It’s NOT a Cave!

What is it like living in an earth-sheltered home?

Humans have been living in earth-sheltered homes since caveman Ug dragged cavewoman Ooga across the proverbial threshold. Mentioning an earth-sheltered home today often conjures up images of a cave-like space that is dark, damp, cold and claustrophobic. It’s not like that!

So what is it like living in an earth-sheltered home? First, some background. Earth (or dirt, soil, sod,…) is a great insulator. Energy-conscious builders take advantage of this property by covering roofs and sheltering walls with 18 inches – to several feet of dirt on three sides. The fourth side is generally a wall of glass facing south to take advantage of passive heating and provide light to the interior. By being under ground, the home uses the Earth’s thermal mass (big “E” intentional) – which has a steady state temperature between 45 and 55°F – as a heat sink or source. This helps keep the house cooler in the summer and warmer in the winter. The passive heating/cooling greatly reduces the amount of energy needed to heat or cool the house to a livable temperature.

We bought our home from the original owner who designed and built it himself. The distinctive eyebrow window wall (a common feature of modern earth-sheltered homes) faces southwest as a compromise between optimum sun exposure and awesome view. All of our main living spaces (kitchen, dining room, living room) and one bedroom are in the earth-sheltered part of the home.

The distinctive “eyebrow” wall of windows and bowed roof of the earth-sheltered part of our home, with the castle tower on top.

The house has an atrium that serves as a transitional space (air gap) between the inside of the house and the window wall. You can think of it as a sun room, garden room, green house or enclosed patio that operates as a thermal buffer. Because it is underground (both with the dirt roof above, and sunken about four feet below ground level), we have not seen it go below 40°F, even when the temperature outside has been below zero. Conversely, when the sun is shining, the temperature in the atrium can reach the high 80’s or 90’s – even in the dead of winter. In the summer, we vent the atrium to the outside to keep air flowing and reduce heat buildup. In the winter, on sunny days, we vent the atrium to the inside of the house to take advantage of the warmer air.

A close up of the eyebrow windows. Behind the exterior windows is the atrium, then the interior windows of the house.

The house came with a propane fireplace and we added a wood stove for active heating. From mid-autumn on, the natural temperature in the main living area is like a balmy meat-locker. After some trial and error, we’ve set the thermostat to 65°F, wear sweaters, and always have a throw blanket handy. With the fireplace or stove going, the living areas are both comfortable and cozy.

The eyebrow window wall lets in huge amounts of light – making this one of the brightest homes I’ve ever lived in. Even in the middle of winter during a snow storm, our kitchen is bright!

Not a high dynamic range picture. Light level inside is comparable to outside. To get a feel for how bright it actually is inside, check out the reflections/shadows on the kitchen counter top. You can see the two sets of windows – inside windows curve immediately behind the countertop (wider wood frames) and the eyebrow external windows 14 feet further across the atrium (thinner wood frames). The wide yellowish columns are the concrete pillars holding up the roof.  It is snowing heavily!

Because the house is sited due southwest (instead of the ideal due south), sunlight pours in during the afternoon. Not so bad in the winter, but it can be too much sun in summer when the rays shine directly into the house for hours as the sun is setting. We haven’t decided how to handle that yet, but I expect some roll down shades will be in order next summer.

So, unlike the dark, dank, damp, claustrophobic cave of our ancestors, our earth-sheltered home is bright, warm, cozy, and spacious. Perfect, right?

Well… there are a couple of things …

The walls of our home are 18 inch thick, rebar-reinforced concrete. That makes this house very sturdy – but difficult to change. There is no simple way to create a conduit from inside to outside the house. Putting in the exhaust chimney for the new wood stove, running wires for the security system or adding a laundry dryer vent required heavy duty, diamond encrusted masonry bit, killer drilling and excavation of the dirt around the external destination. And sparks fly – literally – when said drill bit hits rebar. On a slightly lesser scale, hanging a picture or bracing a bookshelf turns into a half hour long battle between a percussive drill (wimpy rotary drills need not apply) and the “hard place.”

All that rebar essentially acts as a Faraday Cage, blocking electromagnetic waves from sources such as, for example, cell phones. We have, through much experimentation, mapped our downstairs via our own “can-you-hear-me-now-how-many-bars” campaign. Cell reception, except near a window, is pretty much non-existent, hence we cling to our archaic land line phone.

The combination of hard wall surfaces and challenges in hanging things on the wall to soften them makes the inside of the house noisy. Sounds bounce and echo their way throughout. Our large collection of books has helped, as has upholstered furniture and the occasional throw rug – but this is not a quiet home. Ironically, it is well insulated from outside sounds (see previous post).

While the main living areas have remained nice and dry (may they please continue to do so), a leak in the garage/workshop area has us scrambling during wet weather. The previous owner fully disclosed this minor leak when we did our walk through with him. But when the man who, according to local legend, built the house by first pouring the concrete on the hilltop and then used a tractor to scoop out the dirt underneath says, “Yep, there’s a leak in the workshop ceiling, forms a puddle when it’s wet out. I never could find it or fix it. Good luck” – you know you’ve got a problem.

We thought everything was fine. It had rained on and off since we moved in – sometimes really hard rain – but the shop stayed dry. Still-packed moving boxes got Tetris’d into the shop while we struggled to fit everything we own into a house with no actual storage (design choice by original owner – not an inherent flaw of earth sheltered homes). Then came October 2016. It rained for 27 out of 31 days. And as our roof soil reached saturation, the rain worked its way down through the “waterproof” membrane protecting the garage beneath, and started weeping out of the ceiling. Not a few drops from here or there – but everywhere. Kind of like the scene in Amityville Horror, but the ceiling not walls, water not blood.

At first we deployed strategically placed buckets as we shuffled and re-Tetris’d the moving boxes. But eventually we gave up, piled everything up outside the weep zones and layered flattened moving boxes to absorb the puddles. We also put a ginormous tarp over as much of the garage/shop as we could. It helped. Mostly sort of. Then the freeze came and the dripping stopped. Until we had a temporary thaw this week and … well… time to re-re-Tetris and sacrifice more moving boxes.

We don’t know where the leak is coming from or how to stop it. But our engineer brains are spinning furiously to figure out the least expensive way to fix it. Without making it worse. I predict a future blog post  🙂

The final major limitation of an earth-sheltered home is that it is not amenable to remodeling. My husband, a survivor of a couple major remodels in homes past, considers this a huge plus. But it meant getting extremely creative with space to add a washer/dryer, water softener, and wood stove. Before committing to an earth-sheltered home, it is really important to like the basic layout, because changing it is NOT an option.

Our earth-sheltered house is a huge departure from the normal “stick built” ones we’ve lived in before. Yet, it is charming in its own special way, and a very comfortable place to call home.