High Efficiency Tank Water Heaters

Hello again from Olson Defendorf Custom Homes.  We are a custom home builder in Austin, TX.  Today we are going to post about high efficiency water heaters.  

Although tankless water heaters have gotten a lot of attention the last few years, tank-style units offer plenty of efficient options, and in some cases, are actually more efficient.

There’s no arguing that tankless has become a buzzword among the green community, and it might be tempting to blindly jump on the bandwagon. But don’t discount tank-style water heaters too quickly. Advancements in both electric and gas storage water heaters are offering leaps in efficiency that are putting tank water heaters back on the green radar.

Pumped Up Efficiency

Perhaps one of the greatest advancements has been the integration of HVAC heat-pump technology into electric tank water heaters. The combination of the two technologies can produce efficiency ratings as high as 2.3 EF (Energy Factor), compared to the current minimum efficiency rating for a 60-gallon water heater at 0.89 EF, making them one of the most efficient water heating options available.
Often referred to as “hybrids,” these units are more than twice as efficient as standard electric water heaters and cost less than half the amount of money to operate. By using an Energy Star–rated heat-pump model, the DOE estimates that the average household can save almost $300 per year compared to a standard electric water heater. The units do cost more up front (about $1,200–$1,800), but the payback period is estimated to be only three years. They also can earn three points toward LEED certification, versus two for an electric tankless unit out of a total of six points available for water heating. The National Green Building Standard (NGBS) awards 7 points for heat pump units with a 1.5 EF and a maximum 10 points for 2.0-EF models.
A heat-pump water heater operates like a heat-pump HVAC system, borrowing heat from the atmosphere. An evaporator inside the tank uses refrigerant to absorb heat from the surrounding air and transfers it to a heat exchanger that heats the water inside the tank. Cool air is then expelled into the atmosphere. The tank includes electric heating elements to provide back-up heating if necessary.  The general layout of the appliance is similar to a conventional electric water heater, but there are some installation considerations. The integrated heat pump makes the tank a little taller than standard tank water heaters, and they require a condensate drain connection.

The biggest consideration, however, is that heat-pump water heaters require a whopping 1,000 cubic feet of ambient air to operate. Also, because the heat pump borrows heat from the surrounding air, homes in colder climates may require the unit to be installed in a conditioned space, and as a result, may not save as much energy. Basically, homeowners would be paying for another appliance to replace the heat being used by the heat pump—a fact that isn’t taken into consideration in efficiency ratings. At the same time, this means the unit may actually help the AC during warmer months.

Fueling Options

Generally, heat pumps are the most efficient tank-type choice for homes that don’t have access to natural gas. However, builders can still earn one LEED point or one NGBS point by installing a high-efficiency electric tank model. This includes 80-gallon units rated at 0.89 EF or higher, 50-gallon units at 0.92 EF or higher, or 40-gallon units at 0.93 EF or higher. Electric tank models are not covered under Energy Star, so check efficiency ratings closely. Builders may want to look for an electric water heater that has been certified by the Air-Conditioning, Heating, and Refrigeration Institute (AHRI) to ensure that the manufacturer’s high-efficiency claims are valid.
For areas where natural gas is more cost effective than electricity, builders may want to consider using a gas condensing tank-style water heater. Residential models are still in development, but some manufacturers have been marketing their commercial units for residential use, with some condensing models claiming thermal efficiencies of up to 96%—higher than even tankless, which are rated at about 80% thermal efficiency.
The general operating principles of a condensing model are similar to a standard tank water heater, but with better heat exchange. Instead of venting combustion gases outside like a standard gas tank water heater, a condensing model uses those gases to heat the water. The flue in these models also has been redesigned with a greater surface area so that the heat and combustion gases have a longer distance to travel, and, therefore, heat the water more efficiently. Basically, the tank heats up almost as quickly as it’s filled and can provide more continuous hot water, overcoming one of the usage drawbacks of conventional storage water heaters.
Like condensing furnaces, condensing water heaters produce condensation as a by-product of the combustion process, which means builders will need to install a condensation drain. Also, they require electricity and PVC pipe to accommodate the power venting.  Because current models aren’t rated as residential units, builders should know that they don’t have to meet FVIR or low-NOx requirements; however, as of press time, residential units were expected to launch by the end of 2010. Once available, the DOE estimates that homeowners can cut water heating energy use by 30% versus standard gas storage models and greatly reduce greenhouse emissions by taking about 75 therms off their natural gas bill. Installing gas-condensing models can earn two LEED points. And while the NGBS does not specifically mention condensing models yet, gas-fired units operating with an EF of 0.80 and higher are generally eligible to earn 10 points.

Conventional gas tank water heaters also are getting more efficient. In September, Energy Star upped its energy rating requirements for gas tank units from 0.62 EF to 0.67 EF. To meet those levels, manufacturers have to add power to their units, which is why most high-efficiency models are power vented or power direct vented. While these units are easily installed in new homes, they do require additional work in remodeling because the venting system needs to be replaced with PVC. There are a few innovative atmospheric models on the market that are Energy Star rated, but keep in mind that most standard atmospheric models are unable to reach anything above 0.63 EF. Even so, 40-gallon gas tank units with an EF of 0.61 or above will still provide one LEED point, and 60-gallon and 80-gallon models only need to reach 0.57 EF and 0.53 EF, respectively, to earn one LEED point.

 

Another detail to look for on gas water heaters is emissions. While only California has ultra-low NOx requirements (emission levels of less than or equal to 10 nanograms of nitrogen oxides per joule of heat output), some manufacturers are finding a cost benefit in manufacturing several of their units at low NOx rates. There are also several propane-fueled (LP) models available for builders who don’t have access to natural gas. The Propane Education & Research Council claims that LP water heaters are a greener option compared to electric water heaters. “Even though there aren’t any emissions from an electric water heater at the home site, there is a lot of coal being burned to make that electricity,” says Tom Jaenicke, energy advisor to the council.

Setting a New Standard

While tank-style units have certainly come a long way, they do have their limitations. When not in use, they produce standby losses, and, of course, they can run out of hot water. Tankless models address both of those issues, but they offer their own set of drawbacks. Tankless units have a longer payback period (15 to 20 years), and they don’t have stored capacity for high-demand periods. They also have minimum and maximum flow rates, which is especially challenging as more green homes adopt low-flow faucets and shower fixtures.
With shortcomings on both sides, it’s easy to see why manufacturers are now starting to come out with a new form of hybrid: tankless units with small storage tanks. They operate like a tankless unit, but a small buffer tank allows them to overcome some of the negative attributes normally associated with tankless models like minimum flow rates or “cold water sandwiches.” By capitalizing on the strengths of both tankless and storage water heaters, these units can reach efficiencies of up to 90%. However, because they represent a new water heater category, they do not yet qualify for Energy Star, LEED, or NGBS points.
Needless to say, this is an exciting time for the water heater industry. Innovation is at its peak and doesn’t show signs of leveling off anytime soon. A new federal rulemaking has required that as of April 16, 2015, newly built electric tank models with volumes of 55 gallons or greater achieve an EF of 2.05—an efficiency level that isn’t possible without heat-pump technology. Similarly, the ruling calls for gas tank models with volumes of 55 gallons or greater to have an EF of 0.8012, which requires gas-condensing technology. “The 2015 standards will change the way people look at large water heaters above 55 gallons,” notes Tommy Olsen, a senior product manager at Rheem.
While meeting the new standards will certainly require a lot of work on behalf of manufacturers, it’s good news for contractors. With a vast array of greener water heating options—including solar thermal—specifiers no longer have to rely on trends, but instead can choose a high-efficiency model that truly fits their needs.

Thanks to Lisa Bonnema at Eco Magazine for her article.

Central Vacuum Systems

Hello again from Olson Defendorf Custom Homes.  We are a custom home builder in Austin, Texas. 

Today's post is about central vacuum systems.  We get asked a lot about the features and benefits of a central vac.  As you will find out they are more than just for vacuuming. 

If you’re concerned with indoor air quality, you may want to take a first (or second) look at adding a central vacuum system to your IAQ package. In Canada, where windows remain shut for most of the year, these systems come standard in most new homes. Here in the United States, however, many builders still regard the central vac as an amenity and not a green building product. This opinion is changing as more builders become aware of how effective these systems can be in removing airborne irritants and allergens.
In a 2001 study evaluating the health impact of central vacuum systems on patients with house dust allergies, conducted by the University of California at Davis School of Medicine, researchers had two groups of participants use either a conventional or central vacuum system for three months and then switch to the other system. The researchers reported that in all aspects of the evaluation, including sleep, non-nasal symptoms, nasal symptoms, eye symptoms, and even emotions, the use of a central vacuum proved to be “superior,” with reported improvement in allergy symptoms ranging from 40% to 61% when participants used a central vacuum system.
Both the U.S. Green Building Council’s LEED for Homes and the ANSI National Green Building Standard (NGBS) recognize the contribution of central vacuum systems to improved indoor air quality. LEED offers one point, while the NGBS provides up to five Indoor Environmental Quality points for installing a central vacuum system vented to the outside.

Built-in Vacuum System Basics

To understand how a built-in vac would improve indoor air quality, reflect on how a conventional vacuum cleaner works. The device sucks dirt and dust off floor surfaces and captures most of that dust in a bag or canister, with the particles too fine for the filter billowing right back into the room. Even if you’re using a vacuum equipped with a HEPA (High Efficiency Particulate Air) filter, the exhaust air stirs up the dust lying on nearby surfaces, raising a cloud of irritating particles as you vacuum the room. A built-in vacuum, by comparison, captures the dirt and dust and then delivers it to a sealed canister away from the living area.

Central vacuum systems require little maintenance. Unlike conventional vacuums that leak if bags tear or become overfull, the systems have large capacity dust collectors that won’t tear or leak, so they generally won’t release particles into the air even when neglected. But to assure that absolutely no household dust is ever recycled into indoor air, the American Lung Association recommends cleaning with a central vac that vents particles to the outside of the house. Most central vac manufacturers provide this option, and many have high-quality, self-cleaning HEPA filters, such as Beam’s Gore-Tex filter system that screens particles down to 0.3 microns at 98% efficiency.
Central vacuum systems also have larger, more powerful motors than you could lug around on an upright, thereby doing a better job of deep cleaning, especially on carpets. “Central vacuums provide up to five times the suction power of a portable with 100% of the vacuumed dirt removed to a dirt canister,” says Amy Wesely, floorcare marketing manager at H-P Products.

A Three-Part System

A central vacuum system contains three major components: a power unit that holds the motor, a filtration system with a receptacle to collect the dirt, and a network of PVC pipes plumbed through the walls and floors, terminating at inlet valves where users plug in the hose for a host of cleaning tools and attachments.
In the old days, a central vacuum sweeper resembled a powerful shop vac, serving up strong suction to absorb dirt but lacking the belt-driven agitator brushes common on conventional uprights. Since the 1990s, central vacuum tools have improved. They now include powerful electric or air-driven turbine brushes, plus a wide array of convenience accessories from crevice tools and upholstery cleaners to concrete patio scrubbers and pet grooming kits.
The heart of the central vac comes at the power unit, the canister-like element that hangs on the wall and holds the motor and filtration system. Within the canister, a powerful electric motor spins a turbine, creating suction. The power of vacuum systems is measured by “water lift” and air flow. Water lift represents the sucking force the vacuum exerts when applied to a laboratory water column, gauged by how many inches the water in the test column rises. Air flow is measured in CFM, or cubic feet per minute, of air flow without resistance.
A mathematical formula called air watts combines water lift and air flow to rate the overall power (watts) generated by the vacuum. Air watts is recognized by the American Society of Testing and Materials (ASTM) as the best way to measure the actual cleaning force of a vacuum system. You won’t find the Energy Star label on any system. “As an industry, it hasn’t happened because it’s an appliance that runs intermittently without great impact on energy consumption,” says Brian Campbell, product development manager at Electrolux.

Choosing the System

The first step to selecting a central vacuum system is matching the system’s air watt rating to the size of your house. Most manufacturers offer a motor-to-house-size compatibility table to make the calculation easy. When evaluating product quality, select a system with sealed bearings (to keep the dirt out), bypass cooling (a separate stream of air that cools the motor apart from the air that draws in dirt from the home), and the longest warranty available—the longer the warranty, the more confident the manufacturer is about the product.
To qualify for LEED certification points, the filtration system should include a HEPA filter and the option to pipe the exhaust outside. While some manufacturers say the exhaust air in their system is so clean this final precaution is unnecessary, all of the leading air quality certification criteria, including LEED and NGBS, require outside venting.

Noise level is another consideration. Although central vacuum systems’ remote motor location means you can carry on a conversation while vacuuming, quieter systems, as measured in ASTM-tested decibels, indicate better quality in the components used to manufacture the product. Noise reduction usually entails a combination of better motor components, more insulation, and sturdier housing. Mufflers, which mount at the exhaust port, can be purchased both from the manufacturers and after-market accessory suppliers.
Filtration systems come in three basic types: vertical, cyclonic, and inverted. The vertical bag system resembles a conventional upright, collecting dirt and dust particles within a paper bag for disposal. The cyclonic system uses centrifugal force to separate particles from air flow, depositing dirt and most of the dust into a dirt canister for disposal. It requires no added filter, but it must be vented outdoors, as the cyclonic system will not sequester the finest particles. The inverted filter system is similar to the vertical bag, except air is drawn up and across the filter (instead of down into it), allowing gravity to “self-clean” the bag as particles drop off the medium and into the collection bucket below when the system is turned off. The cleanest systems combine cyclonic filtration with a high-quality HEPA filter.
The basic “plumbing,” the tubes and fittings that deliver suction, are generic, much like water pipe that works with any brand. In fact, one manufacturer, Hayden, makes most of the thin-wall PVC pipe and fittings used with all major central vacuum systems. Although it resembles drain pipe, central vac tubing is thinner and of a different diameter, so the two are not interchangeable. Unlike heating ducts, the length of the installation, while consuming more resources, will not appreciably reduce performance. The vacuum remains as powerful at 30 feet from the motor as 3 feet, according to Campbell.
Valve inlets open the airway or seal the system when not in use. The inlets include a low-voltage coupler, which serves to trigger the on-off switch at the motor when you depress the start button on the handle. In new construction, you can also wire for line voltage at the valve to power the agitator brushes for vacuuming carpet. In a retrofit, install the inlet valves within 6 feet of a receptacle to plug in the accessory power cord.
When laying out the valve locations, double-check to ensure you can reach all cleaning surfaces with the standard 30-foot hose. For most floor plans, you’ll need one inlet per 750 square feet of floor area. It’s best to actually survey the cleaning area with hose and handle in hand before deciding on the final location of inlets. You’ll have to supplement the central vac with a conventional lug-around if the inlets aren’t accessible all over the house.

The final consideration for central vacuuming systems is choosing the tools, which include air-powered turbine brushes for hard-surface floors and electric-motor brushes for deep pile carpet. A quiver of hand tools are available to clean crevices, window treatments, ceiling fan blades, car interiors, patio slabs, and pets.
One manufacturer, H-P Products, tackled the most daunting aspect of central vacuuming—hose management—by providing a self-retracting hosepipe. Most manufacturers offer quick-clean amenities, such as Beam’s toekick fitting that sits under a kitchen cabinet for cleaning of spills.
This may all sound like consumer-experience-driven, razzle-dazzle product development, but remember that the most important aspect of any green building component requiring human interface is use. If your central vacuuming system works well and provides convenience, then the homeowner will use it—and breathe all the better.

Thanks for EcoHome Magazine for the article.  Click below to the website.

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