This Farmington home produces more energy than it uses on an annual basis. Pretty remarkable, right? This “net zero” performance deserves recognition; that’s why energizeCT created its annual CT Zero Energy Challenge. And that’s why we are especially pleased to have been recognized for the second year in a row as a Grand Prize Winner! By every measure, we are designing and building the most energy efficient homes in the state.
This bright spotlight shines on the remarkable energy savings we achieve by striking the perfect balance between how much energy the house requires to operate and be healthy and comfortable, and matching it with the “free” energy we can capture from the sun. We employ the intelligence of building science to integrate proven systems and technologies to assure this result.
While we are being awarded for exemplary energy performance, the lucky homeowners are being rewarded with a host of additional qualities well beyond the obvious value of an energy cost of zero. They will be living in a home that is bright and open, consistently comfortable, with healthy and clean fresh air year round. And it is built to endure.
But beyond that, this is a home that fits. Like everything we design, it is aligned with the principles of the “not-so-big-house” which favors quality over quantities of space. It has a simple clean aesthetic that leaves room for select materials and a few special craft features to take the stage. Exterior finishes were chosen for long life and low maintenance. The interior features a nice balance of natural wood. Lower level floors are polished concrete. The whole place looks great!
|Conditioned Area||2392 SF|
|PV System||10 KW|
|Annual Heat Load||3.6 Btu/SF|
|HERS w/o PV||37|
And it flows. As we design we like to think of a home as a screenplay, with spaces setting the stage for a sequence of “scenes”, one leading purposefully to the next. From the moment of arrival and entry, visiting in the kitchen, settling for a meal, or retreating to a quiet corner to spend time alone we are considering how each experience should connect with the other – or not! We want each space to not only look great and work well, but feel good to be in.
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The key to achieving Net Zero Energy performance can be summed up in this simple maxim: Reduce, then Produce. What this means is that if we can be miserly about the amount of energy the home requires to maintain comfort and meet occupant needs we can match that load with a rooftop solar array.
The energy “load” (the amount of energy required) for heating is both the largest AND the one we can reduce the most. The same efforts reduce the cooling load, though this is much smaller to begin with. After reducing these loads we focus on hot water. A heat pump water heater cuts this load by more than double compared with conventional options. Lighting is dramatically reduced by using LED lamps and we install the most efficient Energy Star appliances. This leaves the “plug loads” which power all our other “devices.” How much energy these require depends alot on how people use them.
The PV array that converts sunlight to usable electricity is sized to match these loads. For this house it is sized a bit larger, in anticipation of the purchase of an electric vehicle.
- Heating Savings 83%
- Cooling Savings 51%
- Hot Water Savings 63%
- Other Energy Savings 32%
Savings compared to a conventional Code Built equivalent of this home
The Home Energy Rating System (HERS) Index is the industry standard by which a home’s energy efficiency is measured.The projected annual energy costs for the home are compared to the projected costs for the HERS Reference Home to show projected annual energy cost savings. The reference home is the rated home reconfigured according to the 2004 Energy Code and federal minimum equipment efficiency standard and equals 100 on the HERS scale.
Capitalized Annual Savings
Capitalized Annual Savings are the net present value of the annual energy cost savings compared to the HERS Reference Home. This calculation uses the current market assumptions for energy cost inflation and the homeowner’s mortgage interest and a 30% marginal tax rate. It is a way to quantify the value of the avoided costs of energy for this versus a conventional home over 30 years. In other words, this is money you won’t need to spend on energy!
THE BUILDING’S PARTS
We construct the building with super-insulation on all SIX surfaces: Walls, Roof, and below the Slab. We are obsessive about air sealing to eliminate losses from air infiltration. We use high performing tilt turn triple glazed windows with large areas of glass on the south facade with “high solar heat gain coefficient” glass designed to capture the “free gains” from the sun (but shade them in the summer).
When we build like this we don’t need a complicated heat distribution system. We use high efficiency ducted minisplit heat pumps with only one supply duct on each level of the house. The indoor environment is so stable that it maintains even temperatures with only this small amount of heat provided.
The heat pump water heater produces hot water efficiently. A balanced heat recovery ventilation system assures constant fresh air at a rate optimized for health. The heat recovery assures very little energy is lost.
Finally the 10KW PV System produces more energy than the house consumes on an annual basis. This home is “Net Positive!”
|Ceiling||Loose Fill Cellulose||R 83|
|Above Grade Walls||Dense Pack w/ Polyiso foam||R50|
|Foundation Walls||Dense Pack w/ Polyiso foam||R 55|
|Windows||Triple Glazed||R 6.3|
|Air Leakage||Blower Door Test||0.49 ACH50|
|Heating/Cooling||Fujitsu 18 KBTU Ducted Minsplit||11.3 HSPF / 19.7 SEER|
|Hot Water||Stiebel Elron HPWH||2.51 EF|
|Ventilation||Zehnder Comfoair 350||84% Efficiency|
DRAWINGS AND PERFORMANCE ANALYSIS
These drawings show the floor plans, elevations and framing, and section details of the project. In addition there is the project’s Performance Analysis Report produced by our HERS Rater and Energy Star Certifier, Home Energy Technologies. Through the process of analysis and verification of this project the owner qualifies for rebates that amount to $5-7K.
This Project was the Grand Prize Winner in the energizeCT Zero Energy Challenge. This video was produced to showcase the project and the features that contributed to that result. We are grateful for this program and its intention to highlight the ability to achieve Net Zero Performance in homes of exceptional comfort, health, durability, and energy security