BUILD YOUR ENERGY INDEPENDENCE · PASSIVE SYSTEMS
No mechanical systems. No electricity. No fuel. A well-sealed, well-insulated home with the right shade and ventilation stays comfortable longer in any outage and cheaper to heat and cool every other day.
EVERY DAY
A well-insulated, well-sealed home costs 20–30% less to heat and cool. Every improvement here pays back on every utility bill for the life of the house.
DURING AN OUTAGE
A tight house holds temperature longer when the HVAC stops. It stays warmer in winter outages and cooler in summer ones — buying hours of safety for household members before conditions become dangerous.
FIRST PRIORITY
Most homes lose 25–40% of their conditioned air through gaps and cracks — not windows, not doors, but penetrations that no one has ever addressed. Sealing them is inexpensive and delivers immediate results.
The biggest leaks are typically in the attic — around light fixtures, plumbing and electrical penetrations, the attic hatch, and where interior walls meet the attic floor. These are invisible from the living space but measurable with a blower door test.
Secondary leak points: around window and door frames (the framing, not the glass), at the base of exterior walls where they meet the foundation, around fireplace dampers, and behind electrical outlets on exterior walls.
A professional blower door test costs $200–$400 and produces an infrared map showing exactly where air is moving. Worth doing before any major sealing project to prioritize the work.
Most attic air sealing uses two products: caulk for gaps under a half inch and low-expansion spray foam for larger gaps around pipes, wires, and framing members. A homeowner with a Saturday and $100 in materials can address the most significant leaks in a typical attic.
Around windows and doors: remove the interior trim, apply low-expansion foam in the gap between the frame and rough opening, and replace the trim. This is a half-day project per door or window and meaningfully improves both draft comfort and energy performance.
Weatherstripping on exterior doors compresses and loses effectiveness over 5–7 years. Replace it when you can feel air movement around the door frame with your hand on a windy day.
INSULATION
Insulation resists heat transfer. R-value measures resistance — higher is better. Where you add it and in what order determines your return on investment.
PRIORITY 1
The largest surface area and the greatest temperature differential in most homes. Heat rises directly into an under-insulated attic in winter; summer sun heats the attic to 140°F+ which radiates down into the living space.
DOE recommended levels: R-38 to R-60 depending on climate zone. Many older homes have R-11 or less.
PRIORITY 2
The rim joist — where the floor framing meets the foundation wall — is often completely uninsulated and exposed to outdoor temperatures in older homes. Cutting rigid foam to fit and sealing edges with caulk is a half-day project with disproportionate impact.
Target: R-15 minimum. Use rigid foam board cut to fit between joists and sealed with foam.
PRIORITY 3
Wall insulation is harder to add without opening walls — typically done during a renovation or residing project. Blown-in insulation through small holes in the exterior is a less disruptive option for existing walls.
Homes built before 1980 often have little or no wall insulation. Verify before adding it to a priority list.
SOLAR CONTROL AND MASS
Shade a window from outside and you block heat before it enters the glass. Shade it from inside with a curtain and you've already let the heat into the room — you're just keeping it from spreading further.
Exterior options: deciduous trees on the south and west sides (bare in winter for solar gain, leafed in summer for shade), fixed overhangs sized to the latitude, exterior roller shades, and awnings. All work without electricity.
A mature deciduous tree on the west side of a house reduces summer cooling load by 10–25%. It takes years to grow but costs little to plant and does the work for decades.
Dense materials — concrete, brick, stone, tile, and water — absorb heat slowly and release it slowly. A concrete floor in a sunlit room absorbs solar heat during the day and releases it at night, smoothing temperature swings without any mechanical system.
For existing homes, the most practical additions are tile or stone flooring in sun-exposed rooms, interior brick walls, and filled water containers (dark-colored 55-gallon drums in a sunspace, for example) that absorb solar energy during the day.
Thermal mass works best when it's directly in the sun's path. Mass shaded from the sun year-round is just a cold thermal sink — it absorbs heat from the room rather than from the sun, which is counterproductive.
NATURAL VENTILATION
Natural ventilation uses wind pressure and thermal buoyancy — warm air rising — to move air through a building without fans. Done correctly, it keeps a house comfortable on mild summer days and cools it rapidly on summer nights.
Open windows on opposite sides of the room or house. Wind pressure is higher on the windward side and lower on the leeward side, pulling air through the space. The larger the opening on the windward side relative to the leeward, the faster the airflow.
For stack effect ventilation — useful when there's no wind — open low windows on the cool side of the house and high windows or vents on the warm side. Rising warm air pulls cool air in at the bottom.
During a summer outage: close everything during the day, open for cross-ventilation after dark when outdoor temperatures drop below indoor. A box fan in one window accelerates the process.
A whole-house fan installs in the ceiling between the living space and the attic and pulls large volumes of air through the house when operated with windows open. It cools a house far more rapidly than an air conditioner and uses a fraction of the electricity — 200–700W vs. 3,000–5,000W for central AC.
During an outage, a whole-house fan running on a battery station can cool a house in 15–20 minutes on a mild summer evening. It is one of the highest-value low-power applications for a battery station in a warm climate.
Use only when outdoor air is cooler than indoor air — typically after 9 p.m. in summer. Don't run with the air conditioning on; they work against each other.
Affiliate disclosure: New World Survival earns a small commission on purchases made through links on this page, at no cost to you. We only recommend gear we'd put in our own kit.
RELATED GUIDES
Safe heat sources when passive systems aren't enough in a winter outage.
What to do during a summer outage when passive systems need backup.
Add a wood stove to complement a well-sealed, well-insulated envelope.