Home remodeling and retrofitting both offer vast potential to improve comfort, functionality, sustainability, and efficiency.

According to the U.S. Department of Energy, the typical HERS score, a measure of energy usage, for existing resale homes is 130. The score for the average new home is 100, a 23 per cent improvement. Yet the U.S. issued about one million building permits in 2013, and the existing housing stock consists of approximately 130 million units, most of which are more than 10 years old. Obviously, older homes offer massive potential for energy conservation.

Some conservation measures can be done immediately, independent of other remodeling projects. Upgrading lighting and appliances are good examples. Air-sealing can usually be done any time as well. Whenever possible, it makes sense to look at the entire home as a group of systems and decide how to cut energy use.

Looking at the entire home as a project helps people to evaluate the project’s sustainability, as well. Decreasing a home’s energy use by 20 per cent while filling three dumpsters bound for the landfill has a large environmental impact. The “cradle-to-cradle” concept, developed by American architect William McDonough and German chemist Michael Braungart, proposed the idea of “ecologically intelligent design.” This concept aims to eliminate waste entirely, but in practice helps to define more ecologically sound choices, however imperfect.

Examples include choosing low-VOC or no-VOC paints and carpets, or choosing locally made flooring that can be repurposed years later in the next remodel. Vinyl flooring, in contrast, has no re-use value and will be waste.

Apart from the presence of toxic materials like asbestos, the most sustainable choice is usually to re-use as many of the existing materials as possible. Does the house need new siding, or would painting be adequate? Even though vinyl siding is not a green material, if it’s already on the house, the greenest choice is to leave it there rather than tear it off and send it to the landfill.

Those looking to remodel or retrofit a home should begin with an energy audit. A trained auditor will point out where the home is wasting energy, including air leaks and inefficient appliances. Some utilities will share this cost with the homeowner. Rating systems like LEED, Green Star, and Energy Star will require this type of professional evaluation.

After the energy audit, it is important to create a master plan for the remodel, making sure to start with the cheapest and easiest retrofits.

Replace incandescent light bulbs

Lighting accounts for about 12 per cent of energy used in the average American home. Replacing all the old bulbs with LED or CFL bulbs saves about $6 per bulb per year, just in energy costs.

Seal air leaks according to the energy audit.

Using caulk, canned spray foam, and weatherstripping, seal air leaks from ceiling light fixtures and access panels into the attic, around the foundation and mudsill, and around pipes penetrating the walls.

Seal ductwork in unconditioned spaces.

According to Energy Star, 20 per cent of the air in the typical home’s duct system leaks out through holes, leaks, and poorly connected ducts. This is a major problem if the ducts are located outside the conditioned area of the home. After sealing leaks, insulate the ductwork.

Add storm windows.

New windows take decades to return the investment in efficiency, but simple storm windows offer most of the same energy-efficiency benefits. New windows do have other advantages, such as improved functionality and sometimes appearance.

Add attic insulation.

Depending on the home’s attic, this could be simple or a great hassle. It’s not very expensive, though, and is one of the prime areas for energy savings. Energy Star specifies R-30 to R-60 for attics, depending on location, which requires 10-20 inches of total insulation.

Replace the water heater.

Water heating consumes about 14 per cent of the typical American home’s energy. Newer, more efficient models will save energy, especially high-efficiency tankless water heaters. Their high installation cost will delay their payback by years, though.

Replace heating and cooling equipment.

Heating and cooling claim more than 40 per cent of the energy used in the average American home. If the home has a 25-year-old furnace that’s rated as 68 per cent efficient, a homeowner can save $27 per $100 of existing heat cost by replacing it with a new 90 per cent efficient model, and after air sealing and insulating, smaller heating and cooling equipment may suffice.

Replace appliances.

Not that long ago, the typical refrigerator was an energy glutton. In fact, newer refrigerators use only 25 per cent as much energy as older models, which is crucial, as they’re always operating. Other appliances have less of an impact on overall energy use, as they don’t consume much energy when not in use.

Plant trees.

One particularly effective energy-efficiency improvement that’s often overlooked is the cooling effects of trees.

“Trees properly placed around buildings can reduce air conditioning needs by 30 percent and can save 20–50 percent in energy used for heating,” notes the USDA Forest Service.

Of course, trees will have little effect on the home’s microclimate when they’re small, but many varieties will grow more than one metre per year, and will provide useful shade within three years. Planting trees on the home’s west side will provide more effective shade than planting on the south side in the northern hemisphere or north side in the southern hemisphere.

Taken together, all these steps will offer another benefit: a home much friendlier to solar power. These energy efficiency steps will drastically cut the amount of electricity the home will use, making a smaller and cheaper PV array practical. Note that PV professionals size their arrays at 120 per cent of the estimated load so grid-connected systems will pay for themselves over time.