WINTER IS ON THE WAY, WHAT ARE YOU GOING TO DO ABOUT THIS?

Weatherizing Homes to Uniform Standard Can Achieve $33 Billion in Annual Energy Savings

With winter around the corner some homeowners may be thinking about plugging all the leaks in their home to make them less drafty. Imagine if every homeowner in the country did that-how much energy could be saved? 

Using physics-based modeling of the U.S. housing stock, researchers found in a new study that upgrading airtightness to a uniform level could achieve as much as $33 billion in annual energy savings.

Currently people who weatherize can get their homes about 20 to 30 percent tighter. But they're not sealing all the cracks. There's still quite a bit left on the table, and those extra leaks and cracks could potentially save a lot of energy. Energy impacts of envelope tightening and mechanical ventilation for the U.S. residential sector. while researchers need to figure out how much energy is wasted from leaky homes and determine the optimal standard of airtightness-one that would maximize energy savings while minimizing the cost of achieving those savings.

This is an important question because the residential sector-113 million homes-uses about 23 percent of total U.S. source energy annually. (Source energy includes site energy, the energy consumed by buildings for heating and electricity, as well as the raw energy required to transmit, deliver and produce it.) Heating and cooling accounts for about half of the site energy used in residences.

The largest potential savings are in the hottest and coldest climates. As new air enters homes through leaks and cracks, it has to be cooled or heated. Although the trend has been towards building tighter houses, the science is still not settled on the best ways to minimize leaks. More research is needed to figure out what are the most effective ways to weatherize.

The researchers considered five levels of tightening:

• "average" tightening, 
• "advanced" tightening, 
• the International Energy Conservation Code (IECC) standard, 
• the R2000 standard (common in Canada, tighter than IECC) 
• and the "passive house" standard, the tightest and most difficult to achieve.

They found that upgrading all homes to be as airtight as the top 10 percent of similar homes (advanced tightening) would decrease energy demand by 2.6 quads annually-out of the total 22 quads of source energy used by the residential housing sector-leading to roughly $22 billion in savings in energy bills. Reaching the IECC standard would yield savings of 3.83 quads in annual source energy, yielding $33 billion in savings.

The study found that the IECC standard offered most of the benefit that the tighter standards would yield. Moreover this standard is likely more achievable than the tighter standards. According to their analysis, raising the U.S. housing stock to the IECC standard would reduce airflow in homes by a median value of 50 percent.

The analysis in the study factored in the energy costs of increasing ventilation where necessary to maintain good indoor air quality. A separate analysis looked at the energy cost of only bringing the housing stock into compliance with ASHRAE 62.2, a national ventilation standard for homes that ensures sufficient ventilation for human health.

Leave us a comment on what you are doing to achieve a tighter, more energy efficient home this winter.

SOLAR TECHNOLOGY

Low-priced plastic photovoltaics

Solar cells and panels, which tap the power of the sun and convert it to electricity, offer a green - and potentially unlimited - alternative to fossil fuel use. So why haven't solar technologies been more widely adopted?

Quite simply, they're too expensive, Researchers have come up with a technology that might help bring the prices down.

To collect a lot of sunlight you need to cover a large area in solar panels, which is very expensive for traditional inorganic - usually silicon - photovoltaics. The high costs arise because traditional panels must be made from high purity crystals that require high temperatures and vacuum conditions to manufacture energy potential.

A cheaper solution is to construct the photovoltaic devices out of organic compounds - building what are essentially plastic solar cells. Organic semiconducting materials, and especially polymers, can be dissolved to make an ink and then simply "printed" in a very thin layer, some 100 billionths of a meter thick, over a large area.

Covering a large area in plastic is much cheaper than covering it in silicon, and as a result the cost per Watt of electricity-generating capacity has the potential to be much lower.

One major difficulty with doing this, however, is controlling the arrangement of polymer molecules within the thin layer. Scientists have developed an advanced structural probe technique to determine the molecular packing of two different polymers when they are mixed together. By manipulating how the molecules of the two different polymers pack together, they have created ordered pathways - or "nanowires" - along which electrical charges can more easily travel. This enables the solar cell to produce more electrical current.

This work highlights the importance of the precise arrangement of polymer molecules in a polymer solar cell for it to work efficiently. Researchers and scientists expect polymer solar cells to reach the commercial market within 5 to 10 years.

SOME ( A REAL LOT OF) ASSEMBLY REQUIRED

IKEA rolls out consumer solar panel systems in British stores

I'll take the Billy bookcase, the Karlstad sofa, and a pack of solar panels in black.

Don't laugh it may be true some day.

IKEA stores in Britain this week began selling rooftop solar panel systems, giving the industry a boost after rounds of feed-in tariff cuts and freezes.

The Swedish retail giant confirmed Monday it would roll out the systems to 17 of its stores in Britain in coming months in partnership with Chinese panel-maker Hanergy Solar U.K. after conducting trial run this summer at an outlet in Southampton, England.

Believed to be the first time photovoltaic energy systems have been made available through a mass-market retailer, IKEA's move comes a year after feed-in tariffs paid to British panel owners were slashed from 69 cents per kilowatt to their current 23 cents.

IKEA announced the consumer roll-out after using solar panels extensively to help power its own facilities. Under its corporate sustainability program, the retailer has installed more than 250,000 panels across its stores worldwide and is aiming to produce as much energy as it consumes by 2020.

The price of a standard 3.36-kilowatt PV system for a semi-detached home would run about $10,800, including value-added tax, with 15-percent discounts available under IKEA's Family loyalty program.

Steve Howard, IKEA's sustainability chief, told The Wall Street Journal despite likely low profit margins, the retailer wants to build PV systems into "a real business."

They're becoming easier to sell thanks to the volatility of energy prices, he said, adding, "You don't have to care about the environment and climate change, you can just care about the finances."

After a surge of PV panel-buying when Britain first introduced its feed-in tariff scheme, the number of homes installing rooftop systems has dropped as the FIT has gone down. The British Solar Trade Association says the solar market is currently installing about 100,000 solar systems per year -- far below the projected 300,000.

It will be interesting to see which model prevails. Either way, IKEA's move represents a big bet on solar panels' potential to shake their reputation as boondoggles and become the latest sleek status symbols for the modern home. The company has already begun the work of recasting their aesthetic image, suggesting that its solar panels resemble "flat-screen televisions."