Thorntree Commons at Suttons Bay
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Our Vision

More Information

WHO WE ARE
THORNTREE GUIDELINES
MASTER DEED & BYLAWS
THORNTREE SITE PLAN
LEED AND SUSTAINABILITY
PRESS RELEASE: 3/13/06

Conceptual Designs

OPEN LETTER TO ARCHITECTS
DESIGN: JANA K. VANDER GOOT

Articles

WHY BUILD GREEN?
TEN PRINCIPLES
DR. JONG-JIN KIM: EXCERPTS
A VISIT TO TRYON FARM
LETTER FROM HANNA DONIGER
A SOLAR ENVELOPE HOME
HYBRID HOMES
CONSIDERING LEED FOR HOMES

Thorntree Commons

Green Building Design Guidelines

1. Introduction
2. Building Requirements
3. Appendix: Recommended Practices

INTRODUCTION

If there is one single motivating concept behind Thorntree, it is this: the future will be profoundly different for the generations to come. This seems evident in the midst of soaring energy prices, unreasonable dependence on non-renewable resources with all of its consequences, degradation of air and water quality and of the natural environment in general. What we are experiencing today, the destructive direction in which we are headed as a culture and as a species, will not change unless we do something about the ever-increasing stresses we place on our natural resource base. The world is constantly becoming socially and economically smaller; globally we share much more immediately in the effects, both positive and negative, that each of us has on our surroundings. The consequences of neglect will continue to challenge us at the local and global level.

Thorntree will be my home and I will be a part of its community. This is where I, along with the rest of Thorntree's residents, can contribute in a real and transformative way. For the concept of a better residential community to be of value, it has to be concretely demonstrative of its goals and place realistic demands on those who have chosen to live there.

In drafting the Master Deed and Bylaws for Thorntree Commons, I have drawn upon the professional experience and wisdom of all of those who have worked alongside us on the project. This list is long and includes Professor Jong-Jin Kim, Ph.D. and his graduate students from the Taubman School Of Architecture and Design at the University of Michigan, many consultants at workshops locally and across the Midwest, Leelanau area builders, Suttons Bay Village and Township authorities, friends, family, individuals who have already decided to live at Thorntree and others who are considering it, Thorntree's neighbors, my realtor and marketing persons, all of the representatives of banks who are willing to stand behind a project like Thorntree, my attorney, and others. Each has brought a perspective that I have valued and considered. In the end, of course, it is my responsibility to make the decisions that will shape Thorntree.

All of the above considerations and my own research into what is feasible and reasonable have influenced Thorntree's Master Deed, the key points of which are outlined in summary below for the benefit of potential Thorntree residents. Anyone interested in perusing the full Master Deed can do so on the Master Deed page.

The extent to which we commit to change, our degree of mindfulness with respect to the protection of our natural environment and the ways we consume, will be crucial in determining the outlook for our quality of life. We can make a difference, but it all has to happen where we live. Great and noble concepts cannot be borne out unless they are adapted to something real and manageable in our own communities. We hope that we will be able to achieve this with Thorntree Commons, and to serve as an example for what is possible in like-minded communities across the country and the world.

Sincerely,

David Bahle, Thorntree Commons, Developer

Thorntree Commons:

Building Requirements

Site-Work and Indigenous Plantings

1.   Clearing: Strategies of select clearing of trees must be implemented, and clear cutting will not be allowed. Attempts should be made at preserving any trees of significant age, size and species on each unit and in all common areas.

2.   Landscaping: Typical high-maintenance, chemical-dependent lawns are neither suitable to the topography nor environmentally consistent with Thorntree's green commitment. Landscaping at Thorntree is best described as preservation and the reintroduction of indigenous plants. Lawns are not permitted. As much as possible homes should be sited to work with the contours of the land, to minimize environmental disturbance.

Building Massing and Layout

1.   Setbacks: Side yard, ten feet. All other, ten feet.

2.   Size Of Homes: Setting limits on the size of homes is an important tenet of Thorntree's Green commitment. Placing reasonable limits on both footprint and total square footage reduces the impact on the immediate environment and lessens the overall demand on energy resources. Setting limits encourages good design and better space utilization with all the inherent cost savings.

A "conditioned space" is any living area which employs a mechanical system or device to maintain a comfortable temperature year round. The maximum "conditioned" area at Thorntree is 2600 square feet.

The basic footprint consists of main floor square footage. If the required garage is attached, it is included in the maximum footprint limitation. If the garage is integral, as in the lower level, a larger main floor living area is made possible. The maximum "footprint" at Thorntree is 1500 square feet.

Beyond this footprint is an allowance for "unconditioned" spaces such as patios, decks, porches, utility/storage spaces, exterior balconies and the like. The allowance for total "unconditioned area" shall be reviewed on a case by case basis as a part of the architectural approval process, taking into consideration the issues of preservation, the enjoyment of one's property and respect for other member's property.

Sunspaces designed for seasonal solar gain that contribute to energy conservation are not counted either in maximum "conditioned area" or "unconditioned area" formulae.

Out of respect for those with an immediate or reasonably anticipated need for single-floor living, the maximum foot print allowance is increased to 1800 square feet. The total "conditioned area" allowance remains 2600 square feet.

All homes are required to have an attached or integral garage. Minimum size is 240 square feet. Maximum size is 440 square feet.

Building Envelope

1.   Super-Insulation: Minimum R-values (a measure of thermal resistance) of R-60 at ceilings, R-80 at attic, R-30 at exterior walls, R-36 at exposed floors, R-20 at vented crawl space walls, R-20 at slab edges, R-20 at the interior face of basement walls, and R-20 at the exterior face of basement walls are required.

Windows and Doors

1.   Windows With Low U-value/ high R-value: Windows must have a U-value (a measure of thermal transmittance) of .25 or lower and an R-value (a measure of thermal resistance) of 4 or higher.

Mechanical Systems

1.   High-Efficiency Gas Furnaces/Boilers: If a gas fired central heating system is employed it must have an AFUE ("Annual Fuel Utilization Efficiency") rating of 90% or greater.

2.   Programmable Thermostats: Programmable thermostats are required.

Indoor Air Quality

1.   Carbon Monoxide Detectors: At least one carbon monoxide detector should be installed at each floor of the residence.

2.   Garage Air Barriers: Caulking and sealing common wall along with sufficient and dedicated ventilation to protect living area from automobile exhaust gasses.

3.   Radon Detectors and Piping: Install vent stacks with suction fans to draw radon gases out of the ground below the house and expel it to the outdoors, if radon is detected.

4.   Isolate Combustion Units: Gas furnaces/boilers should be located in insulated spaces that are thoroughly sealed and separate from the conditioned living spaces of the house.

Lighting Systems

1.   Exterior Lighting**: Exterior light fixtures and design must protect against light pollution.

Home Appliances

1.   Energy Star: All basic home appliances must be Energy Star certified or have equally high energy efficiency ratings.

It is the responsibility of every licensed residential builder/designer to be fully informed as to local codes. Thorntree is subject to both Township zoning regulations and the Michigan Residential Building Code, 2003. These regulations, of course, pertain to all home construction in the Township.

**We recommend that all members become familiar with the Green Built Traverse Green Builder's Manual ("Green Built Builder's Manual") and the EEBA Builder's Guide to Cold Climates 2004. We've drawn upon these books extensively in formulating our regulations. To have them as a part of your home building reference library will help you to understand all aspects of the construction process and formulate your priority list for a green built home.


Appendix: Recommended Practices

Note: Some non-mandatory practices, marked with a single asterisk (*), are still in discussion within the environmental community. We encourage residents to research these recommendations and come to their own conclusions in determining material choices and building practices.

Further, these suggestions are not static; new and better concepts, materials, and practices emerge constantly, and as such we welcome ideas from all who share our environmental goals. Your contributions can be a part of this document and help to make Thorntree an even better development.

Site-Work and Indigenous Plantings

1.   Erosion Control: Erosion should be minimized by keeping in place as much of the local vegetation and trees as possible, as well as by maintaining silt fencing during construction.

2.   Minimize Earth Moving: The amount of cut and fill needed to accommodate new construction should be minimized.

3.   Storm Water Runoff: Permeable materials such as poured-in-place pervious asphalt, poured-in-place pervious concrete, block and concrete modular pavers, and plastic or concrete grid pavers are recommended for driveways and walkways. Durability should be assured by manufacturer as it relates to snow removal processes.

4.   Indigenous Plantings/Xeriscaping: The planting of native Michigan trees, plants and shrubs is encouraged. Any new vegetation should be planted in accordance with shading or wind-blocking strategies. Thorntree is recognized as having significant woodland wild bird habitat. We encourage members to plant intentionally to create and improve woodland bird habitat. (Saving Birds Thru Habitat, www.savingbirds.org)

5.   Recycled Plastic for Decking, Fencing and Landscaping: The use of recycled plastics for decking, fencing and landscaping applications is preferred to the use of pressure-treated lumber.

Building Massing and Layout

1.   Building on Southern Slopes: Whenever possible, homes should be located on the southern side of slopes for passive solar gain (heating and lighting).

2.   Wind Deflection: The massing of each residence should be articulated in such a way that it deflects wind rather than traps it.

3.   Steep Roof Pitches: Steep roof pitches are recommended to shed snow.

Passive Heating

1.   Optimize Building Massing: Homes should have a rectangular floor plan, elongated within 15 degrees of the East-West axis.

2.   Provide Proper Glazing: Maximize glazing at southern face of building, but provide shading for summer months and movable insulation for winter months.

3.   Provide Thermal Mass: Install high thermal mass materials such that they collect solar energy during the winter.

4.   Consider Trombe Wall: Design a trombe wall at the south face of building, and calculate the thickness of mass based on solar exposure. A trombe wall is a sun-facing wall, separate or insulated from the foundation, built from material that can act as a thermal mass (such as stone, concrete, adobe or water tanks), combined with an air space, insulated glazing and vents to form a large solar thermal collector.

5.   Building on Southern Slopes: Whenever possible, homes should be located on the southern side of slopes for passive solar gain (heating and lighting).

6.   Provide Sunspace: Design a glazed sunspace to be located between the exterior of the building and the living spaces.

Passive Cooling

1.   Encourage Natural Ventilation: Provide high windows on the leeward side of the building, in combination with low windows on the prevailing wind side, to encourage natural convection that will force warm air out of the building during the night.

2.   Air Conditioning: Homes without central air conditioning are encouraged, but if central air is used consider a boiler/hydronic heating system in conjunction with a down-sized central AC system with tubular duct-work.

3.   Roof Ventilation: Provide adequate roof ventilation to allow heated air trapped in attic spaces to escape and thus assist in natural ventilation.

4.   Channel Breezes Into House: Plantings should be used to help guide breezes into the house and assist with passive cooling during summer months.

5.   Provide Operable Windows: As many windows as possible should be operable to promote passive cooling and natural ventilation.

Building Envelope

1.   Alternative Insulations**: Cellulose fiber or soy based spray-on insulation should be considered as an effective insulator for the building envelope. Also, high density rigid insulation should be utilized.

2.   Prevent Air Infiltration**: The residence should be properly sealed to prevent air infiltration or leakage.

3.   Prevent Thermal Bridging**: Framing techniques that minimize the amount of thermal bridging at the exterior walls of the residence should be utilized. Refer to the Green Built Builder's Manual or the EEBA Builder's Guide to Cold Climates for specific air infiltration prevention techniques.

4.   Air Leakage Tests**: A building envelope air leakage test should be conducted at first practicable time during construction to locate any air leakage and infiltration areas and correct if necessary.

5.   Fireplace Draft Blockers**: Draft blockers should be used to prevent air infiltration through the flue.

6.   Attic Stair Covers: Attic stair covers should be installed and insulated to R-19.

Windows and Doors

1.   Prevent Air Infiltration**: The space between window units and rough-framing should be sealed to prevent air infiltration.

2.   Operable Windows: As many windows as possible should be operable to promote passive cooling and natural ventilation.

3.   Double Pane Windows**: All windows should have double pane glazing with argon gas between the panes.

4.   Skylights: Skylights should be equipped with movable insulated covers to prevent heat loss during the winter, and should be designed with low U-value glazing.

5.   Tight Sealing Windows**: Windows that create tight seals when closed, such as awning and casement windows, are recommended.

6.   Shading Devices**: For East and West facing windows, operable vertical sun screening is recommended. For South facing windows, horizontal screening should be installed to block summer sun and allow winter sunlight into the building.

7.   Steel Exterior Doors: Steel exterior doors with foam insulation and with quality weather-stripping are preferred to solid wood doors due to their higher R-value.

8.   Solid Wood Interior Doors: Solid wood doors from certified sources should be used for interior doors.

Water Conservation and Recycling

1.   Shower Heads and Faucets: Low-flow shower-heads and kitchen faucet aerators should be installed.

2.   Greywater Collection: A greywater collection system should be installed to collect water from roof runoff as well as greywater from building systems.

3.   Dual-Flush Toilets: Dual-flush toilets should be installed to prevent unnecessary water usage.

4.   Washing Machines: High efficiency horizontal axis clothes washers are preferred to top loading washers.

5.   Indigenous Plantings/Xeriscaping**: The planting of drought-tolerant native-Michigan trees and shrubs is encouraged. Any new vegetation should be planted in accordance with shading or wind-blocking strategies. Landscaping with slow-growing, drought-tolerant plants should be considered.

Sustainable Materials

1.   Zero VOC Products**: Zero VOC ("volatile organic compound") paints and adhesives should be used in the construction of the home.

2.   Wood Flooring: Virgin wood flooring should come from certified forests, and it should be finished with plant-based hard oils or waxes instead of polyurethane finishes.

3.   Reclaimed Wood: Reclaimed wood is recommended as an alternative to virgin wood and it should come from local sources.

4.   Bamboo, Cork and Linoleum Flooring*: Bamboo, cork and linoleum are alternative flooring materials that are recommended because they come from replenishable sources.

5.   Carpet: Only carpets that are approved by the Carpet and Rug Institute's Green Label Plus program should be used, and underlayments and installation techniques should be carefully considered.

6.   Paper-Based Countertops: Paper-based countertops made with paper from sustainably harvested forests should be considered.

7.   Concrete with High Fly Ash Content*,**: Concrete with high fly ash content should be used at foundations and slabs.

8.   Oriented Strand Board, Not Plywood**: Oriented strand board sheathing should be used instead of plywood sheathing as floor decking and exterior building sheathing.

9.   Composition Sidings**: Composition exterior sidings are recommended as an alternative to wood sidings.

Mechanical Systems

1.   No Air Conditioning: Homes without central air conditioning are encouraged, but if central air is used consider a boiler/hydronic heating system in conjunction with a down-sized central AC system with tubular duct-work.

2.   Air to Air Exchanger: An air to air heat exchanger should be installed if there is no central air conditioning, in order to provide adequate ventilation and dehumidification for certain rooms.

3.   Hydronic Heating: Hydronic heating systems are recommended. Use of this system, along with passive cooling strategies, could result in the design of a "ductless" house.

4.   Multi-zone System: A multi-zone system or zonal dampers should be installed for greater efficiency.

5.   Ceiling Fans: Ceiling fans should be installed in living spaces and used to assist with passive cooling.

6.   Whole House Fan: A whole house fan should be installed to assist with passive cooling in the summer.

Indoor Air Quality

1.   Low and Zero VOC: Only building products, household products, cleaning products and furniture that have low or zero VOC ("volatile organic compound") content should be used.

2.   Duct Filters: Duct mounted filters should be installed at all supply registers.

Lighting Systems

1.   Exterior Lighting**: Exterior lighting should either be placed on a timer or on a motion detector.

2.   Insulated Downlighting Fixtures**: Install down lighting rated for use in insulated spaces when recessed fixtures are used in a ceiling with an unconditioned attic space above it.

3.   Compact Fluorescent Bulbs**: Compact fluorescent bulbs with an electronic ballast and high CRI ("Color Rendering Index") values should be installed wherever possible.

4.   Light Tubes**: Light tubes, reflective tubular skylights that work on a principle analogous to fiber-optics, should be utilized as a day lighting alternative to electric light in some situations.

Home Appliances

1.   Tankless Water Heaters*: Tankless water heaters are preferred to conventional water heater systems. It is advisable that hardness water testing be done prior to installing a tankless system.

2.   Energy-Efficient Refrigerators: Refrigerators with freezers on top and refrigerators on bottom, with no amenities such as ice makers or water dispensers, are recommended. It is also recommended that the unit not be located near heat-producing appliances.

It is the responsibility of every licensed residential builder/designer to be fully informed as to local codes. Thorntree is subject to both Township zoning regulations and the Michigan Residential Building Code, 2003. These regulations, of course, pertain to all home construction in the Township.

**We recommend that all members become familiar with the Green Built Traverse Green Builder's Manual ("Green Built Builder's Manual") and the EEBA Builder's Guide to Cold Climates 2004. We've drawn upon these books extensively in formulating our regulations. To have them as a part of your home building reference library will help you to understand all aspects of the construction process and formulate your priority list for a green built home.