Aside from its beauty, this Colorado Springs, Colorado, residence known as Krafthaus has another redeeming quality: It has a HERS Index score of -1. This remarkable feat results in an energy savings of $7,177 per year. The HERS score is a nationally recognized industry standard for measuring a home’s energy efficiency. According to HERSIndex.com, a home with a HERS Index Score of 130 is 30% less energy efficient than a standard new home. A home with a HERS Index Score of 70 is 30% more energy efficient than a standard new home. The lower the number the better, obviously. A score of zero means the home is Net Zero, so a score of -1 is off the charts, so to speak. 

According to RESNET (Residential Energy Services Network – https://www.resnet.us), the average HERS score for homes nationwide is 61. Given the average size of an American family home of 2,531 square feet (Statista.com) when compared to this home’s 4,194 square feet of livable space, that’s a remarkable feat indeed. 

That was achieved through a number of means. The home’s exterior walls are 100% ICF, made by Fox Blocks. There’s also 569 square feet of interior ICF and 3,467 square feet of 4-inch foam insulation. The home has a 1,607-square foot LiteDeck attic floor and 1,607 square feet of BCI flooring with gypcrete for the second floor. ICF was also used on a 200-square-foot bridge over a culvert at the home’s entry, and a 146-square-foot frost wall below the porch for a total of 5,336 square feet of ICF. It took only 68 days to install all of that, out of a 64-week construction schedule. The home was completed in April 2020 for $1.2 million.

The homeowners’ primary desire was to build a home that adhered to the “whole building” approach to design and construction. This approach takes into consideration how every component of the building will work together: the walls, the windows, the insulation, etc. The owners did quite a bit of research on concrete construction. They were attracted to concrete because of the durability, security, safety, and the low maintenance quality. The husband was interested in the benefits of protection from natural disasters while the wife was attracted to the quietness of ICF, given that they were building in such a windy area. They were looking for a contractor with experience in ICF and selected a contracting team that also distributes Fox Blocks ICF, so the choice in ICF brand was clear.

The home was built on land with a high water table (4 feet below grade), making a basement impossible. An attic was provided for storage, and a LiteDeck concrete lid on the main house provided additional safety from fire and tornados, which the homeowner was concerned about. With views of Pikes Peak in the background, the architectural control committee mandated that the home could not obscure any other homeowner’s views. It’s location also meant dealing with extreme weather: periodic wind-driven snow and extremely cold temperatures. The builders dealt with snow drifts of 4 and 5 feet and daily wind gusts.

The ICF installers, High Performance Structures, had 20 years of experience and it showed in the construction of a large curved window wall, requiring custom cutting of each ICF block. The ICF LiteDeck attic floor and ceiling required rebar in the channels every two feet, allowing them to span large distances without needing either dropped beams or posts. With walls up to 27 feet tall, the engineer required 8-inch core ICF for the radius walls so the standard radius block could not be used and it all had to be custom cut.

“The final building is a masterpiece,” says Mike Kennaw of Fox Blocks. Indeed, with such outstanding architectural features as a great room with a two-story radiused window-wall with panoramic views. There is a large front porch and an upper deck off of the second floor loft area that face west to enjoy the expansive views. The attic with the LiteDeck floor is a sun-lit space separated from the main floors. The homeowner uses it as a workshop, and the concrete makes it completely separate, so no dust or residue from using power tools enters the main area of the home. 

The guest suite with a separate entrance and 8-inch ICF demising wall between the main house has become a great temporary office for the owner who is working from home due to COVID restrictions. All of these touches are complemented by stained concrete floors which provide beautiful, durable, easy-care floors.

The homeowners invested in water-to-water geothermal heating and cooling. Geothermal systems are often water-to-air, which means heating goes through the floor and for cooling runs through ducts like traditional air conditioning. However, this home has no ductwork at all and the cooling goes through the floor. With the water-to-water geothermal heating and cooling, a 10KW PV solar panel system, and the installation of the Tesla Power Wall (a backup system that stores energy in its batteries for future use when there is no sun), the owner is consistently selling energy back to the grid.

Thanks to the builder’s and Fox Blocks’s work on educating the local Habitat for Humanity about ICFs, the organization decided to build new townhomes out of ICF block. This upcoming project, called the Trailhead Townhome project, will be watched closely by other Habitat for Humanity organizations and could impact the many future Habitat builds.

Phil Drotar from EnergyLogic, who provided the Energy Star Certification for this home, said the -1 HERS score made it the lowest scoring home he’d tested in Colorado Springs. It’s almost certainly the lowest HERS score in all of the United States. In 2020, the home with the lowest HERS score in all of North America was the Sofia Court home, which you can read about on pages 24 to 26 in this issue. That home scored 26.