Insulation

Building an Earthbag and Stone Rainwater Storage Cellar

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I decided to build a simple recessed cellar in my yard that would serve a variety of functions, including rainwater storage, root cellar and space for vermiculture (worm bins). All of these require relatively cool but not freezing conditions, so digging into the ground was a good way to accomplish this. It seemed like the easiest approach would be to build this primarily with earthbags.

First I calculated how large it needed to be in order to hold the two large (275 gallon) water tanks I intended to buy, as well as provide enough space for produce and worms. It was a tricky business to fit all of this in the space available, especially because I had to work between existing underground irrigation pipes.

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Recycled Glass Insulation

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Recycled glass insulation by Knauf
Recycled glass insulation by Knauf

I’m always on the lookout for sustainable natural building materials. Recycled glass insulation is not only made in part with recycled glass, it’s also effective at reducing energy costs and improving the acoustics in homes and businesses. EcoBatt insulation caught my eye because it appears to be the largest brand of recycled, non-toxic glass insulation in the US. A few other brands are listed below, some of which are available in Europe.

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Hempcrete

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I’ve been aware of the value of what is called “hempcrete,” a mixture of lime and hemp hurds (an agricultural byproduct), for several years. But I’ve never learned much about how to prepare it, partly because industrial hemp cultivation has been illegal in the United States for the last eight decades, since it is related … Read more

Green Magic Homes

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I stumbled upon an interesting approach to creating underground housing. The manufacturer of the system calls them Green Magic Homes. Basically the structures are composed of prefabricated sections of molded composite material that are connected together to create a variety of shapes. They are waterproof and will not rot, so they are quite durable. Once the sections are erected, which can happen very quickly, they can be coated on the outside with foam insulation (generally needed in most climates). The idea is to cover the whole house with earth to protect it and to take advantage of the thermal benefit of going underground. Unfortunately, the system can only support about 7 inches of soil, so if you want more than that it may be necessary to add additional reinforced concrete.

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Thermal Performance Data on an Earthbag Dome

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Awhile ago, I wrote to you asking if you had any recommendations for stabilizing our 14′ (inner diameter) scoria dome tank house which had started to fail as a result of the bags breaking down. I wanted to give you an update.

Beldar
We paid a crew last November to shotcrete it inside and out, and it is performing very well. I just wish I knew whether it was the mass of concrete or the insulation of the bags. Probably a combo. I am interested to see how it performs once the mass has heated up a bit this summer.

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Does Insulating Paint Really Work?

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For many years I have wondered about the effectiveness of various products that advertise that they can insulate roofs and walls by simply painting them! The technology is said to stem from the science (developed by NASA) of protecting space vehicles by coating them with tiny ceramic spheres that reflect heat, so that they don’t burn up when re-entering the atmosphere. Some products consist of an additive for paint, while others are specially formulated paint.

When I realized that I wanted to insulate the 1940’s adobe house I had bought, I began to wonder whether this might be a simple solution to accomplish this. In researching this possibility I discovered that there were conflicting opinions about whether such a paint could work. The manufacturers claimed that many tests have proven their effectiveness and there were some testimonials from individuals or businesses that made similar claims. But I couldn’t find any independent studies that I considered actual validation of the concept.

Not being willing to proceed blindly with painting my entire house with expensive paint on the assumption that it would improve the thermal dynamics of my completely thermal mass walls, I decided to conduct an experiment that would accurately inform me exactly how effective the paint might be. I conceived of a situation that would simulate the thermal mass walls that were left open to the ambient atmosphere over several days. There would be one setup painted as prescribed with the insulating paint and then a second control setup that was identical, except without the insulating additive. Embedded within each of these would be a wireless thermometer probe to keep track of the separate interior temperatures.

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I found some perfectly uniform 16’X16″X3.5″ concrete blocks for sale at my local building supply store quite cheaply, so I bought ten of these. Next I acquired the insulating additive (Insuladd was the brand name) and used some exterior latex paint that I already had on hand. I thoroughly mixed the additive to some of the paint and kept some of it in its original form for the control. Then I painted half of the concrete blocks with the insulating paint and half with the control paint, applying two coats of each.

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