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Eco House

Project Members

Topher Elderkin

Caitlin Vaughn

Nathan Pavlovic

We will be designing an eco-effective heating system for EcoHouse.

Heating and Cooling in EcoHouse

Introduction

The idea of establishing an “ecohouse” on the Grinnell College Campus “devoted to experiential examination and practice of sustainability, and serving as an example of sustainable living for the Grinnell College campus and the wider community (EcoHouse Proposal, 2008)” has surfaced in the past few months and has been met with support at all levels of the college. This house would examine the impacts of current college-provided housing, and would then seek to reduce or eliminate those negative impacts. It is widely known that one of the greatest impacts any contemporary inhabited space has on the wider world is its energy usage. Thus, to achieve its goals, EcoHouse will need to significantly reduce its energy use. To this end, this report examines how a hypothetical EcoHouse could reduce the energy use associated with heating and cooling the house, which is estimated to make up approximately 45% of a building’s total energy requirements (Iowa Energy Center, 2006). Specifically, we will examine possibilities for improving home insulation and installing a whole house fan, programmable thermostat, and solar hot water heating system.

Programmable Thermostat

A programmable thermostat is one of the simplest and cost effective ways to reduce a house’s energy use. This device works like any other thermostat, controlling the temperature of the home. However, a programmable thermostat allows residents to preprogram different temperatures for different times of day or different days of the week. This can reduce energy use by lowering the temperature at night, or during the day when no one is at home (US EPA, 2005). A typical programmable thermostat costs from $50 to $100 (Iowa Energy Center 2006).

Insulation

The Rocky Mountain Institute reports that a single family can spend up to $680 per year on heating and cooling expenses for their home. Such expenses are exorbitant given the simple money saving and earth friendly renovations one can make to a home. In fact, the RMI suggests that heating and cooling costs can be reduced by as much as 50% when one addresses issues with “the building envelope”—a home’s walls, roof, and windows. (Rocky Mountain Institute 2004)

When trying to make a home efficient, it is important to make the building envelope as “tight” as possible so heat does not leave the space. It is especially important to examine insulation in the attic, outside walls, and foundation of a home. Insulation comes in a variety of different forms, though the following four types are the most popular and usable:

--Rolls and batts made from mineral fibers like rock wool or fiber glass

--Loose-fill products are also made from mineral fibers but come in shreds or nodules and are then blown into a space. When the insulation is blown in it fills empty spaces within the wall or attic.

--Foam insulation is especially useful when filling in spaces where a thicker or studier product is desired.

--Foam in Place insulation, like loose-fill products, can be blown into walls.

Insulation is measured in “R values”—the higher the R-value, the better it is at resisting the transfer of heat. Within a home, different types of insulation are used. For instance, the insulation used in the attic would have a much higher R-value (and thus, exhibit greater thickness) than the insulation used in the walls of the home. The U.S. Department of Energy makes recommendations as to what R-value of insulation is appropriate for different geographical regions.

The building that will most likely be used for EcoHouse was built in 1900 and last renovated in 1990. In order to become “green”, it will need serious improvement to its insulation. According to Facilities Management officials, it will take approximately six months to reinsulate the attic, exterior and interior walls (Rick Whitney personal communication). These changes will most likely happen during the 2009-10 school year. The most expensive kind of insulation is the foam variety, but according to the U.S. Department of Energy it is the most ideal product for resisting the transfer of heat in cold environments (U.S. Department of Energy 2006). Therefore, it seems that if the college can afford it, the foam product would be the most advantageous to our needs. Regardless of what variety is used, reinsulating EcoHouse may be one of the best ways to make the structure efficient and green.

Whole House Fan

A whole house fan serves to cool a house by drawing cool air into a house at times when outside air is cooler than indoor air, especially at night. Such a system can eliminate the need for air conditioning in some regions and would most certainly reduce the operating time for air conditioning units in this area significantly. The benefits compound with improved insulation and proper use of windows and shades, and appropriate thermal mass could be used to moderate the temperature further.

A whole house fan is a relatively simple device, and can be purchased for about $150 to $350 (Southface Energy Institute, 2006). It can be placed in the ceiling between the house and the attic in any central location, such as a hallway. When installing a whole house fan, it is important to ensure that adequate vents in the attic are provided so that air drawn from the house can escape to the outside. If vents are not provided, or if gaps from the attic to the house are not properly seal, the hot air can be pumped back into the house.

There are two major drawbacks to a whole house fan. Firstly, the fan represents a hole in the ceiling insulation of the house, opening the door to massive heat losses during the winter. This, however, can be overcome rather simply by constructing a fan cover for either the house side or the attic side, or both. The cover would serve to eliminate energy loss due to both conduction and convection. The second drawback to a whole house fan is that, unlike an air conditioning unit, it does not dehumidify the air, and it can draw dust and pollen into the house. This should not be of much concern, unless residents have special allergenic needs, in which case it may be best to purchase an air filter rather than forgo a whole house fan.

Solar Hot Water Heating

There are many ways to go about providing hot water for a house; the most prominent of these are currently based on electric heating, provided by large fossil fuel or nuclear power plants, or burning natural gas and/or propane. However efficient, neither of these methods are as renewable, as plentiful, or have anywhere near as few negative by-products as the sun: the source via which solar hot water heating technology draws its energy. Solar hot water heating is currently recognized as one of the most financial efficient renewable energy application, and is widely applied around the world.

The basic conceptual design is quite simple. Solar collectors of varying designs absorb the suns energy, it is stored as heat, and used to increase the temperature of the house’s water tank in lieu of gas burning or consumption of other non-renewable resources. Based on resources, financial and otherwise, as well as contextual factors, a wide variety of designs have been created to facilitated the practical application of this concept. The most basic solar hot water heater is simply a tank of water inside an insulated box with appropriate glass on one side tilted south (in the northern hemisphere). This design has the advantage of being completely passive with no moving parts to power whatsoever. However simple, it is not nearly as effective at producing hot water, especially in cold climates, as others that require more materials .

In order to cheaply and effectively retrofit a potential eco-house with solar hot water, one would need to take into account the climate in Grinnell as well as the current state of the house in question. The design I would recommend would start with a basic gas hot water heater and build on it. If at all possible, I would try to acquire an uninsulated tank either from a manufacturer or, worst case, remove the tank’s insulation. South-facing solar collectors would be placed on the roof or on the ground. The copper tubing that comes out of the collectors would be filled with an propylene glycol/water mixture, and would wrap around the tank with the same copper tubing/panel combination and that are found inside solar collectors. Then, the newly outfitted tank would be wrapped in heavy insulation to prevent heat loss. This design would allow the sun’s energy to be transferred into the copper plates, to the heat transfer fluid, back out of the plates wrapping the tank and into the water inside. This retrofitting would need to be equipped with a pump to circulate the heat transfer fluid and a temperature sensor to assure that it only ran at appropriate temperatures. Another temperature sensor(or the same one) could be equipped to regulate the use of the gas backup heater.

Conclusion

There exist numerous improvements that could be made to the proposed EcoHouse to reduce its energy use associated with heating and cooling. Efficiency could be increased by upgrading current insulation, installing a whole house fan, utilizing a programmable thermostat, and heating water with solar energy. Because of the large contribution heating and cooling make to the energy use of a house, reducing this use is of primary importance for renovating a house to reduce the negative impacts in has upon the environment.

Clearly much more could be done to improve the efficiency of heating and cooling EcoHouse, however. With proper, in depth knowledge of the unique space EcoHouse will come to occupy, we could perform further assessment of the best technologies discussed above, delving into specifics such as equipment size and model. Knowing the currently form from which heat is attained, possibly oil or gas burning, we could analyze the possibility of transferring to a new heat source, such as geothermal heat pumps, passive solar heating, wood burning or wood gasification heaters, or air-source heat pumps. However, the viability of these options is so dependant on specifics of citing and the building itself that we have chosen to forgo a discussion of those options in this report in favor of an analysis of more readily accessible improvements. This report serves, then, as a starting point from which project managers of EcoHouse can depart as they begin to improve the efficiency of heating and cooling the house and its water.

Works Cited

Elderkin, Richard. Solar Water Heating consultation

Iowa Energy Center. 2006. “Home Series 2: Home Heating and Cooling.” Retrieved

        March 3, 2008 from 
	http://www.energy.iastate.edu/homeseries/downloads/HomeSeries2.pdf

 Southface Energy Institute. 2006. “Whole House Fan.” Retrieved March 2, 2008 from 
       http://www.southface.org/web/resources&services/publications/factsheets/housefan.pdf

Rocky Mountain Institute. 2004 “ Energy Efficiency.” Retrieve March 3, 2008 from

       http://www.rmi.org/sitepages/pid206.php  


 Tonnesson, Roy.  Solar Water Heating(SWH) in a Cold Climate
        Course Reading Materials

 US Department of Energy. 2006. "Energy Savers: Insulation." Retrieve March 3, 2008 from                  

      http://www1.eere.energy.gov/consumer/tips/insulation.html

 US Environmental Protection Agency. 2005. “A Guide to Energy-Efficient Heating and 
        Cooling.” Retrieve March 4, 2008 from  
        http://www.energystar.gov/ia/products/heat_cool/GUIDE_2COLOR.pdf

Whitney, Rick. Insulation consultation. 29 February 2008.