Mike Maines 9/17/19

Guidelines for designing and building a Pretty Good House

 1.      Economics

Key to the PGH approach is balancing expenditures and gains. Where other programs use specific energy-use targets or other criteria, and the building code establishes a baseline (“the worst house you can legally build”), a PGH goes above code until it stops making financial sense. On some new homes, that may be not far above code, and on other projects performance may rival that of a Passive House, but in most cases it will be somewhere in between those two standards.

How do you decide what makes financial sense? One approach is to look at the payback--the time it would take for an upgrade to pay for itself. A better way is to look at the return on investment, or ROI. Energy and maintenance costs are fairly steady and easy to predict, so you can choose what level of return you would like to see. Using a simple formula, ignoring the effects of compound interest and inflation, improvements with ROI of 5% or higher are generally a good investment. Even a 2% ROI may be competitive with secure investments such as CDs. Lower ROIs may not make financial sense but should be considered if there is an environmental benefit, such as lower embodied carbon emissions.

Another aspect of economics to consider is first costs vs. lifetime costs. Investing in higher quality materials that last longer than inexpensive materials is one way to achieve this.

Economics comes into play when discussing  new homes vs. renovations. In many cases an existing home can be purchased for less than a comparable new home, and the carbon footprint of the existing home already exists. But if the existing home has older, under-performing windows, a lack of insulation, poor air sealing and inefficient equipment, it may not be cost-effective to improve it enough to reduce operating costs to the level of what you can do with a new home.

2.      Team Approach to Building

You may be capable of doing everything required to design, build and maintain a new home or renovation, but you will probably get help with some or all of the tasks required. Choosing the right team members can make a big difference on project going smoothly.

The design team is involved in planning the project. They may include licensed architects and engineers, possibly licensed landscape architects or interior designers, professional building designers and consultants, design/build contractors, or you can do it yourself. While it’s not hard to create a basic design, there are a lot of pitfalls and things to know so it may make sense to involve design professionals to help plan your project. 

The financing team provides the capital for your project. A few lending institutions will provide green mortgages, which consider the added value and reduced operating costs of a high-quality, energy-efficient home. Or you may be able to self-finance your project, in which case ROI may be even more important than for projects with outside financing.

Builders, contractors, tradespeople and craftspeople build your project. Ultimately the project is in the hands of this key group. As with designers, building high-performance homes requires a different type of knowledge, so look for a builder experienced or at least interested and educated in high performance building.

The maintenance team keeps your project in good condition after it’s built. Using low-maintenance materials and equipment can minimize the need for this group, and there are a lot of tasks a homeowner can do on their own, but make sure you have support for the materials and equipment you select. 

Getting these professionals together during the design stage is a good way to make sure everyone is rowing in the same direction and to address any issues well before they happen.

3.      Climate - where are you building?

The International Code Council has divided the country into climate zones that help determine what qualities are important for homes in a given location, per their IECC Map. Each zone represents locations with progressively higher heating degree days, used to calculate how much heat a house will need to stay warm in winter. Sometimes confused with the USDA plant hardiness map, which shows the lowest average annual temperature and is not relevant for home design. At the borders of the climate zones and in micro-climates within climate zones there may be different conditions than at the center of the climate zone. The country is further divided into “dry,” “moist” and “marine” zones. A similar, useful map is from the US Department of Energy’s Building America program, which classifies regions into Hot-Humid, Mixed-Humid, Hot-Dry, Mixed-Dry, Cold, Very Cold, and Marine zones. The IECC map is what designers and code officials generally use.  

Zone 1 is hot and includes the southern tip of Florida, as well as Hawaii, Guam, Puerto Rico and the Virgin islands. (From what I’ve heard, Hawaii isn’t particularly hot, but it’s also never cold, so it fits this zone.)

Zone 2 is hot and includes most of Florida, the gulf coast and southern Arizona.

Zone 3 is mixed, with both heating and cooling needed to maintain comfort. It covers much of the south, from Georgia and the Carolinas west to northern Texas, Oklahoma and southern New Mexico, and much of California. 

Zone 4 is mixed, covering most of Virginia and Maryland west to southern Kansas and southern New Mexico, and also the Pacific coast of Washington, Oregon and far northern California.

Zone 5 is considered a cold climate, including southern New England and New York west to the Rocky Mountains, and the bulk of Washington, Oregon, Nevada, Utah, northern Arizona and northern New Mexico.

Zone 6 is solidly cold climate and is where the Pretty Good House team is based; most of us work in Zone 6 and a bit in Zone 5. We have a climate dominated by heating, but technically we also need some cooling in summer to keep temperatures within comfort ranges. Zone 6 includes most of northern New England, northern Michigan, most of Wisconsin and Minnesota, South Dakota, most of Wyoming and all of Montana. 

Zone 7 is very cold, including the northern tip of Maine, part of Michigan’s upper peninsula, the northernmost parts of Wisconsin, Minnesota and North Dakota, and parts of the Rocky Mountains. Zone 7 also includes most of Alaska.

Zone 8 is sub-arctic, i.e., wicked cold.

The climate zones are sub-divided into Moist, Dry and Marine categories. The dividing line between Moist (A) and Dry (B) runs roughly north-south, just east of the continental divide at the Rocky Mountains, with the east being Moist and the west being Dry. The Pacific Coast has its own designation as a Marine climate.

For our Canadian neighbors (or neighbours): according to building scientist Allison Bailes in his Energy Vanguard blog, your climate corresponds to the following US zones:

Vancouver: 4C

Toronto: 5A

Ottowa, Montreal and Quebec: 6A

Calgary: 7B

Changing climate. Like it or not, the world’s climate zones are shifting due to climate change, primarily due to human activity. The results are hard to predict accurately but most scientific models show that by 2050 climate zones will have shifted about 500 miles toward the poles. In Maine, we can expect to have a climate comparable to today’s Virginia climate. We all need to do what we can to mitigate climate change, but we should also plan ahead for future requirements—before long, we will need less heating and more cooling and dehumidification than we do now.

4.      Design

Design covers a wide range of topics. On the one hand, it’s simply the planning stage of a construction project. On the other hand, it’s where all of the critical decisions are made, including how the house will look and be experienced by its occupants and visitors. Some of the key elements to consider regarding design:

Location. Is the house in the city or the countryside? Packed in tightly with its neighbors or on enough land to be a farm? Are shops, jobs and services available nearby, or do they require travel? Are public transportation or bicycling options, or does any travel require a vehicle? These are some of the many issues regarding location.

Size. When we developed the Pretty Good House guidelines, we came up with the following targets for building size: 1000 sq. ft. for one occupant; 1500 sq. ft. for two occupants; 1750 sq. ft. for three occupants, and 1875 sq. ft. for four or more occupants. The national average is much higher, and many people find it easy to live in smaller spaces. The important thing is to deeply consider how much space you really need, consider flexible spaces and clever storage solutions to reduce the amount of space needed, and get rid of stuff you don’t need. House size relates directly to resource use and cost, so the smaller the better.

Orientation. The ideal house, from an energy point of view, in cold climates, will face south, with some windows (but not too many) on the east and west, and few or no windows or doors on the north. There will be a south-facing roof to support photovoltaic panel installation. But every site is different, and compromises need to be made. Fortunately, windows, doors and solar panels keep getting better. But it’s still best to keep the house oriented within 30 degrees of south, if possible.

Shape and complexity. The larger the surface area of exterior walls and roof is for a given floor area, the less efficient the building is to build and heat (or cool). The most efficient surface-to-area shape is a sphere, but that’s not practical to build. (Sorry, Buckminster Fuller.) The next most efficient shape is a cube, so boxy two-story homes are common for high-performance homes. Single-story homes, especially ones with a lot of corners, will generally cost more to build and will use more energy than a comparable two-story home. Complicated rooflines are also more expensive than simple roofs and more difficult to insulate well. Complicated rooflines are also more prone to leaking over time and may provide less area for roof-mounted PV arrays.

Beauty is in the eye of the beholder, but for a house to be loved by more than its owner it should follow societal rules for what makes an attractive house. You may choose to follow historical styles, contemporary styles or a blend of the two.

Comfort and performance. These two are closely linked; a big part of what makes a high-performance house high-performance is that it’s comfortable to live in. The building envelope should be air sealed and insulated well enough that an occupant does not feel too hot or too cold or feel drafts. A well sealed and insulated building envelope requires a smaller and more affordable affordable heating system.

Integration of trades. In conventional homes, the various tradespeople that come through during construction do what they need to do, usually without a lot of thought to how it will affect other trades. A better approach is to plan ahead so everyone knows what to expect and so there are no conflicts. A good general contractor (and the design professionals) should be familiar enough with all trades that they can direct traffic in the right direction. This is often a downside to owner-built homes; although it’s possible to build a very good house without a lot of experience, there is a lot to know and to anticipate, and it can be helpful to have a GC on board who has been around the block a few times, preferably with other high-performance homes.

5.      Envelope basics

Every house needs to keep rain and cold (or hot) air out, and conditioned air inside. In a Pretty Good House it’s easiest and best to identify dedicated control layers, following Dr. Joe Lstiburek’s list, in order of importance:

A rain control layer

An air control layer

A vapor control layer

A thermal control layer

Rain control layer. If you can’t keep the rain (or other precipitation) outside your building envelope, none of the other layers really matter. Make sure your house will shed water before worrying about other control layers. Many traditional practices are effective, but others have been updated. Notably, despite popular opinion, siding is almost never fully watertight, and many windows and doors will eventually leak. Good flashing details, a rain screen gap and a good WRB (water resistive barrier) will make sure rain stays outside.

Air control layer. You may have heard that a house needs to breathe. That’s not accurate; it needs to control vapor movement, but air leaks are a bad way to do that. It’s far better to create a nearly airtight structure, using one or more air control layers in the building envelope.

Vapor control. Water vapor—that is, H2O dissolved into air—is often the cause of moisture-related problems in buildings. There are various ways to address vapor control.

Thermal control. Mainly referring to insulation, it also involves windows, doors and other penetrations in the building envelop. Insulation is measured in R-value, which considers all three forms of heat movement: conduction, convection and radiation. Window and door insulating ability is measured using U-factor, which is simply the inverse of the R-value. (U-0.2 windows are equivalent to R-5 walls.)

6.      Envelope Details

Basic physics. Two rules to keep in mind: warm air rises, and heat goes to where there isn’t any. That’s contrary to the common “heat rises,” which is not accurate. But all things equal, warm (or moist) air is slightly more buoyant than cooler (or drier) air and will tend to rise. But the dramatic difference in temperature you may have experienced in older or poorly built homes is largely due to air leaks, allowing air to enter at the basement or first floor level and to exit at the roof, carrying warm (and moist) air with it. When you stop those air leaks, and have a thermally efficient envelope, you will experience much less difference in temperature at different stories of your house. On the other hand, heat goes to where there isn’t any, so poorly insulated areas will conduct heat to the cold outdoors. Even more than energy and carbon concerns, mold and fungus are the things we worry about the most. Warm air can hold more water (in vapor form) than cooler air, so when warm air is in contact with a relatively cool surface, the moisture condenses out of the air and accumulates as liquid (or adsorbed) water. The psychrometric chart shows us what will happen at different temperatures and humidity levels. Keeping the indoor relative humidity below 50% is safe, and above 20% provides occupant comfort.

Roof venting (or not). A vented roof is usually more forgiving than an unvented roof, and in many cases it’s easier (and cheaper) to build it that way. But in some cases, an unvented (or “hot”) roof is desirable, and there are ways to do it safely. They usually involve using closed-cell foam, in either sprayed or board form, so for carbon emission reasons we generally avoid hot roofs. The primary reason for venting a roof is to allow moisture to dissipate before it becomes a problem. There may also be a slight reduction in roof temperature, leading to potentially longer-lasting roofing, but the effect is minor.

Rain screens. Perhaps the single most important thing you can do for your walls is to include a rain screen, which is like venting for your walls. Even a tiny gap of 1/16” allows water to drain, extending the life of the wall and the cladding. Bigger gaps allow faster and more complete drying. Ideally, provide at least ½” gaps, open to the air at both the top and bottom of the wall.

Air barriers. You should be able to draw a cross-section of your house and trace a continuous line around the entire perimeter, representing the airtight layer. The airtight layer is not a single material, but a collection of materials with connection details that create a relatively airtight building, typically measured in air changes per hour at 50 pascals pressure, or how often the total volume of air in the house would be replaced with a roughly 20 mph wind blowing on the house. A good target is 1.0 ACH50, but 1.5 or 2.0 ACH50 is still Pretty Good. If you can get below 1.0 ACH50 you will save a few dollars per year and improve building durability. The Passive House standard is 0.6 ACH50, and the tightest homes in the country are 0.1 to 0.2 ACH50. Another measure of airtightness is measuring the air leakage per surface area. Do not confuse the airtight layer with the vapor control layer; in some cases they may be the same material, but they serve different purposes. The term “airtight” makes some people feel claustrophobic, but there is always enough air available that you won’t suffocate, especially with the high-efficiency mechanical ventilation used in tight homes. Windows and doors are always part of the airtight layer. Concrete in good condition is a good air barrier.  

Vapor retarders. Classified by how open they are to water vapor movement (borrowed from the Building Science Corp’s website):

Class 1 vapor retarder, 0.1 perm or less. (May also be called vapor barrier.) Also considered vapor impermeable.

Class 2 vapor retarder, more than 0.1 perms and up to 1.0 perms. Also considered vapor semi-impermeable.

Class 3 vapor retarder, more than 1.0 perms and up to 10 perms. Also considered vapor semi-permeable.

Vapor permeable (or vapor open) is a material greater than 10 perms. 

In old homes there is often no vapor retarder, homes less than 50 years old often have plastic or foil vapor retarders, and Pretty Good Houses have a variety of them, depending on the location. Under slabs (either basement floors or slab-on-grade foundations) by code you need at least a 6-mil vapor retarder, but for better durability and radon control use 10- to 15-mil polyethylene. Vented roofs are forgiving, so painted drywall, a Class 3 vapor retarder, may be enough but a Class 1 or Class 2 vapor retarder is generally considered better. When it comes to walls and unvented roofs, things get tricky. A new type of vapor retarder called variable permeance membranes (or smart, or intelligent membranes) are effective and forgiving for these locations.

Sorption and solar drive. Now we’re getting nerdy. Everyone knows the term absorb, which is when a material takes in water. Adsorption is when water vapor adheres to a material’s surface. Together they are called sorption. A more general term is moisture accumulation. In general practice in the building world we often call it condensation, though that technically is a different process. Solar drive, or solar vapor drive, occurs when a moisture-loaded material such as wet siding or cladding is exposed to direct sunlight, the sun has enough radiant energy to push the moisture through the material and into whatever is behind the cladding. Rain screen gaps are an effective barrier to solar vapor drive, especially when they are fully vented, but a WRB is also necessary.

Foundations. Every house needs a foundation, but there are many types to choose from. In New England, foundations with full basements are common, and are relatively inexpensive square footage. But they are also susceptible to moisture issues, the amount of concrete required has a huge carbon footprint, as does the insulation needed (but not always used) with a full foundation. Other options include crawl spaces, slab-on grade, and pier foundations. Each has pros and cons, but all can work with proper detailing.

7.      Windows and Doors

Even the best windows and doors on the market perform much worse than even an average wall, but they can also allow solar energy into the house, and of course light and views are important. Doors can provide an excellent way to go in as well as out of the house. Three numbers to look at when considering windows and glazed doors are:

U-factor (or U-value). As previously noted, the inverse of R-value. (In fact, U-factor is what we use in energy modeling; R-value was created as a marketing effort to help consumers understand heat flow.) A code-minimum window in climate zone 6 is U-0.32, equivalent to R-3.1. Pretty lousy, but better than the single-glazed windows in older homes. A Pretty Good window should be U-0.2 or lower, equivalent to R-5.0 or higher. The best windows on the market today are around U-0.09, or R-11. Generally speaking, triple glazed windows are necessary in a zone 6 PGH, but some double-glazed windows may work for some houses.

SHGC is the next most important number, the solar heat gain coefficient. This measures how much solar energy a glazing allows into a house. Insulating blinds help slightly but are vastly less effective than using better windows. Sometimes high-SHGC, or high-gain, windows are desirable, typically in south-facing walls. Other times low-SHGC, or low-gain, windows are better, especially on east- and west-facing windows. The range is from about 0.25 SHGC to 0.8 SHGC. The Energy Star program only recognized low-SHGC windows, but often higher SHGC is desirable.

VT is visible transmission. Sometimes noted as VLT, or visible light transmission, but that term is redundant. Below about VT 0.40, glazing will appear tinted.

There are a variety of coatings and glazing configurations available, but choosing glazing is a process of balancing perfect numbers with what is available in the style and price range you want. Different numbers are desirable in different climates.

Window Options. Operation type is the first big thing to think about. For highest performance, European (or European-style) windows with tilt/turn operation generally offer the highest performance. They have big, beefy frames that sometimes include internal insulation, and the operation is different from what most Americans are familiar with—turn the handle one way and they swing into the room, like a door; turn the handle the other way and the top tilts into the room a few inches, like a hopper. They have multiple gaskets and usually feel like a bank vault door. For American-style windows, there are the traditional double hungs, common since colonial times, and not greatly improved since then—they tend to leak air, especially over time, and while double-glazing is now common, only a few brands offer triple glazing. The window police won’t come after you if you use these on your Pretty Good House, but in general they are best avoided or left to auxiliary spaces like garages and sheds. (Horizontally sliding windows are essentially the same thing, turned on edge, and no better when it comes to efficiency.) Out-swinging windows, sometimes called crank-outs, can be a good alternative, in the form of casements (which hinge outward, like a door) or awnings (hinged at the top, opening out at the bottom) because they don’t impact interior space but seal better than sliding windows because they compress against gaskets when they close, instead of sliding up and down on a track. Only a few brands approach the performance of Euro-style tilt/turns. Since the glazing typically performs better than the frame, one large window performs better than multiple small windows. Consider using fixed windows where possible—not every window needs to open.

Exterior doors can match the windows, or they can be a different brand and type. Often the front entry and garage doors will be different from the windows, but patio, deck or balcony doors will match the windows. Good glazing performs better than even a good frame, so perhaps paradoxically, a fully glazed door is usually better than a solid door. Exterior doors of all types are prone to leaking and should be protected with a roof of some sort.

8.      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.

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.

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.

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.

9.      Mechanical Systems

Mechanical systems include the equipment needed to heat, cool and control humidity in a house, and also the plumbing system. The primary reason for mechanical systems is occupant comfort. The building envelope keeps out the worst of the weather, but humans are wimps and we like the indoor temperature and humidity to be within a certain range. For the most part, the building itself doesn’t care how warm or cold a house is. Most people prefer the indoor temperature to be 65°F to 75°F in winter, and 68°F to 80°F in summer, and for the relative humidity to be at least 20% and no more than 60%. High humidity levels exacerbate the risk of mold and fungal growth, so we try to limit indoor RH to 50% or less. People also experience radiant heat loss or gain, the opposite of the radiant heat you feel from the sun or a woodstove. Even when there is no draft, or air leakage, being near cold surfaces, particularly windows, will make a person feel colder than being in a room the same temperature but with surfaces the same temperature. This is one of the biggest arguments for triple-glazed windows; their energy savings may (or may not) be hard to justify, but they always provide greater comfort than windows with higher U-factors.

Performance-based. For the most part, the Pretty Good House concept seeks to simplify the complexity of high performance building by providing rules of thumb and guidelines. When it comes to heating and cooling systems, though, rules of thumb don’t work very well, so some form of energy modeling is necessary. Building codes usually require ASHRAE Manual J calculations for room-by-room heat loss, which can be accurate but often are fudged to make things easier for the supplier or contractor. Oversizing equipment is often not desirable, as heat pumps work most efficiently near their maximum capacity and their efficiency drops off dramatically if oversized. Dehumidification is an important part of air conditioning does not happen with oversized cooling equipment.

Energy Sources. Burning fossil fuels on site has a long history, but it comes with risks to health and safety, and a lot of embodied carbon as well as carbon emissions. With the drastic reduction in the cost of photovoltaic (PV) panels for on-site energy generation, the efficiency of electricity-generating plants, and the option to buy “green” power produced by wind turbines, dams and solar farms, most Pretty Good Houses aim for all-electric energy sources.

Choosing a Mechanical System. Pretty Good Houses in cold climates are usually a good fit for air source heat pumps (ASHPs) for heating and cooling. The most efficient type is the familiar units mounted high on a wall, but at some reduction in efficiency you can also choose from ceiling-mounted units, ones mounted low on the wall called floor units, or various ducted systems. In some situations ground source heat pumps (sometimes erroneously called geothermal systems) can make sense, but they usually require a lot of energy to pump water through long lengths of pipe or deep wells, and risk contaminating groundwater in the case of failure. Plus their initial expense is usually much higher than air-source heat pumps. ASHPs are available that will operate down to -20° or lower, so don’t believe contractors who say they don’t work in cold climates—find one familiar with this type of system. When there is a good (or Pretty Good) building envelope, it’s not necessary to have an ASHP head in every room—it’s more cost-effective to use small amounts of electric resistance heat in auxiliary rooms like bathrooms, mudrooms and sometimes even bedrooms. Woodstoves or fireplace inserts can provide supplemental heat, but they come with several concerns, including indoor air quality, keeping the building airtight and the particulate exhaust of the woodstove, which is a potent greenhouse gas.

Ventilation. In a Pretty Good House, mechanical ventilation is necessary to have good indoor air quality. The best approach is to use balanced ventilation with heat recovery. Heat Recovery Ventilators (HRVs) exhaust stale air from the house and they use a simple radiator-like system called a core to pre-heat or pre-cool the incoming fresh air. With an Energy Recovery Ventilator (ERV), moisture is also transferred. A couple of systems are available that can switch between the two types. Most systems are ducted from a central unit to the main spaces in the house, exhausting from areas that create moisture and odors, and supplying to living and sleeping areas. Others are point-source ventilators, meaning they ventilate single rooms. Which system is best depends on many factors, including climate, occupancy, and whether bathrooms are on the same system as the rest of the house. Some homes use exhaust-only ventilation, essentially leaving a bath fan running on low speed continuously. This usually saves money initially, but the energy saved using balanced ventilation eventually pays for itself, and because the incoming air is filtered instead of coming in through random gaps in the structure, the indoor air quality should be higher as well.

Plumbing. Use low-flow fixtures, especially in drought-prone areas, but with climate change areas that traditionally have plenty of water may see extended droughts, so learn to conserve this precious resource. When possible, design rooms that use water—kitchens, baths, laundry—so they are near each other. This saves a little on installation costs, but the greater impact is that it reduces the amount of water wasted before hot water reaches the tap. Insulating hot water lines saves energy, even when in conditioned space, and insulating cold water lines prevents condensation. Systems that recirculate hot water so it’s always available are usually not a good alternative because of energy consumption, though some are better than others. For creating hot water, the best systems for Pretty Good Houses are air-source heat pump water heaters. In creating hot water they cool and dry the air around them, so they need a lot of air flow, which doesn’t work in every house with the typical all-in-one units. Split systems use an indoor water tank and an outdoor heating unit, which cost more but have other benefits: they fit in confined spaces, their CO2 refrigerant is much more benign than typical refrigerants and they avoid the complaint some homeowners have that the units cool down the room they're in uncomfortably. On-demand or tankless electric water heaters use huge amounts of energy and are not a good choice in a PGH. Solar thermal systems, which use solar energy to heat domestic hot water, are usually less cost-effective than PV panels with a heat pump water heater, but may be worth considering in some situations. If you can’t use any of those systems, opt for an electric resistance water heat and wrap it in extra insulation.

10.   Electrical and Lighting

Lighting can be divided into two categories: natural and artificial. Daylighting, using windows and other glazing, reduces the need for artificial lighting during the day. At night, or in areas where daylighting can’t reach, LED lighting has revolutionized the field. Available in different fixture types and different lighting colors, from 2700 or 3000K, which can be very similar to incandescent lighting, to 5000 or 6000K, similar to sunlight or halogen lights. Good lighting design includes a mix of general or ambient lighting, focused or task lighting, and decorative or ambience lighting. Low-profile LED fixtures that replace “can” or recessed lights are particularly versatile and loved by designers, homeowners and electricians alike.

Equipment and Appliances. “Plug loads,” including appliances such as refrigerators and devices such as TVs and phone chargers, use a lot of energy, so at minimum choose Energy Star rated appliances when available and compare the amp-hours different equipment needs to do the same task. You may save money initially with low-cost bath fans, for example, but higher efficiency units use electrically commutated motors, which run much more efficiently than cheaper, mechanically commutated motors.

Phantom loads occur when appliances, equipment and devices continually draw a small amount of current to keep their capacitors charged so they turn on quickly, or to stay connected to the internet. When possible, place devices like these on a power strip that you turn off when not in use. 

Penetrations, specifically where electrically-powered equipment and devices require holes in the building envelope—such as exterior lighting, exterior outlets, and electrical service entrances—need a bit more care than they get in typical homes. There are various gaskets, sealants and flashing materials available for this purpose, but don’t leave it to your electrician to make their penetrations air- and water-tight; that’s the job of the general contractor.

Photovoltaic generation. The falling cost of photovoltaic (PV) systems now makes producing your own power a viable option in many places. Living off-grid is generally much less practical than being tied to the energy grid. Most states offer net metering, which pays people for providing power to the grid, usually via PV panels. When annual on-site energy production equals the energy used on site, the house is considered “net zero,” “net zero energy” or “zero net energy” (NZ, NZE or ZNE). For roof-mounted PV arrays, the roof surface should ideally face south at roughly the same angle above horizontal as your latitude (i.e., here at the 44th parallel, roof slopes of about 40-45° are ideal) but newer panels operate efficiently at angles far from ideal. Another option is a ground-mounted array, which may make maintenance easier and allows fine-tuning the position. In either case, the direct current (DC) generated by the panels goes to an inverter where it is converted to alternating current (AC) power, which is then fed to the grid. Or, for off-grid homes, the DC power is stored in batteries, which then goes through an inverter to create AC  power for home use.

11.   Verification

Prescription: It’s all well and good to say a building is high performance, but without some kind of verification, there is no proof. Most high performance designers, architects, builders and consultants will use some form of energy modeling software to evaluate the components of a system. Anything from Ekotrope or BEopt to Passive House Wufi Passive & PHPP. Each of these energy modeling software allows the team to evaluate the most cost effective measures to meet your energy metrics and goals. Having an energy model done does not mean that you have to participate in a program. However, there are many great programs available to help guide your project to your end goals. From LEED, Energy Star, DOE Zero Energy Home, Passive House (US or International), Living Building Challenge and more. Even if you don’t want a certification. The more familiar your team is with the principles of these programs, the better your whole project will be.

Commissioning: But once the house is built, it’s also critically important to perform tests on the various systems. From blower door testing for air infiltration, to mechanical testing to be sure you’re providing the right levels of fresh air to all of your spaces. Having your designer/architect/consultant present during construction to test, verify, and evaluate all of these components will help to ensure that your home performs the way you intend it. It’s also important to connect the homeowner with the systems so that they are aware of how to operate, clean and maintain the system. And that you work with a local installer who is available to service systems should you ever have an issue.

Verification: It’s also important to track your systems once they are installed to ensure they are working properly and giving you the output desired. Verification and tracking can be as simple as monitoring the output of your solar array to data loggers installed within your wall cavities to verify moisture levels at different times of the year. We often recommend simple verification measures like a humidity sensor to make sure your indoor environment remains healthy. You can start with a simple $10 unit or measure much more of your indoor air quality metrics with a unit that tracks CO2, airborne chemicals and VOC’s, humidity, temperature, particulate matter (dust), NO2, CO, ozone & air pressure.

What you verify and how you verify it depends on the specific targets you’re trying to achieve. And maybe, just a little bit, on how nerdy you are!

12.   Owner/Occupant Behavior - move in day and beyond

Energy modeling makes certain assumptions about how occupants will use a building. We generally use average behaviors: we assume the heating and cooling will be at certain setpoints; we assume that windows will remain closed in cold weather and that ventilation systems will be allowed to run as designed. Occupants can be creative in the ways they break the rules, though, so it’s important for them to be educated on how to operate their Pretty Good home. This website is one of many with that as a goal, but in reality, every home should come with an owners’ manual, a collection of documents that explains how to operate the complex machine we call a house. You can’t buy a toaster without an owner’s manual; houses should come with one too. Be proud to show off your Pretty Good, high-performance house—educating others on a first-hand basis is a great way to spread knowledge of this better way to build. Once you experience a high performance house, it’s hard to go back to standard housing, and growth is exponential—so spread the word.