ZERO ENERGY HOME
SEBC SOLAR HOME OF THE YEAR
In August 2008 ECS Solar Systems of Gainesville won the Southeastern Builders Conference Grand Aurora Award for the Solar Home of the year. The home was a part of the U.S. Department of Energy - Building America Program for Zero-Energy Homes. The purpose of this federal initiative is to first demonstrate the feasibility of constructing ZEH’s and then to foster a market transformation through wide spread implementation.
The 1772 sq. ft. heated and cooled home has been monitored by the Florida Solar Energy Center. The home achieved the Zero Energy goal of producing as much electrical energy as it used even during the hottest summer months. The home produced and sold back to the grid as much energy as it used resulting in a breakeven utility bill.
The Solar hot water system eliminated 98% of the homes requirements for hot water. Water heating is typically 15 to 25% of a home utility bill. The rest of the electric bill was eliminated by the solar electric system because of the energy efficient features built into the home by Ken Fonorow, President of Florida Hero and member of Department of Energy’s Building America Team. Ken used an integrated whole house approach design for hot humid climates in the Building America Program. The breakthrough High Performance Home enabled the home to be healthy, comfortable and achieve zero energy even in the hottest summer months with only 3150 watts of solar electric power. This is less than 2 watts of solar power per square foot of floor space.
The first question everyone asks is “How long will it take to get my money back for a Zero Energy Home”. The answer to that question requires looking at the benefits of investing in conservation measures besides the solar electric and hot water systems. Since Solar Systems are exempt from property tax how you recoup your dollars invested in a Zero Energy Home depends not only looking at the increase in the home’s equity value but the fact that all energy savings are nontaxable. This means that the after tax rate of return on your investment can be over 8% a year at a utility rate of only $ 0.12 a KWH.
A Zero Energy Home approach requires the homeowner thinking of the home as an investment in energy conservation, solar hot water, and solar electric power as a way of pre paying your present and future electric bills. The homeowners’ investment in this home not only eliminates the current electric bill but hedges against all future electricity increases.
The secret to maximizing this investment was using intelligent conservation measures using the whole house design building practices as defined by the Building America Program for hot humid climates. The SEBC Award home required less than 2 watts of solar electric power per square foot of floor area versus 10 watts per square for a home built to minimum Florida Building Standards. An “Energy Star Home” would have still required 8 watts per sq. ft. of floor space.
A savings of $ 50,000 to $ 80,000 in the cost of a solar electric system is made possible by having a Heers rater building science professional, like Ken, specify energy efficient design features that move the Department of Energy E-Rating or energy rating from 100 (standard home) or 85 (Energy Star) to a 20 E-rating on the home. This results in being able to build a Zero Energy Home of 1700 to 2800 sq. ft. of floor space with3,200 to 5,000 watts of Solar Electric power and a Solar Hot Water system.
Solar Electric Power costs around $ 8 to $ 10 per watt. If this home had been built to minimum Florida standards it would eliminate only 20% of the home requirements and in practical terms increase the home Solar Electric cost to $ 32 to $ 50 per watt. This is because it would have required 10,000 to 15,000 watts of solar electricity to get to Zero Energy instead of 3150 watts. The solar hot water and solar electricity system produced or eliminated 12,000 KWH per year. Over 15,000 KWH per year were eliminated because of the conservation measures design for the home by Ken Fonorow of Florida Hero. This resulted in a savings of $ 24 to $ 40 per watt required for “upsizing” the home Solar System for a home built to minimum Florida Standards
A Zero-Energy Home will require about 400 to 600 sq. ft. of south facing roof or 500 sq. ft. to 750 sq. ft. of an east or west facing roof for this Solar Electric and Solar Water Heating System. The roof should get five hours of sun between 9:00 AM and 4:00 PM. The most efficient way to minimize the initial cost increase that will be associated with a ZEH occurs during schematic design phase. Critical decisions are made at this early period which will have a profound impact on the homes ultimate performance. The home’s orientation, the amount and location of windows, the location of the mechanical system and associated duct work, the location of the water heater, overhangs depths, etc. need to be taken into consideration. This is also the time to make sure that there is contract language which quantifies critical performance standards. An example would be to establish a maximum acceptable level of duct leakage.
Once the schematic design phase is completed the various components and systems must be considered within an integrated systems approach. This represents a fundamental shift from the “old school” of building construction which took a component approach. A systems approach considers the interrelationship and impact of combinations of the systems, materials and components to optimize the performance of the home while minimizing construction costs.
For example, if better performance windows are selected then a smaller AC system may be used. Ideally, the savings from the right sized AC system can be reallocated to pay for the better windows which allowed the smaller system to be selected in the first place.
It is important to understand that there is no “list” or article that will provide appropriate guidance for the ZEH homebuilder. Each home represents its own set of issues which must be dealt with within a systems approach. Site conditions, home orientation, available fuel sources, health related issues, Federal, State, Utility and/or local incentives, as well as, budget restraints will be unique for each home.
Fortunately, a prospective home builder does not need to become a building science expert to build or renovate a home to be a high performance ZEH but they would benefit by using a professional comprehensive design group that can act as system integrators, from conceptual design through final commissioning. It is possible now to build homes that produce as much energy as they use on a yearly basis, while maintaining superior IAQ (Indoor Air Quality) and comfort in a cost effective manner.
