Key Ingredients in the Recipe for a Modern Green Home

Any pastry chef worth his salt will tell you the key ingredients found in a New-York style cheesecake. Sour cream, cream cheese, eggs, sugar, flour, and vanilla. Without these essentials, the creation just won’t be New York-style cheesecake. It’ll be something else.

The same is true for modern green homes. Ask any experienced green home architect or designer which ingredients go into the making. The answer is those I’m about to cover. Whether the target for your home is net-zero, passive house, LEED platinum, or zero energy, your green house will include these features. These are the same ones generally required by every well-respected green-building certifier.

It’s wise to become familiar with the ingredients of a modern green home. Without them, you won’t be sure of relishing comfort, health and all the other rewards these residences have to offer.

High-Performance Shell

The number one energy-efficiency feature to look for in every modern green home is commonly referred to as a “high-performance shell.” “Shell” itself refers to a building’s exterior enclosure. This is including the roof, floor and outside walls, windows and doors. What makes a shell high-performance compared to a conventionally built shell? To be considered high-performance, a shell should deliver a Home Energy Rating (HERS) of 35 or lower, even before adding a renewable energy feature. The insulation and air sealing required to achieve this rating will vary a bit with climate, but as a general rule the shell will have ..

• Passive house level air sealing;
• High levels of insulation (walls >R40, roof >R60, and foundation >R30);
• Triple glazed windows and doors;
• No thermal bridging (no breaks in the insulation layer);
• Passive solar orientation and window shading
• Enhanced moisture protection—shell components remain dry.

When designed and built properly, a high-performance shell provides long-term durability, energy-efficiency, minimal heat transfer, air infiltration, comfort and protection from moisture at minimal additional cost. The high-performance shell is fundamental to all modern green homes simply because it offers much-added value.

Balanced Ventilation

A “balanced ventilation” system—which ensures the air inside a home is fresh and healthy— is a key feature of a modern green residence. A system of this type removes unsafe fumes from cooking, VOCs, mold, and other sources, while silently reclaiming over 90% of heat energy. For you, that means healthy indoor air and low energy bills. Three characteristics to look for in these systems are:

• Fully ducted distribution;
• Sensible recovery efficiency (SRE) greater than 70%;
• Air-delivery-efficiency rating of >1 cfm/w.

Energy-Efficient Heating & Cooling Systems

Regardless of climate, a modern green home, with its high-performance shell, is simpler to heat and cool than a traditional home. In fact, comfortable indoor temperatures can be maintained with small, “point source” heating and cooling systems. Ideally, these systems use environmentally-friendly (i.e., non-petroleum based) energy sources. Point source systems commonly found in modern green homes include:

• Electric heat pumps—for house heating and cooling and for domestic hot-water heating;
• High-efficiency propane boilers—for house heating and for domestic hot-water heating;
• Wood-pellet boilers—for house heating and for domestic hot-water heating.

Energy-Efficient Lighting & Appliances

While lamps, toasters, computers, and other appliances account for just a small percentage of a home’s total energy demand, recent innovations in the design of these product types offer great opportunities for maximizing efficiency. For example, an older refrigerator will typically use three times as many kilowatts per year than a modern, Energy Star-rated refrigerator found in a modern green residence.

Similarly, modern LED and compact fluorescent lighting fixtures specified in green homes use up to 80% less electricity than conventional, incandescent light bulbs. These kinds of reductions in usage, across the board of a home’s appliances, can add up to significant savings.

On-site Renewable Energy

When all the energy needed annually to operate a home can be generated on-site, it’s said to be “net-zero.” A truly modern green home, equipped with renewable energy systems, will easily achieve net-zero usage. Also, since the annual energy needs for a green home are low right from the start, the size and cost of the needed systems are lower than in a conventionally built home. The most common approaches to producing on-site energy for a home are:

• Solar electric/photovoltaic panels;
• Biomass—cord wood and wood-pellet burning boilers and stoves;
• Solar water thermal collectors;
• Wind turbines.

Water-Conserving Plumbing

In a rainy, snowy climate like New England, it’s hard to imagine that the world’s supply of clean drinking water is limited. But the shortage is real and reducing water use in our homes is a way to do something about it. (To learn more about the global water crisis, read “Ready or Not: An Evaluation of State Climate and Water Preparedness Planning.”)

You can still have a hot shower and properly working sinks and toilets in a modern green home. The difference is you’ll manage them with water-conserving plumbing. What’s more, since treating, heating, pumping and removing wastewater from homes uses energy, using less water means energy savings.

Contemporary green homes generally achieve water conservation using these features:

• U.S. EPA WaterSense-labeled plumbing fixtures;
• Well insulated domestic hot water piping;
• Energy-efficient domestic hot water heating systems;
• Heat recovery from domestic wastewater using gravity-film heat exchangers.

Sustainable Materials

So far I’ve focused on the energy-efficiency features of a green home, but another key goal is to leave a light footprint on the environment over the home’s entire life cycle. This is where careful selection of building materials comes in—how particular materials affect both the environment and occupant health.

When architects think about how building materials impact the environment, they assess all stages of product life beginning with raw material extraction all the way through to recycling. These assessments are also known as “life cycle” or “cradle-to-grave” analysis or “eco-balance.” Based on the latest analyses, green home material choices, when available, will be:

• Organic (e.g., slate, wood) as opposed to man-made, petrochemical-based (e.g., acrylic, composite);
• Local (within a 100-mile radius of building site);
• High in recycled content;
• Environmental product declaration (EPD) verified;
• Labeled and certified by trusted sources.

To determine how construction materials will affect the residents of a home, the modern green home designer will consider something the EPA calls “source control.” Conventionally built homes can have indoor pollutants arising from paints, plywood, particleboard, glues, foam insulation, combustion from cement, and other sources. Modern green homes are designed to eliminate or reduce these by using:

• Balanced ventilation of combustible appliances (e.g., gas clothing dryer);
• Non-toxic materials (containing zero or low formaldehyde and VOCs);
• Non-toxic paints and stains (containing zero or low VOCs);
• Radon remediation systems.

Sustainable Landscaping

Have you driven by a new housing development and thought how sad it is that the land is completely razed in preparation for building—devoid of any trace of the trees and vegetation that grew there naturally? The sustainable landscape for a green home setting is planned to be both attractive and in balance with the local climate and environment. The green home landscape can help clean the air by reducing greenhouse gases, safeguard water by intercepting pollution in runoff, and restore habitats. Here are the practices/features employed in sustainable landscaping:

• Irrigation-free design—rainwater/greywater irrigation when required;
• Careful placement of large shade trees to provide summer cooling;
• Retention of appropriate existing and specification of new native plants;
• Low maintenance design;
• Permeable paving surfaces to reduce runoff;
• Inclusion of fruit trees/vegetable gardens;
• Water capture via rain gardens;
• Reduced mown lawn area.

Now you’re familiar with the ingredients found in every modern green home. But did you notice that there’s one essential ingredient missing? Just as it is with cheesecake, the real magic of the recipe comes from what happens next: the elements must be blended together by the creator with care, in specific ways, to achieve the desired, exceptional result.

In the building of a green home, this masterful mix of the technical components you’ve learned about here is the last key ingredient: design. Since it’s such a large and important one, it’ll be the sole subject of my next article. I hope I’ve left you hungry for more!

posted by Carol Miklos on 21.06.20

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