Papercrete / Paper-adobe: Insulation and Thermal Mass

My fascination with paper adobe / papercrete has always been with making a dense mix because insulation is only a part of the equation which leads to energy conservation and comfortable living. Insulation only evens out temperature swings, or perhaps more to the point- a good jacket keeps you warm in winter so long as your body is producing heat. Stop producing heat and gues what, pretty soon you get cold even if you have a whole lot of insulation. The idea behind thermal mass is to collect heat or coolness and store it, and having good insulation on the outside of thermal mass insulates that thermal mass. A down jacket is a good example of an insulation barrier on the outside of that which you’re trying to keep warm- you. It makes basic sense when you apply it to a person. Same thing applies to houses– put the insulation on the outside if you want to insulate the structure from the outside temperatures, period. Putting it inside the wall and then having a brick wall outside of that is pitting thermal dynamics and the laws of nature against your wallet when it comes time to pay the heating and cooling bills.

Quick notes about paper adobe when the volume of paper and the volume of adobe are roughly equal in the mix: it makes a dense block, has a lot of mass and holds nails and screws almost as well as wood but it doesn’t burn or smolder. Adding lime reduces the possibility of mold growth if the material stays wet somewhere down the line during the life of the structure, and also increases insect resistance. (Boric acid would also help with this.) Then adding an insulating jacket of lightweight papercrete or paperadobe would insulate the thermal mass and produce an energy efficient house. A house composed of insulative blocks can only be energy efficient without thermal mass in temperate climates. Remember, adobe homes in the desert are much cooler than wooden houses filled with insulation because they have slab or earthen floors tapping the heat sink of the earth, which is much cooler than the mid-day air temperature, and the dense adobe walls take a long while to conduct the heat energy of the sun toward the inside of the living space, and those same walls are conducting coolness outward, creating an often very nice temperature in hot climates. Such a structure with an insulating jacket becomes a truly efficient house. Even in cold climates, so long as you dig below the frost line, the temperature of the dirt or rock is a fairly constant 55 degrees everywhere in the world. Tap into that and build a home with a lot of thermal mass and insulate it on the outside and you’ve got winter licked. So often I read about folks putting insulation between the floor and the ground and I wonder what planet they think they’re on, except that sure- going barefoot might be more comfortable if you insulate your floor that way, but its going to cost you in terms of the viability of your house being able to regulate temperature without smacking your pocket book upside your head for the life of the house.

I could be wrong, but I’m going to assume that something without paper in it would make a better thermal mass building component, because the paper is going to act to some degree as an insulator. So maybe dense paperadobe isn’t ideal in terms of its thermal mass characteristics. I do like the fact that dense paperadobe holds nails, screws, etc. and when hit with a sledge hammer only dents isntead of shattering like a brick or concrete block of the same dimensions. As pointed out in other posts, you don’t have to build your walls out of thermal mass to use thermal mass effectively: you can have barrels of water, a trombe wall, a geothermal exchange heat pump, etc…

The thing to remember is that you need insulation on the outside of the house, which is where papercrete shines because that’s what papercrete is: a building material that’s also excellent insulation. You still need thermal mass unless you’re fine with the traditional wooden-framed house concept of building an insulative box into which you pump heat and cooling.

Update: I’ve come across examples of non insulated homes built inside of greenhouses in cold climates such as Sweden. They can grow food year round. I have a 1,000 square foot greenhouse on the south side of one of my buildings, an upcoming project is to wax the inside of the corrugated plastic roof panels with carnuba wax dissolved by odorless mineral spirits and sprayed on, then buffed. I’m planning this due to the myriad information coming out about how there are hundreds of chemicals in plastics that cause endocrine problems aside from the one they isolated a few years ago- biospherol A  aka BPA.