fbpx

Wolfworks won our third CT Net Zero Challenge for this high performance home in Mansfield that achieves exceptional energy performance and affordability by integrating today’s most advanced building practices with lessons from the beloved New England farmhouse style. The home is being recognized for the way it is constructed to require 80% less energy than a code built home.

This 2017 CT Zero Energy Challenge award winner demonstrates that building a high performance home is achievable today, while also representing the technologies and techniques it takes to get there. When you achieve this level of energy performance it becomes easy to balance all the buildings energy needs with solar energy. By designing to optimize “free gains” from the sun in the winter and adding a solar photovoltaic system to provide all the energy the home needs on an annual basis this home will have no energy expense each year, now and always. It is a “net zero energy” home.

The home was designed and built to provide lasting beauty, feature enduring craft, and from the start will have low energy use baked in. And with all these features, by keeping it small and simple, the budget was kept manageable. This kind of comfort is made possible by thick walls and tight construction. This means less energy is required to heat and cool the space, which is easily accomplished with a small, high efficiency mini-split heat pump. Constant fresh air from a balanced heat recovery ventilation system assures better health. Hot water is produced efficiently by a heat pump water heater.

  PROJECT DATA

Conditioned Area1895 SF
Bedrooms3
PV System7 KW
Annual Heat Load6.3 Btu/SF
HERS w/o PV36
HERS w/PV-3

PORTFOLIO

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.

CLICK TO ENLARGE IMAGES

 

PERFORMANCE STRATEGIES

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.

  BUILDING LOADS

MMBtu/Yr.Annual Cost
Heating5.9$309
Cooling2.5$134
Hot Water3.2$171
Other Loads18.3$964
PV Production-$1662
Total$147
  • Heating Savings 81.4% 81.4%
  • Cooling Savings 56.4% 56.4%
  • Hot Water Savings 76.5% 76.5%
  • Other Energy Savings 23.9% 23.9%
  • Total Energy Savings 96.5% 96.5%
Savings compared to a conventional Code Built equivalent of this home

HERS INDEX

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!”

  PROJECT SPECS

LOCATIONTYPEVALUE
CeilingLoose Fill CelluloseR 70
Above Grade WallsDense Pack w/ Polyiso foamR50
SlabEPSR 24
WindowsTriple GlazedR 6.3
Air LeakageBlower Door Test0.44 ACH50
Heating/CoolingFujitsu 18 KBTU Ducted Minsplit11.3 HSPF / 19.7 SEER
Hot WaterStiebel Elron HPWH2.51 EF
VentilationZehnder Comfoair 35084% Efficiency
PV7 KW

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.

PROJECT VIDEO

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

Pin It on Pinterest

Share This