The lightweight cement-fiber tiles for roofing have a relatively low embodied energy over a 60-year life cycle compared to other roofing options mainly due to the durability of the material. It is expected that one replacement will be required over this period. The lightweight product does not require special truss design and comes in a variety of colours and profiles (tile, shingle or slate). Concrete, though it is a high emitter of greenhouse gases, has lower embodied pollution than asphalt or polymer-based products. Natural products, like slate, are excellent but costly. The cement-fiber siding was chosen for similar reasons, with the addition of having a better fire rating that vinyl or wood options. Insulation was a more complicated system to assess. The fiberglass batt and cellulose insulation have low embodied energy values and good insulation values. The insulation value for these materials, however, will decrease substantially if poorly installed (compressed), if they sag within the wall cavity, or if the materials become wet. Chemicals used as fire retardants or to prevent mold growth have been linked to human health issues. Some research indicates that the actual insulation value including infiltration is not a good over time as published values suggest. The urethane (that does not use ozone-reducing blowing agents) and Icynene are both derived from non-renewable petroleum resources, and both are much more costly than fiberglass batt or cellulose insulation. Urethane has the highest embodied energy due to its high density, but it also has the best insulation value. The urethane insulation is very rigid once it has cured, and has a closed cell which prevents moisture build-up. Both of these insulations seal the envelope, reducing unwanted infiltration through the envelope. At first analysis, the urethane was eliminated due to the high embodied energy, the source from non-renewable resources, and the high cost. Further analysis showed that the superior insulation value over time (and the ability to better seal the home) had an energy return. The following chart indicates that each inch of urethane added to the wall envelope reduced the heat loss. The energy return shows the number of years that it would take to offset the additional embodied energy by the heat loss reduction.  It is recommended that soy-based urethane be used in the home, with an area dedicated to Icynene for research purposes. A standard 2x6 envelope construction with 5” of urethane insulation will be used, with 8” to be installed in the roof system. The estimated energy return for the additional insulation will be approximately 8 years for the walls, and 12 years for the roof – well within the 60-year life cycle of the home. Foundation: Options for foundation design to reduce embodied energy, reduce heat loss and allow for easy routing of wiring and piping were assessed. The recommendation based on good insulation value, ease of construction, and low embodied energy was the use of Insulated Concrete Forms (ICFs). Forms produced with polymers that reduce greenhouse gas emissions and ozone depleting blowing agents will be selected. Water: The Civil Engineering Technology students enrolled in Environmental Engineering were tasked with an assessment of water reduction technologies, greywater retention and reuse, stormwater retention and reuse, and domestic water heating technologies including solar and demand water heaters. The results have not yet been integrated into the whole home design, but results favoured low-flow devices (toilets, faucets, shower heads) from an embedded energy perspective. Greywater retention and reuse was not deemed environmental at this time, though stormwater retention and reuse showed marginal but positive results. The difficulty with water is valuation. In Lethbridge water to the domestic user costs approximately $0.50 per cubic meter (or 1000 litres). About 20% of the value can be attributed directly to energy use in the purification of water and treatment of wastewater before it is returned to the river. It is extremely difficult to justify water retention and reuse systems on an energy or cost basis. For a greywater system, the energy embodied in plastic retention tanks and in the filtration and recirculation system is not recovered by the energy saved in the treatment of water through the city infrastructure. Furthermore, since a majority of this water returns to the river after treatment, it is not lost to the ecosystem or hydrologic cycle. In this case, students determined that the most environmentally responsible approach to domestic water in the city is using the existing infrastructure. Stormwater retention and reuse has similar barriers: compared to domestic treatment of irrigation water, the plastic storage tanks take a long time to ‘payback’ embodied energy. Stormwater is diverted to the river and is not lost to the hydrologic cycle, though it is responsible for higher levels of pollution reaching the riparian ecosystem. One positive aspect of stormwater retention is a temporal displacement from rainy season to dry season: Storing water on site from rains can be used to irrigate the landscape during the dry season, helping in maintaining minimum river flows. The value of a healthy river ecosystem is substantial, but difficult to quantify. The students recommended a stormwater retention system on this basis. Research in domestic hot water indicated a reasonable energy return for solar heating, and for demand heating systems. As these systems can be integrated into home heating systems, the recommendations will be discussed later in the report. An example of student work is included in Appendix C. Other student work. As part of national accreditation, the technology students are required to complete an independent research project. Two groups chose to apply their skills in research related to The Living Home: one in rainwater harvesting, and the second in the operation of a green roof. Interior Design & Merchandising students have been involved in the selection of materials for the interior of the home, which is an ongoing project for spring 2008. Multimedia students, as part of their classroom curriculum and through their practica, have designed the project logo and have created interactive animations illustrating heat loss and embedded energy for different envelope materials, and net heat loss through windows with a range of R-values. The results of these projects are available on the project website at www.thelivinghome.ca. Heating Systems: There are few options to heat a residential home. The three main approaches include: natural gas-fired furnace with warm air distributed through the home; natural gas-fired boiler to heat water which can be distributed through the home as in-floor heating or through radiators in each room; and ground source heat pumps (GSHP) systems. Assessment results indicate that the efficacy of ground source heat pumps depends on the source of electricity. In general, the GSHP system uses a constant soil temperature to gain a 4 to 1 coefficient of performance – this means for every one unit of electrical energy added, four units of heat energy is delivered to the home. On the surface, this is an attractive increase in energy efficiency, and another attraction is that the system can both heat and cool the home, as well as meet a percentage of energy demand for domestic hot water. Electricity is the source of energy required for the GSHP, and the ‘greenness’ of the electricity depends on the source of generation. In Alberta, 50% to 80% of electricity ranges is generated from coal, the remaining comes from natural gas and alternative sources depending on the demand. Coal produces approximately twice the greenhouse gases as natural gas for each kWh of electricity generated, not to mention a considerable amount of other pollutants such as heavy metal and particulates. In other words, electricity is Alberta is dirty. There are a number of schemes to make coal a cleaner technology, but “a 2007 study by the Massachusetts Institute of Technology (MIT) concluded that the U.S. Department of Energy’s main program to demonstrate large-scale CCS [carbon capture & storage] is not on track to achieve rapid commercialization of key technologies. Locating, testing, and licensing large-scale reservoirs where carbon dioxide can be stored is a particularly urgent task” (Flavin, Building a Low-Carbon Economy, 2008). There are arguments that buying green credits or green electricity will offset the negative impact of coal-generated electricity, which may have some validity for some consumers, but the design team chose to work with the present (extending into the next two decades) reality. The results shown below indicated that as electricity becomes cleaner, GSHP systems can reduce the production of greenhouse gases for home heating. Future home heating decisions will have to monitor progress in clean electricity generation.  The other options include a high-efficiency natural gas furnace or boiler. Both of these systems offer the lowest environmental impact over the next few decades. Peak natural-gas production in North America gives some pause for concern, but the impacts are complex and difficult to assess. Indoor air quality is also reduced with any combustion source within the home. Proper installation and maintenance, however, should reduce rogue emissions to a negligible level. The recommendation is to install a high-efficiency gas furnace with filtration (MERV 16 after construction to MERV 4 during occupancy) and an energy recovery device for the ventilation / makeup air. An alternative, based on final quotes, is a high-efficiency water boiler with exchange coil for air heating, or floor heating coils. One advantage of the boiler system is to integrate the domestic hot water heating system. Other Technologies: Solar heating of domestic hot water will have an energy return in less than two years, though financial payback is considerably longer. The area for solar panels is limited to the domestic hot water requirements: for an average family of four two 4 foot by 8 foot panels are adequate. This will provide 100% of the summer domestic heating requirement and 50% of the winter heating. To size the system larger will mean that the system will overheat or energy will have to be removed from the system which is illogical. The summer domestic water heating sets the limit for sizing, and this is true whether or not the panels are used for hydronic heating (since one does not generally need home heating in the summer). If solar is to be used for hydronic heating, a second system would be required – one that could be shut down and drained when not required. Solar (photovoltaic) panels also have a reasonable return on energy of less than 5 years when used optimally. Without net metering electricity back onto the grid, this payback could extend significantly (since the only return is for energy used when the home is occupied, which depends largely on lifestyle). Fortunately, Alberta has legislated that net-metering opportunities be made available for microgeneration in the home. Unfortunately, greenhouse gas emissions is not the only impact of manufacturing solar panels: roughly 13,000 litres of water is used in the creation of a 6” silicon wafer; and other pollutants are released such as arsine which affects the blood and kidney; arsenic compounds which affect the lungs and is a carcinogen; cadmium compounds which are linked to cancer and kidney disease; carbon tetrachloride a carcinogen which affects the liver and is a greenhouse gas; diborane, phosphine, and germane affect the blood, kidney and pulmonary system; hydrogen fluoride, hydrogen selenide, hydrogen sulfide which can be irritants affecting cardio and intestinal systems; lead used in soldering affecting blood, kidney and reproductive system; nitric acid, phosphorous oxychloride, selenium compounds, tellurium compounds, to name a few. It is difficult to compare the relative impacts of different pollutants on the environment, so the question remains if PV panels are environmentally friendly. Used well, PV panels will reduce greenhouse gas emissions (by making fossil fuel use more efficient), but this ignores the affect of other emissions. Financial payback is over 100 years at present electricity rates, but the costs of PV panels has been dropping rapidly while the efficiency of the arrays are improving. The recommendation is to install a 1 or 2 kWp capacity of PV panels on the home. This is a marginal decision that will be tempered by the educational opportunity. This does not support the zero-energy home philosophy of embedding large amounts of energy and pollution on a home to eliminate operating energy use. It is our view that reduction of electricity use should be pursued before the further consumption of resources to make PV panels. The recommendation for building systems includes:
Home Details & Layout: The Living Home will be located in Lethbridge in the Sunridge development. SunRidge was advanced by the City of Lethbridge as the first community of its kind employing ‘green’ building practices and technology to promote sustainable growth. The size of the home has been minimized to what the current residential market will accept. The layout also reflects current minimum lifestyle expectations. The design of The Living Home will be used as an educational opportunity to challenge some of these expectations in further residential development in the city. Plans for the home are available at www.thelivinghome.ca Ongoing Design Requirements: Concurrent with the construction of The Living Home (during Environmental Week in June 2008), the interior design of the home will be completed with recommendations for environmentally friendly furniture to be used during the open-house period. Recycling and composting facilities will also be integrated into the home design. Lighting is currently being designed to provide appropriate intensities and reducing energy demand. Appliances are being similarly evaluated for the home. Landscaping will include porous surfaces for decks, sidewalks and driveways; xeriscaping with drought tolerant plants appropriate to the region. Deer-proofing will also be integrated into the design. The garage will include a green roof that is accessible from the home to promote and research the technology, and provide an enjoyable space outside. Fencing options will be also evaluated. Research:During the construction of the home, the research phase of the project will be initiated, beginning with a waste identification and measurement project. Efforts will be made during construction to reduce waste. The waste that is produced will be measured and diverted from the landfill, if possible. We have invited Alberta Environment to use this home in a pilot study for Construction & Demolition (C&D) waste, which is a current initiative of the government. Multimedia students will be supported in a time-lapse photography project of the home construction, as well as creating construction video to identify efficient and effective building practices. The students will also be populating the project website with current information to promote communication with the community. After construction, the home will be monitored for indoor air quality, and the consumption of utilities like electricity, waster and natural gas. A post-occupancy study will continue the data-gathering with people living in the home. These results will be compared with a ‘control’ home over the same period. The project team presented at the district Teachers’ Conference in 2008 and invited interested schools to design research projects that could be integrated into the home. All results will be provided as open source through a creative commons – the data and interpretation of the data will be transparent to everyone in order to promote objective discussions around the efficacy of the design decisions. The purchase of instrumentation and services required for research has been generously supported by the Alberta Real Estate Foundation (AREF), and AACTI. Fiber-Cement Tiles/Slate-Like Roofing: Environmental Benefits and Consequences Jeff Hilliard [with permission per FOIP] Lethbridge College This paper will examine the environmental benefits, and consequences, of using Fiber-Cement Tiles/Slate-Like Roofing compared to the industry standard. I studied the manufacturing process of this material, the raw resources used for production, the embodied energy and pollution, and the overall impact of these tiles on the environment from the cradle to the grave. I advocate the use of Fiber-cement tiles in the continually expanding construction industry. The following presentation supports my proposal, and contains information on raw materials, the manufacturing process, cost, embodied energy and pollution and the life cycle of the material. John Morley once said, “[n]ature, in her most dazzling aspects or stupendous parts is but the background and theatre to the tragedy of man”. At our present rate of global industrialization, any environmental efforts put forth by independent campaigning organizations to preserve our fragile ecosystem seem futile. With such doomsday theories as Global Warming becoming a reality, it is becoming more likely that the daily wonder of nature we take for granted may escape our future generations. That is why I believe we must seize every environmentally friendly option in our everyday lives in order to preserve nature for the children of tomorrow. And where better to start than with the construction of our own homes? New age materials, such as Fiber-cement tiles, are manufactured with the purpose of being environmentally friendly. Even though some consider them high in toxicity and a contributor to greenhouse gas emissions, Fiber-cement tiles should become the status quo in the roofing industry. The advantages of their use are numerous and significantly overshadow any detriments. These tiles are reusable, highly durable, efficiently produced and long lasting. This paper is the investigation of the environmental benefits of using Fibre-cement tiles in place of the industry standard. When looking for a material comparable to the classic wood shingle, one need not look further than the Fiber-cement shingle. Although they have only become readily available for consumer purchase over the past couple of years, they are already considered a synthetic equivalent to the wood shingle (Lippiatt, 2007, p.135). The production process requires less cement than the traditional tiles and bricks on the market and is able to make use of readily available fibers. The finished product is lighter, stronger and costs less than the industry standard. This new age material also displays a long list of properties beneficial to the construction industry. A common misconception about Fiber-cement tiles is that the cheaper production costs result in a lower quality material, but this is not the case. These tiles have a significantly longer life span than wood or asphalt products. Lippiatt (2007) deduced “[f]iber cement shingles are composed primarily of portland cement, fly ash, organic fiber and fillers” (p.136). Figure 1 provides a look at the comparative percentage of these and the other product components.  Descriptions of the constituents listed in Figure 1 are described in the BEES 4.0 manual:
The manufacturing process for Fiber-cement is quite straight forward; however, a special machine called a vibrator and the appropriate moulds need to be purchased (TILZ, 2005, p.1). According to Lippiatt (2007), “[f]iber cement is manufactured by blending the raw materials; the blend is then cured to produce shingles. Energy- of the types and amounts given below [in Figure 2] - is required for blending and curing of the final product” (p.137).  Lippiatt (2007) also states:
It seems that nearly every new age material on the market today is either made from recycled materials or can be easily recycled itself, but this just isn’t the case for Fiber-cement tiles. They are neither made from recycled materials nor able to be recycled after they’re replaced. “When the shingles and underlayment are removed…all materials (shingles, underlayment, nails) are assumed to be disposed of in a landfill, and are modeled as such” (Lappiatt, 2007, p.139). Since Fiber-cement tiles are still relatively new to the consumer market, I wasn’t able to find a price through domestic distributors. It may prove beneficial to look at some out of country suppliers. While conducting my research, I came across an article stating that the United States and Chile have superior manufacturing techniques (Asbestos-Institute, 2007, p.1). Another benefit that comes with using Fiber-cement tiles is its impressive list of user friendly properties. Infolink (2007) examines the Eternit Slate tile from manufacturer FA Mitchell:
Embodied energy refers to the amount of energy required to process all aspects of a material. It is usually measured in MJ/m^2, and can be determined by multiplying the weight of the material (kg/m^2) by the energy required (MJ/kg). This equation yields an output of 47.62 MJ/m^2. According to the website Greenspec (2007), this is a relatively low and environmentally friendly embodied energy. Embodied pollution is the amount of pollution created when manufacturing a material. I wasn’t able to find any numerical values for the production of Fiber-cement tiles, and although Lippiatt (2007) stated no waste was generated, it can be safely assumed that a significant amount of pollution is generated from the transportation of the raw materials alone. Production of a material hardly ever comes without pollution. Depending on your source, the life span of Fiber-cement tiles is between 25 years to 45 years. When the time does come to replace your roofing, be sure that a new layer of organic felt is applied as the underlay beneath the new shingles (Lappiatt, 2007, p.138). A cradle to the grave representation of Fiber-cement tiles can be seen in Figure 3.  As stated before, after the shingles and underlayment are removed, they are to be disposed of in a landfill (Lappiatt, 2007, p.139). Due to its notable list of properties, low embodied energy and use of readily available and environmentally friendly raw materials; I believe Fiber-cement tiles could have a positive impact on both the construction industry and the environment. However, since they are still relatively new to the market, they still have some wrinkles that need to be ironed out. I was unable to find any information on pricing of this material, or the pollution associated with its production. These are two of the most vital aspects designers have to consider when choosing a material to use on a project, and their absence has left a void in my research. Therefore I cannot recommend this material take the place of the industry standard at this time. Hopefully the trend continues toward new age and environmentally friendly materials, so that we may preserve nature’s beauty for future generations. Eternit slate from FA Mitchell. (2007, July). Retrieved November 7, 2007, from http://www.infolink.com.au/articles/Eternit-Slate-from-FA-Mitchell_z61258.htm This source provides an extensive list of properties for fibre-cement tiles. It also provides a brand and manufacturer name for the tiles. Fiber-cement tiles. (2005, August). Retrieved November 7, 2007, from http://tilz.tearfund.org/Publications/Footsteps+21-30/Footsteps+21/Fibre-cement+tiles.htm This source gives detailed information on the production and properties of the material. It also gives the name of a distributor of the needed production equipment. Lippiatt, B. (2007). Generic fiber cement shingles. Building for Environmental and Economic Stability Technical Manual and User Guide, 4, 135-139. This source provided extensive information on Fiber-cement shingles. The information ranged from life cycle to raw materials. Old-world roof tile tradition and the fibre-cement industry: a winning combination for Chilean roofing products manufacturer. (n.d.). Retrieved November 7, 2007, from http://www.asbestos-institute.ca/rooftile.html This source provides an example of how fibre-cement tiles can be used in place of the industry standard. It also provides information on what the tiles are made up of. Pitched roofing materials compared. (2007). Retrieved November 11, 2007, from www.greenspec.co.uk/html/materials/pitchedroofs.html This source provides an overview of Fiber-cement tiles. It also includes information on embodied energy. Thermal and moisture protection > siding and roofing > fibre-cement roofing tiles (07320). (n.d.). Retrieved November 7, 2007, from http://oikos.com/green_products/category.php?category_id=296&name=Fiber-Cement%20Roofing%20Tiles%20(07320) This source provides a list of companies that manufacture Fiber-cement tiles. It also provides contact information for each company. The Living Home – Insulation (Walls = 40.6 m³; Roof = 37.9 m³)
The Living Home – Roofing (164 m²)
The Living Home – Siding (253 m²)
Environmental Engineering (CIV257) Group Project [with permission per FOIP] Innovative Water HeatingMost homes have a standard 50 gallon hot water tank that supplies hot water to the home. In recent years other methods for heating your water have become more economical and available. For instance in Okotoks 52 homes in a subdivision have their home and water heated by garage mounted solar panels. (Drake Landing Solar Community, http://www.dlsc.ca/index.htm). Solar heating is one innovative method to heat your water. The sun heats up a fluid, typically glycol, which passes through the solar panels and then down to a heat exchanger to transfer heat to your water tank. This method supplies about 50-60% of the required energy to heat your water and can vary depending on the season. That is why it is typically accompanied by a small hot water tank. Another way to heat your water is through instantaneous gas heaters. No tank is required; your water is simply heated in a small heat exchanger right before it comes out of your faucet. Our research focused on natural gas water heaters. Although electric heaters are an option we chose not to focus on them for the following reasons: the cost of electricity is higher than natural gas but because natural gas prices are on the rise we have incorporated a range of prices. Burning natural gas produces carbon dioxide but electricity is produced mostly from burning coal which emits far more carbon dioxide. We feel that for now natural gas is more cost effective and environmentally friendly. The methods of water heating that we will look at are standard hot water tanks, evacuated tube solar heating, evacuated tube solar heating with instantaneous heaters, and instantaneous gas heaters only. Standard Hot Water Tanks The typical home has a standard hot water tank that heats the water through a gas burner or electric heating element. The transition to more energy efficient systems can be difficult with a shortage of skilled laborers who can install such systems. With hot water tanks being around for so long and getting more efficient it’s hard to justify the cost of new technology. The average cost to install a hot water tank is $800 where a solar heating system can cost around $4000-$5000. The hot water tank is getting more efficient with insulated tanks and pumps circulating the water in the lines to reduce the time for hot water to reach the end use. You can buy an insulator to put on your tank separately that increases the efficiency by minimizing heat loss. This insulation may be wanted in the summer but not the winter because the tank and pipes can give off heat to the home. Energy Required to Heat Your Water Efficiencies of water tank heaters according to the government of Nova Scotia department of energy (variations depending on altitude and age):
Electric old: 85% Stand alone Natural gas conventional: 70% Stand alone Natural gas high efficiency 93% Required amount of energy to raise 1 kg (1 liter) of water 1 C: Specific heat capacity water - 4.187 kJ/kgK http://www.engineeringtoolbox.com/water-thermal-properties-d_162.html Energy required raising the temperature of water from 10 C to 60 C: Electric new: 50 K* 4.187 (kJ/kg*K) / 0.90 = 232.61 kJ/L Electric old: 50 K* 4.187 (kJ/kg*K) / 0.85 = 246.29 kJ/L Stand alone Natural gas conventional: 50 K* 4.187 (kJ/kg*K) / 0.70 = 299.07 kJ/L Stand alone Natural gas high efficiency: 50 K* 4.187 (kJ/kg*K) / 0.93 = 225.11 kJ/L
1. Purchase costs include our best estimates of installation labor and do not include financial incentives. 2. Operating cost based on hot water needs for typical family of four and energy costs of 9.5¢/kWh for electricity, $1.40/therm for gas, $2.40/gallon for oil. 3. Future operating costs are neither discounted nor adjusted for inflation. 4. Estimates for tankless gas water heaters are based on the federal EF rating method, which may over-estimate the efficiency of tankless water heaters in houses. http://www.aceee.org/consumerguide/waterheating.htm#lcc Although water tanks are cheaper than other systems it is important to look at how environmentally friendly they are. One way to do this is to look at how much energy they use and their embodied energy. Embodied energy is the amount of energy that it takes a manufacturer to produce a product. This is based on the type of material and weight of the product. The high efficiency heater is model PH199-55 (http://www.htproducts.com/phoenix.html). General Information
Energy Use (Raising the water temperature 50 C)
Weight breakdown of each tank
Embodied Energy
Since the high efficiency water does not have a standing pilot light money and energy can be saved. The monetary payback on a pilot light is 77 years for the highest gas price according to the following graph:  The energy payback is only 5 months as seen in the graph below:  Although these new tanks are more energy efficient than conventional tanks there are new systems available that may be more expensive but are even more environmentally friendly. Less gas and electricity is used to heat water and less water is wasted when solar heating and instantaneous heaters are used. Solar Heating Solar water heaters consist of a collecting panel, tubing, glycol solution, a small pump and a heat exchanging tank. The glycol solution is pumped through the panel where the infrared radiation from the sun warms it. The glycol then travels to the heat exchanger where it warms the water before it enters secondary heating device. These systems efficiently use the sun’s energy to heat the water reducing the need for gas or electric water heating. There are three different types of solar water heaters. The first are formed plastic (PVC) panels. Water is pumped through the black panels and is heated by the sun. These panels are efficient only in warm temperatures and are normally used for heating pools. The second type of solar water heaters are flat plate collectors. These collectors contain a thin absorber sheet, which is usually made of copper that is painted black, and is backed by a coil. The system is encased in an insulated case with a glass cover. The coil contains glycol that absorbs the heat and transfers it to the water tank. These systems are much more efficient but measures must be taken to avoid freezing as it would cause extensive damage. The third type of water heaters are evacuated tube collectors. These collectors are the most efficient and use a glass tube that is vacuum sealed. Inside is a second tube made of metal or glass containing a fluid (usually alcohol) that when heated changes state from fluid to a vapor. The vapor then rises in the tube and heats the glycol solution which is then pumped to the storage tanks (See Fig. 1). These systems are capable of boiling the water in the tank if adequate heat is not removed from the system. Cold temperatures have little effect on the efficiency of the system and it can capture solar radiation from various angles due to the round tubes. The suns rays remain perpendicular to the tube at most angles.  Fig. 1 Evacuated Tube http://www.bfasolar.com.au/graphics/evacuated-tube_cross_section.png System for The Living Home For The Living Home we chose to use evacuated tube collectors due to their high efficiency in cold weather. Another reason we chose this system was because it can heat up to 60% of a home’s hot water. This system can decrease the reliance on secondary heating system such as a hot water tank or instantaneous heater. The system we chose cost $4835.00 and comes with: 22 solar tubes (2.2 m2/panel), solar pump, pipes and storage tank and could be retrofitted to an existing secondary instantaneous hot water heater. This system is more expensive but the energy payback is increased. On all paybacks an assumption is made that the solar tubes will heat 50% of the water demand (225 L/day at 80% efficiency, raised 52 C is 1863 MJ/month or 22350 MJ/year). The total embodied energy of only the solar heating system is 5095 MJ.  The energy payback for this system was around five and a half months. Also by reducing the natural gas needed, green house gases are also reduced by half or approximately 10 tons over 20 years.  Monetary payback for the system varies depending on gas prices. Based on a range of gas prices the payback looks as follows: 
Solar Heating with Instantaneous HeatersInstead of having the typical auxiliary hot water tank to accompany the solar heating system, instantaneous heaters could be used as well. The hot water pipes running from the water tank heated by the solar panels would have instantaneous heaters installed close to the faucets. These heaters would act as secondary heaters. Once the solar heating tank starts to run low on hot water the instantaneous heaters would sense the temperature drop and kick in. The price for such a system is around $6400 (Solar $4835 and two instant heaters $1600). Advantages of Instantaneous Heaters
Disadvantages of Instantaneous Heaters
In the morning the hot water you use would come mostly from instantaneous heaters because during the night the solar panels aren’t absorbing energy and the water tank will lose heat. As the sun comes out the water tank is heated and the hot water used in the afternoon and early evening come from solar heating. Later on in the evening if the hot water runs out then the instantaneous heaters kick in. Embodied Energy The TK-Jr instantaneous heaters we looked at each weigh 30 lbs (13.6 kg) and have an embodied energy of approximately 1135 MJ. This is assuming that each unit’s weight is made up of approximately 18% copper pipe, 10% aluminum, and 72 % steel. Water is wasted when a faucet is run until hot water comes out. This can take up to a minute. With instantaneous heaters all this water is not wasted. How much energy does this save and how long until it pays back the embodied energy of the heaters? This all depends on how many times people use their faucets per day. The following graph shows how many years it would take to payback the embodied energy of two TK-Jr’s (2270 MJ). This is based on the assumption that it takes one minute for hot water to flow out of the fixture with a water flow of 8.32 L/min and 3.6 MJ/m3 of water.  So we are looking at a range of 8-20 years pay back depending on how often you use a faucet. The more water you waste the more you save. Considering 20 years is the life of the heater this does not seem worth it. But if we look at the energy we save by not having a pilot light continually burning natural gas it is a different story. A pilot light burns between 18000-20000 BTU/day (19-21 MJ/day) which is about 630 MJ/month (http://www.wisconsinpublicservice.com/home/appcalc_gas.aspx, http://www.builditsolar.com/Projects/Conservation/PilotLights.htm). Considering two TK-Jr’s have an embodied energy of 2270 MJ it is only a matter of months until enough energy is saved that they are efficient.  From this graph we can see that it only takes 3.6 months for enough energy to be saved for it to be energy efficient. From this stand point instantaneous heaters are more environmentally friendly compared to hot water tanks which have an embodied energy of 3100MJ and have pilot lights burning continuously. By comparing the embodied energy of the entire system, solar panels and two instantaneous heaters (7364 MJ), to the accumulation of the solar heating payback as discussed in the previous section, pilot light payback, and water payback we can see how long it takes for a total energy payback.  According to this graph it will take about 4.7 months for the entire system to be energy efficient. Money Payback What about the money saved with no pilot light burning and less wasted water? This all depends on natural gas prices. The higher your gas prices the more money you will save by having no pilot light. The following chart is based on a range of gas prices:  For a pilot light burning at 0.021GJ/day with a price of natural gas of $5.50 you save $3.50 a month, with a price of $8.65 you save $5.50 a month, and with a price of $11.80 your save $7.50 a month. Since two TK-Jr’s cost $1600 and the Solar Heating Tubes cost about $4800 our total system costs about $6400 and it takes almost 72 years for a person paying $11.80/GJ to get a payback. This is because the cost of natural gas is not that high, especially when talking about a pilot light. Water cost 50 cents per cubic meter in the City of Lethbridge. The following graph shows how long it would take to payback this system based on water savings:  At this rate it would take 157 years to payback only looking at water. The average house hold (3-4 people) uses approximately 225 l/day of hot water which is 82125l/year. Using the following equation we can determine how much energy it takes to heat water from 8-60 degrees Celsius based on an 80% efficiency (Instantaneous efficiency) in a year: (52 K* 4.187 (kJ/kg*K) * 82125 kg) / .80 / 1000000 = 22.35 GJ This is about 0.061 GJ/day to heat your hot water. Since solar heating can contribute 50% of the energy required to heat your water money can be saved on gas. The saving on this are based on the same range of gas prices.  Only looking at the gas saved with a rate of $11.80/GJ it would take about 49 years to payback. The total actual payback for the whole system would include the savings on water, pilot light, and gas heating. By combining all these previous payback prices our payback is as follows:  The payback period drops down to about 24.5 years with the highest gas price. From an environmental stand point instantaneous gas heaters are a good idea. They have less embodied energy than storage tanks and no pilot light constantly burning gas. Even though the entire systems payback period is about 25 years your instantaneous heaters are not working as hard as compared to an instantaneous system only. This may extend the 20 year life they are expected to have. Instantaneous Gas Heaters OnlyThis last method is very similar to the previous one except that the model type would change and the solar heating system would be gone. Instead of using the smallest type of heater, the TK-Jr ($797), which can only supply 1 to 2 bathrooms we would upgrade to a T-K3 ($1457) which can supply 2 to 3 bathrooms. The house would still only require two units in the same place. The total system would cost around $2900-3000. Embodied Energy By changing the model type it increases the embodied energy from 2270 MJ (2 TK-Jr’s) to 2990 MJ (2 T-K3), which increases the payback for water and gas as follows:  The energy payback time increased by 2-7 years.  The previous energy payback for the TK-Jr’s was 3.6 months while for the T-K3’s it is only 4.8 months. Money Payback Since the price of twoT-K3 is about $2900 the payback from a pilot light is seen below.  Looking at the highest gas prices it would take about 32 years to payback the two units. The payback on water is the same as the previous system except that the price of our system has gone down by $3500.  With only water saving it would take about 71 years. The total savings from gas and water are as follows:  It would take 22 years to payback the whole system. Recommendation There are two things to consider when deciding on a system for the Living Home: cost and energy. Here is a summary of all the systems we have considered:
If you want to save money and still be energy efficient the best option is two T-K3 instantaneous heaters. The energy payback is 4.8 months and the money payback is a little over the 20 year life of the heaters. If you want to save the most energy the best option is the evacuated solar heating tubes with two TK-Jr instantaneous heaters. Even though it has a high embodied energy, the energy payback is 3.6 months. This means that compared to the instantaneous heaters they save far more energy. |
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