20 Nov Radical Home Retrofit

I firmly believe that buildings which take advantage of natural and locally available energy, water and materials are the wave of the future. Because of this my family and I live in a net zero energy home and have intentions of going further with our deep green home retrofit. Here’s a summary of what we’ve done so far and an outline of our future plans:

History – Retrofit 1.0

From 2007 to 2010 we made modifications to our house in North Austin to achieve net-zero energy use. This means that we generate as much energy on-site as we consumes over the course of a year. To achieve net zero the house features 32 208-W Sharp PV solar panels, a solar thermal water heating system, a high-efficiency air-source heat pump, LED lighting, improved attic insulation and revamped HVAC ductwork. Also, to insure net zero energy use, we have only electric appliances and heating systems. We usually drive on sunshine, too, since we use our custom electric vehicle for getting around town most of the time.

Take a virtual tour: Green Home Tour blog post.

Draft Plan – Retrofit 2.0

The whole process of planning and executing the plan below would make fantastic blog material and a great site for monthly open-house events!

Part 2.1 ~ Walls & Windows

Siding – Replace old, rotting siding press board panels with natural siding materials and wall insulation. Some possibilities include Texas-sourced cedar and clay-lime plaster on reclaimed pallets. Possible natural insulation materials require some research.

Windows – Replace rattling, single-pane aluminum frame windows which don't seal tightly and have ripped screens with double-pane windows with Anderson or Pella wood/metal frame windows. It has been recommended to me that most of the capital investment in windows should go to south and west windows (6 of our 9 windows).

Part 2.2 ~ Solar on Standing Seams

Roof – replace asphalt shingles with a standing seam metal roof. This long-lasting, highly leak resistant roof covering will decrease attic heat gain and make an appropriately clean, healthy surface to collect rain for potable use.

Solar PV upgrade – Though our seven-year-old panels probably have another 20 years of useful life left, they could be donated to a worthy cause. They could then be replaced with the latest and greatest panels with DC power-optimizers, or microinverters. The addition of a system performance monitoring system would also be great. Additionally, the panel mounting system could be upgraded to demo a more efficient bracket-mount approach by Roof Tech.

Part 2.3 ~ Rain, Rain Don't Go Away!

Rainwater Harvesting for potable indoor use. The challenge will be finding the room in our small-ish backyard for 20,000 gallon tank. We may need to take out a tree, or move a fence. Fortunately our concrete slab house was re-plumbed through the attic before we bought it, so getting the water to the faucets seems doable.

Part 2.4 ~ Icky Effluents

Graywater Irrigation System – This is where the real fun kicks in! In order to use your effluent for irrigation, it must be “graywater” (soaps/surfactants), not black (sewage). This would necessitate composting toilets, or some other on-site treatment system. Also, since food residues currently go down the kitchen sink and we have used our washer for soiled cloth diapers or feminin products, some creative strategies may be needed to insure our home's effluent is gray only.

All of this plan is technically feasible. The interesting challenges seem to lie in the financing and building codes/regulations. What a feat it would be to pull it off! And what a solid, tangible stand for a world where everyone can live sustainably even in the city!