All photos via 100Khouse
I have not paid nearly enough attention to the work of Postgreen, the Philadelphia developers of economical and very interesting houses. Preston at Jetson Green nailed their 100K House as "the perfect trifecta of elements necessary in a green project: style, sustainability, and affordability."
Now they have completed the M&M; house (designed by Interface Studio Architects), which certainly cost more than 100K, but is built to Passivhaus standards. It demonstrates that one really can mix simple, economical materials and good design with incredible energy efficiency. And I just love that stair made from Parallam stringers and OSB treads.
Like most homes built to passivhaus standards, it is relatively small and boxy; every jog and protrusion costs money and heat loss. It is a tight, efficient plan.
The exterior is as simple and straightforward as the plan. I think it might could have used a few more windows on that side elevation, which I believe face south, but whereas in typical suburban houses vinyl windows are as cheap as the walls, in a passivhaus they are anything but- they have to be rated at R-9. It becomes a tough call- a tradeoff between cost, balancing heat gains and heat losses. And for those who find the design a bit boxy, have a look at the existing houses next door- that's the style.
It's all about the details; a passivhaus has tremendous insulation (R-50 under the basement slab, most houses have none) R-53 roofs and R32 walls. Every joint has to be designed to eliminate any chance of a thermal bridge or an air leak; look at that red vapour barrier going from under the slab and taped to the wall. And the one inch of foam squeezed in between the slab and the foundation. Those are the kinds of details that make a house tight as a drum. No wonder the designs are kept simple.
The simplicity carries through on the interior- even the floors are OSB, what would be considered subflooring in most houses.
The clients seriously upgraded the kitchen to this very jazzy bamboo number; I think it was a mistake, it seems out of place with the OSB and cement, not edgy and rough enough. But other than that, the M&M; house is one of the best demonstrations I have seen of clean, simple, urban infill design. It is a house that is so efficient that its projected utility bill for the year is exactly zero, without covering its roof with expensive technology. (it does have a two kilowatt array but that's a drop in the bucket) Instead, they do it with insulation, design, size and detailing. That's the way it should be done.
More at the 100K House blog.
Nic Darling of Postgreen explained a year ago the secret of how they do this so well, in Quote of the Day: Building Green Houses is Like "Polishing a Turd", about why most green building costs so much:
Most of the builders and developers reporting high premiums for pursuing LEED are still trying to build the exact same home they have always built. They are simply adding features to make that same house energy efficient, healthy and sustainable. This addition gets expensive....
So, they polish the turd. Rather than redesign the house that has been successful for them in the past, they add solar panels, geothermal systems, high end interior fixtures, extra insulation and other green features. The house gets greener. It gets certified, but it also increases significantly in cost. Since the features are add-ons and extras, the price rises as each one is tacked on.
More Interface Studio and the 100K House in TreeHugger:
At A Clean Break: Interface Studio Architects