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Building My Net Zero Energy Home: Design Priorities

6/21/2012 7:41:00 PM

Tags: Super Green Net Zero Energy Home, net zero energy, green homes, efficiency, passive solar, design guidelines, design priorities, Dan Chiras

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 .



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Post a comment below.

 

Donald Eyermann
7/20/2012 4:54:17 PM
We're producing an AICF (asymmetrical Insulated Concrete Form, which combines great insulation with thermal mass to achieve an ultra efficient home with less environmental impact, less embodied energy and locally produced components as opposed to dual row wood studs at an effective spacing of 12". And certainly thermal mass plus insulation is better than just insulation alone. (adobe walls perform better than insulated walls). Then we utilize solar heating with heat storage and direct geothermal cooling. We integrate solar photovoltaics with electric vehicles as well as reycling and reclaimed materials plus less material waste....another significant issue with wood stud homes.

uphillhouse
6/29/2012 4:07:37 PM
My wife and I just completed a net-zero house in upstate NY with many of the same characteristics. Many of the items on the list are a good starting point. I would recommend checking GreenBuildingAdvisor.com which includes a lot of great green building information for many climate zones. This list is a good starting point for a house in a very cold climate, but as another commenter suggests, there may be other options for other climate zones. Other things to consider in any climate, orientation to the sun, air tightness

Shawn Maloney
6/27/2012 3:23:44 PM
An additional consideration to the list of great building ideas may be the use of thermal reflective insulation. Several studies have shown that if used properly, with a 3/4" air gap on one side, you can increase the R value of a wall from R19 to R30. It's inexpensive and can be used in hundreds of applications. The other benefit is that it actually "reflects" a large amount of the radiant heat away rather than "absorbing" it like a typical insulation does. I am trying to restore my 1789 colonial using the most efficient products and found that a combination of polyiso foam, radiant barrier and blown cellulose have given me the biggest return for the least amount of money.

Greg Byrd
6/25/2012 3:55:48 PM
Most of the plans and checklists for zero energy houses and other high-efficiency house designs seem focused on building a house in the northern or western portions of the country. An essential problem for those of us in the southeast (especially Florida) is passive cooling. While it can be done, humidity is a huge challenge when trying to keep cool down here. Cooling is as big a problem in the South as heating is in the North but many designs and discussions of passive solar only focus on the low-hanging fruit of passive heating. Anyone willing to delve into passive cooling in a humid environment or are we just throwing in the towel on that challenge?







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