Carl Nystrom wrote:What is the soil type you are working in? I think your plan sounds good - you are suggesting doing a cut-and-cover method with drainage "to daylight" which is great. When building things underground, water intrusion is an issue. If you are at the toe of a slope, there will be more water than if you were higher up. How much area there is upslope, how much rainfall you get, how fast your soil drains, and how deep the water table is will all be important to know.
Abraham Palma wrote:"I would suggest to place stairs inside the cellar. This way the cool air near the ground doesn't leave the room every time you open the door.
Also, the higher the building, the more stratification you get, with warmer air near the ceiling, cooler air in the ground. To encourage stratification, use shelves made out of isolating materials (not metal) and drawer-like stands (hold temperature better whenever you open the door).
Since your roof is not exposed to sun, you only have to worry about outdoors temperature for isolation. You didn't say where you live, but if your cool/hot cycle is fast (guaranteed cool summer nights), then you don't need to add isolation to the walls, provided they are thick enough. You may add the extra insulation layer later if you think you need it.
Do you plan on using an insulated/airtight door? If so, maybe look for one with a small glazed area, so you get some dim light inside, saving the electric installation, wished you to close the door while browsing for your stuff. Torchlights/candles can be used at night.
I live in Australia, that timber is bad in the soil.
but I'm not sure how well Eucalyptus will preserve underground.
- earth walls have high levels of lateral pressure