Remodeling a home is possibly one of the highest levels of “green.” It is one of the best sustainable housing initiatives around. While researching the remodeling industry I came across the website dubbed, Home for Life. The site includes a wealth of resources that explain opportunities to upgrade an existing home’s energy and resource efficiency to reduce environmental impact. The website is a product of Remodeling Magazine, a Hanley Wood publication. Read more
Do attic fans lower the cost of cooling your home?
Are solar attic fans worth installing? Common sense suggests they would be but are powered attic fans really a good idea for energy efficiency based on research and science? I have a master’s of science degree and my initial belief was it made sense. It just seems logical that a cooler attic would lower the cost of cooling the house in summer. While researching radiant barriers for the attic and reflective paint (Kool Seal Premium White) for our metal roof, I came across a few articles strongly suggesting powered attic fans were a dumb, and possibly dangerous, idea based on science. Here’s what I found so far and why I removed my attic fan:
- The Scientific Spin on PAVs (powered attic ventilators – fans): Cooling off hot attics with powered attic ventilators (PAVs) seems like a good idea. After all, doesn’t cooler attic air mean less work for the HVAC system, longer shingle life, and reduced energy costs? Unfortunately that’s more myth than fact.
- Drawbacks Of Powered Attic Ventilators:Powered attic ventilators, already suspected of using more energy than they save, can also create excess moisture, structural problems, discomfort, and combustion safety problems for home occupants, according to a recent study. John Tooley of Natural Florida Retrofit, and Bruce Davis of Alternative Energy Corporation’s Applied Building Science Center in North Carolina, presented “The Unplanned Impacts on Houses by Powered Attic Ventilators” at the 1995 meeting of the Energy Efficient Building Association.The paper describes research conducted on eight homes over a period of three months. As a result of this research, Davis said that he wouldn’t recommend the use of powered attic ventilators. He emphasized, “If someone chooses to use a powered attic ventilation strategy, they need to do additional performance tests and take responsibility to be sure that it won’t cause other problems.” The potential for hazardous conditions is particularly high in homes with combustion gas appliances, because the ventilators can create negative pressures that cause backdrafting.
- Energy Star: Attic Fan Ventilation – Attic fans are intended to cool hot attics by drawing in cooler outside air from attic vents (soffit and gable) and pushing hot air to the outside. However, if your attic has blocked soffit vents and is not well-sealed from the rest of the house, attic fans will suck cool conditioned air up out of the house and into the attic. This will use more energy and make your air conditioner work harder, which will increase your summer utility bill.
- Ask the Builder: Powered Attic Fans – Attic Insulation Facts: “I used to recommend PAVs [powered attic ventilators – fans] for houses, but I don’t anymore.”
- Building Science, Unvented Roof Summary Article
The best solution appears to be making sure your attic is well insulated and well-ventilated using passive vents and natural air flow. Inspect your attic insulation and ventilation, or have a contractor do so for you. Just add more insulation or natural (passive) ventilation, if needed. Both measures will reduce the cost of cooling and heating your home; no electricity required and they are perfectly quiet.
ADDITIONAL ENERGY EFFICIENCY RESOURCES
- Contact the local power company website and local energy associations for more information on constructing an energy efficient home in your area.
- Building Science Corporation, Unvented Roof Summary Article: Excellent resource with in-depth research and hard-core science. Building Science is dedicated to teaching and providing factual information concerning building science and energy efficiency. This resource is used extensively by builders “in the know” when it comes to energy efficiency.
- Building Science Guides and Manuals: Good place to start if you want reference documents for some of the most important building science topics.
- Building Science Information Sheets: Fact sheets and overviews; another great place to start for those relatively new to the field.
- Energy Star : The Energy Star website has extensive information on energy efficiency.
- Geothermal Heat Pump Consortium: Geothermal is the most energy efficient method known today for heating and cooling. However, you will benefit by first making sure your home or building is insulated properly and as air tight as possible (within the limits of the appropriate building codes and safety concerns) before considering an expensive geothermal system.
ENERGY EFFICIENCY PRODUCTS
Whether or not you are using an attic fan and you own a fireplace, a great product to consider is a fireplace plug. Battic Door sells several energy conservation products including a simple fireplace plug; stops drafts and saves energy by sealing the chimney when not in use:
The Fireplace Draft Stopper is an inflatable urethane chimney plug balloon pillow measuring 38″ x 16″. A round Fireplace Plug is also available. It is quickly and easily installed in the fireplace just below the damper level. The Fireplace Plug can be adapted to work in almost all fireplaces. Even if you have an unusual construction, the Fireplace Plug can be successfully installed in less than 2 minutes.
The Fireplace Plug is provided with 5 “slittable” areas that can be cut to provide an opening for a damper handle. As the Draftstopper is inflated it seals around the damper handle sealing the opening (helps reduce energy costs). Easy, quick and clean installation.
My metal roof was red, hot, and desperately needed painting. After spending some time inspecting the roof, I quickly realized how incredibly hot the red paint became even on a modestly hot spring afternoon. Why repaint the roof red since it gets so hot? I thought there must be a better solution so I started investigating roof paints. Fortunately, I wasn’t the only one wondering if a lighter-color roof would reduce heat gain inside the attic and save energy. Also, I quickly learned a lot about “reflective” paints, radiant heat, and the best ways to insulate the attic to reduce cooling and heating costs.
One research article I found informative and one I recommend reading is, Cool Roofs For Hot Climates by Dan Parker, a senior research scientist with the Florida Solar Energy Center (2003). The following is from the article:
Reflective roofs work because they stop the rooftop heat before it ever gets going. The sun’s rays hit the roof at the speed of light, and at the speed of light they bounce back into space. White or light-colored materials work best, but some new dark pigments reflect enough invisible infrared radiation to reject a lot of solar energy. And whether you’re applying tile, metal, membranes, or even asphalt shingles, choosing a more reflective version seldom adds cost.
The figure below graphically depicts the best solution for energy efficiency is a reflective white metal roof:
After reading this article and numerous others, I painted my metal roof with Kool Seal® Premium White Elastomeric Roof Coating which I purchased at the local hardware store (ACE Hardward has it here in Richmond, VA).
Additional Metal Roof Information
Roof Costs and Energy Savings: According to the Metal Roofing Alliance, white-painted metal roofing has the highest solar reflectance value of any roofing product available and can save you up to 40% of your annual energy bills.
According to statistics from McGraw-Hill Construction Research and Analytics®, the number of homes with metal roofs has more than tripled over the past decade, moving metal from 3% of the overall U.S. market to 10%.
Some homeowners’ insurance programs allow discounts for homeowners with specific weather-resistant metal roofing products. Contact your insurance agent to determine if your home qualifies.
Photo taken after the 1991 Oakland, California firestorm. Burning embers destroyed all of the homes in the neighborhood, except the masonry home that was roofed with Stone-Coated Steel Roofing. While all of the neighbors fought (without success) to save their homes by watering down their asphalt roofs, burning embers did not ignite the steel roof. The house with the steel roof survived while all others around it were destroyed. (SOURCE: Metal Roofing Alliance: Lower Your Insurance with Weather-Resistant Metal Roofing)
Kool Seal® Premium White Elastomeric Roof Coating
FEATURES AND BENEFITS
(SOURCE: Provided by the manufacturer, see product description, surface prep, etc. here – PDF)
- Energy saving up to 35%
- Reflects 90%+ of the sun’s rays
- Designed to be durable in any climate
- Higher solids for better coverage
- Forms a thick rubber-like blanket of protection
- Expands and contracts – clings to your roof in all temperatures
- Protects against moisture
- Cured elastomeric film is mildew and algae resistant
- Helps to absorb sound
- Environmentally compliant
- Soap and water cleanup – while wet
Energy Efficient Roofing Video by Tod Miller
Other Useful Articles Pertaining to White Roofs:
- Metal Roof Retrofit on a Hurricane Damaged Home by: Dave Chasar, PE. A before/after energy comparison of shingle roof verses white metal roof replacement; includes monitored data collected at the home over several years.
- Metal Roofing Alliance – www.metalroofing.com
- The Cool Metal Roofing Coalition – www.CoolMetalRoofing.com
- Energy Star – www.EnergyStar.com
There are several helpful videos that explain Geothermal energy and the operation of geothermal heat pumps (GHP). Geothermal is considered the most efficient way to cool and heat your home or business with respect energy efficiency. As we come across geothermal videos we’ll publish them for you. Here’s what we have so far on geothermal:
Geothermal Ground Source Explained
Geothermal Heating and Cooling – How it Works
Geothermal heating and cooling uses the relatively constant temperature of the earth below the ground to heat and cool. Geothermal systems use 40% to 70% less energy than conventional systems. While conventional furnaces and boilers burn a fuel to generate heat (traditional HVAC systems), geothermal heat pumps (GHP) very efficiently use electricity to transfer heat from the earth into buildings; your home or a commercial building. In fact, the most efficient fuel-burning heater can reach efficiencies around 95%. That sounds great but consider a geothermal heat pump that transfers up to 4 units of heat for every unit of electricity needed to power the system. What this means in comparison is geothermal energy results in over 400% efficiency.
A geothermal heat pump transfers heat stored in the earth (soil, surface water or ground water) into a building during the winter, and transfers it out of the building and back into the ground during the summer. In other words, the ground acts as a heat source in winter and a heat sink in summer. The technology is used for space heating, cooling, and hot water.
PROS of Geothermal
The US Environmental Protection Agency considers geothermal the cleanest and most energy efficient heating and cooling (HVAC) system for any home.
Geothermal heat pumps cost significantly less to operate than traditional HVAC systems; you benefit from lower monthly utility bills. And, geothermal systems have fewer moving parts which tends to lower maintenance costs compared to traditional HVAC systems. In addition, GHPs equipped with a device called a “desuperheater” can heat the water in your home. During the summer heat that is taken from the house is used to heat the household water (hot water supply). In the winter, water heating costs are reduced by about half.
Tax credits are available to home owners that install geothermal systems (until 2016 currently). And, tax credits are dollar for dollar reductions in the amount you owe in taxes – every dollar credited is one dollar less you pay in taxes. Tax credits are far better than tax deductions which only reduce your taxable income. The IRS energy tax credit program is called the“Credit for Residential Energy Efficient Property” and the purpose of the program is to encourage people to build green.
Geothermal Tax Credit Summary:
- 30% of cost with no upper limit for ENERGY STAR qualified geothermal heat pumps
- Expires: December 31, 2016
- Details: Existing homes and new construction qualifies. Both principal residences and second homes qualify. However, rental properties DO NOT qualify for geothermal tax credits.
- More information on Energy Star and Geothermal Tax Credits
- Some restrictions may apply and it is recommended that you consult your accountant and/or the specific IRS code for all of the details.
NOTE: All geothermal heat pump components certified by the manufacturer in the “Manufacturer Certification Statement” will be covered by the 30% tax credit according to the IRS (see IRS code for details), as well as the installation costs associated with these components. There may be some add-on components that will not be covered such as an emergency back up system and the ducts. According to certain IRS guidance, these components are not directly related to the efficiency of the covered geothermal heat pump property.
IRS Guidance: Notice 2009-41 Section 3. (1)(e) Qualified geothermal heat pump property expenditures are expenditures for equipment which uses the ground or ground water as a thermal energy source to heat the dwelling unit or as a thermal energy sink to cool the dwelling unit, meets the requirements of the Energy Star program which are in effect at the time that the expenditure for such equipment is actually made (even if under § 25D(e)(8) the expenditure is deemed made at a later time for purposes of determining the taxable year for which a taxpayer may claim the credit), and is installed on or in connection with a qualifying dwelling unit. (SOURCE: Energy Star: What parts of a geothermal heat pump are covered by the tax credit?)
CONS and Disadvantages of Geothermal Systems
The initial capital cost for geothermal systems is higher, often 2x or more higher. The upfront cost is the main disadvantage and it might take anywhere from 2 to 10 years to recover your initial investment through reduced utility expenses. Another possible disadvantage might be the availability of a qualified and experienced contractor in your area. It is typically easy to obtain references for contractors that are experienced with the installation of traditional HVAC systems but you might find it more difficult to obtain references for geothermal contractors.
The installation of the equipment in the ground requires heavy equipment (backhoe for horizontal loops or drilling equipment for well installation). In most cases, there is a cost associated with landscaping. For example, horizontal loops require up to 250-300 feet of trench per ton; a 3,000 sq. ft. home might require a 4-5 ton geothermal heat pump. The loop and trench design is highly dependent on your situation; the size of your yard, accessibility, etc. You may incur the expense of removing a fence or other landscaping. Also, the yard will almost always require landscaping after digging the trenches and/or installing vertical wells. Heavy equipment does tear up a yard.
Most GHP require the system to be “running” to produce hot water. However, newer systems are being designed that will produce hot water without the main system running. Read about ClimateMaster’s “Q-Mode” and the Trilogy 40 (see below) – a new development in technology that allows hot water to be produced without the system running. Also, WaterFurnace’s 7 Series (41 EER) run very efficiently with variable speed compressors. Little energy is used while running the system in a powered-down state that allows for hot water production (not as much of an issue with the latest and greatest GHP systems introduced this year, 2012).
Evaluating Geothermal Heat Pumps
Ground source heat pumps are rated in terms of Coefficient of Performance (COP) for the winter. The higher the COP, the higher the efficiency. Where gas furnaces have COP values in the 0.78 to 0.94 range, ground source heat pumps have COP values in the 3.0 to 5.0 range.
When comparing geothermal heat pumps, first determine the EER; the EER is the ratio of effective cooling (heat removed) to the energy used at maximal load. EER is the standard measure of cooling effectiveness for geothermal heat pumps. One way to compare both the COP and EER is to review the list of Energy Star qualified GHPs. Until recently (July 2012), the highest EER rating currently available was 30; note that many Energy Star qualified heat pumps have EERs as low as 17.
ClimateMaster facilities operate in Oklahoma City, Oklahoma; the GHP units are manufactured in the United States. They offer a complete line of geothremal heating and cooling systems. For example, the TRANQUILITY 30 DIGITAL series units are two stage with a variable speed fan and a variable speed loop circulation pump for added energy savings. They also feature advanced “iGate” controls, a stainless steel drain pan, and coated air coils for durability. The THW series water to water units are higher temperature units for hydronic systems and provide higher water temperatures for improved heating. The TMW models are for normal temperatures. All of the units are backed by a warranty. (visit the products page at climatemaster.com for more info)
ClimateMaster recently announced that their new Trilogy 40 geothermal heat pump (GHP) had been certified by the Air Conditioning, Heating, and Refrigeration Institute (AHRI) to exceed 40 EER under ground loop conditions.Therefore, this makes the Trilogy 40 significantly more efficient for cooling; it is now one of the most efficient commercially available GHP. Also, note that 40 EER is more than twice as efficient as some Energy Star qualified GHPs. The following is from the ClimateMaster website:
The Energy Department’s Oak Ridge National Laboratory has partnered with ClimateMaster — a leading manufacturer of geothermal and water-source heat pumps — to develop an appliance that could provide space conditioning and all domestic hot water needs while consuming at least 50% less energy than conventional minimum efficiency equipment.
The partnership between the Department and ClimateMaster began in 2008 in an effort to develop a more efficient ground-source integrated heat pump. Based on field tests and analysis, the new Trilogy 40 Q-Mode™ could save about 60% of annual energy use and cost for space conditioning and water heating in residential applications compared to new minimum efficiency conventional systems. Also, it’s about 30% more efficient than any other available ground-source heat pump [Editor’s note: The statement that it is “30% more efficient that any other availabe” was true when the statement was published. However, Waterfurance recently released the “Series 7” GHPs (41 EER) which are significantly more efficient than their Series 5.
ClimateMaster Press Release: Oklahoma City, OK March 19, 2012 – ClimateMaster announced an efficiency breakthrough with introduction of the Trilogy™ 40 series, the first geothermal heat pumps ever certified by the Air Conditioning, Heating, and Refrigeration Institute (AHRI) to exceed 40 EER at ground-loop (GLHP) conditions.
The revolutionary new Trilogy™ 40 utilizes variable speed technology to provide an extremely wide range of heating and cooling capacities, with the ability to perfectly match loads to as low as 30% of maximum. In addition, patent-pending Q-Mode™ technology produces year-round domestic hot water on demand, even when space conditioning is not required.
The Trilogy 40 Q-Mode series is the outcome of a five year collaboration between ClimateMaster and Oak Ridge National Laboratory (ORNL), which was sponsored by the U.S. Department of Energy (DOE) Building Technologies Program. Based on field tests and analysis by ORNL, the Trilogy 40 Q-Mode can save 55–65% of annual energy use and cost for space conditioning and water heating in residential applications versus new minimum efficiency (SEER 13) conventional systems and 30–35% versus current state-of-the-art two-stage geothermal heat pumps. (Read the full press release from ClimateMaster here)
WaterFurance offers a wide variety of geothermal units using the latest technologies. They are backed by one of the best standard warranties in the industry according to a few website geothermal forums. (visit the product page at www.waterfurnace.com for more info)
The WaterFurnace 7 Series is a new level of innovation and performance with all new advanced controls mated with variable speed compressor technology. Featuring the highest efficiencies (Over 40 EER and 5.3 COP ISO/AHRI 13256-1 GLHP) available in AHRI, the 7 Series is available in 3 variable speed capacity sizes (3 to 5 ton) with Danfoss Variable Speed Compressors.
Company Description: WaterFurnace Renewable Energy, Inc. specializes in the design, manufacture and distribution of geothermal and water-source systems. It’s the United States subsidiary companies are WaterFurnace International, Inc. (WaterFurnace) and LoopMaster International, Inc. (LoopMaster). In December 2010, it incorporated two Australian subsidiaries: WaterFurnace International Asia Pacific Pty. Ltd. (WaterFurnace Asia Pacific) and Hyper WFI Pty. Ltd. (Hyper WFI). WaterFurnace designs, manufactures and distributes geothermal water source heating and cooling systems for residential, commercial and institutional buildings. LoopMaster installs geothermal loops for residential applications, does commercial conductivity testing and provides design and installation assistance. Hyper WFI designs, develops and builds devices that limit the inrush current, which electric motors draw upon start up. On January 21, 2011, the Company acquired inventory and fixed assets from Binary Engineering Pty. Ltd. (SOURCE: WaterFurance)
ENERGY STAR Guide to Energy Efficient Cooling and Heating (PDF)
Dept. of Energy Report – Assessment of Hybrid Geothermal Heat Pump Systems
Forbes article: Geothermal Heat Pumps: Waterfurnace verses ClimateMaster
Forbes article: Geothermal Heat Pumps: The Next Generation
Energy Star: COP and EER table for review – List of Energy Star Qualified GHPs
RECOMMENDED READING: The Elephant in the Room, HVAC for High Performance Homes, 2009 RESNET Conference, David Butler – Optimal Building Systems
In new homes, poor HVAC design and installation practice accounts for more energy waste than any other single factor. Unfortunately, when it comes to HVAC, it’s easier to sell high efficiency boxes than high efficiency systems, a distinction invariably lost in a competitive marketplace. As a result, HVAC remains the weakest link in most high performance homes.
As homes have become more efficient, oversized HVAC equipment has emerged as one of the more serious problems in building science. Although there’s general awareness of this issue among industry practitioners, few understand the full extent of the problem or its consequences.
There are numerous reasons why oversizing is a bad idea:
- Oversized equipment costs more and requires larger electrical circuits
- Oversized compressors have a shorter life expectancy
- Excess capacity compromises comfort (larger temperature swings)
- Excess cooling capacity compromises moisture removal, a big deal in humid areas
- Larger compressors and blowers produce more noise
- Excess capacity compromises indoor air quality (less run time = less filtration)
- Excess cooling capacity increases the potential for structural damage from moisture
- Oversized equipment is less efficient, thus increases operating costs
Said differently, right-sized HVAC systems cost less up front, last longer, provide better comfort, improve moisture removal, run quieter, provide better filtration, and cost less to operate. (SOURCE: Optimal Building Systems)
Geothermal Heat Pumps Definitions
GHPs are also known by a variety of other names: geoexchange heat pumps, groundcoupled heat pumps, earth-coupled heat pumps, ground-source systems, ground-water source heat pumps, well water heat pumps, solar energy heat pumps, and a few other variations. Some names are used to describe more accurately the specific application but most are the result of marketing efforts and the need to associate (or disassociate) the heat pump systems from other systems.
Geothermal Heat Pumps – Common Abbreviations
- cfm = airflow, cubic feet/minute
- EWT = entering water temperature, Fahrenheit
- gpm = water flow in gallons/minute
- WPD = water pressure drop, psi and feet of water
- EAT = entering air temperature, Fahrenheit (dry bulb/wet bulb)
- HC = air heating capacity, MBtu/h
- TC = total cooling capacity, MBtu/h
- SC = sensible cooling capacity, MBtu/h
- kW = total power unit input, kilowatts
- HR = total heat of rejection, MBtu/h
- HE = total heat of extraction, MBtu/h
- HWC = hot water generator capacity, MBtu/h
- EER = Energy Efficient Ratio
- = Btu output/Watt input
- COP = Coefficient of Performance
- = Btu output/Btu input
- LWT = leaving water temperature, °F
- LAT = leaving air temperature, °F
- TH = total heating capacity, MBtu/h
- LC = latent cooling capacity, MBtu/h
- S/T = sensible to total cooling ratio
Energy and Environment Links
- American Wind Energy Assoc.
- Biomass Power Association
- Canadian Geothermal Assoc.
- Climate Change Business Journal
- Conserve Georgia
- Energy Efficiency
- Geo Heat Center
- Geothermal Energy Association
- Geothermal Resources Council
- Global Renewable News
- Green Business News
- Matter Network
- North American Wind Power
- Small Wind Systems
- Solar Electric Power Assoc.
- Solar Novus Today
- Solar World “Recharge”
- Solve Climate News
- Sun & Wind Energy
- The Encyclopedia of Alternative Energy and Sustainable Living
- The Tax Incentive Assistance Program (TIAP)
- U.S. Dept. of Energy
- Wind Project Calculator
- Wind Systems
- World of Renewables
Oilobit.com News/Source: Daimler/Stuttgart – The “ÖkoTrend” institute has declared the S 250 CDI BlueEFFICIENCY and the ML 250 BlueTEC 4MATIC to be the most environmentally friendly cars in their class. This is what lay behind the professional journal AUTO TEST’s decision to present its “Winners in Green” awards to both Mercedes-Benz models. Read more
“Our smart has long since evolved into an icon, which is indispensable in the cities of the world,” says Dr. Annette Winkler, Head of smart.
Hat’s off to Family Circle for publishing an energy saving article as fall approaches; good timing. Simple energy saving solutions can result in significant savings as we all know. The article, The Heat is On: and a Plan to Lower Energy Costs, offers a simple break-down of “Light Green, Medium Green and Dark Green” energy saving tips.
CPV systems are poised for significant growth thanks to the confluence of several factors: Renewable Portfolio Standards (RPS) requiring up to 33% renewables by 2020 in key US states, higher efficiency CPV systems, and lower CPV system costs. In the last year alone, over 300 MW of CPV projects have signed contracts with utilities and are now awaiting regulatory approvals and financing.
Thanks to these large projects, CPV technology companies may be approaching the critical mass needed to cost-effectively manufacture their systems and compete head-to-head with non-concentrating PV.
Date: Tuesday, September 27, 2011
Time: 2:00 p.m. EST/11:00 a.m. PST
Speaker: Dr. Jan-Gustav Werthen, Senior Director of Photovoltaics, JDSU; Moderator: Brett Prior, Senior Analyst, GTM Research
Can’t make the live event? Register and the presenters will alert you when the on-demand version is available.
Register to the webinar to hear about the technologies and new breakthroughs that promise continued improvement, including multijunction cell design and high-volume manufacturing techniques. At the end of the event, audience members will be able to ask questions of the panelists and moderator live!
On another note – here are a few helpful links for those interested in solar:
State and Federal Rebates and Incentives: www.dsireusa.org
Improving your building’s energy efficiency:
Join thousands of fellow supporters in a historic call for clean energy: www.repoweramerica.org/wall/#
For those interested in PV systems, GTM Research and Dupont are presenting a webinar. It is for system developers, system designers, EPCs, installers, financiers, engineering firms, and others who specify, recommend, or influence the selection of PV equipment and components (cells, modules, etc.) for PV installations. The event is sponsored by DuPont.
Over the next five years, photovoltaic (PV) systems will achieve grid parity in many major global markets with low-cost, high-efficiency systems that have 25 or more years of system life. A driving factor in achieving grid parity is the quality and durability of materials in PV cells, modules and other system components. This seminar will explore the crucial role of materials in determining the efficiency, reliability and cost of PV systems. Discussion will focus on key considerations, and provide guideposts for those who specify or influence the selection of PV components.
Date and Time: Thursday, July 28, 2011 at 2PM (ET). For additional info and to register for the PV Systems webinar visit Greentech Media here.