by Lloyd Alter –
A Deep Energy Retrofit is defined as ” a whole-building analysis and construction process that achieves much larger energy cost savings—sometimes more than 50% reduction—than those of simpler energy retrofits and fundamentally enhances the building value.” They can be hard to do, working with an existing building with so many special conditions and limitations. There is also still a lot of science that has to be resolved, and no single pat solutions.
That’s why this renovation of an 18th century house is so interesting. Architect Jeff Geisinger has not only done a really interesting renovation, but he has shown the how and why in such wonderful graphic form so that the client (and the rest of us) can understand the how and the why.
The architect describes the project:
A new double-height space gives a sense of connection to the living areas and brings natural light into the heart of the house. The design preserves and expresses the 18th-century heavy timber building frame, juxtaposing new and old. A new stair provides a clear circulation pattern while incorporating additional storage and informal seating areas.
At 475 High Performance Building Supply, they go into more detail about the problems of working with such an old house.
With a recently re-clad exterior and no way to expand outward, this project had to make the most out of limited interior space. The clients were understandably unwilling to give up much at the walls. Jeff compromised by furring the wall inward by about an inch with a new staggered line of studs that provided a thermal break (see drawing at right). This also had the nice added benefit of squaring the wall.
They also make an important point that is often missed and misunderstood:
Airtightness Before Insulation
We like to say “airtightness trumps insulation”. This project perfectly illustrates that truism. Even without the thermal break, the airtight INTELLO [a so-called “smart vapor retarder] potentially added about R-4 to the wall assembly by optimizing the insulation performance. Airtightness provides greater comfort, resilience and cost savings – essentially for free.
© Jeff Geisinger
In many renovations, people just pile on the insulation. But in fact, you can have too much of a good thing; it can take up a lot of space, and in old brick or stone buildings can actually cause deterioration of the wall. You can actually save a lot of energy just by properly tightening up the envelope. As this graph demonstrates, air sealing reduced the heating load almost as much as the insulation (roof + wall) did- a full 16 kWh/m2. It is just a tiny bit less than changing the windows. Yet it is so often overlooked or underestimated. A writer I admire once wrote: “Most old buildings merely slow the wind down. They are abysmally hard to heat, as any reading of period novels will tell you. I cannot support using energy to heat sentiment.” However this house shows that to be patently untrue.
There’s so much going on here; technical sophistication, retaining the old while adding new bracing and support in such an upfront way, serious energy efficiency, historic preservation and wow, what wonderful and thorough presentation and documentation.