Hempcrete: A Carbon-Negative Insulation

Hempcrete Moderates Indoor Humidity and Temperature, While Being Fire, Mold, and Insect Resistant

The next frontier in green building is emerging as carbon-sequestering materials. Incorporating such materials into tight, energy-efficient building shells has the potential to fully offset the 40 percent of total greenhouse-gas emissions that structures contribute to global warming. One such material is hempcrete, an innovative insulation that is better for people and the planet.

Hempcrete, or hemp lime, as it is sometimes called, is made from the woody core of the cannabis plant combined with lime and water. Hemp is fast-growing (typically 3-4 months), likes a wide range of soil and climate conditions, and requires no pesticides. An acre of hemp can sequester an impressive 10 tons of carbon dioxide, more than an acre of trees can sequester in an entire year. When turned into hempcrete, the carbon remains locked in the inner woody layer. The lime binder also sucks up carbon. However, cultivating it does require a good amount of water.

The insulating value per inch of hemp is comparable to fiberglass insulation (R-2.5-3), yet it has none of the harmful synthetic ingredients that fiberglass and most other commercial insulations contain. Hempcrete acts like a toxic-free sponge that absorbs moisture from the surrounding air when it is humid and releases it again when it is dry. This ever-adjusting behavior creates a healthier relative indoor humidity and an improved sense of comfort. It has good sound-dampening properties that also contribute to good indoor environmental quality.

The use of hempcrete is growing rapidly in Europe. It has been used in Paris since 2012 and is now being government-funded in subsidized social housing projects. It is also getting traction in the U.S. but was hindered by a later start because of the legal ban on all hemp uses, only recently lifted.

Although made from the woody core of Cannabis sativa, hempcrete is highly fire-, mold-, and insect-resistant, due to the lime envelopment of the plant elements. Not surprisingly, all the other parts of the plant can be turned into other products. The only negative for hempcrete seems to be that it costs more than fiberglass insulation, about double, although that differential will diminish as it gains market share. The product comes in various forms: batts, blown-in, blankets, and rigid boards.

Hempcrete is part of a class of composite building materials that has received negative-carbon-material classification, and among these, it is the top negative-carbon performer. Many other building materials are now being made and analyzed for their carbon-storing properties. The optimum is to create carbon-storing buildings that also operate on renewable energy, making them zero-net-energy and zero-net-carbon structures.

Ending Our Addiction to Natural Gas Will Not Be Easy

Addressing Climate Change Needs Workers, Investors, and Innovators to Be Involved

The Philadelphia Gas Works, founded in 1836, is the oldest gas utility in the country and still one of the most substantial with its 6000 miles of service lines and more than half a million customers. The nation’s largest gas utility is our SoCalGas Co. The reality, however, is that today all gas providers are facing existential threats from the quickening energy transition that aims to convert buildings from gas to electricity.

The gas industry has gained several decades of reprieve by promoting gas as the bridge fuel between coal and renewables. Nevertheless, as the urgency to address climate change has increased and the monitoring of methane leaks from gas pipes (three million miles of gas pipelines nationally) has revealed gas to be almost as dirty as coal, time is running out for gas.

Increasingly, cities’ climate action plans are targeting achieving carbon neutrality by 2050 or sooner. Banning gas from new construction is a relatively easy first step and will be policy in California in a few years. Much thornier is how to get gas out of existing buildings: Almost 60 percent of the country’s 120 million houses use natural gas.

The first step in a comprehensive approach to decarbonizing the nation’s energy infrastructure would be to improve energy efficiency in equipment and delivery systems and reduce consumption. The second would be to electrify as many cars, space heaters, water heaters, and cooktops as practical, using electricity from renewable sources. The third would be to replace as much natural gas as possible with low-carbon alternatives such as biogas, hydrogen, or synthetic gas (a liquid blend of hydrogen and ammonia or methanol designed for easy transport in existing pipelines), which combust without carbon emissions.

The gas infrastructure is old and in need of repair, but spending on pipeline maintenance above what is required for immediate safety is unwise. One strategy, beyond minimal repairs, is to select a neighborhood, convert it to a clean alternative, and then shut off that section of the gas system, thus reducing the size of the network. Another option is to develop a geothermal district. Ground-source heat pumps can tap temperatures deep underground to provide neighborhood heating and cooling. Installation costs are high, but operating costs are negligible. Gas line rights-of-way could be used for geothermal pipes.

The American Gas Association (and SoCalGas) has promised to use more biogas and create hydrogen/biogas blends. These cleaner alternatives need to be pursued, but costs are high, and scope appears to be limited to supplanting only a fraction of natural-gas use.

Reining in climate change requires many solutions. Gas utilities and the 98,000 workers employed in the gas industry need to be part of the picture. Repairing unsafe infrastructure, developing geothermal systems, and expanding renewable natural gas would use the expertise of many of these workers.

Greening a Bathroom

Bathrooms, along with kitchens, are the most expensive spaces to construct in a home, because of the plumbing needed, the greater density of lighting and numerous appliances. To create a sustainable bathroom, it must be energy efficient, use minimal water, be comfortable, non-toxic, quiet and basically maintenance free.

California codes keep nudging all new and remodel construction to be more sustainable. Consequently, any remodel project today triggers upgrading ALL plumbing fixtures throughout the home or business. The most recent State standards are: 1.8 gallons per flush for toilets; 1.2 gallons per minute (gpm) for bathroom faucets and 1.8 gpm for showerheads, giving California the toughest standards of any US state. For comparison, these flows are about a quarter or less of what was standard 3-4 decades ago.

Not only are these standards saving hundreds of billions of gallons of water each year, but also lots of energy and greenhouse gas emissions, since 19 percent of energy consumed in California is used to pump, transport, treat and heat or cool water.

Selecting an efficient and effective showerhead has become easier in the last decade, due to the Federal WaterSense program. To carry the WaterSense label, a showerhead must list its flow rate, which must be below the maximum allowable federal standard, and meet strict user satisfaction standards. A popular WaterSense model by Niagara, rated at 1.5 gpm and receiving stellar customer reviews, costs only about $8.

A promising development that cuts water consumption even more is the atomizer mist technology. Showerheads using this approach disperse water through millions of microscopic droplets into an effective wet area while saving 70 percent of water. Similarly, with sink faucets, the fine mist produced is a 98 percent reduction in water use, with no loss in functionality.

Controlling humidity in bathrooms is key to promoting health. Good natural ventilation (operable windows) as well as effective air-moving equipment avoids mold, mildew and rot. A good bathroom fan needs to move about 150 cubic feet of air per minute while having a noise rating of 1 sone or less, making it virtually unnoticeable.

The leading green-building thinking today emphasizes all electric homes, where the loads are minimal, and the power needed is produced on-or-off-site by the sun or wind. LED lighting and super-efficient equipment keeps loads to a minimum without sacrificing performance. Hot water can also be heated by solar electric panels or directly by solar thermal panels. Water and heat can be additionally saved by on-demand hot water delivery. At the push of a button, a pump turns on, rapidly bringing hot water to faucets while pushing the cold in-line water out into the cold-water lines rather than wasting it down the drain.

Good insulation, high performance windows, using only non-toxic materials and avoiding carpeting are additional strategies to improve sustainability in bathrooms and are even more important for the entire house. Savings on water and electricity are often easily calculable. Putting a price on good health is not easy but for most of us it is priceless.

An Option to Replacing Old Windows

Swapping out old single glazed windows with high performance dual or triple pane units is costly. Moreover, it is often not allowed in historic buildings. Architectural historians insist on maintaining the appearance and character of windows in classic old buildings, irrespective of their performance.

According to the US Department of Energy, around 30% of the energy used to heat and cool our homes is lost through inefficient windows, even though windows often make up less than 10 percent of the surface area of a house.

A less costly possibility, rather than replacing inefficient windows, is to install an insulating window film. Glazing films have been around for more than 50 years, but high performance films only in the past decade. They have evolved along with the great gains in window technologies. Coatings and films have become standard in high quality windows. The large choice of offerings can yield greater or lesser heat gain, visual clarity, ultraviolet blocking and insulating values, to name a few of the available options.

The cost of replacing residential windows can easily be $125 per square foot or more. Window films such as 3M’s Thinsulate Climate Control film offers good performance for a fraction of the cost. This type of low emissivity or “low-E” film improves the insulation value of a typical single pane window to approximate a double pane unit (up to about 92 percent). The emissivity rating can be as low as 7 percent, meaning that 93 percent of a room’s heat is reflected back into the space and doesn’t escape outside. Low-E coatings reduce heat loss in winter and heat gain in summer. As a result, the initial installed cost of $5-$15 per square foot (depending on film type and size of the job), is a 2-5 year return-on-investment (ROI). The comparable ROI for replacing old windows with high performance units is 30-50 years.

Some of the recently introduced low-E films have high visible light transmission (VT of 70 percent), meaning they have basically no impact on views-no darkening and no distortion. Furthermore, these coatings block 99 percent of ultraviolet rays to fully protect furniture, rugs, upholstery and artwork from fading. Window film application does not require a professional installer. Professional installation, however, is highly recommended for quality purposes and to have the 20-30 year warrantee apply. Installation by professionals takes only minutes per window. Full curing of the film takes a few days to a month.

For reasons of energy savings, modest cost, comfort and fade protection, low-E window films are important to know about.