Aerogel is a low density solid state material derived from gel in which the liquid component of the gel has been replaced with gas. The result is an extremely low density solid with several remarkable properties, most notably its effectiveness as thermal insulation. Continue reading
How to avoid the five most common errors builders make when it comes to energy, health, and resource efficiency.
While green building technology continues to improve and new green products continue to evolve, they’re only “lipstick on a pig” if the home isn’t also energy efficient, built to last, healthy, safe, and affordable to maintain. Continue reading
A typical family spends about a third of its annual heating and cooling budget — roughly $350 — on air that leaks into or out of the house through unintended gaps and cracks. With the money you waste in just one year, you can plug many of those leaks yourself. It’s among the most cost-effective things you can do to conserve energy and increase comfort. Continue reading
Insulation is applied to ductwork to enhance thermal performance and prevent condensation and dripping. Duct thermal performance needs enhancement since air transported through a supply duct is at a temperature different than that of the surroundings. Insulation reduces the rate of thermal loss to those surroundings. Without insulation, the air would need extra heating or cooling in order to arrive at the design supply air temperature. Return air ducts only need to be insulated if they pass through environments that adversely affect the return air temperature. Exhaust air ducts normally do not need insulation. Supply air ducts may be left un-insulated if they run exposed through the space being conditioned; this arrangement also reduces system first cost.
Insulation prevents condensation and dripping from ducts. Un-insulated cold air ducts very often have surface temperatures below the local dew point. At this temperature, condensate will form and eventually drip off, causing an uncontrolled accumulation of moisture on the outside surface of the duct. Duct insulation eliminates the formation of condensate and consequently prevents rusting and staining.
Extra heating (or cooling) energy required to compensate for reduced thermal performance of un-insulated duct has a negative effect on the HVAC system’s life-cycle cost. Therefore, duct insulation always presents an optimization problem. Since insulated duct costs much more than un-insulated, the recommended air velocity becomes a key factor in optimization. For instance, a higher air velocity reduces duct surface area and thus insulation cost.
Because of the relatively small temperature differences between supply air ducts and the spaces through which they ductwork are routed, a one-inch-thick fiberglass blanket is almost always sufficient. Insulation should be wrapped around the duct’s exterior. A protective cover with a vapor barrier such as an aluminum foil, referred to as FKS, should be included in insulation specifications. Care must be exercised to protect exterior insulation integrity where insulation comes in contact with hangers, supports, and other structural members. Interior duct insulation (lining) should not be used in laboratory or cleanroom applications because the insulation tends to entrain microscopic particles into the airflow.
Special consideration must be given to ducts exposed to weather. Lagging materials or heavy metal covers over the insulation are commonly used to protect ductwork. A life-cycle cost analysis may be necessary to determine optimum insulation thickness when ducts encounter temperature extremes.
Use lighting controls to automatically turn lights on and off as needed, and save energy. Of course you can save energy by turning off lights when they’re not needed, but sometimes we forget or don’t notice that we’ve left them on.
The most common types of lighting controls include:
- Motion, occupancy, and photosensors
Before purchasing and using any lighting controls, it’s a good idea to understand basic lighting terms and principles. Also, it helps to explore your indoor and outdoor lighting design options if you haven’t already. This will help narrow your selection.
Dimmer controls provide variable indoor lighting. When you dim light bulbs, it reduces their wattage and output, which helps save energy.
Dimmers are inexpensive and provide some energy savings when lights are used at a reduced level. They also increase the service life of lightbulbs significantly. However, dimming reduces an incandescent bulb’s lumen output more than its wattage. This makes the bulbs less efficient as they are dimmed.
Dimmers and CFLs
Unlike incandescents, compact fluorescent lamps (CFLs) do not lose their efficiency with dimming. Some CFLs are compatible with standard dimmers, which will be indicated on the package. Others require special dimming ballasts and bulb holders. Fluorescent dimmers are dedicated fixtures and bulbs that provide even greater energy savings than a regular fluorescent bulb. Dimming a CFL that is not designed to work with a dimmer switch is not recommended, as this can shorten its life significantly.
You can change the lightbulbs and ballasts in fluorescent lighting fixtures rather than replace them.
Dimmers and LEDs
Some light-emitting diode (LED) lightbulbs can be used with dimmers. LED bulbs and fixtures must be designed for dimming, and you may need to replace existing dimmer switches with ones that are compatible with an LED lighting product. The packaging or accompanying instructions will indicate if the product is dimmable and which dimmer products are compatible. Fully compatible LED dimmers are expected to become more common as the LED industry expands.
Motion Sensor Controls
Motion sensors automatically turn outdoor lights on when they detect motion and turn them off a short while later. They are very useful for outdoor security and utility lighting.
Because utility lights and some security lights are needed only when it is dark and people are present, the best way to control might be a combination of a motion sensor and photosensor.
Incandescent flood lights with a photosensor and motion sensor may actually use less energy than pole-mounted high-intensity discharge (HID) security lights controlled by a photosensor. Even though HID lights are more efficient than incandescents, they are turned on for a much longer period of time than incandescents using these dual controls.
HID lightbulbs don’t work well with just a motion sensor, as they can take up to ten minutes to produce light.
Occupancy Sensor Controls
Occupancy sensors detect indoor activity within a certain area. They provide convenience by turning lights on automatically when someone enters a room, and save energy by turning lights off soon after the last occupant has left the room. Occupancy sensors must be located where they will detect occupants or occupant activity in all parts of the room.
There are two types of occupancy sensors: ultrasonic and infrared. Ultrasonic sensors detect sound, while infrared sensors detect heat and motion. In addition to controlling ambient lighting in a room, they are useful for task lighting applications such as over kitchen counters. In such applications, task lights are turned on by the motion of a person washing dishes, for instance, and automatically turn off a few minutes after the person leaves the area.
You can use photosensors to prevent outdoor lights from operating during daylight hours. This can help save energy because you don’t have to remember to turn off your outdoor lights.
Photosensors sense ambient light conditions, making them useful for all types of outdoor lighting. These light-sensitive controls are less effective inside the home because lighting needs vary with occupant activity rather than ambient lighting levels. Many LED nightlights, however, have this feature built in which makes them effective and easy to use.
Timers can be used to turn on and off outdoor and indoor lights at specific times. There are two types of timers: manual timers, which plug into an electrical outlet for controlling objects such as lamps or light strings; and in-wall programmable digital timers (which look like digital thermostats), which automate indoor or outdoor lighting.
Programmable timers are not often used alone for outdoor lighting because the timer may have to be reset often with the seasonal variation in the length of night. However, they can be used effectively in combinations with other controls. For example, the best combination for aesthetic lighting may be a photosensor that turns lights on in the evening and a timer that turns the lights off at a certain hour of the night (such as 11 p.m.).
For indoor lighting, timers are useful to give an unoccupied house a lived-in look. However, they are ineffective for an occupied home because they do not respond to changes in occupant behavior, like occupancy sensors.
Using Timers with CFL and LED Lighting
Timing controls work well with CFL and LED lightbulbs, as they do not interrupt the circuitry. This is especially true with manual timers that use pins for setting the on and off times.
- Manual timers: compatible with LED, CFL, and incandescent lighting
- Programmable digital timers: check the package label to be sure it is compatible with the type of lighting you want to use.
Insulation materials run the gamut from bulky fiber materials such as fiberglass, rock and slag wool, cellulose, and natural fibers to rigid foam boards. Bulky materials resist conductive heat flow in a building cavity. Rigid foam boards trap air or another gas to resist conductive heat flow. Other less common materials included cementitious and phenolic foams, vermiculite, and perlite. Continue reading
Ducts, Furnaces, & Air Handlers Belong Within Conditioned Space
Ducts, furnaces, and air handlers belong inside a house’s conditioned space. The best locations for ducts are insulated basements, sealed crawlspaces, or unvented conditioned attics. If placing ducts in these locations won’t work, they can also be installed in open-web floor trusses (in a two-story house with a centrally located mechanical room) or in some type of soffit, dropped ceiling, or chase. Continue reading