Tag Archives: CCHRC

UAF Sustainable Village Weeks 15-16: solar hydronic

Is it just us, or is this summer going fast?

As the daylight wanes to only 18 hours a day, we are getting situated to capture this heat at the Sustainable Village. The solar collectors are up on the northeast and southeast homes, which both have three 4-foot-by-10-foot collectors mounted on the south-facing wall just under the roof. The system will feed heat into radiant tubing in the concrete floor slabs, and will also dump heat into a 120-gallon solar storage tank in the house. We are adding temperature sensors and flow meters to each system to monitor how much heat is used.

Also, the homes have skin (for the most part), i.e. metal siding. Two green, one blue, and one gray with patches of other colors and salvaged dredge pipe. They look cheerful and also at home in the spruce forest.

 

UAF Sustainable Village Week 14: Sheetrock, insulation & siding

We continued siding, insulating, and Sheetrocking in Week 14. We began hanging a reclaimed steel siding that came from old dredge pipe in the surrounding area. It will provide an accent to the metal siding, adding a cool aesthetic and historical value to the homes.

http://makinghouseswork.cchrc.org/

I’ve seen more solar panels around Fairbanks lately. How do they work and what are the different types?

CCHRC has a 12 kW photovoltaic array that is tied to the utility grid.

Solar is a growing resource in Fairbanks, and there are two different types of panels you may be seeing around town: solar photovoltaic, which generate electricity, and solar thermal, which generate heat for space heating or domestic hot water. CCHRC uses both types of panels at the research center. While they both turn sunlight into energy for your home, they have very different applications. Considering your site conditions and heating, plumbing, and electric systems will help determine if one (or both) technologies would work for you.

 

What’s the difference?
Solar thermal, or solar hot water, collectors absorb heat from the sun and transfer it to water or glycol to provide space heating or domestic hot water.

The two most common types are flat-plate collectors and evacuated tubes. Flat-plate collectors are the oldest and most dominant type of solar thermal. They generally consist of a 4×8-foot glass-encased panel that contains a thin metal sheet, with a dark coating to absorb energy. Beneath the sheet are coils filled with the heat-transfer fluid. Insulation lines the back of the panel to maximize heat transfer to the fluid. Fluid circulates through the tubing, absorbing heat and then transferring it to a storage tank. A typical residential system used to supplement domestic water heating includes two panels.

An evacuated tube collector contains several rows of glass tubes connected to a header pipe. Each tube is a vacuum, which acts like a sealed thermos and eliminates heat loss through convection (due to wind). Because of this, evacuated tube collectors lose less heat to the environment than flat-plate collectors.

A small copper pipe filled with fluid (glycol, water, or some other antifreeze) runs through the center of the glass tube. The fluid heats up, vaporizes, rises into the header pipe, and transfers heat (through a heat exchanger) to another pipe filled with fluid. This fluid carries heat to the storage tank. From here, water can be used for hydronic heating and domestic hot water or converted for other uses.

Solar power
Solar photovoltaic (PV) panels convert sunlight into electricity. They have a silicon sheet that is made up of semiconductors. When light strikes the sheet, part of the energy is transferred to the semiconductors, which knocks electrons loose and allows them to flow freely through connected wires. This flow of electrons is called direct current (or DC). The current then flows into an inverter, which changes it into AC (alternating current), the power used by your appliances. This current can either be used to power appliances (if there is demand), stored in a battery, or returned to the electric grid.

Cold Climate Specifics
Fairbanks is a unique place for solar energy because of the excessive summer sun and the virtual darkness in winter months, which means a few months a year where solar doesn’t contribute much. For example, the 12-kilowatt photovoltaic array at CCHRC produces more than 10,000 kWh from March-September (about 30 percent of the building’s electric demand) but only 1,833 kWh during the rest of the year.

Most households with solar thermal systems use them to offset their primary heating sources. If you want to use solar thermal as a main source, you need some type of seasonal thermal storage system to bridge winter months. PV systems simply offset electricity purchased from the grid in most cases.

With PV, you can produce more power from your panels year-round if you keep them free of snow and change the tilt angle twice a year. The most productive months for CCHRC’s panels are April and May, when they enjoy long daylight hours and also capture reflected solar gain off the snow cover.

Different types of solar thermal panels perform better at different times of the year. For instance, evacuated tube collectors produce more BTUs during the spring and fall shoulder seasons, while flat plate collectors produce more heat during the summer.

Which ones are better to install?
A 1,000 watt PV array will produce about 1,000 kWh a year in the Interior, offsetting $210 in electricity at today’s rates. A two-panel solar thermal system could produce roughly 7 million BTUs a year, offsetting either 54 gallons of oil (saving $215) or 2,050 kWh of electricity (saving $410). In other words, homeowners with electric water heaters stand to save more from solar thermal than those heating with other fuel types.

The actual cost of solar thermal in Interior Alaska (roughly $4-$5 per installed kWh) is lower than solar photovoltaic (approximately $8-$10 per installed kWh). Yet PV panels are still more common in Fairbanks largely because they are easier to install and retrofit, don’t require plumbing, don’t have to be integrated into existing mechanical systems, and have no moving parts (whereas solar thermal systems have fluid and pumps that must be replaced over time).

The actual output and cost of your system will depend on many factors, like the solar exposure of your particular site, the type of heating or hot water system, the type and number of heat exchangers required, and others.

With the cost of conventional energy on the rise, solar is becoming an increasingly attractive long-term investment. Anyone with good solar accessibility may be wise to consider these systems as an option.

Decoding Boiler Terms

It’s easy to get lost in the jargon when shopping for a boiler or other home heating appliance. This article covers some of the common terms you may encounter when shopping for a combustion boiler. If you have questions about what type of boiler is best for you, be sure to talk with a heating professional.

Most oil boilers are mechanical draft boilers, which use a fan to draw in combustion air. There are two main methods of mechanical draft that are common in residential models.
–Induced draft uses a fan to remove flue gases from the furnace and force exhaust gas up the stack (and usually operate at a slightly negative pressure).
–Forced draft uses a fan and ductwork to force air into the furnace, and usually operates at a slight positive pressure.

In mechanical draft boilers, the fan also creates turbulence in the combustion chamber, allowing for a more complete burn. These are typically more efficient than natural draft boilers.

Natural draft boilers rely on the buoyancy of hot combustion exhaust. The exhaust is hot, so it rises passively out of the flue. As the hot exhaust gases exit upwards, the draft causes fresh air to enter the combustion chamber. Because natural draft boilers consume a large amount of air in this process, they are less efficient than mechanical draft boilers. If the air pressure inside the house is less than the air pressure outside, a natural draft boiler can backdraft and poisonous gases such as carbon monoxide could potentially enter the home.

Examples of natural draft heaters are propane water heaters and drip-oil stove heaters.

Sealed combustion boilers use a duct to bring in outside air directly to the combustion unit and not from inside the house. The combustion chamber (where burning occurs) is sealed off from the inside of the home. These boilers are safest, because they are unlikely to backdraft poisonous exhaust gases such as carbon monoxide (CO) into the home.

Condensing boilers are more efficient than standard combustion boilers. A condensing boiler is able to reclaim additional heat from the exhaust gas by cooling it to a point where water vapor from combustion condenses out. The condensation releases the latent heat from the gas, and this heat is captured by a second heat exchanger. The condensate water is acidic (it has the same acidity as some vinegars), so corrosion-resistant materials like stainless steel or PVC pipe must be used for the heat exchanger and pipes. Condensing boilers must have a drain that allows the water to enter the wastewater plumbing system. In older homes with pipes that could corrode, a neutralizing filter can be added to the drain line. These boilers also have a fan to blow the cooler exhaust gas, which is not buoyant enough to exit the flue on its own, outside the building.

Non-condensing boilers are less efficient because they have to operate at higher temperatures to prevent condensation. However, they do not require a drain and can be made of materials such as iron, steel or copper that would eventually corrode in a condensing boiler.

High mass boilers are very heavy, as the name implies. The mass comes from a large heat exchanger, which contains heavy metal, often cast iron, and large diameter pipes that contain a high water volume. The high mass design helps the boilers maintain steady state efficiency. These boilers take longer to heat up when they are started, so they should not be short-cycled, or turned on and off frequently, as this will lower their efficiency.

Low mass boilers have a smaller heat exchanger that does not contain a large mass of metal or iron. While short-cycling a boiler (or turning it on and off frequently) is never ideal, a low-mass boiler will generally respond better than a higher mass design, as it takes less time to heat up. These boilers also have less standby loss when they cool down, because they do not have the mass to retain a lot of heat while firing.

How does user behavior make a difference in my home’s efficiency?

Many people focus on the building envelope – the amount of insulation in the roof, the R-value of the walls, how many panes the windows have. Others think first of appliances – is the refrigerator certified as an ENERGY STAR appliance? What is the efficiency of the boiler? Does the hot water heater have a high energy factor? Are the lights incandescent bulbs, LEDs or CFLs?

Certainly all of these things have a role in making buildings energy efficient. However, there is an even more important factor that is often overlooked–the behavior of occupants. An oft-repeated saying in the building industry is “There is no such thing as a zero-energy home, just zero-energy homeowners.” Efficient buildings can’t reach their full potential if residents have energy-intensive habits. On the other hand, inefficient buildings can see large performance improvements just by changes in residents’ habits.

There are two main parts to energy efficient behavior: the types of appliances you buy and the way you use them. For example, do you own a large-screen plasma TV or a modest one? Both your consumer decisions and pattern of use play into your personal energy efficiency. For example, if you buy a 15-watt CFL floodlight and keep it on all the time, you may still actually use less than a 75-watt lamp that you turn off when not in use.
When it comes to your habits, remember what your mom and teachers probably used to tell you: Turn off lights when leaving a room; don’t leave the faucet running when you brush your teeth; take shorter showers; and put on a sweater instead of turning up the thermostat.

Changing habits can be difficult or uncomfortable, however, so there are also other options.

Many behavior elements can be addressed with technology:
· If you constantly forget to turn out the lights, or find yourself leaving on an outdoor light for hours while waiting for a spouse to come home at night, consider installing lighting controls. Motion sensors that can turn on and off lights are available for as little as $30 at home improvement stores.

· Programmable thermostats can be used to turn down the set temperature automatically while residents are away at work or asleep, and turn up the set temperature when residents are at home and awake. They can be programmed in 5 minutes – and offer savings on heating bills throughout the winter with no extra work.

· Do you have a number of devices plugged into the wall (phone chargers, TV, computer, etc.)? These devices draw a small baseline amount of current, called a phantom electrical load, as long as they are plugged in – even when they are turned off. Remembering to unplug everything can be difficult, but there are solutions. Plugging everything into a power strip means you only need to turn off one switch. Also, a smart power strip will shut off the current to peripheral devices such as a monitor and speakers when a central device, like a computer, is turned off.

· Do you have an electronic calendar on your phone or attached to your email? Use it to add automatic reminders for maintenance tasks, such as the yearly check-up on your heating appliance, or changing filters on a forced air distribution system. Remembering basic maintenance tasks improves the efficiency of equipment and prevents breakdowns.

· If you need to replace an appliance anyway, consider purchasing an Energy Star-rated one.

How else can you make your home more energy efficient? Go to www.cchrc.org or the website or Golden Valley Electric Association (http://www.gvea.com/resources/save) for more ideas.

Other resources on saving energy:
http://www.akenergyefficiency.org/
http://www.uaf.edu/ces/
http://www.energyhog.org/

Sustainable Village Week 9

During Week 9, we installed ceiling vapor barriers, continued plumbing and wiring work, and started working on the electrical hook-up for the homes. After heavy rain over the weekend, and the ground is still frozen a few feet down, the site was temporarily transformed into a mud pit. This made it interesting to navigate heavy equipment and dig a trench for the power line. Nevertheless, we will have electricity by the end of the week!

Student carpenter on her view of the UAF Sustainable Village

Takpaan Weber is a UAF student from Anaktuvuk Pass, a small Iñupiat village in the Alaska Brooks Range. She describes her experience working on the UAF Sustainable Village and other low-energy experimental prototype homes she has helped build in rural Alaska.

Sustainable Village Week 8

Framing is underway on the 4th and final house. Workers began applying ceiling vapor barriers and Grace rain and ice shields (which act as a drainage plane) to the fully framed homes. Now we’re exploring options for siding and interior finishing, looking at a combination of donated, market-value, and reclaimed materials.

Vapor Barriers & House Wraps: Where and Why

House wraps, such as Tyvek, are permeable enough to allow water vapor through but will stop bulk water like rain.

Vapor barriers and house wraps are a critical part of controlling moisture and air flow in and around your home. Working in conjunction with your walls, floor, and roof, the right type and application of these products will help you to conserve energy, prevent mold growth, and maintain the structural integrity of your home. Not using these products or using one incorrectly can wreak havoc.

 

Vapor Barriers
A vapor barrier, also known as a vapor diffusion retarder, is a layer of material designed to slow or nearly block the movement of water vapor. How much a vapor barrier impedes the movement of water is referred to as its permeability rating or, for short, “perm” rating. So it’s a bit misleading to use the term vapor barrier because many materials in this category do allow some moisture through. 6 mil thick plastic sheeting is a typical vapor barrier material prescribed by codes in extreme cold climates, as it’s perm rating is extremely low.

All homes generate moisture indoors. Cooking, bathing, breathing – all these activities create water vapor. Ventilation, which is essential to exchange moisture-laden air with clean dry air, helps to reduce the quantity of moisture in your home, but not enough to eliminate the need for a vapor barrier. Without a barrier, moisture can penetrate your walls and roof spaces.

Approximately 98 percent of water vapor in a home travels by air, but the remainder moves by diffusion – through solid materials such as the studs in your walls. When these materials become cold in winter, condensation forms and can trigger mold growth and other problems. The extreme air pressure and temperatures differences that occur in Fairbanks in winter exacerbate condensation problems. And, in the case of modern construction, tight building envelopes can serve to concentrate moisture problems in the absence of adequate ventilation.

House Wraps
House wraps, on the other hand, are designed to be permeable enough to allow water vapor to pass through them, but will stop bulk water like rain from passing through – sort of like Gortex in clothing. In addition, house wraps can help minimize the movement of air in and out of the exterior walls. Losing air from a house in an uncontrolled manner means that you are losing heat. This loss amounts to extra fuel costs and can become a burden on your budget.

To effectively repel water and reduce airflow, house wraps must be detailed correctly and applied using the manufacturer’s recommended methods and adhesives. All those protrusions through your walls such as vents, electrical connections, and architectural features must be carefully accounted for. The right types of house wraps can perform an important job in windy places by stemming significant heat loss.
Now comes the tricky part: some house wraps can also serve as vapor barriers and vice versa. Placement and permeability is also a fairly complicated issue. There may be certain cases when house wraps are not necessary, but when used are almost always placed on exterior of a house and over its sheathing.

More
The placement and permeability of vapor barriers and house wraps are addressed by building codes, but vary by region. Vapor barriers are required in Fairbanks. This article only touches on the details required to choose and install vapor barriers and house wraps. You can find resources at the CCHRC and the University of Alaska Fairbanks Cooperative Extension Service to help you make the right decisions. Doing your research up front can save a lot of problems later on.

Sustainable Village Week 6: trusses and T-shirts


During Week 6, we started framing the third (SE) house and laying out trusses for the two northern homes. Two more UAF students   began working at the site for a total of four. The crew is jelling and construction is on schedule! It warmed up to 65 degrees this week, and the T-shirts and bug dope came out. Next week we are planning to finish roofs on the northern homes and begin plumbing and electrical work. Then we’ll add sheathing and trim. Meanwhile, we’ll begin framing the fourth and final house, which will likely have the Reina Wall–a double wall with thick blown-in cellulose insulation developed by local builder Thorsten Chlupp of Reina, LLC.