Above. Partial back view of our design for an eco-house for a small suburban lot next to our main Neo-Terra site
We began retrofitting our present house at Neo-Terra in 1999, and have taken it perhaps as far as it is reasonable to go. In 2010 we discovered a real innovation in eco-house design, the Passiv Haus from Germany, and turned our attention to the alternative: designing a proper passive solar house on an adjacent village lot. For a PASA workshop in 2011 we presented the two sides of eco-efficient housing: retrofitting an old house and building a new one. We shared our experiences and results from our retrofits, and our best ideas and preliminary design for a solar home based on a new concept current in Europe, but just then being introduced to the United States: Passive House.
You can find our presentation, "From Farmhouse to Eco-House: Retrofitting and Building New," in both its full text version with all details and links to key sources and its shorter Power Point version. The full text version is divided into four parts:
PART 1. COMPETING CONCEPTS FOR GREEN HOUSING
PART 2. PASSIVE HOUSE DESIGN IN NEW CONSTRUCTION
PART 3. PROPOSED DESIGN FOR A PASSIVE HOUSE ON OUR LOT
PART 4. APPLYING PASSIVE HOUSE TO RETROFITS
Lessons Learned from Retrofits
In Part 4, we apply the Passive House principles retrospectively to the retrofits we had undertaken on our own house. The Passive House framework provides a clear benchmark against which to compare our retrofits. Here are the lessons we learned, and what we might have done differently:
1) Until everything is done, you will not realize the savings you had hoped for. Leaving something undone – insulation, windows, infiltration reduction – is equivalent to leaving windows or a door open all winter. In our case, we didn’t have the money to do it all at once. Moreover, it takes time to investigate alternatives, figure out what you can do yourself, talk with and line up contractors. If you wait until August to start a retrofit, you may find yourself finishing in mid-December. That’s how long it took us to get the windows installed.
2) Technology and building practices are changing rapidly in response to rising energy prices, and more widely shared assumptions on global warming and the destructive aspects of petroleum and natural gas development. Using less energy is better for us, other species, and the planet. We expect to see Passive House becoming a new standard for residential and commercial construction and retrofits as it already has in Europe.
3) Focus on the building envelope; this must be highly insulated and airtight at all points for energy use to be dramatically reduced. The Passive House mantra is “build tight and ventilate right.”
4) With the benefit of the Passive House standard, we should have used more insulation – more layers of foam board!
5) In addition, we should have reduced total window area by reducing the size and number of windows in the living room during that retrofit in 2001. These five windows – five pictures with matching casements -- were the largest in the house, and therefore, the most expensive to replace. Even our R-20 wall was much better than our new R-7 windows. An R-30 wall would have been even better. Retaining all five large picture windows was a mistake.
6) We would urge anyone contemplating a flat plate solar hot water system to go with a drainback system rather than a pressurized glycol system. A drainback system is foolproof, doesn’t require glycol because it drains when the sun is not out, or in the event your power fails. A glycol system does not drain, could overheat and compromise your collector fluid, spring a leak, or blow your pressure release valve.
7) Be skeptical of performance claims. The simple fact is that energy prices are still too low to yield reasonable payback periods for many improvements. Therefore, verify claims on payback periods by doing your own math, and talking with those who have used the technology or made an improvement. Get their performance data and assessment and apply to your own case. While tax breaks act as an inducement, they can distort the picture of what is really going on.
8) If, while making a retrofit, you find that you (or the contractor) have made a mistake, stop work and correct it right there! The stakes are too high. Once you put the siding on, it is too late. You will forever regret it (or the next owner will realize just what a dope you were).
9) One lesson Wes Jackson applied in the design and construction of the new research building at The Land Institute was to take a manufactured metal building you could purchase inexpensively on the market, and insulate it properly from the inside. This is much cheaper than designing and building a custom structure.
Above: We used a Wiley Solar Asset to analyze solar insolation
Above: Environmental analysis of house and site
Above: Side view looking up hill, with solar analysis for greenhouse
Above: View from south, showing drainage, other details
Above: Artists rendition of new eco-house on the site in winter