Designed by Arkin Tilt of Albany, California and built by Cowan & Gentry Construction of Belmont, California, the main Hostel building serves a dual purpose. During the summer, it is the kitchen and dining hall for our summer camp. While the Hostel is open, it is the kitchen/dining/living room for the guests and is rented groups for meetings and retreats. The building is located in the same place as the previous Hostel and the design had to accommodate all uses. The new Hostel has been awarded three architectural awards: The American Institute of Architects (AIA) national award as one of the 10 best sustainable projects in the country, an award from the California Council of the AIA, and a Pacific Gas and Electric Company award for energy efficiency.

Location
The Hostel is situated as far up the south-facing hill as possible, so it gets more sun in the winter. The screened porch, high ceiling, and operable windows allow for natural ventilation in summer. 

Passive Solar Design
Careful window placement allows for optimal  natural lighting. Wide eaves keep the sun out in the summer. 

Thermal Mass
Six-inch thick concrete walls halfway up in the main room, a full concrete wall in the back, a rammed earth wall on a large concrete pad, and concrete floors provide extensive thermal mass, which helps keep the room warm in the winter and cool in the summer. 

Radiant Heating
The Hostel uses a Ground Source Heat Pump to provide heat and some hot water heating. Four zones are heated; the main room, the manager’s apartment, a guest cabin (Liz’s Lodge) and the bathroom. Each zone can be controlled individually. There is no heating in the kitchen; however, there is a swamp cooler. Radiant heat differs from forced-air heating in that you don’t turn up the thermostat and get instant change. The building mass provides temperature stability-- we aim for a year-round temperature of 65 degrees.

Hot Water
The domestic water is preheated by the heat pump. There are also flash heaters that use electricity to heat the water on demand to 120 degrees (as required by the Health Department). 

Solar Energy
Due to the Hostel’s location in a shady valley with hills on the South and East sides of the buildings, we decided against installing any kind of solar panel. Instead, we put solar panels on the Wolken Education Center roof, where solar energy is accessible and abundant.

Ground Source Heat Pump
A heat pump provides radiant heating to the Hostel through tubing in the concrete floors.

In this sealed system, water with antifreeze is circulated through five 200’ deep wells in the ground, where the temperature is 53 degrees. There are plastic pipes in the wells which are filled with bentonite clay for insulation.

By the time the water had passed through each well, it should reach a temperature of 53 degrees.  The water then goes to the control room where heat is extracted by a heat pump similar to those in refrigerators. This heats the water that is circulated through the floor in the radiant heating system and is also used to preheat the domestic water.

The system is quiet – there are pumps to circulate the water in the control room, but no noisy fans or ducts. The system does not circulate dust, pollen, or pollutants like typical heating systems do, nor does it grow mold. The system heats objects more than it heats the air, so the furniture and the floor will be warmer than the air during the winter.