|Home | Insulation | Conserving Energy
Heating | Books | Links
New Articles and Guides:
Bleed a Hot-Water Radiator
Bleeding the radiators will lower the pressure in your system, so you might have to slowly add water to increase the pressure. Do this by opening, then closing, the valve on the water pipe above the boiler. In fact, you may need to add water while bleeding the radiator in order to purge the air from the system. This is where a helper will save on trips up and down the stairs. If you’re unfamiliar with your system, call a pro. How much pressure you need depends on how high the water has to rise. The basic rule is 1 lb. of pressure for every 2 ft. of rise. Your gauge may read in pounds, feet or both. A basic two-story house, with the boiler and expansion tank in the basement, needs 12 to 15 lbs., or 25 to 30 ft., of pressure.
Clear a Steam-Radiator Vent
Flip a Switch and Save $200 or more!
Here are eight (8) quick furnace fixes anyone can do…
Look for simple solutions first…
A furnace can be intimidating—especially when it’s not working. However, there is good news from furnace repair pros. Roughly a quarter of all service calls could be avoided with easy fixes that cost little or nothing. Here, you’ll learn about the common culprits and what to do about them.
1. Check the thermostat to make sure it’s on:
Before you assume you have a furnace problem, check the thermostat to make sure it’s actually telling the furnace to turn on. Thermostats, especially programmable ones, can be complicated, and the more options a thermostat has, the more that can go wrong.
• Make sure the switch is on "Heat" rather than on “Cool.”
• Check the temperature setting.
• Compare the temperature setting to the room temperature. Set the temperature five degrees higher than the room temperature and see if the furnace kicks on.
• Make sure the program is displaying the right day and time, as well as A.M. and P.M. settings.
• Trace the thermostat wires back to the furnace to check for breaks, especially if you’ve done any remodeling recently. If you find a break in one of the thin wires, splice the line back together and wrap it with electrical tape.
• Replace the battery. If you have a power outage with a dead battery, you’ll lose your settings and the thermostat will revert to the default program.
• Open the thermostat and gently blow out any dust or debris. Make sure it’s level and firmly attached on the wall, and that none of the wires coming into it are loose.
• If you can’t make the program settings work, you can bypass them altogether. Simply punch in the temperature you want with the up/down control and then press the “Hold” button. That will switch on the furnace if the thermostat programming is the problem.
TIP: Lost your owner’s manual? Most major-brand manuals are listed on the Web—just go to the manufacturer’s Web site.
2. Check shutoff switches and breakers:
It sounds unbelievable, but furnace technicians often find that the only “repair” a furnace needs is to be turned on. Look for a standard wall switch on or near the furnace—all furnaces, no matter what age or type, have one somewhere. Check the circuit breaker or fuse for the furnace as well. Make sure the front panel covering the blower motor is securely fastened—there’s a push-in switch under it that must be fully depressed for the furnace to operate.
3. Change filters:
The owner’s manual shows where the filter is and how to remove it. Change inexpensive flat filters at least once a month. Make sure that the arrow points toward the furnace. Inspect pleated filters once a month. Hold them up to the light, and if you can’t see the light clearly through them, replace them. Manufacturers say pleated filters are good for three months, but change them more frequently if you have pets, kids or generate lots of dust.
4. Make sure the gas is on:
Just as with switches, someone may have turned off a gas valve and then forgotten to turn it back on. Trace the gas line back from the furnace to the meter, and if you see a handle that’s perpendicular to the gas pipe, turn it so it’s parallel.
If you have an old furnace or boiler, you may have a pilot light. Remove the front panel and the burner cover and check to make sure it’s lit.
5. Make sure the chimney exhaust flue is clear:
Drawn by the warmth, birds sometimes fall into the chimney exhaust flue. Turn the furnace off and the thermostat all the way down, then dismantle the duct where it exits the furnace and check for debris. Be sure to reassemble the sections in the same order and direction that you took them out.
6. Flush out drain lines:
High-efficiency furnaces can drain off several gallons of water a day in heating season. If the drain lines become restricted by sediment or mold growth, the furnace will shut down. If the drain hose looks dirty, remove the hose, fill it with a mixture of bleach and water (25 percent bleach), then flush it after several minutes.
7. Look for blocked or leaky ducts that can restrict airflow:
If your furnace comes on but one or two rooms are cold, first make sure all the room registers are open. Then examine any ductwork you can get access to and look for gaps between sections or branching points. Seal any gaps between sections of duct with special metal duct tape. Don’t use standard cloth duct tape—it quickly deteriorates, and it may also cause ducts to leak if it was used to seal sections in the past.
Also check for handles protruding from the ductwork. These are dampers or air-conditioner bypasses—make sure they’re open.
8. Clean away Leaves and debris from heat pumps or intake and exhaust vents:
If you have a furnace that vents out the side of the house, make sure nothing is blocking the intake or exhaust. If either of the pipes is covered with screen mesh (like window screen), replace it with 1/2-in-mesh hardware cloth. If ice is clogging one of the pipes, you have a bigger problem somewhere in the system. Clear it off and call a technician to find out why it’s happening.
If you have a heat pump, clear away grass and leaves from the fins of the outdoor compressor unit. Before heating season starts, hose it down gently from the top to rinse dirt and debris out of the housing.
• Reduce hot water usage by replacing high-volume shower- heads with low-flow heads (2 to 3 gallons per minute). Save up to $40 per year.
• Have a furnace tune-up to clean and adjust burners and improve fuel-burning efficiency.
• Fix leaky faucets; dripping hot water can cost $35 per year.
• Buy gas stoves with electronic ignition rather than pilot lights.
• Replace recessed light fixtures with air tight models when you remodel.
• Install a reflector (shiny aluminum foil over cardboard will do) behind radiators to reduce heat driven into and through the wall. Save 5 percent.
• Have your air conditioner serviced to clean hard-to-reach evaporator coils and adjust coolant pres sure to achieve maxi mum efficiency.
Finally—a light that turns itself off
Are your kids are always switching on the lights in the laundry room, storage room and pantry and never turning them off? Sometimes the lights burn all night, even for days, before you discover the light streaming under the closed doors. Here’s a solution: buy a wireless motion-sensing light adapter ($20 at home centers) and aim the sensing unit straight down the wall inside the top of the door. The light automatically turns on when it senses that someone is after a can of tuna or wants that special T-shirt out of the wash, and then turns off.
Furnace filter reminder
Whenever you buy a new box of furnace filters, write the months of the year on the individual filters (and change them monthly). That way, you’ll always know when you last changed the filter.
1 Lower the indoor temperature a few
degrees in winter (you’ll save about 2 percent per degree). Set it even lower at night and a full 10 degrees lower when you’re on vacation.
2 Close the fireplace damper when the fireplace isn’t in use. If it’s never used, seal the flue with a plastic bag stuffed with insulation.
3 Open shades and blinds to let in sun J light during the day and close them to reduce heat loss at night. For cooling, close them during the day.
4 Close off unused rooms and lower the temperatures by adjusting the registers and dampers. You’ll save up to $50 per year.
5 Clean your furnace’s blower fan with a soft brush and vacuum cleaner.
6 Ventilate and cool your home with window or whole-house fans during the cooler hours of the day.
7 Fill clothes washers and dishwashers for more efficient energy use, rather than cleaning partial loads.
8 Skip the dishwasher’s drying cycle (and cut the energy use by about half!).
9 Wash clothes in cool rather than hot water.
21 Money- and energy-saving ideas that don’t cost a dime:
10 Clean clothes washer and dryer lint screens after every use.
11 Turn off lights not in use. Reduce bulb wattage and use dimmers.
12 Clean refrigerator coils with a soft brush annually, or more often if you have pets that shed.
13 Run major appliances late in the evening or early in the morning when electric loads are less (off peak).
14 Flush your garbage disposer with cold water rather than hot. Grease solidifies in cold water and will wash away.
15 Cook more efficiently using microwaves, Crock-Pots and pres sure cookers.
16 Turn off room air conditioners when you leave for an hour or more. You can quickly cool the room later.
17 Recycle. Reuse. Take your bike instead of your car.
18 In warm weather, set the thermostat higher (75 to 78 degrees F) and rely more on ceiling and table fans for cooling, even when the air conditioner is running.
19 Reduce humidity in bathrooms and kitchens with exhaust fans. When dehumidifying a basement, keep basement doors and windows closed.
20 Consider higher-efficiency appliances when purchasing new refrigerators, freezers and dishwashers. The energy savings usually pays back the extra costs within a few years. The same goes for furnaces and water heaters.
21 Lower your water heater setting to 120 degrees F for both energy savings and safety. (Measure hot water temperature at a faucet with a cooking thermometer if the water heater setting isn’t calibrated in degrees.)
Energy Saving Q&A
Heat-reducing window film
Q. My son’s west-facing bedroom gets very hot in the spring and summer. Will a window film help, and if so, can I install it myself?
A. A heat-control window film will help keep your son’s room cooler, and yes, you can install it yourself. These films reflect the sun’s heat and ultraviolet rays, and reduce glare without obscuring the view. Applying the film takes about 30 minutes per window. The film should last about 10 years. Prices vary with film size. A 3 x 15-ft. film (which can cover two to three windows) costs $30. The film is sold at home centers and hardware stores. Gila is one company that makes heat-control film (www.gilafilms.com).
Different types of film are available, so get the one designed for heat control. The film can be applied to any window, including double-pane low-e windows, although they already reduce radiant heat loss and gain.
One drawback is that the film may void the manufacturer’s warranty for the seal on double-pane windows. If the window warranty has already expired or reducing excessive heat is more important to you than a warranty, apply the film. Otherwise, consider options such as installing shades, awnings or shutters, or even planting a tree on the west side to block the sun.
Straight scoop on triple glazing
Q. I’d like to replace the drafty single-pane windows in my house. Is upgrading to triple-pane windows a good idea in cold climates where it’s often below zero in the winter?
A. In cold regions, triple-glazed windows can save 2 to 3 percent of your heating bill, compared with double-glazed windows. From a cost standpoint, it’ll take a few decades to recoup the 10 to 15 percent upcharge to go from low-e double-glazed windows to triple-glazed. For example, if you pay $1,000 per year in energy bills, have 20 windows in your house, and 22 percent of your energy is lost through your windows (which is average), then each window is losing $11 worth of energy per year. A triple-glazed window will reduce that loss by about $1, so it’ll take 35 years to cover a $35 upcharge for triple-glazing. Of course, if your energy bills and energy loss are greater, you’ll recoup the cost sooner. However, the investment may be worth the cost in terms of comfort. Triple glazing will reduce condensation, which will allow you to maintain a higher indoor relative humidity in cold weather. These windows also reduce cold drafts. If you don’t want to pay for triple-pane windows through out the house, get them for the north- and east-facing rooms, where you’ll get the biggest payoff.
Most of the major window manufacturers in the United States don’t offer triple glazing. But here are two that do: Marvin (marvin.com) and Weather Shield (weathershield.com). Many Canadian window manufacturers offer triple glazing. Alpen double-pane windows were recently featured on the diy network program Deconstruction: Windows. We were impressed.
Duct booster for cold rooms
Q. Our son’s bedroom, located at the end of a long hallway, stays about 10 degrees cooler than the rest of the house. How can we direct more heat to just that room? We have forced-air heat.
A. First check to make sure all the dampers con trolling heat to that area are open; there can be as many as three. The damper in the floor- or wall-mounted register can be seen using a flashlight and can be adjusted by moving a lever or wheel on the register. Often there’s another damper in the branch duct leading to the register. This is controlled by a wing nut on the side or bottom of the duct; when the wing nut is aligned parallel to the duct, the damper’s open. In some cases there can even be a damper in the main trunk line, usually controlled by an L-shaped lever on the side of the vent.
If all the vents are wide open, consider installing an in-duct air boosting fan. This $25 part won’t create more heat, but will pull more air to the trouble spot.
If you install the air-boosting fan, bear in mind:
• Install it as near as possible to the cold room.
• You can wire it to a manually controlled switch or to the furnace’s blower fan, so the booster fan turns on every time the furnace blower fan kicks in. Follow the manufacturer’s instructions and all applicable codes.
• Installing it can be a pain. It’s usually easiest to remove a few duct support brackets, drop down and remove one or two sections of round duct, install the booster fan, then reinstall the whole works.
• These fans can also be used to improve the circulation of a gravity-type warm-air furnace
Green Building Basics:
Building Green and Indoor Air Quality:
Getting to Zero Energy
So what does all this mean when Monday morning rolls around and everything at the office is the same as it was last week?
There is no such thing as the perfect green home. Every house is unique. Each is built in a specific climate where there are varying amounts of sunshine; winds blow from a different direction by season and each site affords different views. Local building products are available or not, there will be small children in the home, or not. and so forth. There is no single green building solution that meets all possible conditions.
The best way to start is to take on some aspect of green building and get really good at it. Don’t try to do everything at once. Take on energy conservation and increased R-values in walls and roofs. Get a blower door test done on one of your homes. Try changing the paints and finishes you have always used. Test materials in your garage or on your own home. See what works best for you and your trade con tractors. Identify the resistance points in your company or with your trades. Education is the top priority any time you are making changes in your business. Let them know why you are making the changes.
At the same time, there are certain inevitabilities that will affect all of us. Climate change will bring about increasingly weird weather. Floods and droughts will be more frequent, occur in strange places, and last longer. Hurricanes will become more intense as the oceans warm. More frequent and unusual tornados will strike unexpected places. The weather is unpredictable even when it is normal. Build to withstand the harshest weather conditions you can imagine for your region.
We will reach “peak oil” during the life span of homes built today. What that means is that all forms of energy will become increasingly expensive and with little forewarning by the powers that be. Natural gas is in greater demand just as it is starting to decline from existing wells in the U.S. How much will heating and cooling our homes cost in 5, 10, or 20 years? All we know is a lot more than it does today.
Fresh water will be one of the things that is most radically affected by climate change. When and where it rains will shift all over the globe. Snow pack in mountain areas that pro vide the water for agriculture in the summer may be hardest hit. Less snow pack means less irrigation water, which affects food prices. Since globalization is so entrenched, particularly when it comes to food, when climates are impacted in Chile food prices go up in the U.S. Grains are particularly vulnerable to fluctuating water availability. China’s grain is irrigated with fossil water that is predicted to go away in as little as two years. Their demand for wheat will affect U.S. wheat prices. The price of corn is already rising as it is diverted away from food to produce ethanol.
We are not growing old trees anymore. The ones that are still standing are the ones that anchor the forest ecologies of the world. At the current rate of deforestation and clear-cuffing, our forests are destined for agriculture, even if that means replanting with mono-cultures of Douglas fir or eucalyptus. Our voracious appetite for wood, paper, and other forest products makes for a dire future for the planet’s forests (the lungs of the planet—our primary defense against climate change) and all the wildlife that lives within their protective canopies. If we don’t reverse this trend soon, many of the plants and animals we take for granted will be seen only in zoos and arboretums.
Time for Change Is Now
This story can go on and on. We are at a critical juncture in the history of humans on earth. With 40% of the world’s resources going into buildings, 66% of the electricity generated used for heating, cooling, and lighting buildings, the demand for new coal-burning power plants grows ever stronger. China is planning to build one coal-burning power plant a week for the next 20 years. There are 154 new coal-fired plants on the drawing boards in the U.S. in 42 states. There are currently about 600 coal plants in the U.S. that, according to the Union of Concerned Scientists, burn 1.4 million tons of coal every year.
It’s time to start planning, designing, and building homes that reduce the need for new coal-fired plants and help us prepare for the inevitability of more expensive power. Building homes that produce as much energy as they consume and allow their owners to collect and store rainwater are things that we can do now.
Build for the Future
Let’s take it step by step with a summary of what builders can do to create the home of the future.
Siting: Face the long axis of the house south. Size the windows for optimal passive solar gain. Size the thermal mass on the floor or illuminated walls relative to the glazed areas for a higher solar contribution. Provide enough south-facing roof area to accommodate current or future solar collectors. Plan early for landscaping that will help with shading the east and west windows in summer to reduce cooling loads.
Foundation: Always consider any foundation material as part of the building system. From slabs to crawl spaces to basements, insulate them as well as possible on the exterior before backfilling. Grade foundation drainage away from the house and backfill with gravel that will allow water to flow to the foundation drainage system to prevent hydrostatic pressure on the foundation wall.
Framing: Always use advanced framing techniques with FSC-certified lumber. In cold climates, frame walls for R-24 or higher insulation. Insulation should reduce or eliminate the cavity effect by preventing air movement between the studs (structural insulated panels are one model of no-cavity effect). Place 1 in. of closed-cell rigid foam on the exterior of the sheathing to keep the dew point of the wall outside of the cavity. Install a drainage plane, and flash all penetrations and intersections perfectly to protect the building from moisture for its entire life span.
Rooting: Use the longest-lasting material you can afford that is designed for your climate. Make sure the entire roof assembly creates an air barrier from the living space below, which means no open areas around plumbing, duct work, or chimneys. Insulate 50% higher than code requires.
Windows: Install low-e windows at a minimum. Wherever possible, install super glass in fixed-glass locations. Design for solar gain and reduce exposure to western summer sun. Casement windows usually have better air sealing and can be opened to catch breezes. Use windows with a solar heat gain factor of 0.33 or lower for east and west windows, especially in hot climates.
Plumbing: Optimize the design of the plumbing using a trunk and branch system. Reduce the size of supply lines to /8 in. to maximize flow and reduce heat loss. Install a sealed combustion water heater with an EF of 0.62 or higher. Insulate all hot water lines throughout the house. Install an on-demand hot water pump. Reduce flow rates at all fixtures and faucets below code. Conserve as much as possible. Use dual-flush toilets. Pre-plumb for gray water segregation.
HVAC: Install only high-efficiency sealed-combustion furnaces and boilers with efficiencies above 90% and air conditioners with 14 SEER or higher. Better yet, use evaporative cooling in dry climates. Make sure the mechanical equipment is sized properly to meet the dramatically reduced energy load of the house and no more. Provide for fresh air with mechanical ventilation. Keep equipment and all ductwork inside the insulated envelope. Reduce air pressure differentials throughout the house. Seal all ducts with mastic. Have the ducts tested. Consider geothermal heat pumps. In humid climates, a well-sealed and insulated house may require central dehumidification when temperatures are moderate but humidity is high.
Electrical: Design daylighting to provide light to all rooms in daytime use. Design electric lighting carefully for the tasks and uses of each room. Use dimmers and occupancy sensors to minimize lighting requirements. Reduce electrical loads everywhere. Install compact fluorescent bulbs or LED fixtures wherever possible. Provide circuit switches to cut power to “always on” phantom loads. Install the most efficient appliances possible. (Energy Star isn’t always the minimum-load appliance.)
Insulation and Air Sealing: More is always better. Insulate today to 50% above local code or DOE recommendations for your area. Make the thermal envelope continuous by eliminating thermal breaks or cold spots. Inspect for perfection of installation. Eliminate any air movement inside the wall cavities and through the building envelope. Create an uninterrupted building envelope with the insulation in contact with the air barrier. Keep the dew point outside the envelope by using exterior rigid foam. Use spray foam insulation between garage and all adjacent lining spaces. Use spray foam or spray insulation on all band joists, preferably where any two materials meet. Conduct a blower door test. A well-sealed house, with proper ventilation, will maintain more comfortable humidity levels year round, reducing or eliminating the need for humidifiers in cold months and reducing the need for air-conditioning in warm months.
Siding and Decking: Use siding that is as long lasting as the intended life of the building. Cementious siding or real stucco is fire resistant as well as durable. Don’t use wood siding or decking unless it is FSC certified. Install re cycled-content composite decking.
Solar: Integrate solar hot water systems with radiant heating systems. Provide ample space for hot water storage to meet the heating load requirements. Install enough PV to meet at least 50% of the electrical load of the house. Install a battery back-up system if you want protection for variable grid availability. Use feedback metering to tell you how much electricity you are using at any given moment. Look for net metering in your area that allows you to sell your “extra” electricity back to the local utility through the grid.
Indoor Air Quality: Eliminate as many synthetic materials from inside the envelope as possible. Be aware of the constituent chemicals in all surfaces and finishes. Use zero-VOC paints and finishes. Seal formaldehyde-based products before installation. Eliminate solvent-based products from all adhesives and finishes. Provide adequate ventilation to every room. With forced-air systems, install MERV filters rated 6-12. Make sure that houses using forced-air systems have effective air sealing. Install a heat recovery ventilation unit.
Landscaping: Install landscaping that is native to your location. Plant drought-tolerant species. Use landscaping to help reduce cooling loads, especially around east- and west-facing windows. Plant edible landscaping for people as well as birds, butterflies, and wildlife. Install a water catchment system based on your annual rainfall.
Taking Steps Together
The only way to prepare for the future is to bring our focus home, literally and collectively. Cities across the country are leading the charge to become Kyoto compliant. In many cases that means reducing their carbon dioxide production by 25% or more. Some cities, such as Portland, Oregon, have already achieved their goals.
But a city is merely a collection of families. If each family takes responsibility for its consumption patterns, its carbon production, and shops locally, we can make a huge difference. We want to keep our sales tax dollars in our communities. Especially around energy. When we fill our gas tanks it is taxed once and all the profit leaves the community and typically the state. The profits end up in Saudi Arabia, Houston, or Washington, DC. That doesn’t help pay for firemen, policemen, teachers, and the folks who run our communities.
If we keep our dollars local, by not buying fossil fuels, the money saved provides local jobs. It can go toward movies, dinner, clothes, and books from companies that pay local sales tax. Those savings are cycled three to eight times before they leave the community. What that means is the city collects three to eight times as much sales tax when energy is saved than when it leaves the community and is sent to oil and gas companies.
In the past it was common practice to build to code and let the government tell us how and what kind of homes we should have. From this point on it is imperative that we determine what the standards should be for our communities. Through LEED and the NAHB green build ing guidelines the building industry is leading the transition to a more sustainable future. It takes every one of us to lead in our own com munities. Your customers are waiting for you to provide the kind of energy-efficient and environ mentally appropriate homes that they want. Take a step forward and see if your market responds. Join a local green building program. Start one if there isn’t one. See the Resources for help in learning more about green building guidelines.
All of this may be seem overwhelming but each step is a basis for creating homes that are self-reliant, resilient, and versatile. The scale of environmental changes facing us is enormous and unpredictable. It is only common sense to begin making our homes right for the world we really live in. Future-proofing your home is one of the smartest investments you can make today for your customers and your company.
Energy Basics and Heat Transfer
TIP: Insulation and air leakage both play a big role in the energy usage of most houses. Always seal air leaks when you insulate a house.
IN DETAIL: The greater the temperature difference between
one area and another, the faster heat moves. A cup of hot tea cools quickly
at room temperature because the temperature difference is large: about
90°E Iced tea takes about twice as long to warm up, because the temperature
difference is about half (40°F).
IN DETAIL: The largest energy use in most houses is
heating and cooling (about 55%). Therefore, improvements to the building
envelope and mechanical systems have the most potential to save energy.
Understanding Heat Transfer
You don’t need to be a heating engineer to know how to install insulation. But by under standing how the mechanisms of heat transfer work and their relative importance in your home, you can better decide how to approach to any weatherization project that you undertake.
Heat transfer is the movement of heat from indoors to outdoors in the
winter, and from out doors to indoors in the summer. If heat transfer
didn’t occur, your house would always keep you cozy and warm in the winter and cool and comfortable in the summer, without the use of a furnace
or air conditioner.
There are three forms of heat transfer: conduction, convection, and radiation. Of the three, conduction and convection are larger in magnitude— how fast the heat moves—and radiation can have a big influence on the comfort inside a house. Let’s look at how each of these mechanisms operates and affects your home.
Heat flows toward cold
Conduction refers to the movement of heat through solid materials. Conductive heat loss always moves from the warm side to the cold side of a material. For example, if you have a cup of hot coffee outside on a cold day, the heat will move through the cup and out into the cold air around it (or into your hands to help keep them warm). On the other hand, if the weather is hot and you have a cup of iced tea, the heat will move from the warm air, through the cup, and into the tea, warming it.
Different materials allow conduction to happen at different rates. For example, we may use a steel pan on the stove to efficiently transfer heat from the stove burner to our food because steel is a very good conductor of heat. For the same reason, steel framing in an exterior wall performs poorly from an energy-efficiency standpoint. Thermal insulation describes a number of products designed to slow conductive heat loss in walls, ceilings, and floors. Common types of insulation, such as fiberglass, cellulose, and polystyrene foam, are poor conductors of heat (for more on insulation, see chapter 4).
It’s important to remember that heat flows through solid materials toward cold in any direction. A house may lose more heat down through an uninsulated floor in a sunroom than it loses up through the moderately insulated ceiling of the same room, The reason attics are usually insulated to a higher degree than walls or floors is not because heat rises; it’s simply because the ceiling usually contains more space to hold thicker layers of insulation more cheaply and easily than any where else in a house. The old saying “heat rises” is misguided—heat actually moves in every direction. However, that saying does have some truth to it, which brings us to the next subject: convection.
Heat moves on air
To an engineer, convection describes heat transfer through the movement of fluid. Convection, to an engineer, is a much more complex subject than we need to understand for weatherizing homes. For our purposes, convection can be thought of as heat transfer through air movement. What causes air to move? Three main forces cause air to move through your house: the stack effect, mechanical systems, and wind. In a typical house, convection is almost as important as conduction and , because it’s often misunderstood, I will go into some detail discussing it here.
The stack effect. The first convective force, the stack effect, is what is meant by the saying “heat rises.” W is really meant is, “warm air rises when surrounded by cold air.” In the winter, a house is very much like a hot—air balloon that is too heavy to lift off from the ground. If you were the pilot and wanted the balloon to go up, you would turn on the burner and add more heat; this would intensify the force pushing up the balloon by increasing the temperature of the air inside the balloon. Similarly, the amount of force pushing air through your house is proportional to the temperature difference between the indoor air and the outdoor air. This is an important concept for understanding the basics of air leakage in relation to indoor air quality and fresh—air ventilation. Because the stack effect is driven by temperature, it’s a more important force in severe climates than it’s in mild climates.
If you were piloting a hot-air balloon and wanted to descend, you would let some hot air escape by opening a flap at the top of the balloon. When you open the flap, warm air escapes from the top and cooler air rushes in from the bottom to replace it. Similarly, when you heat your house in the winter, warm air leaks out of holes at the top, and cold air leaks in at the bottom to replace it. Another way to picture this is to imagine holding a cup of air upside-down in a pan of water. The air in the cup, like the warm air in your house, is lighter—more buoyant—than the water, which is heavy like the cool, outdoor air. If you poke a small hole near the top of the cup, the air will leak out slowly, and the water will come in from the bottom at the same rate to replace the air (see below).
TIP: Don’t just pack the ceiling with insulation because you can access the space. Remember that heat can just as easily escape through a poorly insulated floor.
IN DETAIL: Most combustion appliances, such as furnaces, water heaters, and fireplaces, draw their combustion air from inside the house. When they’re working properly, they act like exhaust fans, drawing in air to supply oxygen for combustion, then exhausting combustion gases up the chimney or out the vent pipe. Some appliances, known as power vent or induced draft, have blowers that push the combustion gases out. These blowers (shown below) are even more similar to the simple exhaust fans found elsewhere in the home.
Wind. People think that the wind causes most drafts, but in most houses, the effect of wind is quite small. Although the pressure may be greater than the stack effect when the wind is blowing, it’s a part—time occurrence; the stack effect operates 24 hours a day, 7 days a week, all year long. If your house is perched on a cliff or smack in the middle of a treeless plain, the wind may have a larger effect but, for most homes, the stack effect dominates the air movement.
One way to compare the seasonal impact of the stack effect versus the wind effect is to ask yourself whether you would rather have me give you $10 a month or $1 a day. The $10 feels like more on the day I give it to you, but you’ll be about three times richer if I give you $1 every day. So it’s with the stack effect: Although it’s per haps not as dramatic a source of energy loss as windy days are, it adds up over time to be a far greater energy cost.
Mechanical systems. In addition to the stack effect and wind, fans move air through houses. Exhaust fans, combustion appliances, and furnace air handlers move air in predictable and unpredictable ways. Exhaust fans push air out of a house—when they are working properly—and that air is replaced by outdoor air leaking in through openings in the building. Typical exhaust fans include kitchen and bathroom exhaust fans, dryers, and occasionally central vacuum systems (when they are vented to the outside). Combustion appliances, especially furnaces and boilers, contribute even more to air exchange when they are operating, which is when the weather is at its coldest.
Even more significant than exhaust fans are duct systems. Furnace and air conditioner fans are not intended to move air in and out of a house; how ever, if the ducts are leaky—and many are—your furnace fan may push a lot of air through your home. Like the furnace combustion air, an air handler runs the most when the temperatures are extreme, so ducts leak the most when it costs the most to reheat all the air that leaks out.
Whether the mechanical systems or the stack effect moves more air in a year varies from house to house, depending on the climate, the construction of the home, the size and location of leaks in the ductwork, and many other factors. In many homes, the air exchange caused by mechanical systems, though mostly unintentional, is the dominant force of convective heat transfer. Later, we will discuss controlling air movement in homes; combustion equipment; and sealing duct leaks.
The Stack Effect in Summer
One misunderstood aspect of the stack effect is that it reverses in hot weather. If the outdoor air is hotter than the indoor air, the heavier air in the house tends to sink and leak out through the bottom; it’s then replaced by warmer outdoor air that comes in through the top of the house.
To use the cup analogy, a house in the summer is like a cup full of water that is held upright. If you poke a hole in the bottom of the cup, the water (which is heavier) dribbles out the bottom and the cup fills from the top with air (which is lighter) at the same rate. People who leave upstairs windows open on a hot day thinking that the hot air will escape because “heat rises” are mistaken—they are actually opening a large hole through which hot outside air can be drawn into the house.
Although it’s true that the upper floor of a home tends to be much warmer on a summer afternoon, that is not because the heat is rising inside the house. It’s because superheated air is being drawn from the attic and roof deck into the upper part of the house through hidden air leaks—and through open windows and skylights.
Heat moves through space
Radiation is heat transfer from one object to another through space. Like conduction and convection, radiation depends on a temperature difference, but this time between the surfaces of objects rather than across a material. While conduction moves heat through solid materials and convection depends on air movement, radiation happens only when there is a direct line of sight between two objects of differing temperatures.
Radiation plays a much smaller role than conduction or convection in the heat loss from a house in the winter. The type of window glass can influence radiative heat loss to some extent (see chapter 5). Radiation is, however, the primary factor in solar heat gain. Solar gain is a good thing in the winter (it adds some heat from the sun to your house for free), but it’s also the largest driver of air-conditioning loads in the summer. In any season, radiation has a large impact on comfort. A person’s comfort level actually depends more on the average temperatures of the surrounding surfaces than it does on the air temperature in the room (see the top drawing on the facing page).
The biggest role radiation plays in a home’s comfort is due to the surface temperatures of glass. In the winter, glass is usually the coldest surface in a house; in summer, it’s the warmest. A room with lots of glass may be uncomfortable in both hot and cold weather. Uninsulated or poorly insulated walls, ceilings, and floors also create cold surface temperatures in the winter (or hot ones in the summer). Cold surfaces add to the problem of conductive heat loss by making people feel less comfortable. When people are chilly, they turn up the thermostat, driving the heat loss even faster and costing them even more.
TIP: Glass is usually the coldest interior surface in winter and the warmest in summer. Rooms with a lot of glass may be uncomfortable in both seasons.
WHAT CAN GO WRONG: Furnace air handlers should not move air in and out of a house; they are designed to move air around the house. Normally, as air is heated, it’s released into the house through supply ducts; house air is brought in through return ducts to begin the cycle again. However, leaky ductwork in attics, basements, and other areas can push air out side the house, acting like an unintentional exhaust fan. In fact, research has found that, in many homes, duct leakage accounts for the majority of air moving in and out of the house when the furnace blower is running.
Next: The Thermal Boundary
The Ultimate Guide to Green Do it Yourself -- Save Energy, Save Money:
4: Cooling Season
5: Windows and Doors
Special Section: Understanding Replacement Windows
6: Smarter Lighting
7: Conserving Water
Special Section: Your Automobile Gas Mileage
8: Appliances and Water Heaters
10: Resources and Links for learning more about energy efficiency
How to Cut Your Energy/Utility Bills and Save the Environment:
Environmentally-Conscious/Green Building and Remodeling Tips:
Changing to an Eco-Friendly World (Large-Scale Changes):
Energy: A Balanced Perspective
Millions of Americans are renovating their homes every year. Whether because of changing lifestyles or simply because houses are getting old and outdated, more money is spent each year on renovation than on new home construction. Buildings are responsible for 40 percent of energy flow and 40 percent of material use worldwide. The U.S. Environmental Protection Agency (EPA) has stated that “indoor air pollution in residences, offices, schools, and other buildings is widely recognized as one of the most serious potential environmental risks to human health.”
From another perspective, remodeling is an opportunity to make a difference in the world. As increasing numbers of people upgrade furnaces, cabinets, and toilets, they can have a positive impact on the world, including less fossil fuel pollution, less resources depletion, and lower health risks. Reusing existing buildings may be one of the “greenest” things we can do.
We are not suggesting that installing solar hot water heaters will stop greenhouse gas emissions from reaching what some experts predict will be levels higher than at any time in the last 50 million years. Remodeling your kitchen with certified sustainable wood will not stop the annual destruction of an area of biodiverse, old growth forest equal to the size of Nepal. and installing a low-flow toilet will not replenish our dwindling water supply. But green remodeling is energy-efficient, resource-efficient, healthy for occupants, and affordable to create, operate and maintain. Room by room, it is a way you can make a positive difference in your home.
If more and more people renovating use green remodeling strategies, the remodeling industry would have a significant role in saving the air, land, and waters we are degrading at unprecedented rates.
So you want an efficient, resourceful, healthy kitchen that will change the world? We’ll help you. We’ve divided this Section into a room-by-room survey to give you an overview of the stages of the building process for each particular remodeling project — so you can make connections to our more in- depth coverage of specific green features in later Sections.
Keep in mind that, underlying this simple format, we are still considering the house as a whole. In other words, the addition of a large bathtub might add 1,200 pounds to the load capacity of the floor, which will require additional structural support — arid this in turn will have an effect on such things as adjoining walls or pipes that service the entire house.
The descriptions of remodeling for each room are by no means complete: there are always more innovative ideas that can be applied to specific situations and , as technology improves, new ways to save energy and resources, improve air quality, and so on. Use the room descriptions as a guide for discussion with your architect and contractor, and refer to the checklist at the end of each description to locate more information on specific features. Always keep an open mind to new ideas — and choose whatever works best for your renovation project.
Is your home the enemy of your budget and the secret all cash cow for your fuel supplier?
The rising costs and shortages of oil, gasoline, natural gas, and electricity are front-page news. Instead of joining the panic, take effective action that will bring your household fuel costs under control with simple projects you can do right now to save money this winter.
• A thorough insulation job can save up to 50% on your fuel bill year-round.
• Cleaning your furnace can cut heating bills by up to 10%.
• Small changes in your daily habits can save you hundreds of dollars a year.
Fuel conservation does not have to equal discomfort.
• Set your thermostat back just one degree and save.
• Buy a humidifier humidity levels affect how you feel the cold.
Here’s how we can help…
Besides the tax rebates offered in many states as an incentive to solarize
your home's power, there are many other reasons to take a new look at going
solar. Originating as a space-program technology, photovoltaic (PV) panels
are a rapidly-evolving technology that is quickly becoming a more realistic and accessible option for the average homeowner.
Made of thin films of chemically treated silicon laminated to protective panels, PV panels can be placed almost anywhere there is an unobstructed path to southern sunlight. They are both an alternative and a supplement to the vast centralized power grids most of us are linked to via lines strung across the nation on stanchions and poles. They can reduce our country's dependence on fossil fuels and overseas suppliers, and lessen the pollutants and greenhouse gases associated with large power plant generation.
PV panels vary in size but are generally about two feet by four feet and less than an inch thick. Cells are often grouped and mounted on PV roofing shingles or laminated to a variety of surfaces including plastic and glass. Panel size and grouping configurations depend on the required electrical load and other factors. When panels are mounted on the structure they are powering -- whether it's a space station or a suburban ranch -- the panels are referred to as integrated PV systems.
These systems are not quite plug-and-play. PVs produce DC (direct current), yet most home appliances and electrical systems use AC (alternating current). Unless you are running DC equipment (which is possible on certain building types), chances are you will need a DC to AC inverter. and because sunlight is not constant, some type of backup power needs to be in place for use at night and on overcast days. This backup can be in the form of a battery array or a grid-tied or utility-tied (battery-free) system. Some states allow utility-tied systems with battery backup; these require code approvals and special equipment.
Although PVs have a somewhat high initial cost, this can be compared against the payback period -- how long it takes for the system to pay for itself. Payback periods are calculated based on your energy savings and the purchase of any surplus PV power by local utilities (called "net metering"). Careful building design strategies and various tax-rebate programs can mitigate these costs. In general, a medium-sized house with average power needs can run on a PV system generating anywhere from 2.5 kilowatts to 10 kilowatts (kW). A rule of thumb is to allow $10,000 initial cost outlay per kW, so a good budget projection for a 2.5 kW system is $25,000.
The California Energy Commission offers cash rebates of up to $4,000 per kW. Other states including Alaska, Arizona, New York, Oregon and Washington also have tax incentives and cash rebate programs. Check with your utility company or visit the Database of State Incentives for Renewable Energy web site at www.dsireusa.org/dsire for a comprehensive overview of state and federal incentive programs.
One can also do a lot to minimize PV operating costs in your own home. Big refrigerators, air conditioners, pool equipment and conventional computer monitors use a great deal of energy, pushing you closer to the 5 kW or 10 kW range. For this reason architects are now being called upon to design "high performance" and "fully integrated" buildings -- structures designed from the ground up to conserve energy and make the fullest use of building components. In a house, this translates to use of superinsulation, natural light maximization and efficient artificial lighting, passive solar design strategies, south-facing insulated windows, energy-efficient appliances and climate-control equipment.
Programs are now offered by state governments and private companies to train solar installers, and they are becoming widespread enough that you can find them on the Internet or in the phone book. One can also obtain design and consultation assistance from a few companies that specialize in renewable energy products and systems for homes and businesses.
Attention fellow Californians!
Support environmentally-conscious transportation projects and initiatives in our state. These projects do not necessarily require you to donate money. Rather, your letter- and email-writing endorsement to local and federal governments -- as well as grass-roots advocacy -- are the crucial instruments of support here. Share these links -- and the info contained in them -- with your non-aware family, friends and work mates.
California High-Speed Rail Authority -- Established in 1996, the California High-Speed Rail Authority is charged with the planning, designing, constructing and operating a state of the art high-speed train system.
The proposed system stretches from San Francisco, Oakland and Sacramento in the north -- with service to the Central Valley -- to Los Angeles and San Diego in the south. With bullet trains operating at speeds up to 220 mph, the express travel time from downtown San Francisco to Los Angeles is just under 2 ½ hours. Intercity travelers (trips between metropolitan regions) along with longer-distance commuters would enjoy the benefits of a system designed to connect with existing rail, air and highway systems.
Consisting of nine members (five appointed by the Governor, two appointed by the Senate Rules Committee, and two by the Speaker of the Assembly), the Board is responsible for implementing a statewide high-speed train system for California.
CalCars.org -- CalCars is a group of entrepreneurs, environmentalists, engineers and other citizens working to spur adoption of efficient, non-polluting automotive technologies. They're building demand among highly receptive markets to encourage auto makers to produce 100+MPG "no-sacrifices" high-performance, clean hybrid cars. They originated in response to interest in advanced automotive technologies, support from current owners of electric, natural gas, bio-fuel and hybrid vehicles, and the realization that fleets and early adopters have the buying power and resources needed to jump-start the market for better cars.
BuildingGreen.com: an independent company committed to providing accurate, unbiased, and timely information designed to help building-industry professionals and policy makers improve the environmental performance, and reduce the adverse impacts, of buildings. They offer both print and electronic resources to help you design and build construction projects from a whole-systems perspective and take an integrated design approach that minimizes ecological impact and maximizes economic performance.
Green Books: an independent UK publishing company producing books on a wide range of environmental and cultural issues. Their books (where the publisher is listed as 'Green Books') are printed on a minimum of 50% recycled paper, and wherever possible 100% recycled paper, including Cyclus Offset, Five Seasons 100% Recycled Paper, Corona Natural and Revive. The book covers of recent titles are made of 50%–100% recycled materials.
Google.org : a philanthropic/non-profit branch of Google, the Search Engine. plug-in hybrid electric vehicles and vehicle-to-grid technology.
Environmental Design Library: Green Design / Sustainable Architecture: Resources: Sustainably designed buildings aim to lessen their impact on our environment through energy and resource efficiency. This guide will lead you to information on this topic and give you strategies for locating newer materials.
Solar Energy International: SEI works cooperatively with grassroots and development organizations to meet sustainable development goals with renewable energies.
Interstate Renewable Energy Council (IREC): The Interstate Renewable Energy Council’s mission is to accelerate the sustainable utilization of renewable energy sources and technologies in and through state and local government and community activities. The Interstate Renewable Energy Council (IREC) supports market-oriented services targeted at education, coordination, procurement, the adoption and implementation of uniform guidelines and standards, workforce development, and consumer protection.
Worldchanging.com: a go-to source for forward thinking, solutions-based journalism that takes a big-picture approach to sustainability.
New! Go GREEN UK with our new line of environmentally-conscious products: Browse our GREEN CATALOGUE
Our core beliefs:
Our topical focus:
Faryal.net was founded, is based and operates out of southern California, USA. A KH network.