Energy Upgrades for Existing Homes

Information on how to build an energy efficient home is easy to come by these days—but what if you can’t start from the ground up? What about the 18 million homes that already exist in California? Are those of us living in existing homes relegated to changing light bulbs and adjusting thermostats?

Not at all. Enter the Home Performance contractor. Home Performance is the discipline of applying building science and retrofit techniques to existing buildings, and the results can be dramatic; numerous case studies cite total measured energy used by the home reduced by as much as 70%!

Building science developed in the 1980s along with sophisticated equipment making possible the measurement and study of buildings. By applying these tools and scientific principles, we now know how to transform the energy performance of buildings.

The good news doesn’t stop there. It turns out that many of the same retrofit measures that reduce energy use also improve the quality of indoor air, humidity and moisture levels plus the overall longevity of the structure itself. The benefits are many and varied, from reduced indoor allergies to less frequent dusting to decreased home repair work.

But what goes into an energy upgrade? Since every home is unique, a good Home Performance contractor starts by running tests to understand exactly what is needed for the specific building. With this data, the contractor then recommends the upgrade measures for maximum improvement.

Because most homes are “leaky”—that is, air can pass more or less freely between indoors and out, the first priority is to stop the leaks. Typically, we spend energy (and money) to heat or cool our indoors, but, because of leaks, we end up heating or cooling the outdoors. Home heating and cooling is by far the biggest use of energy in homes, so stopping this energy wastage represents a key first step used by the Home Performance contractor.

Most of us think of windows when we think of building air leaks, but the science shows us that windows are usually not the main culprit. Because warm air rises (the stack effect), most air escapes at the top and bottom of buildings, through the attic and the crawlspace. Consequently, air sealing is one of the most important strategies. With this single measure, both energy use and indoor air quality can be improved.

One caveat, this work should be done by a professional trained in building science and home performance. Tightening a home can have unsafe side effects. For example, if gas appliances are present, there is a danger of trapping noxious, life-threating fumes inside the home. A professional will understand these risks, and will use test equipment to verify that they’ve been avoided.

Natural Cooling Strategies

Since most of us have limited tolerance for hot weather, and since air conditioning consumes a lot of electricity, it is important to first consider natural strategies when seeking ways to cool a building. Architects and builders have largely stopped using these techniques over the past 100 years, but because they utilize simple approaches to cooling, they save both energy and money.

Breezes help moisture evaporate from one’s skin—one of the body’s main methods for cooling off. In fact, many natural cooling techniques boil down to one basic principle: keep air moving. Funneling our afternoon breezes through our buildings (predominately from the Southwest in Santa Barbara) is ideal for cooling. It is possible to optimize the channeling of these breezes through our buildings by carefully choosing the type and location of windows and doors. Casement windows offer maximum ventilation area for a given glass area, while also providing ways to catch and direct airflow.

Openings through opposite exterior walls create maximum air currents, namely cross ventilation. Openings in adjacent walls produce air turbulence, which also enhances cooling. A combination of small low inlets and larger outlets achieves the best and fastest indoor air movement. A size ratio of 1:3 between inlets and outlets increases the speed of air movement by 2 ½ times (the Bernoulli principle).

The effectiveness of ventilation can be further enhanced by pre-cooling the air before it enters the home. Trees can both shade windows and cool the afternoon air currents. Deciduous trees are best, because they shed their leaves in winter to allow the sun and its warmth in. Almost any vegetation between a building and the approaching breezes will cool the air as the plants release water vapor through transpiration. Moisture evaporating from a pond, fountain or supplied by a mister also remove heat from air.

Trellises, building overhangs and awnings are simple yet effective strategies for keeping a building cool by limiting solar gain. Exterior shade screens prevent direct sunlight from striking a window. Awnings block light and heat whereas shade screens allow some light through. Shade screens are lightweight, durable, inexpensive and can block between 50 and 90 percent of the sun’s heat directed toward a window. Most often they are motorized for optimum sun control. Awnings are similarly most effective when motorized.

Another consideration is a building’s color. Dark-colored exteriors absorb 70-90 percent of the sun’s radiant energy, some of which is transferred into the exterior walls resulting in heat gain. In contrast, light-colored surfaces reflect most of the heat away.

Cooling Without Air Conditioning

As we increasingly experience summer weather during winter months, some locals are deciding to add air conditioning to their homes. Air conditioning draws significant electrical power, most of which is generated from fossil fuels, thus exacerbating the warming that this equipment is designed to counter, at least indoors. Even when powered by renewable energy, caution is advisable, since the production of any AC equipment uses a lot of resources.

If not air conditioning, what other options make sense? Adding exterior shading devices over windows that are bathed in the sun’s heat is one possibility. These can be trellises, with or without deciduous vines; canvas awnings that are fixed, manually adjustable or even motorized; fixed eyebrow extensions; vertical louvers or fins for east and west facing windows; or mesh solar shades that slide in vertical tracks on either side of the window which can cut out as much as 80% of the heat.

These exterior shading strategies are more effective at controlling solar gain than interior shading blinds or curtains. Well-designed sun control and shading devices can dramatically reduce building peak heat gain, while also improving visual comfort by controlling glare and reducing contrast ratios.

Another option is to change the glass in south facing windows to high-performance glazing that has a very low shading coefficient (SHGC-solar heat gain coefficient). Such glazing greatly reduces the need for exterior shading elements. To carry out this change, sometimes just the glass panels in old windows can be swapped out. At other times the entire window frame and sash need to be replaced to get optimal performance. This latter approach is expensive but does have advantages beyond just keeping unwanted heat out.

Top performing windows can also attenuate outside noise and keep the place warmer on cold winter days. Putting an operable window in a key location, where perhaps none existed before, can allow residents to open a house to cool early morning air on hot days, thereby implementing an effective natural cooling strategy.

Consider adding insulation to your existing walls and attic. In most cases this is less expensive than installing air conditioning equipment and helps not just to keep the house cool but also quiet and, when desired, warm as well. It definitely saves on heating and cooling bills. There are at least five materials and approaches to insulating existing houses: loose-fill cellulose, dense-packed cellulose, loose-fill fiberglass, dense-packed fiberglass and injection foam. Application skill is important for achieving a complete, high-performance thermal barrier, so getting the help of a professional is advisable.

A final, low-cost cooling option is to install Casablanca ceiling fans in the main rooms of a house. These don’t lower temperatures but they move air, thus making us feel cooler. If a room has a central ceiling light, a combined fan-light fixture can easily replace it.

Consider exploring these options before automatically turning to air conditioning.

Specifics for a Resilient House

Structural Considerations:

Meet or exceed current seismic codes for tie downs, lateral (sheer) bracing, masonry chimney supports, etc.

A building’s ability to flex and absorb vibration is as important as how strong it is when it comes to earthquake resistant design. Install expansion joints to allow a building to move without damage during seismic activity.

Fire Resistance:

Use non-combustible materials for the building shell: 3 coat plaster, cementitious siding, clad or metal frame windows, clay or concrete roofing tiles or standing seam metal roofing. Avoid exposed wood outside. If have exposed wood, coat with water-based intumescent paint.   Avoid attic venting [use foam insulation (Icynene) to meet code]. Consider metal gutters integrated with metal facia. Use gutter guards to keep gutters cleaned out. Since eaves are one of the most vulnerable areas, cover with non-combustible material like plaster or cementitious boards.

Make deck surfaces non-combustible with tile or masonry combined with plaster skirting and plaster or metal guardrails.

Make structure super tight to prevent/minimize smoke intrusion.

Top chimneys with ¼” mesh spark arrestors.

Install state-of-the-art flame and ember resistant foundation vents. Use similar vents for soffit, ridge and gable openings, if they exist, but try to avoid. Brands to consider are Vulcan, O’Hagin, FAMCO, Ember Out and Brandguard.

Establish defensible space around your home, by planting fire resistant landscaping, keeping trees limbed up and cleaning debris around the house. Absolutely no wood or other combustible material should be stored near the outside of your house.

Protect from Extreme Weather:

Reinforce structure to withstand severe wind loads (basically same steps as for seismic strategies)

Prepare for heavy precipitation and flooding. Use deep overhangs (suggest 24”) to keep much of the rain away from the house. Use gutters, downspouts, French drains, soil slopped away from structure and site swales, infiltration basins and catch basins to let water penetrate ground and protect the building from heavy storms. (Can use gutter system to capture and store rainwater for future irrigation).

Provide permeable surfaces at patios, walkways and driveways to absorb storm water.

Build drainage planes behind wall skins to allow trapped moisture/water to escape and drain out at base of walls.

Pay special attention to basements and crawlspaces where water may collect. Locate mechanical equipment and electric panels above grade. Attic spaces are ideal for such equipment (furnaces, boilers, AC equipment, and water heaters).

If located in a flood plain or the coastal zone, think about rising seas, storm surges and even possible tsunamis. Elevate the main living quarters and install breakaway walls at the lower level. This is standard practice in Hawaii.

For Survivability:

Employ passive solar design strategies. Create a tight shell with substantial insulation, thermal breaks, thermal mass, strategically placed windows, natural ventilation, stack ventilation, and moveable shading devices on the sunny sides of the house. Maximize daylighting. These steps can save operating costs and assure a reasonable level of comfort when heating/cooling equipment is out of commission.

Go All-Electric with Backup Storage:

Use Energy Star or better appliances or equipment. Use heat-pumps for heating, cooling, hot water and clothes drying. Install a magnetic induction stove for cooking. (Emergency back up for cooking could be a Coleman camp stove using propane cannisters). Generate your electric power with photo-voltaic panels and a backup storage system (maybe Sonnen-a German battery). Arrange your electric circuitry for survivability. Run your refrigerator, cooker, some minimal LED lights, your media/information center and at least one receptacle for charging phones off the battery backup system. A Yeti Tundra 65 cooler makes an effective emergency backup for frozen foods when power goes out.

Consider an electric vehicle or bicycle (electric or pedal) in case of an extended power outage where gasoline will not be available. Avoid a diesel generator for backup. Fuel may not be available plus it contributes to the climate crisis.

Develop an Emergency Water Supply:

Stored water, perhaps collected rainwater, can be purified/filtered with an MSR Guarding Purifier System.