Is a “Pretty Good House” Good Enough?
This concept of a home that strikes a balance between construction cost and energy performance is a guideline for builders and architects looking for an alternative to complicated green-building certification programs.
Industrially made products tend to work pretty well. Part of the reason for that is the process that creates them. Any new product starts as a design, from which a prototype is made and tested. The results of the tests go back to the designers, changes are made, the costs and benefits of each change are analyzed, and the process repeats. Most products go through several iterations. Eventually, the manufacturer’s finished product reaches the market at a known price and a consistent quality. Consumers can compare that price and quality with similar items before choosing.
Building doesn’t work like that. Custom-home builders and renovators make the prototype and finished product simultaneously. We can make an educated guess at how a house will perform, but the testing occurs when the owners move in. The variables of climate, size, site, and owner behavior all have effects that make comparisons difficult. Still, we try to find meaningful ways to compare houses, in part by designing with known systems and components that can be compared to each other through various rating systems. The most basic system is the building code, and it has only two grades—the house passes or it doesn’t. The other rating systems are all voluntary. Some systems—such as EPA’s Energy Star Homes and DOE’s Zero Energy Ready Homes—are governmental, but most are administered by private nonprofits. I’ve worked with both kinds, including LEED for Homes, Passive House, Energy Star, Zero Energy Ready Homes, and the Thousand Home Challenge. Each system exposed me to new ideas and approaches. The Passive House Planning Package (PHPP) software at the heart of Passive House is a great tool and is useful even if you’re not pursuing Passive House certification. The HERS rating from RESNET is often suggested as the likeliest universal metric for comparing houses. While Zero Energy Ready Homes’ impact has yet to be felt, I like its flexibility and emphasis on renewables.
All the rating systems do a good job of providing a framework for planning a project and reminding all the parties of important things to keep in mind, but none of them are perfect.
Is actual certification worth it?
No rating system has penetrated the residential real-estate market to where it has an observable impact on the price of a house. Whether or not rated homes even perform better has been the subject of much debate. This is partly because the ratings are based on the design and construction of a house, not on its actual performance.
TVs vary wildly in energy consumption; people’s comfort at different thermostat settings varies; one family may be obsessive about closing doors and windows, while another may have kids, dogs, and cats in and out dozens of times a day. My company built a LEED-certified house several years ago, and only after completion did the owners tell us they liked dramatically different temperatures in their bedrooms. One of the homeowners ended up leaving a bedroom window open in winter. This lack of post-occupancy data collection means that our understanding of the various programs’ effectiveness is necessarily limited.
There is one program, the Thousand Home Challenge, that does measure post-occupancy energy use. Designed for existing houses, it measures only reduction in energy consumption from a baseline taken by the occupant prior to the improvements. But even that is subjective. I’ve heard Linda Wigington, the force behind the program, talk about wearing a coat, a hat, and a scarf indoors so that she could keep the thermostat in the low 50s. This may be a good test of one’s toughness or competitive spirit, but it doesn’t provide widely applicable lessons.
One problem with rating systems is that many of them can lead to “point chasing,” in which the builder or the designer tries to make up for one flaw that costs system points by incorporating somewhat dubious features that gain system points. In some programs, cost/benefit analysis seems to be lacking. My one experience with the Passive House program for existing homes, called Enerphit, would have required a level of foundation insulation whose cost would have been grossly in excess of the cost of any energy saved.
Certification gives all the parties a reasonably objective standard and creates a community of participants who can share experiences and best practices. It helps to raise the bar for specific projects and, through participation, the industry in general. On the other hand, commissioning—that is, the process of turning a building from a construction project into an occupied space, and the ongoing maintenance of its systems—and how the house actually performs get little attention. There is reassurance from a rating that a threshold has been reached, but you are playing by their rules whether or not you agree with all the particulars. The cost of certification is another sticking point; consultation, modeling, and fees can cost thousands of dollars.
Should you go it alone?
Home-rating systems are good for people who want feedback about whether they’re on the right track. But a smart builder can get the same results going it alone. I facilitate a monthly building-science discussion group that’s attended by builders, carpenters, architects, engineers, energy auditors, insulation contractors, and other fans of building science. Back in 2011, we had a series of terrific discussions on the subject of what a “Pretty Good House” (PGH) would look like. We realized that plenty of people choose not to use a rating system, and we wondered if there was a way to frame a conversation about planning a project with energy efficiency and low-impact design in mind, while keeping a sharp eye on the budget and the balance between initial and long-term costs.
The Pretty Good House title was meant as a joke, but the name struck a chord. We batted around a minimal level of quality for our area and then shared our ideas on GreenBuildingAdvisor.com. That spawned another series of conversations on websites all over, including treehugger.com and energyvanguard.com. PGH was even mentioned in the New York Times.
A PGH in Georgia would differ significantly from one in Maine (dampening rather than strengthening solar gain, for example). Houses in mountain and desert areas would have different issues with moisture and humidity than coastal or lakefront houses. Density, lot size, orientation, projected occupancy, and access to utilities can all factor in. The goal of a PGH is to find the sweet spot between expenditures and gains—the best mix of affordability, comfort, and efficiency possible. For example, how much insulation is enough? Would that answer differ if part of the house’s energy were supplied by PV? One approach is a decision tree to show a builder, designer, or owner how one decision can affect the rest of a project. It might look something like the list below.
I sometimes describe the PGH as being like open-source software: It’s out there and it’s free, but it can be modified well or poorly. I worry that it may be an excuse for people to avoid the hard work of thinking their project through rigorously or to make unnecessary compromises because of easily overcome hurdles, but I hope it’s a way for them to develop their own best solution.
What would your Pretty Good House look like?
The Pretty Good House
Good design A Pretty Good House looks good and feels comfortable. Good design is simple, so it’s easier to build well. Chopping up a roof with dormers and peppering walls with bump-outs creates opportunities for ice dams and air leaks, and it requires extra labor and materials.
Layout Careful room planning for flexible use can allow a smaller home to work better than a larger home with a poor design.
Orientation Can you make space for PV on your roof without other tradeoffs? Where will the rain go? Can it be harvested? Will snow or rain from the roof block the entry?
Energy modeling Perform this during the design by working with a consultant or by using software such as the DOE’s free web-based ResCheck.
Foundation Basements can be cheap square footage, or they can be expensive unnecessary spaces. They’re also prone to moisture problems.
Air-sealing Plan the air barrier for continuity. Trouble spots are where materials join (e.g., where foundation hits framing) or where planes don’t align (e.g., where walls hit roof). The air-leakage rate should be no more than two air changes per hour at a 50 Pascal pressure differential.
Insulation Include sufficient framing depth for the desired R-value. Insulating sheathing requires thought about window, siding, and door installation. In my area (climate zone 6, coastal, 7000 heating degree days), R-10 under the slab, R-20 foundation walls, R-40 walls, and an R-60 roof are a good start. Understand seasonal vapor drive and how different materials can trap condensation and lead to mold or rot.
Mechanicals Get the orientation, shading, and insulation to where you can downsize the heat and air conditioning. These costs may break even. Consider a service core for plumbing and wiring to keep them out of exterior walls for energy efficiency and to group them for easy upgrades in the future.
Air quality Avoid products that contribute to poor indoor-air quality, but don’t go crazy. The poison is in the dose: How much exposure will anyone have? Focus on the big sources of off-gassing, such as flooring and furniture.
Windows The best window insulates like a lousy wall. Skylights make even lousier roofs than windows do walls. Plan each to maximize natural light and minimize heat loss, and consider upgrading to triple glazing.
Solar panels The dropping cost of PV may be changing the equation. There may come a point where it’s smarter to focus more on energy production than on energy saving.
Universal design Can your house accommodate people with limited mobility? Avoid floor-elevation changes, especially on the first floor. Can a ramp be put in later if needed?
Reversibility What happens if you repair or renovate the structure? Can you replace insulation and keep the thermal boundary intact? Can materials be replaced without damaging the substrates?
Nonmonetary costs Think about hidden environmental costs. Spray foam is a great insulator, and vinyl is a cheap and functional siding, but both products have environmental drawbacks. Bamboo flooring is eminently renewable, but it comes at a transportation cost. That doesn’t mean you shouldn’t use those products; just balance their costs and their benefits.