This is the third and last (I think) post on this tiny house concept. To recap, a few weeks ago I spotted a cool little Austrian hotel room online and blogged on it here. It occurred to me that a small house could be built out of large concrete storm drain pipe. I chose to imagine using four big 12 foot diameter by 8 foot long sections as the basic building blocks for this concept home. This seems to be the largest standard size concrete pipe you can buy. After adding flat floors the total square footage of four of these big pipes would be about 320 square feet. Not exactly a tiny house but definitely small and plenty of space for a small home or vacation rental.
I think this design works the best. It would be the simplest to build and would require the least amount of on-site concrete work. The four sections could also be lined up in a row but the entry would be lost. The southern orientation adds a passive solar benefit and would help warm the home in the summer. The added insulation provided by the earth berms would provide the thermal mass needed to naturally regulate temperature year round. Only the main living space faces south but I think this would be sufficient to keep the space comfortable. Placing the bedroom in the back would also give the home owner a place to escape on particularly hot days.
While digging into the pros and cons of building underground I learned that the main trouble with underground homes is moisture from condensation and water infiltration. Since these pipes are meant to carry water and are well engineered I suspect a little waterproofing on the outside and good draining back-fill would solve the water infiltration problem. Condensation sounds like the biggest problem and solved by insulating the exterior of the concrete with foam. There is also good information at monolithicdome.com.
You see cold concrete walls collect condensation just like a cold drink on a hot day. The reason is simple. The cool surface condenses the moisture in the air as air passes over it. To solve the problem all you need to do is keep the room temperature about the same as the walls. The exterior layer of insulation sounds like it does the trick.
Most of the other design changes are actually in the furniture and storage. As spaces get smaller everything needs more consideration. For example instead of adding interior walls to divide a space why not build floor to ceiling cabinets to divide spaces? Furniture should also serve a dual purpose and if necessary be designed to transform to fill other needs. The fold out sofa is the most common piece of furniture. Fold out tables can serve as desks, tables, and other work spaces. Chairs could also be designed to be comfortable in a variety of different uses.
The other difference with this design are in the exterior spaces and windows. There’s a distinct entry courtyard for more privacy and a friendlier place for visitors to approach the house. The patio outside the bedroom would provide a nice cool and shaded place that extends the usable living space in good weather. The front patio outside the living/kitchen area would probably be used the most by the home owner and could be finished to meet their individual needs. I’m also thinking that the shape of the tube really demands round windows. To keep costs lower three curved pieces of glass could be made to fill the spaces left around the framed in sliding door. A french door could also be used but the style should probably be kept fairly modern.
This was fun. I kept trying to master Google SketchUp enough to draw this little house in 3D but the learning curve is just a little too steep. I’ll keep at it though. It will be a fun tool for future brainstorms and designs.