roof Design

  • Historic side

The strategy in the roof design entails keeping the historic roof intact and placing the new, super insulated roof on top of it. This keeps materials from the old roof from entering the waste stream and preserves the historic appearance of the interior. The bow trusses used to support the historic structure have been evaluated by a local structural engineer. The trusses are capable of handling an additional 15 psf over the entire roof area. Structural Insulated Panels (SIPS) are being used because they are a lightweight, high R-value material that fit the barrel vault shape of the historic roof.

Modeled roof system with WUFI software to determine how best to achieve high R-value and also deal with moisture within our super insulated roof assembly design
Cover historic roof with Insulspan structural insulated panels (SIPS)
R-50 for 12" SIP
Weight: 4 psf
Local supplier (Blissfield, MI)
Cover SIPS with outer layer of Dura-last TPO
White, reflective surface minimizes radiation
Won't contribute to heat gain in building or urban heat island effect
Local supplier (Saginaw, MI)
  • Annex side
Use flat roof reinforced to carry additional weight of PV and solar heating panels
R-40 for 12" thickness

Wall Design

  • Historic side

Built second wall inside the brick/block walls to accommodate super insulation while preserving historic appearance and keep block from entering waste stream. Modeled wall system with WUFI software to determine how best to achieve high R-value and also deal with moisture within our super insulated wall assembly design

Historic brick/block layer 8" thick
Weep holes at base of wall to drain moisture from behind masonry layer
Drainage plane 1" thick
This air layer helps control thermal bridging by separating the inner wall from the outer wall
Also helps control moisture build up in the wall by providing a path for condensation or rain water to run down to weep holes
Firring blocks 1" thick
Controls thermal bridging by holding stud wall away from drainage plane behind masonry
Polyiso rigid foam board 2" thick, 2 layers with staggered seams (total of 4" thick)
Cellulose blown-in insulation (and wood studs) 5" thick
Absorbs and dissipates moisture like a living organism
Contains fire retardant and mold inhibitors
Gypsum wallboard 1" thick, 1/2" reused from existing, 1/2" new material
Total thermal resistance for the walls is R-42
Total wall thickness is 18.5"

Floor Design In addition to being a component of the super insulation strategy, the floor of our building will house the tubing for the radiant heating and cooling system we are installing. This system may require maintenance and tuning, so our floor system allows easy access and still provides insulation value.

  • Historic side
Existing 4" concrete slab
Leveling course of slag/sand 0-6"
Pex tubing for cooling system
2" polyiso foam
1" slag/sand
Pex tubing for heating system
Reclaimed solid core flush doors as finish floor
Total thermal resistance for the floor is R-??
  • Annex side
Existing 4" concrete slab
2" polyiso foam
1" slag/sand
Pex tubing for heating system
Reclaimed brick or other masonry product as finish floor
Total thermal resistance for the floor is R-??

Window and Door Design

  • Windows
Double-glazed, low-e
Window to wall ratio less than 0.27
U-value less than 0.27
All windows operable to permit natural ventilation
Windows in the historical facade must closely resemble the original showroom windows.

For more information, please see the Green Garage's Sustainable Window Design

  • Doors??

Thermal Bridging and Infiltration

  • Thermal Bridging

Thermal bridging occurs when a material conducts heat or cold from the exterior of the structure to the interior. An example would be the frame of an aluminum window. The glass may have good thermal properties if it is a gas-filled double pane window. But the frame will conduct the outside temperature directly through the wall and into the space. Where this occurs, a thermal break can be designed. Foam, cork, and plain air are common materials that can be used.

Because our interior wall is not structural, our floor to wall connection is a simple foam-to-foam connection. We avoid thermal bridging within the walls by attaching the foam board to firring that holds the panels away from the stud layer.
Where the bow truss ends penetrate the walls, the cavity will be filled with foam to minimize thermal bridging.
  • Infiltration
All windows and doors, floor joints, truss-to-wall connections, roof penetrations will be sealed to prevent infiltration.
Sealing all air leaks also helps to achieve whole-building pressure differences as part of our ventilation and moisture control strategies.
Each component will be tested during construction to ensure performance is meeting our goals.

Energy Modeling We used Energy-10 energy modeling software to simulate the building's energy use. This was used as a learning tool to help determine how one change in a building function, system or component might affect other systems and components and how it might affect energy use. One way that we could be sure our envelope design was getting close to net zero energy was to compare the existing envelope to the proposed new envelope, without any HVAC system specified. These heat flow graphs shows what the indoor temperature will be through a one year cycle.

Proposed Materials / Suppliers
Development Story

The Super Insulated Envelope - Development Story page contains many images and videos documenting the process used at the Green Garage to design, build and operate our super insulated building envelope.

Related Internal Links

Roof Structural Schematic Design

Moisture Control

Energy Modeling

Sustainable Window Design


Open Points

  • Change === on all pages (Peggy)
  • Short Video (Joe)
  • Edited by Ashleigh
  • Dev. Story is missing "build" "operate" information.
  • Clicking of dev. story doesn't link back to this SIBE page.
  • Envelope strategy : couldn't remove double bullet
  • under "wall design" doesn't follow format, missing "annex" part
  • under "window/door" missing door information