DayLighting; Sun Tubes, Solar, PV, CFL
Minimize infrastructure, minimize moving parts, and minimize operating costs.
Even a cloudy day can illuminate your entire home if you design it correctly to bypass the electronic hardware, and during the summer even indirect natural light through canopied windows can illuminate the home without adding undue heat.Daylighting (passive solar natural light):
- Design the home with south-facing windows in the northern hemisphere to get free solar lighting. Use clerestory windows (tall windows near the ceiling) or transom windows (short windows over doors or other windows).
- Minimize interior walls that block sunlight. Use half walls or 9/10 walls so free sunlight can spill across the ceiling to the other parts of the home (these methods also improve ventilation and passive HVAC air circulation, or you can supplement with an active central ceiling fan).
- Maximize ceiling and wall reflectivity. Use smooth ceilings (not “stucco”-textured or pebbled or flat paint). Use gloss bright white paint (gloss paint is smoother than flat paint; white reflects the most light, which is why snow-covered sunny days can feel warmer, and why in the extreme people go “snow blind” from intense glare) on ceilings and "light shelves" (below windows to reflect light onto the ceiling). Gloss white is a bit too bright on walls for most people but remember that furniture typically reduces the room's luminosity. If the furnished room will be too bright, subdue the walls just enough to be comfortable. For instance, use a flat near-white on the walls, with a hint of blue or red or anything if you want to add a bit of color and differentiate rooms. Lighter colors also make rooms seem larger. Remember that even a small divergence from pure white can reduce reflectivity significantly: “Bone” is about 3/4 as reflective and “Almond” is about 1/2 as reflective.
So far you’ve had no extra infrastructure cost, only walls, windows, and paint that you would have anyway.
- Use “sun tubes” (a.k.a. "light tubes" or "light pipes") to direct free sunlight where needed if the previous methods were not enough. Sun tubes are tubular skylights, basically reflective ducts to channel sunlight. The ducts are lighting infrastructure that cost money but they might save some conventional wiring.
So far you haven’t spent a penny to generate light, you’ve only designed and painted your home smartly to harness freely available light.
OK, eventually it gets dark:
- Use solar storage lights, such as solar garden lights, or solar shed lights, or solar security lights.
You still haven’t spent a penny to generate light but the photovoltaic (PV) and battery infrastructure to store light is a bit pricey.
- Use candles (prevent candle soot from darkening or roughening your ceilings).
The passive techniques help everyone, and the passive and/or the "active" candle lighting especially help off-grid people by allowing smaller generators, battery banks, inverters, bio-diesel processing, etc.
- If you insist on using an AC light bulb as a last resort, use a compact fluorescent lamp (CFL), which is 4x more efficient than an incandescent bulb (converting 20% of electric consumption to light instead of 5%), so a 15-watt CFL provides about the same lumens as a 60-watt incandescent light bulb. LED lights are even better than CFL lights to recuce power consumption and LED lights are best at directional task lighting.
Even a small light pointed up at a reflective ceiling can provide an impressive amount of light.