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.

The 18 Woodland Grove house has a front porch that used locally milled Hemlock for a natural and durable look.

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.

The 18 Woodland Grove house never had a single dumpster.  The builder ensured efficient use of materials and very little waste was generated when compared to a traditional house.

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.

The 18 Woodland Grove house used spray foam sparingly and in only key areas, like the exterior floor framing.  The materials selected were considered for low VOC and Formaldehyde. For example the kitchen cabinets are built with plywood boxes, not particle board to reduce the level of toxins in the home. The indoor air quality is improved by a variety of systems and techniques.  The first strategy is source control.  By constantly removing the stale, humid or contaminated air from the bathrooms and trash can, the ability for the pollutants to dilute throughout the house is reduced.  A balanced supply air is introduced in the home while the stale air is removed.

The indoor air in the home is always circulating and constantly moving at slow speeds, thanks to the ducted heat pumps.  Its so quite and slow that you can’t hear or feel it, but it,s moving around 200CFM on each floor all the time. 

During this circulation it is constantly being filtered and then re-filtered through a massive Aprilaire Merv 13 filter. ASHRAE currently recommends using a minimum MERV 13 filter, which is at least 85% efficient at capturing particles in 1 µm to 3 µm size range. 

Two separately ducted Santefe dehumidifiers maintain healthy indoor moisture levels, reducing mold spores and comfort. 

The RenewAir ERV constantly provides dillution air to each floor, which is supplied into the heat pumps, then redistributed throughout the house.  The system is balanced with the outdoors, ensuring the home is not pressurized or depressurized, further reducing exterior contamination.

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.

Portions of this page attributed to Mike Maines, "Guidelines for designing and building a Pretty Good House". Visit the Pretty Good House website to read more by clicking here.