Project Participants:Gabbart & Woods Structural Engineers
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Gabbart & Woods Structural Engineers
Truckee Rammed Earth Home
Site characteristics or focus during construction or remodel: South-facing downslope lot. Main part of house to be single floor to provide wheelchair accessibility.
Construction Type: Rammed Earth/Pisé. Pisé is a form of rammed earth where the pressure is applied by shooting the earth-cement mixture from gunnite guns. In this case it is shot from both sides of a wall against a core of solid insulation panels. This is the first house to be built this way. It was tried experimentally on a large garage and was so successful that a number of other buildings are being designed using the technique – including low-cost housing for winery workers in the Napa Valley.
The entire main floor is earth-bermed for insulation. Ceiling will be open beam and rafter – using glulams – and planks. There is no attic. A “green” roof will eventually cover the building. This slopes to ground level at the earth-bermed west end of the building. Wildflowers, and low-growing, shallow-rooted perennial plants, such asthymes, will be planted.
Passive Solar System: Almost all windows are south-facing – on the main floor, the south facing walls are mostly window. Some sky-lights. Enormous heat-mass in concrete slab and Pisé walls.
Active Solar System: A solar water heater will be used to preheat the incoming water to the Takagi instant water heater.
Conservation Features: Rammed earth walls, green roof, earth berming, passive solar, high heat-mass, solar water pre-heat, minimal use of wood.
Subjective Evaluation/design considerations: The items on our principle agenda were:
- As close to zero maintenance as possible – inside and out – including, easy to clean! (We have been slaves to our wood-frame houses.)
- Fireproof. (The site is in a forest.)
- Passive solar, earth-bermed, green-roofed, high heat mass, energy efficient. (Our current Tahoe house is passive solar, and despite its leakiness we use much less heat than our neighbors – we have windows open when they are lighting fires! Our Berkeley house also had a passive solar component.)
- Solidity. (We love the feel of thick-walled European buildings. Our current wood-frame house shakes in the wind.All our houses have shaken when someone slams the front door.)
- Minimal use of wood. (Both from a conservationist viewpoint, and, again, the European aesthetic.) This includes not using wood windows – we are using fiberglass framed windows.
- Access from living area to outdoors and garden. We wanted the house and the outdoors to be one – and on the same level, not raised above on a deck.
Simplicity in design – clean uncluttered lines. We wanted the building to be the statement, not its trim.
Why Rammed Earth/Pisé?
It fulfills all our objectives. It is absolutely beautiful.
Rammed Earth houses are very quiet. They maintain a constant temperature for a long time. Because of the enormous heat mass, there is a huge “flywheel” effect in heat storage.
With the Pisé finish on the inside and on the window sills, it doesn’t matter if some rain gets in – which happens regularly in sudden thunderstorms as we like open windows.
The environmental issue: Using the dirt from the site was not feasible because of the unknown quantity of rock present. That meant using “dirt” from a quarry, and quarries are destructive and definitely not pretty. However, in looking at a number of quarries – including the Carerra marble quarry in Italy that has existed for centuries – and comparing the effect to denuded forest lands, I concluded that the quarries did less harm in the long run.
We also looked at the various ICFs – BlueMax, Cempo, Rastra, etc., but could not get the thickness of wall we wanted that way. Also, they all require finish coats – adding to maintenance. Why not just use concrete? Aesthetic choice, plus higher use of locally available materials.
Why a green roof?
Both aesthetics and functionality. Roofs are usually the least attractive part of a building. Since we were building below the street we wanted to look down on something attractive. We also wanted to minimize the building’s look from above.
Functionally, it adds insulation, it holds the snow on the roof that also adds insulation, it decreases runoff, cools the building in summer, and is better environmentally.
Penny & Bob Fink
approx. 7,000 sq. ft.
Date of Construction: 2001-2003
Location: Process Lake Heights
Construction Type: Rammed Earth/Pisé.
Heating Systems: Ground-source geothermal, with hydronics in the slab floors, two propane-fired fireplaces.