Making Houses Work

A 5,000 gallon tank acts as thermal storage in a home heated by a solar thermal system. Photo Courtesy Reina LLC.

CCHRC recently completed a study on how you can use thermal storage as part of your home heating system.

Thermal storage has recently gained interest in Alaska as it has the potential to increase the efficiency of heating appliances, enhance the use of renewable energy in cold climates, and reduce emissions of certain appliances like wood boilers. It is most suited for renewable energy systems such as solar thermal, geothermal and biomass, but can be adapted to a wide variety of heat sources. The report looks at different design considerations and describes several examples in homes around Alaska.

Thermal storage is a common concept. Many households use water storage tanks to provide domestic hot water, which can range from just a couple gallons to more than 100 gallons. Thermal storage also can be used in space heating systems to store heat for a certain period of time. For example, storing the heat from solar collectors in a buffer tank to use at night; storing heat from a wood boiler in a water tank to allow for a hotter, more efficient burn; or storing heat in the ground to harvest later with a ground source heat pump. In each case, thermal storage can be thought of as a “heat battery” because it holds energy to be used later. In this way, it can enable a heat source with intermittent delivery (like the sun or wind) to still meet demand.

Every thermal storage system needs three basic components: a heat source, a storage medium to store the heat (such as a tank of water, rocks or soil), and a discharge method (heat exchanger) to distribute the heat. Technically, any heat source can be used to charge a thermal storage material, however you should select the fuel and storage material based on availability, cost and compatibility with your home’s needs.

Also, many factors will drive the design of a thermal storage system for your home — such as your heating appliance, your distribution system, your heating demand, your lifestyle and many others. The design of the system also will depend on whether the system is being installed in a new home or being retrofitted into an existing one, as retrofits must accommodate the existing distribution system and available space in the home.

There are various applications of thermal storage throughout Alaska. A net-zero heating home built in Fairbanks several years ago uses solar thermal collectors and a masonry heater to charge a 5,000-gallon insulated water tank that provides heat to a radiant floor system.

The tank also heats domestic hot water in the house.

A different system, located at CCHRC, uses a wood-fired boiler to charge an insulated 1,500-gallon tank of water in the lab. The goal was to fire the boiler hot and fast, which produces more Btu and fewer emissions, and save the heat to use when it’s needed, rather than damping down the boiler so the fire lasts longer.

The water tank heats 1,900 square feet of lab space in the building. The tank was sized to hold as many Btu as the boiler could produce in one firing per day and to provide enough heat for the entire lab over a full winter day.

If you’re considering a thermal storage system, the first step is to consider what your goal is. Do you want to use renewable energy instead of fossil fuels? Are you looking for short-term (a few hours or overnight) or seasonal storage? Systems that are recharged daily are smaller and less expensive than seasonal systems.

Check out the report for an overview of various types of systems used in cold climates, case studies in Alaska, and tips for designing your own system.

Report: www.cchrc.org/docs/reports/thermal_storage.pdf

It’s finishing time at the Sustainable Village! The devil is in the details, and we’re detailing ceilings, floors, corners, railings, trim, and everything else. The time lapse shows workers installing beautiful birch paneling on the upstairs ceiling as well as cabinets and appliances.

This week we tried a new building system at the Village–a cellulose REMOTE wall in the SW house. A REMOTE wall has the majority of the insulation value, or R-value, outside the sheathing rather than inside. Up to this point, we always used rigid foam on the exterior. But since one goal of the Village is to test new techniques for both cost and energy use, we decided to try a REMOTE wall with batts as interior insulation and 9 inches of cellulose on the outside.

The house has two sets of studs, with sheathing applied to the inner wall. The inside wall cavity is filled with a recycled batt insulation. The outer wall was wrapped in Tyvek. To insulate the outside wall cavity, we hole-sawed a 6-inch hole in the sheathing in each wall bay (on both floors) and sprayed in 12 inches of dense-pack cellulose. Those holes were patched with poly sheeting and acoustical sealant. The whole wall is 18 inches thick.

We also installed birch paneling ceilings, cabinetry, and ventilation systems in 2 of the homes. The homes are mostly sided and are starting to look very livable!

During Week 12, we insulated walls of the second house with six inches of fiberglass batting on the inside and 8 inches of foam board on the outside. We also blew two feet of cellulose insulation into the roof of the first two homes. Cellulose is made from recycled material like newspaper and cardboard.

We also began installing windows in the homes. All windows are triple-pane, low-e argon filled, designed to minimize heat loss and avoid condensation in an extreme climate.

Each home will be sided with a different color combo, with a mix of metal siding and recycled steel pipe.

Week 11 was a productive one at the Sustainable Village. Workers continued to install EPS foam (2 layers of 4-inch sheets) in three of the homes with a REMOTE wall system. We also sprayed polyurethane foam around the rim joist to seal it up.

Each home has a large, south-facing deck on the second floor. We finished the decks with a spray-applied elastomeric coating, the same stuff used for truck-bed liners, a durable, weather-proof material that is less material-intensive than wood and requires no penetrations in the ceiling. We sprayed foam insulation underneath the deck in the first-floor ceiling to create a warm thermal break.

This week we started hanging Sheetrock in the homes where we had already finished plumbing and electric. The interior is starting to look livable! Now it’s time to select 16 lucky students who will make the Village home. If you’re interested, visit http://www.uaf.edu/sustainability/sustainable-village.

Do you seek a different style of on-campus life? Do you want to know how to grow your own food? Are you excited about monitoring and reducing your energy consumption? Are you aware of your personal carbon footprint? If you answered yes to these questions, consider applying for residency for the 2012-2013 academic year at the UAF Sustainable Village!

By Cornerstone on June 15, 2012

Rendering of one home at the UAF Sustainable Village

The UAF Office of Sustainability is now accepting student applications for residency for the 2012-2013 academic year at the new UAF Sustainable Village. This opportunity is for students seeking a different style of on-campus life, wanting to know how to grow your own food and monitoring and reducing energy consumption.

The UAF Sustainable Village, UAF’s newest student housing, is a student-led and -driven initiative. Students have been integral to all stages of the process: from concept to design to construction. It is a demonstration of environmentally sustainable technologies in a residential setting and will provide hands-on experiential learning opportunities. Students will collect and disseminate information about sustainable building and living best practices, and encourage others to live in a more sustainable way.

The Sustainable Village is open to UAF students, sophomores through graduate. Students interested in living in the UAF Sustainable Village for the 2012-13 academic year need to complete this form and attach a signed UAF Sustainable Village Social Contract /Agreement. Selection is based on application and an interview with the Sustainable Village Committee.

Students interested in being part of the innovative, nationally recognized Sustainable Village and feel personally committed to sustainability, are encouraged to sign up. For more information visit the Sustainability Village website for more information or contact sustainability director Michele Hebert at mahebert@alaska.edu or 907-388-6085.

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.

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.

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.

A simple do-it-yourself rainwater catchment system.

Installing a rain barrel to collect rainwater for non- potable uses is an easy way to help the environment and save money. Water collection systems can be as simple as a rain gutter directed into a barrel or as sophisticated as a buried tank supplied by multiple sources with filtration and pump systems. The easiest way to collect rainwater is to catch it as it drops from your roof and eaves. Of course, this works best if your home has large roofs fitted with gutters, but even a small roof can collect significant amounts of rain.

For every square foot of roof, you can collect a little more than a half-gallon of water per inch of rainfall. Fairbanks has an average of 10 inches of rainfall a year (some years much more, others much less). This means a small cabin in Fairbanks with a 1,000-square-foot roof can collect about 5,000 gallons of water per year–more if you collect snowmelt in the spring.

One thing you need is a tank. Storage tanks can be fiberglass, wood, steel, concrete, plastic, or another material, though plastic tanks are by far the most prevalent in Alaska. If the system will store water during the cold seasons, then outdoor tanks and lines need to be insulated to protect from freezing. Buried tanks should be at least four feet below-grade and are often protected by a top layer of insulation to prevent freezing.

You can often find small above-ground storage vessels at feed stores, or companies that deal in fuel storage, which sell everything from 15 gallon-60 gallon plastic barrels, some with spigots and some without. You may be able to purchase a much larger used tank from local excavation companies (the professionals who install domestic water holding tanks and septic systems) as they replace underground storage systems from time to time. Large new tanks can be found at plumbing stores, excavation companies, or local tank manufacturers.

A basic cistern system involves a series of gutters and downspouts that converge at a centralized collection point that in turn leads into the tank. If the tank is above ground, it may be beneficial if it is fitted with a drain valve and an overflow diverter. Provided the tank is elevated above the demand source, you can use a gravity-fed system to move water. If the tank has access from above, you may be able to move water with a submersible pump attached to a hose. The pump will provide more pressure and a consistent flow rate. Over time, the tank will fill with sediment, which will require cleaning periodically. Also, it’s a good idea to empty and clean the tank each year. This will help control algae growth, but also prevent damage due to freezing in winter. Be sure you support the tank adequately – just one gallon of water weighs around 8 pounds.

In general, the natural process by which rainwater is formed causes it to run slightly higher in acidity. In addition, the characteristics of your particular rainwater can be affected by sulfur and other pollutants in the air (if present), your roofing material, and any debris that may collect in the catchment system such as leaves, pollen, and bird droppings, for example. Downspouts, gutters, or the tank’s opening can be fitted with screens to keep large debris out of the system. More advanced systems include a trap to minimize unwanted matter from getting into your main tank. A trap is basically a smaller tank containing baffles. Water enters this smaller tank first and filters out sediment and other materials. You may want a system for diverting water from the collection system until a good rain has had chance to wash your roof of heavy pollen or other accumulations.

Consider what your roof is made of and ask the manufacturer to make sure your roofing materials are not toxic. It’s possible that old roofs may use asbestos shingles or other toxic materials.

If you’re considering a permanent catchment water distribution system, the acidity of the rainwater may need to be adjusted to reduce the long-term corrosive effects of the water on metal plumbing components.

If you are looking into building an advanced water catchment system, consider going just a few steps farther. Fitted with additional filters and plumbing, a cistern can provide grey water for indoor use and in some cases, drinking water.

For information on designing a system, check these resources:
Rain Barrel Construction by Cold Climate Housing Research Center, GW Scientific, City of Fairbanks, and Fairbanks Soil & Water Conservation District: http://cchrc.org/docs/green_inf/Rain_Barrel.pdf
Water Cistern Construction for Small Houses by UAF Cooperative Extensive Service: http://www.uaf.edu/files/ces/publications-db/catalog/eeh/HCM-01557.pdf
Information on Best Management Practices for rainwater catchment in Alaska: http://cchrc.org/docs/best_practices/BMPRWcatchment.pdf
Other ways to reduce rainwater and pollutant runoff on our website at http://cchrc.org/green-infrastructure.