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…

You 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. I believe architect Mike Reynolds who pioneered Earthships, often uses no true insulating material, relying instead on the laws of thermodynamics to heat and cool largely earthen structures.

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 potential 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. However, I am not sure how to effectively test whether a coating of hard wax would be an adequate barrier. Likely a better solution would be to ensure there’s rapid air exchange / venting for the greenhouse.


9 thoughts on “Papercrete / Paper-adobe: Insulation and Thermal Mass

  1. i was wondering if the papercrete can be a good insulation
    for a house in canada . in the winter `temperature can be as low
    as -30 celcius

    1. I would suggest a papercrete site such as this one: I only have information about what’s worked for me in the high desert. I’d suggest an attached sunspace or trombe wall, and checking out architect Michael Reynold’s sites regarding Earthships (building earth sheltered and rammed-earth tire structures with south facing sunspaces. Near Taos New Mexico they stay at 70 degrees Farenheit year round; it can get to forty below zero farenheit there. I’m planning on adding more thermal mass to my buildings, but with a secondary wall and backfilling the space which seems a lot less work than pounding tires or earthbags, actually.

  2. Have you considered the ability of adobe to release and regain moisture and the accompanying cooling and heating effect that occurs? Wouldn’t putting insulation on the outside of the structure bring an end to that source of heating and cooling? Does paper adobe have the ability to do this like regular adobe does?

    1. Paper adobe wicks moisture more readily than traditional adobe- that’s part of why I made sure to use some lime in the mix as it deters mold and bacteria. The more paper-to-adobe, the more insulative the material, and the less thermal mass it has. You’re completely right that wetting it would act as an evaporative cooler or on days with direct sun might even help warm the building because water is an excellent heat sink– but in winter storms, dampness in the walls can linger until after nightfall and often in winter the night temps dip into the teens, which could easily cause cracking and spalling in my area. Large roof overhangs can address this, as can increasing the lime content because lime doesn’t trap water the same way cements o.

      One could insulate exterior walls with a pourous, light weight paper-adobe or papercrete shell which would transpirate moisture- breatheable buildings are healthier buildings. And at least in my climate, I’m interested in seeing if thermal mass without insulation, in conjunction with an attached greenhouse largely filled with thermal mass water storage can keep temperatures inside the home comfortable through our usually sunny winters with freezing nights.

      1. Thank you for engaging me on this issue! I am very interested in finding out the answer. I plan to retire in Mexico (an hour north of Puebla) in a couple of years and I will build a home there, hopefully out of adobe or padobe or fidobe or papercrete.

        When I referred to the releasing and regaining of moisture and the accompanying cooling and heating effect that occurs, I was referring to the natural humidity or vapor that is in the adobe brick that is released when the outside temperature goes up. This causes a drop in temperature in the brick that is a result of the latent heat of vaporization.

        Here’s what Wikipedia has to say about it. “For example, in the atmosphere, when a molecule of water evaporates from the surface of any body of water, energy is transported by the water molecule into a lower temperature air parcel that contains less water vapor than its surroundings. Because energy is needed to overcome the molecular forces of attraction between water particles, the process of transition from a parcel of water to a parcel of vapor requires the input of energy causing a drop in temperature in its surroundings.”

        This is why the brick gets cooled down during the day. The opposite happens at night. When the vapor in the atmosphere is reabsorbed back into the brick due to the drop in ambient temperature, the brick is warmed back up. This is why adobe houses are warmer at night without adding any heat from an outside source.

        Does papercrete or padobe/fidobe behave this same way? If it does, then it seems to me that putting a cement covering or some kind of insulation on the outside of the structure would keep this process from happening.

        Do you know of anyone who has investigated this issue?

  3. I don’t agree with your vapor transition theory at all. Moisture in the wall evaporates as the outside temperature increases. The wall does not cool down due to this effect, it just remains stable since the heat of evaporation is solar in origin. After the moisture evaporates in the morning the wall then begins to warm as the daytime temperature increases.
    Condensation only occurs upon a surface cooler than the ambient air temperature. The walls will only absorb moisture if the walls are cooler than the air. The moisture is most likely drawn from the warm inside air of the building into the exterior walls as the walls cool down in the night air.
    In winter adobe walls can be a bane rather than a blessing. A lack of insulation requires requires a heating system adequate to maintain a comfortable indoor temperature during periods of extended cold temperatures. Get a good wood stove.

    1. Or an attached greenhouse, sunspace, trombe wall, etc. I currently have an attached greenhouse and will admit that I’ve used my small wood stove twice this winter. The nights are in the teens most evenings (farenheit). It’s late January, and if we have a major cold spell, I’ll have to fire up the wood stove. But I’m building a trombe wall inside the greenhouse, against the south facing wall, which should keep things nice and warm except when there’s a week of solid cloud cover. On sunny days, it gets to 90 or 100 in the greenhouse but a trombe wall would get even hotter and store that heat in barrels of water and release it slowly. On completely overcast days when its freezing outside the greenhouse still heats up to 60 pretty reliably. Any light adds to the greenhouse effect.

  4. I am considering using paper adobe as a plaster on an earthbag dome I am building just above the snow line. I will cover this with breathable paint that does not allow water through. Do you have any knowledge of how it behaves in extreme temperatures?

    I like the idea of using it because of the insulation qualities. The building site experiences freezing temperatures as well as high temperatures in summer.

  5. (four years later…) My paper-adobe mix was applied as a rough covering, though its held up fine from 2008 to present (2014), I’ve been covering it with a finer grade of exterior plaster / stucco. I’ve never been interested in putting a cement based coating over it, for this would prevent it from breathing, nor have I wanted to use any form of additional insulation. I’m not sure how much the transpiration of humidity affects the temperature of my building, as we have single digit humidity much of the year. We do have high humidity in monsoon season, but the rain cools the ambiant air temperature making things quite comfortable. With underground temperature at around 52 degrees here year round, and no insulation in my floor (brick floor atop 2 feet of tamped adobe soil treated with lime to resist mold), this may explain the much cooler temperature inside the structure in summer.

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