Super Insulated Building Envelope
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Contents
What is It?
A super insulated envelope is a passive strategy to reduce energy use by making the building airtight and by using more insulation with higher R-values than a conventional building. Super insulated buildings require less heating and cooling, so 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. The amount of glazing, glazing type, and orientation of the glazing are other important considerations. Super insulated buildings have very low needs for heating and cooling and make a net-zero energy design possible.
- Also known as: superinsulated, superinsulation
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:
- Use in climates with extremes of hot or cold.
- Add the extra insulation to the exterior or the interior during major renovation or new construction.
- Not cost effective in mild climates.
- Difficult to use after the building or renovation is completed.
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 through the building envelope.
- Minimize thermal bridging.
- Reduce energy use of existing building by at least 70%.
- Provide daylight to 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 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
- 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
- Walls in both historic and annex
Build 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"
- Historic Brick/block layer 8" thick
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
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 for this.
- 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.
Show Free Run heat flow graphs for existing and new env. side by side
- Supporting science:
WUFI info
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
Resources
- Comparisons of insulation
- Wall Systems
- [http://www.buildingscience.com/documents/insights/bsi-001-the-perfect-wall Building Science Insight 001: The Perfect Wall
- Oak Ridge National Lab Wall Insulation Guidelines ...nice picture of basic system.
- Oak Ridge National Lab Wall Moisture Insulation Guidelines by Climate
- Vapor Barrier Guidelines Put the vapor barrier on the warm side of the exterior structure.
- Here is the Wall System R Value Calculator
Resources
- Passive Haus Institute
- ZED Factory
To Do's
- E-10 data and modeling
- Change === on all pages (Peggy)
- Short Video (Joe)