Building My Net Zero Energy Home: Design Priorities

http://www.motherearthnews.com/green-homes/building-my-net-zero-energy-home-design-outline.aspx

When building a net zero energy green home, it's best to begin with a list of design priorities...that is, a list of attributes, materials, design features, whatever, that you want to communicate with your architect and builder. If you are new to building, you may need to assemble a design team that meets to suggest ideas in lots of different areas: solar heating, insulation levels, building materials, water systems, solar hot water, solar electricity, finishes, and others. Here's the list I prepared for my architect, James Plagmann of HumaNature Architecture, a gentleman I've worked with for quite a few years.  I am including it here so others can benefit from my experience in energy efficiency, solar energy, green building, etc. 

Design Priority – Chiras/Stuart Residence 

Revised 5/16/2011
 

Footprint 

Original dimensions 34.5 x 45 OD, or 1552 square feet

New dimensions (single story) :  about 26 x 50 or 1300 square feet

Preference – more rectangular so all rooms have access to the sun for passive solar

Heating and Cooling 

Passive Solar heating and cooling, net zero energy

Heat passively with backup 1,000-watt heater in energy recovery ventilator (ERV)

Materials 

All recycled and natural materials

Nontoxic building materials – no VOCs

Minimize waste by designing in 2-foot increments and to dimensions of  Tech Block

Framing – advanced framing to minimize wood use

Roof 

Metal  roof for durability and rain catchment

Gutters and downspout for rainwater catchment – water preferably diverted to buried tank for garden watering

Ensure plenty of south-facing roof for solar hot water system and possible PVs – don’t compromise solar gain with dormers or other features on south side

Foundation 

Poured concrete with R-25 exterior insulation

Surface diversion system to reduce water against foundation  – two feet down, 10-foot apron of polyethylene (two layers) to divert water away from house to minimize mold

French drain below perimeter of the apron to remove water

Slab 

Concrete with fly ash, if possible

R-25

Please pay attention to all penetrations, including floor drains, if any,  to avoid air infiltration

Walls 

R-60 plus

Materials: Double 2 x 4 wall, outside wall load bearing.

Stud spacing:  24 inches oc. 

Insulation:  Two inches high density Icynene --  R-13.6

14 inches dry blown cellulose insulation at 3.2 per inch – R-44.8 

R-value = R 58.4

Ceiling 

Insulation – R-90 to R-100

How do we achieve this?

One solution:

Four inches of high density Icynene (6.8 per inch) between ceiling joists to create airtight seal – R 27.2

20 inches of dry blown cellulose (3.2 per inch) – R-64

Energy heel trusses

 Total insulation = R=91

Limit or eliminate ceiling cans – all ceiling cans should be airtight insulation contact recessed cans

LED and CFL lighting throughout – we need to include as much LED as possible

Floor 

Top cord bearing trusses – approximately 24 inches  

Insulate for sound proofing and possibly thermal performance 

Windows 

All windows – low-E

Wood frame with metal cladding

U factor -- 0.10 to 0.14 (R 7 to 10)

Wood frame with metal cladding. No vinyl or fiberglass windows

Warm edge spacers

South-facing windows – Solar Heat Gain coefficient 0.6 or higher

East and West windows – SHGC 0.35

Visual Transmittance - 0.6 or higher

Air infiltration – 0.3 or less

High condensation resistance

Would like to install thermo shutters on interior of all windows – so please leave room beside windows for attachment and “storage” of thermoshutters

Finishes  

Interior – Hopefully, earthen plaster with earthen plaster finish coat or drywall with earthen or lime plaster finish coat

Exterior – Hardiboard

All nontoxic paints, stains, and finishes


Contributing editor Dan Chiras is a renewable energy and green homes expert who has spent a lifetime learning life’s lessons, which he shares in his popular blog, Dan Chiras on Loving Life. He’s the founder and director of The Evergreen Institute and president of Sustainable Systems Design. Contact him by visiting his website or finding him on .