MARTaK is a 1,200 square foot home located in the foothills of Colorado's Rocky Mountains. It juxtaposes clean Nordic lines and rustic American sensibilities. MARTaK was designed and built by author Andrew Michler, and its name is an acronym composed from the initials of Andrew's family and friends.
With this home, Andrew proved that you can live comfortably on a small piece of paradise off the grid. How did he do it? By cutting energy waste to a minimum. In fact, MARTaK is Colorado's most energy efficient home†.
MARTaK is fantastically utilitarian. It's a certified Passive House building, which means that it is highly insulated and air-tight in order to reduce the need for large heating and cooling. As a direct result of being energy efficient, MARTaK can exist completely off-grid, powered only by a small solar array and deep cycle battery system.
The cherry on top is that MARTaK is incredibly comfortable. "The house I ended up building definitely lives up to its promises in terms of energy conservation, but the biggest surprise is how comfortable it is," says Andrew. "In the winter time if its cold out side you can just sit next to the window and be perfectly comfortable in a t-shirt. It's fantastic."
Read on to discover the techniques and technologies that Andrew used to make MARTaK Colorado's most energy efficient home.
The building's largest wall faces south to maximize the use of the sun for light and heat.
A balance was struck between letting in sunlight for light and heat versus keeping the house well-insulated. Having too many windows creates an uninsulated greenhouse that can rapidly heat up to uncomfortable temperatures in the warmer months or lose heat too quickly in the cold seasons. Many passive solar (not Passive House!) buildings cover as much as 50% of their south-facing walls with windows – a practice that contributed to the unpopularity of passive solar design in the 1970s. Well designed homes today, like MARTaK, have found the Goldilocks zone of window coverage for "just right" light, heat, and energy efficiency.
"My house comprises about 20 percent glass on the south side, which means it neither heats up dramatically, nor loses heat. That balance pays off in simplifying heating and cooling needs," says Andrew.
Andrew installed highly efficient triple-pane windows from Europe that provide excellent insulation. The windows allow heat and light into the home, but not out of it. This is achieved through an ultra-thin layer of reflective metal that coats the interior side of the window. (Incentivized by higher prices for energy, Europeans produce some of the most efficient building materials in the world).
All plywood and structural boards used in the house's construction are taped together religiously. "To do air sealing right," said Andrew, "you have to find religion about making sure that every place where two building elements come together is properly sealed well before they are covered."
Andrew construted large bays (pictured above) for the 18 inches of dense-pack cellulose insulation which he blew in with an insulation blower (pictured below).
The cellulose sits between the taped plywood boards and even more insulation: mineral wool board (pictured above – the fuzzy green walls). In Andrew's words, "this house is essentially a thermal battery bank, if you look at it just from a thermal dynamics point of view."
Imagine that you have hot coffee a mug with a metal spoon in it. Will leaving the metal spoon in the hot coffee cause the coffee to cool faster? Yes! Since metal is a good conductor, heat will travel through the spoon and out into the cold air. The metal spoon is a thermal bridge. In buildings, we want to eliminate thermal bridges. This is a core principle of proper insulation in Passive House construction.
This colorful diagram is Andrew's thermal model of MARTaK's envelope. Notice that there are no thermal bridges where heat energy (in red) can escape from the building's envelope. And if you look closely enough, you'll see that there is no spoon.
Because the building is air-tight for maximum energy efficiency, ventilation is required to circulate breathable air to its living occupants. MARTaK uses a heat recovery ventilator which captures heat energy in outgoing air and infuses it into the incoming fresh air. In the summer, the heat recovery system is shut off so the house receives a steady trickle of cool air. But where does cool air in the summertime come from?
Air coming into the ventilation system is preconditioned by running it through a pipe in the ground (also known as anearth tube). The Earth's cool, constant subterranean temperature is used to heat the air in the winter and warm it in the summer.
MARTaK has a small hydronic heat system (also known as radiant heating) powered by propane, but Andrew has plans to switch it to solar to be more self-reliant. Hydronic heating systems pump hot water through long stretches of pipes in floors or walls to radiate heat.
According to Andrew, "the home’s main heating source is the sun, followed by the 'waste' heat of the occupants and appliances, and then finally a small hydronic heating loop in the wall and at the Heat Recovery Ventilation system."
Additionally, Andrew installed a phase-change material behind the walls in the center of the house. The material changes it's physical state at 74ºF from a solid to a liquid, which causes it to absorb heat above 74ºF and release heat below 74ºF.
Efficient LED lighting is used throughout the house. As previously stated, the house's southern orientation makes fantastic use of daylight to minimize the need for any lighting in the home during the daytime. If you're interested in purchasing LED lighting for your home, check out our guide on choosing the right light for the right room.
A propane water heater is utilized for cooking and other needs.
Andrew took care to build the house nestled between three existing pine trees. They provide shade during the summer – essential to reducing a home's need for cooling.
MARTaK collects its own water with a rainwater catching system on the roof which fills a 1500 gallon cistern. "When I originally put it in, it was illegal, and then it became legal afterwards," says Andrew.
A small photovoltaic solar panel system charges a nickel iron battery bank (to learn more about NiFe batteries, check out our guide on batteries for solar). The small system powers the entire home. Pictured here are the panels, located on the second building on the property.
MARTaK uses Rise Broadband, a terrestrial internet provider. A single satellite dish is pointed in the direction of the nearest internet-broadcasting tower.
MARTaK cost Andrew $225,000 USD and four months to build. Additional time was spent on design and constructing the energy model and on receiving Passive House certification from Passive House Institute. If you're interested in learning more, check out Andrew Michler's wonderful three part series on building MARTaK here.