One of the more interesting aspects of green building is the continual influx of new ideas and products. A product can be made with a lower impact than what it replaces, contribute to greater energy efficiency or produce energy from a renewable source. The following are some products that are either new or have recently become more readily available.
The building enclosure
In a house that’s properly air sealed, more insulation can be the lowest-cost way to increase efficiency — up to a point. The gain in popularity of the Passive House Standard and “net-zero-energy” homes has furthered this notion. The possibility of reducing heating and cooling loads by as much as 90 percent has been accomplished, so the question becomes which one provides optimum value: increasing insulation or producing energy via renewable energy such as solar. The price of solar has come down enough to alter the old equation.
A product that helps to add R-value, or thermal resistance, to walls is Zip System R Sheathing, which comes with either half-inch or 1-inch sizes of foam laminated to Huber zip board sheathing to give an R-3.6, or 6.6 exterior continuous insulation. Adding the 1 inch, R-6.6 sheathing to a 2-by-6 R-19 wall creates an R-25 wall with much less thermal bridging through the wood framing. That is short of the Passive House standard for our area (around R-40), but it’s a significant bump up from what’s legally acceptable by code and even from what’s acceptable by green-building standards.
Spray-foam insulation, which eliminates ozone-depleting and greenhouse-gas-producing chemicals, and can contain recycled content, is also available from a number of manufacturers. Many spray-foam -insulation installers work in our area. (For more information, visit avl.mx/p4.)
Air sealing, which is required for a well-insulated home, can be accomplished in many ways. The old-fashioned ones were the fastidious use of caulk guns and taped house wraps or taped sheathing. Now there are also a few spray-on air barriers, which can be permeable or impermeable, depending on the situation. DupontTyvek is one manufacturer; Stoguard, Henry, Enviro-Dri and W.R. Grace Co. are some others. Spray-ons are more expensive than other methods of creating air barriers (they run about 60 cents per square foot), but they’re easy to use and provide strong results.
Once you have a well-sealed and highly insulated home, heating and cooling are the next big considerations. The geothermal heat pump and the ductless minisplits are the most recent advancements. Both run on electricity, but with new efficiency standards. The best of the geothermal systems can produce up to 5 units of energy for every 1 unit of electric energy — an efficiency rating of 530 percent. They’re much more expensive than traditional heating systems, but are eligible for tax credits.
If you worked on the building enclosure, and you’re building a small home, a geothermal system might not be the best value for you. You might look into the minisplit heat pump system. These have been around for a while and now include a partially ducted version for some applications. There’s also a minisplit that heats water as it cools your house. (Water-heating capabilities have been available with geothermal systems but have only recently been included in air-to-air heat pump systems.) See hotspotenergy.com/air-conditioner-water-heaters.
Many new programmable and smart thermostats are now available to control the operation of your mechanical system more efficiently. The NEST has caused the most stir. The “learning thermostat” follows user habits. It turns itself down and can be accessed through a Wi-Fi network. These thermostats are somewhat pricey (around $250) compared to other programmables, which can cost $75 or less.
Fresh air ventilation
So now that you have a really tight, well-insulated house, you’ll want to make sure you can breathe clean air in it. Heat- and energy-recovery ventilators have been around for years; manufacturers keep coming up with new versions and improvements.
One new version is a ductless HRV for small homes, the Lunos e2 (see figure 1), which I only found available from Four Seven Five in Brooklyn. A pair that works together costs $1,195. They’re claimed to work at 90 percent efficiency at 10, 18 and 22 cubic feet per minute. A pair would work for a 700-square-foot, two-bedroom home, and would meet the Green Built North Carolina ASHRAE Standard 62.2 ventilation prerequisite. Two pairs ($2,195) would work for up to 1,400 square feet.
Heat pump water heaters deserve some mention, although they’ve been on the market for a few years. Several brands are available at home- and plumbing-supply stores. The one from GE — “GeoSpring” — is supposed to be the quietest. Rheem, A.O. Smith, and StiebelEltron also make them. They do take the heat from the air, which means your heating system will have to work a little harder in the winter, but in the summer, they help with air-conditioning and dehumidification. In our region’s mixed climate, they’re an efficient choice; they sell for around $1,500.
Landscaping is often the neglected aspect of green building. A lot of attention has been given to catching rainwater for landscape and garden needs, as well as for flushing toilets. In our area, RiverLink has started the WaterRICH program, which assists and encourages homeowners to install rain gardens and use rainwater on site. The goals are both to reduce the demand for potable water and to increase the infiltration of storm water within the ground, thereby reducing pollution to creeks and the French Broad River.
Living walls and vertical gardens (see figure 2) — which can be grown both indoors and out — are also gaining popularity, and more companies are making the process easier. These gardens can help keep a house cooler and can contribute to cleaner indoor air. They do take regular watering but can also produce herbs and some food crops.
The No-Mow Lawn Seed mix from Prairie Nursery needs very little watering if any and can be mowed once a month for a manicured look — or not be cut at all. This can have a big impact on water use and the impact of lawn moving on air quality.
The big new thing in renewable-energy generation is the cost. We recently priced a 4-kWh solar system similar to one that we installed three years ago, and its price has come down significantly, to $15,000, since then. With the tax credits, the cost after five years is down to less than $3,000 (and the system generates income, selling power through the N.C. Green Power program). The renewable-energy industry has a constant stream of new products, from DOW Powerhouse Solar Shingles (see figure 3), that blend in with a roof to the small Honeywell Wind Turbine, which is gearless and starts generating at 2 mph wind speeds. Solar is making a significant difference is in the developing world, where grid connection isn’t possible and diesel is the only alternative. In many cases, the solar option is not only cleaner and quieter but also cheaper.
Many improvements have been made in appliances; the ENERGY STAR rating is still a good indication of which products are best.
Induction cook tops have become more available. These heat pots and pans directly, as long as they’re made of the correct metal. They cook faster than gas stoves, are more efficient than normal electric cooktops, and can be powered by solar. In a zero-energy house, they’re a good fit, but they’re more expensive: They start at around $1,300 for a 30-inch cooktop.
The new countertop materials, paints and finishes are too numerous to mention. In Asheville, we’re lucky to have local green-building supply stores, which carry these supplies and know which ones are new and better. There’s a continual supply of new products and prototypes of products — and some fade. I post about the ones that make sense to me on Twitter @wncgbc, Facebook and the WNC Green Building Council website. Good luck with your early adapting and innovative efficiency improvements. If you have a great discovery, please share it.
Boone Guyton is a partner with Claudia Cady in Cady and Guyton Construction. He is a longtime member and co-founder of the WNC Green Building Council.