The sweet spot: the intersection of performance & price
How to Design and Build a Pretty Good (or Better) House
By Michael Maines
THE BUILDING STANDARD that’s not a standard and started as a joke takes off… again. Once a month a small group gets together in Portland, Maine to discuss hot topics in building science—the field that covers everything from indoor air quality to solar vapor drive. Hosted by Performance Building Supply, it is a lively opportunity for building professionals and others to debate, network and learn from each other. Back in 2009, our moderator expressed frustration with the lack of consumer buy-in to the various building efficiency programs and the perceived excesses of some of the programs. With the idea of establishing consensus for an energy-efficient, high-quality but practical building standard, he asked the group, “What would a Pretty Good House look like?”
The resulting discussions were engaging and full of sensible ideas; greenbuildingadvisor.com published a couple of blog posts summarizing the concept and asking for input, and the idea spread among performance-minded building professionals and trade magazines all over the US and Canada. It was even mentioned in the New York Times. The specifics of Pretty Good House (PGH) vary with every region; unlike other programs, there is no central organization taking money and vetting results. The central concept is to hit the sweet spot between expenditures and gains. Practitioners who feel they passed the program requirements may feel free to buy themselves a plaque.
How does it compare to other programs?
The residential building code defines the minimum structure that you can legally build. Most of it is about life safety (fire, structural collapse, wastewater gasses) and it provides prescriptive guidance for almost all common situations in construction. In Maine, towns under 4,000 people don’t even have to meet this minimum standard, unless the town voluntarily adopts the code. Left to their own devices, contractors, homeowners and developers who are looking for the lowest initial cost are guided solely by this bar, and many even complain about the minimal effort required to meet its guidelines, either because they don’t know any better or they don’t care.
At the other end of the spectrum, after years of Energy Star, LEED and other programs failing to engage the public the way MPG did for cars (once the government required it), the program currently grabbing the most attention is Passive House/Passivhaus. Originally developed in Germany and based largely on North American research, it provides a framework to design extremely energy efficient homes with high indoor air quality and building resilience. Maine has been a leader in the US Passive House movement, with many designers and builders working under the program.
Passive House’s requirements are few but rigid: you must meet this airtightness level, you must meet that energy use threshold, you must ventilate at this rate, you must use triple glazed windows, and a few others. To meet the energy requirements in Maine, you often end up with 10 inches or more of foundation insulation, or R-100+ in the attic. As a Passive House practitioner, I don’t consider those numbers excessive, but they are still a big jump from what most builders and homeowners are familiar with, and from what the building code requires. Most importantly, they cost more to implement, and they require more attention to detail than many builders are used to or typically reserve for things like interior trim.
Other programs, such as Energy Star and LEED, are less stringent on energy use but have other requirements that may or may not make sense on a given project. One program that is currently catching attention is the Living Building Challenge, which is a holistic approach to designing and building super high-performance, low-energy, healthy buildings. It appeals to those seeking to do the best for the planet and themselves, but meeting its requirements for netpositive energy, net-positive water, net-positive waste and other admiral goals mean that only ten projects have been certified in the ten years the program has existed.
The Pretty Good House concept is the antidote to all that complexity, primarily seeking find the balance between expenditures and performance, but also considering health, comfort, and the environment, with no hard and fast requirements. It provides guidelines to help those who say, “I want to build or renovate, but I don’t know what I am doing, where to start, or what to ask for.” It is flexible; nobody is telling you what to do, just suggesting, “Have you considered this?” and “Think about this before you do this.” It represents a range of performance, always better than code minimum and tailored to the situation.
If you want to design and build to code minimum, that’s your prerogative. But you will be left with a home that costs more to heat, cool and maintain than necessary, that may be vulnerable to moisture damage and mold growth, and that will not be as comfortable or resilient as it could be. If you want to go all-out on one of the premium programs, that’s great. We need leaders to set examples of what can be accomplished. But if you just want… a Pretty Good House, what would that involve? Every home performs as a series of interrelated systems. The Pretty Good House (PGH) model looks at twelve interrelated categories to consider as you
plan and build your home.
Economics. This is the key aspect to a PGH that seems to be missing from every other program. The least expensive option on day one is often not the least expensive once other variables are factored in, such as maintenance and annual energy costs (which can add up quickly). A PGH finds the sweet spot between expenditures and gains. And one of the fundamental concepts of a PGH is to factor the projected savings that will result from lower energy bills into the firstcost equation, so that you can decide whether you want a 5% or 10% return (or a 15-year payback, or other metric) on energy upgrade investments. A basic energy model—a computer simulation of how a home will perform, typically costing $200 to $500, provides the necessary information to make an informed decision. More detailed energy models are more accurate, but also cost more to put together.
Team. Very few homeowners can undertake the entire process themselves. On the design end, you may consider working with an architect or professional designer, engineers, energy consultants, or you may choose a pre-designed home. On the construction end, there are the builder or contractor, subcontractors, sometimes a developer, lenders, appraisers, and building inspectors. Although there are countless stories of adversarial relationships between these individuals, a better approach is to consider them all important members of your team. Write down what is important to you for your project to achieve, and interview potential team members with those goals in mind to ensure that everyone is on the same page from the start.
Climate + Site. Criteria for a Pretty Good House in southern Maine will look somewhat different from one in northern Maine, and very different from one in New Mexico. The US Department of Energy describes climate zones, which affect building assemblies; and the heating and cooling criteria are used in energy models to predict energy use. Your particular site will also affect things like wind speed (and resulting structural loading) and solar access. Additionally, like it or not, the climate is changing and there are things to consider because of that. The building code provides some climate-specific guidance, and a qualified designer, architect, builder or energy consultant can tailor systems to your project’s needs.
Design. “Design” includes every aspect of planning a home, but this is what most people think of when they think “design:” aesthetics, layout, comfort, simplicity, and connection to the site. In a PGH it also includes total size. For the most part, PGH designers aim for 1000 to 2000 sq ft as a reasonable range for most projects. It is important to think critically about every space and building element—do you really need a separate formal dining room, or a guest bedroom just for resale? Can you do without dormers, which cost extra and tend to leak ? And don’t forget beauty—a home needs to be loved in order to be valued. Sarah Susanka’s “Not So Big House” series, based loosely on Christopher Alexanders’ classic tome, “A Pattern Language,” can provide guidance.
Envelope: Thermal. How does the house deal with heat loss and gain? In a heating-dominated climate like Maine’s, it’s a big deal. Passive solar gain (while controlling overheating), thermal bridging, R-value and U-factor, radiation and thermal mass, and the effects of airtightness and water vapor control all need to be considered. PGH recommendations for Maine include a minimum of R-5 windows, R-10 under a basement slab, R-20 on foundation walls or under a slab-on-grade, R-40 walls and R-60 roof, though an energy model can tell you the economic effect of adjusting those values.
Envelope: Water + Air. Most builders can figure out how to keep rain from getting through the roof and walls, but there are other ways that water in all its forms must be controlled. Rainscreen walls, vapor permeance of materials, vented vs. unvented roofs, and various foundation systems all have their strong points and weak points. But with water (and its sidekick, mold) as an enemy to health and long-lasting construction, this category is something that materials and techniques developed over the last 80 years often do not handle well when used conventionally. Airtightness is another big change. Anyone who says “a house has to breathe” has already failed Modern Building 101. Good houses control air leakage. The original PGH called for 2.0 ACH50 (Air Changes per Hour, meaning that without mechanical assistance, at 50 Pascals positive or negative pressure—equivalent to a 20-mph wind blowing on the house—all the air in the home is replaced every two hours). Once you understand the concepts, getting to 1.5 or 1.0 ACH50 is not much harder, and comes with improved energy efficiency, building durability and mold resistance.
Windows + Doors. Unthinkable just a few years ago, windows and doors are now readily available (and affordable!) that exceed R-11 (U-0.09), which resist heat flow better than many older walls. They also allow free solar energy into your house—which is great when it’s cold out, not always so great when it’s hot out. There are ways to manage heat gain using different coatings on the glass, adjusting the amount of glass on each façade and with the use of exterior screening devices such as awning-type overhangs or sliding shutters. Triple glazing is not a hard requirement in the PGH, as it is with Passive House, but often makes economic and environmental sense. The best-performing windows typically operate as inswinging tilt-turns, but conventional casements, awnings and fixed units can also be used. Even good old double-hungs are allowed, though discouraged by the Pretty Good Window Police because they tend to leak more air than other types.
Materials + Structure. Perhaps most important here is the effect of volatile organic compounds (VOCs) on occupants’
health. Many conventional building materials contain VOCs, including vinyl flooring, plastic shower curtains and carpeting. People are becoming more sensitive to harsh chemicals in their environments, and low-VOC options abound, so it just makes sense to minimize these poisons where possible. Also in this category are minimizing material use, including through “advanced framing,” which keeps the important members and removes the redundant pieces; sourcing locally when possible and considering the lifecycle cost or global warming potential of products. As with food, less processed is often healthier, though there are exceptions.
Mechanicals. Heating, ventilation, air conditioning and plumbing. A Pretty Good House requires less energy to operate than a code-built (or worse) house. How much better? That depends how far you go with other measures, but the cost-benefit approach usually results in improving the building envelope to the point where you can reduce the heating system to one or two mini-split air source heat pumps, though other systems can also work efficiently. Mechanical ventilation is necessary, usually in the form of a Heat Recovery Ventilator (HRV) or Energy Recovery Ventilator (ERV). Both systems should be designed by somebody who knows what they’re doing, or else you will not have optimum efficiency or comfort. Also in this category are the various domestic hot water systems (currently favoring air source heat pump water heaters when appropriate), renewable energy generation (and due to drastic reductions in price in recent years, solar PV is finally a good investment), low-flow plumbing fixtures and insulated pipes.
Electrical. This primarily includes lighting and appliances. With a good design, natural daylighting can do a lot, but artificial lighting is still needed. Fortunately, LED fixtures are now on the market that are affordable, cast an attractive light color, have a long lifespan, and are extremely efficient in their energy use. Appliances should minimize energy use; choose Energy Star whenever possible, and look closely at low-energy, zero-emission electric induction cooktops. Any building envelope penetrations (such as exterior lights and outlets) need more attention than they typically get to control air and water infiltration.
Verification. Other programs usually require some form of third-party verification, but with a PGH it’s optional. It starts during construction; quality builders use a blower door to test for airtightness, so they can catch air leaks while they are still accessible. Though not required, having an independent energy auditor review your plans or inspect the project can be a good investment. Home energy monitoring is another way to verify performance; various forms of data collectors are available and affordable, to keep an eye on everything from electricity use to heat and moisture flow within the building envelope. As Peter Drucker famously said, “What gets measured gets improved.”
Owner/Occupant Behavior. Your car, lawnmower and even your coffeemaker come with an owner’s manual. Your home is the biggest, most complicated thing you own—shouldn’t it have its own owner’s manual to explain what things are and how to maintain them? Modern homes are inherently complicated, and most owners or occupants need education on how to best operate their home. The energy model (you did do an energy model, right?) won’t typically account for occupant behavior such as keeping a window open all winter, however. Another owner responsibility, should you choose to accept it, is to spread the word— building Pretty Good (or Better) just makes sense, so tell your friends and family that they should be building to at least this standard as well. If they are still in the dark ages, where code minimum is too hard to reach, well, eventually they will figure out that everyone else is building better houses than they are.
Where to go from here?
“How do I design and build a pretty good (or better) house or renovation?” Prettygoodhouse.com is a website in development that will answer that question, as a roadmap to guide homeowners and professionals through what can be a complicated process. The basic site should be up by the time this goes to print. In the meantime, spurred by a joke that all we really needed to explain Pretty Good House concepts was a coloring book, Helen Watts, a Maine licensed structural engineer, has created a couple of excellent graphic handbooks. Go to Etsy.com and search for Pretty Good House, volumes 1 or 2. Greenbuildingadvisor.com and buildingscience.com are both chock full of excellent information, though they can be overwhelming for novices. Or talk to a local professional—pretty much everyone who advertises in this magazine is conversant in the Pretty Good House approach, or can recommend someone who is. G&HM
Key components of a Pretty Good House in Maine
One of the things that people seem to like about the PGH concept is that there are no hard-and-fast rules. Another is that specifics vary with climate. To fully describe what should (or should not) be in a PGH we would need a lot more space than we have here. To keep things simple, here is a snapshot of the key elements for a Pretty Good House in Maine:
Low operating costs. Thanks to an efficient building envelope, including well-designed high-performance windows, efficient equipment and durable materials and assemblies, a PGH will provide extremely low operating costs. In Maine, a PGH should have R-5 windows, R-10 insulation under a basement slab, R-20 on foundation walls or under a slab-on-grade, R-40 walls and an R-60 have roofs, and building airtightness measured with a blower door at no more than 2.0 air changes per hour at 50 pascals pressure, and preferably no more than 1.0 ACH50. These low energy needs mean that a photovoltaic array sized for Net Zero annual energy can be affordable and easily pay for itself with resulting savings on energy expenses.
Healthy indoor air quality. Thanks to mold-resistant building assemblies, no fossil fuels burned on site, materials that don’t off-gas harmful compounds and continuous, properly sized mechanical ventilation (usually with filtered supply air), a PGH provides a steady supply of healthy indoor air.
Good design. This means they are no larger than necessary (a good goal is to aim for 1000, 1500, 1750 and 1875 sf for 1, 2, 3, and 4+ inhabitants, respectively); contain simple forms that are not complicated to build; have roofs that shed snow and rain; and are attractive— houses need to be loved to be maintained. Also, homes should include accessible design, aka Universal Design, to function for people of varying physical abilities.
Energy modeling. This enables informed decision-making and helps to ensure that equipment is correctly-sized.
Limit embodied energy. Choose natural materials and support the local economy when possible.
This article is reprinted from the spring 2017 issue of Green & Healthy Maine Homes. Subscribe today!