More On Passive Houses, LEED-Certified Homes, and Net-Zero Buildings

Are high performance homes viable and appropriate for the mass market? Do they provide what their builders advertise? Are they worth the effort, or is it more greenwashing?

Why do I ask that? According to a 2005 report by the U.S. Energy Information Administration, buildings consume 48 percent of the energy—and over 70 percent of the electricity—used in this country every year. I think that’s a result of cheap energy for so long, but things are changing. “Energy independence” is a new theme, but it’s going to be challenging in the land of oversized McMansions.

Let's hope the time for these is past.

Let’s hope the time for these is past.

We’ve been accustomed to low standards for new construction and for remodeling for so long because of cheap energy. What if, during the housing boom of the last 15 years, homeowners and builders had emphasized energy efficiency instead of flashy items? I’m thinking of things like adding massive amounts of insulation, sealing the house against air leakage, and upgrading windows, rather than Viking ranges and granite countertops and showers with multiple jets, not to mention excessive square footage.

I’m not opposed to those elements (with the exception of excessive square footage), but I do think that more rigorous standards for energy and resource efficiency are more important. We must build structures that are more sustainable, energy efficient, and resource efficient first, and then add the other elements. Simply raising the minimum standards for housing is a huge first step.

Is the Passive House standard appropriate?

In my last post I explored Passive Houses. I like the Passive House standard because it’s about designing efficiency into the home with a heavily insulated, nearly airtight envelope. It’s so well insulated that the incidental heat produced by bodies and appliances can provide all the heat needed in some climates. Even in colder climates Passive Houses dispense with a standard HVAC system in favor of a heat- or energy-recovery ventilator and a small backup heater.

The Passive House standard is defined by results, not by methods. There are three benchmarks to hit: for air-tightness, for heating, and for overall energy use. There are some principles to follow as well, such as eliminating thermal bridging, and superinsulating, but they’re a means to an end. The three benchmarks are tough to achieve, though, so you tend to see the same methods employed to reach the standards.

A Passive House in Austria shows the typical simplicity of the design.

A Passive House in Austria shows the typical simplicity of the design.

A Passive House is quite simple but not easy, and the house either hits the target or it fails to. Thousands have been built in Europe and more are underway in the U.S., where the standards are under review because of the energy load required for dehumidification. We may see the standards tweaked to address regional differences such as high humidity.

In any case, Passive Houses have shown that it’s possible to drastically cut energy use in a home—up to around 90% in some cases compared to a standard American home with a HERS rating of 100—with building design, rather than additional hardware. Passive vs. active techniques, essentially.

Other standards for improved homes exist, as well. The U.S. Environmental Protection Agency runs the Energy Star program, which requires homes to use at least 15% less energy than a home built to the 2004 International Residential code standard, which results in a HERS score of 85 or better. That’s better than nothing, but doesn’t seem very ambitious. A Passive House should score in the range of 20-30. A net-zero home scores at 0.

LEED takes a different approach

The LEED for Homes standard, in contrast to Passive House, addresses a variety of factors in building an environmentally friendly home. This standard, from the U.S. Green Building Council, aims to “promote the transformation of the mainstream homebuilding industry toward more sustainable practices. LEED for Homes is targeting the top 25% of new homes with best practice environmental features.” The standard will be updated in 2013.

LEED for Homes, which requires independent, third-party verification, focuses on eight areas: indoor air/environment, site development, site selection, water savings, materials selection, energy efficiency, resident awareness of a home’s performance, and innovation. By following the LEED for Homes approach to these factors, you can build a home that:

  • provides a healthy indoor environment with few pollutants and abundant fresh air
  • minimizes water use
  • uses more sustainable materials and uses them efficiently, minimizing waste
  • minimizes energy use
  • is sited and built so as to minimize its environmental impact, and to have efficient access to needed services, businesses, etc.
  • costs less to operate and is sustainable over the long term.

The U.S.G.B.C. has targeted the standards to the top 25% of new homes, but other groups are applying them in the mass market. This is a fantastic idea!

Habitat for Humanity in Kent County, Michigan, has committed to the LEED Gold standard of certification. That’s not as good as Passive House standards for energy use, but it is impressive, especially since Habitat homes are meant to be affordable. (I have not seen a cost/square foot or sales prices for their projects, but have asked for that information. I’ll post it when I see it.)

This page at their site provides a good summary of LEED standards with some research done by the Alliance for Environmental Sustainability. The AES reports that annual savings on electric, heat, and water should total at least $1000 per home. Other Habitat groups around the country are taking the same approach, including LEED townhomes in St. Paul, Minnesota, which I think is a great option, as not everyone wants or needs their own yard and accompanying maintenance. Plus, townhomes can be built to a higher density, making better use of buildable lots, with the potential of preserving existing open space.

I’m encouraged to see the progress LEED, Passive House, and other sustainable techniques are making in improving housing in the U.S. And while no standard can be perfect in every situation, it seems to me that the ideal house project would use the performance standards of the Passive House, and the sustainability criteria of LEED.

Next I’ll have a look at net-zero homes.

The Farmhouse Media is all about living sustainably with

  • green building
  • permaculture
  • green cities