8.      Materials

Local is good. While we can get materials from nearly anywhere on earth, buying locally supports the local economy, typically keeps the carbon footprint smaller, and makes a house a product of its environment instead of a cookie-cutter house that could be anywhere.

Efficient Framing and Waste Reduction. Advanced Framing, or Optimum Value Engineering, uses only the structural members that are necessary, instead of relying on rules of thumb and tradition to guide construction. The amount of waste generated on an average construction site is staggering—a single roll-off (aka dumpster) of 30 to 40 cubic yards is equivalent to 20 to 40 pickup-truck loads of waste, and most projects require multiple roll-offs. (It’s almost enough to make you wonder if outlawing plastic straws is worthwhile.) Anything that reduces this amount of waste is a step in the right direction.

Toxins and Indoor Air Quality. Most Americans spend a lot more time indoors than outdoors, and the indoor air quality of most homes is worse than the air outside. Volatile organic compounds (VOCs) are not always health hazards, but some are—notably, formaldehyde, which occurs naturally in some materials and in the past has often been used as a binder in composite materials. Many petroleum-based products release phthalates, or plasticizers, which are health hazards. Spray foam and other materials release isocyanates, which cause flu-like symptoms or worse. Combustion appliances release deadly carbon monoxide in their exhaust, which can be indoors. The solution is to use materials and equipment that do not contribute to poor indoor air quality, and to use filtered mechanical ventilation, which typically leaves the indoor air quality higher than that of the outdoor air.

Embodied Carbon. This is the key aspect of PGH 2.0, and key to slowing the arrival of the worst effects of climate change. Carbon dioxide is the most common greenhouse gas, after water vapor. Other greenhouse gasses are compared to carbon dioxide, as a way to describe the severity of their effects on the atmosphere. It is more properly called carbon dioxide equivalent, but the term “embodied carbon,” or closely related “embodied energy” and “carbon footprint” are nearly interchangeable. Operating energy relates to the energy used once a building is in service, and it’s important. But the next decade is a critical time for reducing carbon emissions, so if the materials used to reduce carbon emissions have high embodied carbon, they are a net negative to the environment since it would take decades for the "pay-off" from the increased energy efficiency to balance out the upfront "carbon load". Some materials sequester carbon, and can be net carbon negative—that’s a good thing. Others have very high embodied carbon, including concrete and most common types of foam, so aim to reduce or eliminate those from your Pretty Good House.