Tag Archives: CCHRC

How do tankless hot water systems work and are they really more efficient?

Tankless hot water systems, also known as on-demand heaters, only produce hot water when you call for it—by turning on the sink, shower, or other appliance. They heat water instantly as it runs through a pipe and deliver it to your point of use, so you don’t have to store hot water in a tank and heat it all day. These on-demand heaters can be powered with propane, natural gas, or electricity.

You can save energy with this kind of system because you’re not paying to heat water when it’s not being used and you eliminate stand-by heat losses. Another benefit is that you never run out of hot water, unlike a tank system.

But a tankless system is prone to control and pressure issues. One problem is that on-demand heaters can produce bursts of cold water. For instance, if you finish taking a hot shower and turn off the water, the heater will shut off but the water in the pipes will remain warm (because they’re insulated). Yet the water inside the heater will cool off. So the next bather thinks the water is hot, jumps in, and soon gets a blast of cold water making its way through the pipes.

Another limitation of tankless heaters is that they can only heat a certain amount of water per minute. So if the washing machine is turned on during a shower, the hot water is split between the two uses, reducing water pressure all around. The good news? Both of these problems can be solved by adding a couple accessories to your system.

You can prevent cold bursts of water by adding a small, 2- to 10-gallon electric water heater (like a mini water tank) in between the tankless water heater and the point of use. This creates a buffer between sections of chilly water and your showerhead. The heater and installation will cost about $450.

The pressure issue can be fixed by adding a large pump to the system that can push enough water through the heater to accommodate multiple hot-water users at once. Adding the pump will cost about $650.

These add-ons drive up the price of a tankless system from around $300 (for the low end) to more than $1,000. Meanwhile, a hot water tank costs between $200 and $900. If you can live with idiosyncrasies like variable temperature and pressure, and don’t want the add-ons, then the tankless system will pay off in just a few years (thanks to energy savings). If you desire a system that is free of idiosyncrasies, the payback period will be much longer.

Emergency Housing at Crooked Creek

CCHRC staff examine flooding damage at Crooked Creek homes

CCHRC is working on a housing project in the village of Crooked Creek that symbolizes a new way of responding to disasters in rural Alaska. The Kuskokwim River flooded the village in May, damaging or destroying half the homes in the town. The Alaska Division of Homeland Security and Emergency Management asked us to quickly design nine new energy efficient homes that could be built before winter.

 

We’ve created a design that is simple—it can be built by the many volunteers involved—flexible—it can be applied to homes with different sizes and floor plans—and tight—it can be heated with far less fuel than existing homes. The entire structure-walls, floors, and roof-will consist of a single system of 2x4s, so the homes will be quick and easy to build. This project is a milestone for rural housing because it adds an energy efficiency focus to the emergency-response building process. It recognizes that even replacement housing needs to be efficient, climate-specific, and durable.

We’re adapting techniques from prototype houses that we’ve tested in other villages, like Anaktuvuk Pass and Quinhagak, such as spraying foam insulation against metal siding to create a complete thermal envelope. The building sites will be elevated above the floodplain on gravel pads.

This is part of a larger plan with the Alaska DHS&EM to create regionalized, grab-and-go models that can respond to different disasters all over the state.

Our project partners include the Alaska DHS&EM, the Village of Crooked Creek, the regional corporation Calista, AVCP Regional Housing Authority, and Samaritan’s Purse.

How to heat your home using the cold ground

Our new report shows that ground source heat pumps are an effective and affordable technology for parts of Alaska, including Fairbanks, Juneau and Seward.
In this video, CCHRC researcher Colin Craven discusses how heat pumps work and what you have to think about before installing one in Alaska.

Is a hot water heater blanket always more efficient?

Putting a blanket on your hot water heater saves heat that you would otherwise lose to the air, a process known as jacket loss. But in some cases, allowing your hot water heater to shed heat could be more efficient than space heating. It depends on the type of hot water system and heating systems you have, how efficient they are, how much water you use, and many other factors.

Our building science research team is studying the interaction of these systems to determine when a hot water blanket is helping, or hurting, your overall home efficiency.

“Our theory is that it depends on the circumstances, and you can’t make an absolute general statement of one over the other on any of these questions,” says CCHRC building energy economist Nathan Wiltse.

We will simulate a highly efficient home, where any difference in energy use could likely be attributed to appliances. We will use energy models to test various configurations—water tanks versus on-demand heaters, high versus low water usage, boilers versus furnaces, the temperature settings of these systems, etc.

For instance, what if you have a radiant floor system set at 110 degrees, and a hot water heater set at 140 degrees? You may assume you’re better off using a hot water heater blanket, because it requires more energy to maintain the hot water tank at 140 than the floor loop at 110.

But if you have a 65-percent efficiency boiler and a highly efficient water heat, it may actually be better to allow those jacket losses. We won’t know til we run the simulations.

We’re going to create a matrix of the scenario results to show a number of the factors at work. We plan to share it sometime in January, so you can compare your own home heating information and see what might be the most efficient for your house.

Press Release: Report shows heat pumps economically viable in Alaska

laying the ground loop at Weller Elementary School

Ground source heat pumps offer an economically viable heating option in some places in Alaska, according to a new report from UAF’s Alaska Center for Energy and Power and the Cold Climate Housing Research Center.

The study found that the systems, which extract heat from the earth, are technically and economically viable in areas with high heating costs and low electric costs. The report, funded by the Denali Commission, offers the first in-depth assessment of ground source heat pumps in Alaska.

“There recently has been quite a bit of excitement about ground source heat pumps, as people are seeking more affordable heating options. Our report helps explain the technology in the context of Alaska, and analyzes its potential throughout the state,” said co-author Colin Craven, head of product testing at CCHRC.

There are roughly 50 heat pumps in Alaska, including high-profile commercial installations at Weller Elementary School in Fairbanks and the Juneau Airport Terminal as well as several residential installations around the state. A heat pump transfers energy from the earth or water to use for heating or cooling. The system consists of underground tubing filled with heat-transfer fluid, an electric pump and a heat distribution system.

Researchers reviewed the industry in Alaska, interviewed ground source heat pump owners and assessed the performance and economic viability of the technology in five cities: Fairbanks, Anchorage, Juneau, Bethel and Seward. They compared the cost and performance of heat pumps with traditional heating systems in an average-sized new construction home in each city. They found that heat pumps could match or beat other heating systems in Fairbanks, Juneau and Seward.

“Even though the ground source heat pumps have high up-front capital costs, which is what deters people from installing them, they end up costing less over 15 years just because you save so much money on annual energy costs,” said Dominique Pride, graduate researcher at ACEP and co-author of the report.

The systems are most economical in Juneau and Seward, where heating oil is expensive and electricity costs are low. They also potentially make sense in Fairbanks, which has more expensive electricity than Southeast and Southcentral but also higher heating demand and costs, thus more room for energy savings.

The analysis found the pumps are not economical in Anchorage, which has low heating and power costs thanks to inexpensive natural gas. And they are not viable in Bethel and most of rural Alaska because of its extremely high electricity costs.

In addition to economics, researchers looked at cold climate considerations on system performance, including the impact of ground source heat pumps on soil, as extracting heat could create more permafrost if the ground temperature doesn’t recover in the summer. Researches plan to install a pump at the CCHRC next year to further study the effects and viability of the systems.

CONTACTS: Julie Estey, 907-590-0879. Molly Rettig, CCHRC communications coordinator, 907-450-1772, molly@cchrc.org. Marmian Grimes, UAF public information officer, at 907-474-7902 or via e-mail at marmian.grimes@alaska.edu.

Which energy efficiency investments are best for my house?

foam insulation on the wall of CCHRC's Mobile Test Lab

That’s what an energy model will tell you.

How much insulation to use is one of the most common questions in the construction industry–among both contractors and homeowners. A steady increase in energy prices, along with growing material costs, makes it important to find the sweet spot between energy efficiency and affordability.

The Alaska Housing Finance Corporation provides standards, called Building Energy Efficiency Standards, or BEES, for different regions of Alaska to help guide these decisions. Home builders using AHFC mortgage loans must comply with these standards, but they also provide a good reference for anyone building in Alaska.

An energy model will tell you if you meet these standards. It’s a computer modeling program that runs a series of heat-loss and performance calculations for every single component of your house. You plug in the dimensions and construction details of all the exterior walls, roof, windows, foundation and floor, along with info about your heating and electrical systems, and you end up with a model of your home’s performance. The program also factors in climate data. You can change insulation values, construction types, heating appliances, and fuel prices to test a variety of conditions.

The best time to do the modeling is before you build, as it gives you the most flexibility to make changes. The best approach is to hire a state-certified energy rater to plug your house plans into the program, which should run between $350-$700 (but probably toward the lower end). You are required to get an energy rating anyway if you are using an AHFC funded mortgage loan to make sure you meet their standards. If you want to try energy modeling yourself, you can download a public copy of the AK Warm modeling program here (the one used in the state of Alaska).

Energy modeling is a powerful tool that can provide long-term savings and peace of mind with minimal up-front investment. Remember, though, that occupant behavior and awareness will also have a great impact on your home’s performance. A house bursting at the seams with teenagers will perform differently than the same one occupied by a retired couple.