The Nauhaus approach to combines the high-tech green building strategy of air tight construction and controlled ventilation with the natural building strategy of “breathable” (hygroscopic) walls in combination with natural and non-toxic finishes. The result is the cleanest indoor air you’ll ever experience.
sounds sort of scary, something more important for a spaceship than a house. Does closing your house off to natural air flow really make sense? Until the widespread use of insulation in the last half century, houses allowed ample airflow with the outside without the need for mechanical ventilation. The problem is that heat moves out (or in during Summer) with that air, creating huge energy losses. This is not only expensive, but since most heating in conventional buildings comes from combusting fossil fuels (reactivated solar) it is also a major contributor to air pollution and our present climate change crisis. In heating and cooling climates, we really have no choice but to reduce this energy hemorrhage by installing a layer of insulation between our indoor space and the great outdoors. For a number of years now, all new buildings have been insulated and even a moderately well-insulated building now needs some form of mechanical ventilation to create air exchange when it is either too hot or cold to have the windows open. Once you’ve reached that point, it simply makes sense to maximize the efficiency of that ventilation. This is accomplished in two ways: (1) reducing air leakage through the building envelope (floors, walls, and roof) and (2) using an energy recovery ventilator.
- can be reduced through the use of careful construction detailing and the installation of high performance windows and doors. Each Nauhaus undergoes an air leakage performance examination, called a “blower door test” as part of the construction process. It is our goal to reach standards defined by the Passive House Institute requiring an air exchange rate of 0.6ACH @ 50pascals. If you don’t know what that means, trust us, that’s tight!
- An is a device containing a high efficiency, low volume fan and a heat exchanger. As indoor air is exhausted the heat exchanger removes heat either from the outgoing indoor air (winter) or the incoming outdoor air (summer) to achieve fresh air with only minimal energy loss.
For some purposes, such as irrigation to an elevation below a house, all that’s required to create a functioning rainwater harvesting system is to install a tank to collect water exiting roof gutters, along with basic sediment filtration and simple plumbing such as a hose bib. The addition of special filters, a pump, more complex plumbing, and a few other components can produce potable (drinking) water. The size, type, and application of rainwater harvesting systems are variables specific to each project. Each Nauhaus is designed with the potential to provide all the domestic and irrigation water required for building and homestead inhabitants.
is the creation of air exchange by channeling wind through a building. It is accomplished by opening doors and windows that have been placed to encourage cross ventilation through an interior space. Buildings only need energy recovery ventilation when conditions outside require that doors and windows be closed. In most climates, there are extended periods of the year during which interior comfort can be created through natural ventilation and other passive means.
There are two reasons.
- A central Nauhaus concept is to increase connection to the outdoors. Ideally, we want the building to be the mediator in a mutually beneficial partnership between people and the land. Air tight construction is part of that strategy because it allows us to drastically decrease the resources required to heat and cool a building, therefore lowering our demands on the land, whether in the form of firewood, coal, or oil. Still, whenever possible, we want to forgo machinery and create a direct connection to the sites, sounds, and smells of our surroundings by opening doors and windows.
- The core goal of the Nauhaus system is to create human habitats that work with the environment. This is not an abstraction. Only if we nurture the environment that nurtures us can we hope to survive. This is the essence of sustainability. To serve this goal, we use machinery and technologically advanced systems in the Nauhaus when they significantly increase building resource efficiency, thereby reducing pollution, climate change impact, and natural resource degradation. In our approach, then, technologies that require electricity are utilized for maximizing efficiency and tweaking comfort variables. However, we make sure that baseline comfort and everything essential for survival are achievable by passive and low-tech means. This means that a Nauhaus will continue to function and be a useful living space providing adequate interior temperatures, clean air, and water without exterior input other than periodic combustion in a small wood stove. In “passive mode” a Nauhaus would need to rely on natural ventilation to create air exchange.
"Breathable walls" is a phrase that is sometimes misunderstood. There are those who use this phrase to describe a building system that creates meaningful air exchange through the wall volume of a building without substantial heat loss. We are unaware of the existence of such a wall system. For us, the term “breathable wall” refers to the ability of a wall volume to take on water vapor in response to changing humidity levels in the surrounding air. The technical term for this is “hygroscopicity”. Hygroscopic walls can be a boon to indoor air quality because in many situations they will contribute to lower indoor humidity levels. Since high humidity is both uncomfortable and a prerequisite for most mold and fungal growths, lower humidity means better indoor air quality.
A breathable wall assembly usually consists of a large percentage of cellulose either alone or in a binder, though earthen materials such as rammed earth and adobe can be breathable without added cellulose. Other examples of hygroscopic wall systems are plastered straw bale, cob, cordwood construction, and a mixture of clay slurry and straw pieces called “clay-slip straw”. We are currently using a mixture of industrial hemp chips (shiv) in a lime-based binder called Tradical® Hemcrete®.
Breathable walls work especially well with natural ventilation strategies in mildly humid climates because mechanical dehumidification is not possible when the windows are open. Our primary design climate is very humid, so we combine breathable walls with whole house dehumidification to create a system that will handle all situations. Based on personal preference, the concept is to let the walls and windows do the ventilation and dehumidification through most of the warm weather, closing windows and turning on the dehumidifier only on particularly humid days.
When it comes to materials use, we’re not purists. If based on a lifecycle analysis we believe that a material will save more pollution and toxic emissions through the life of a building than was required to make it, we will consider using it. For example, many people are surprised to find that we use petroleum based foams in our buildings, both under an earthen or concrete floor and, on some projects, in the roof. We feel these are sensible choices given our present options and the urgency of our need to reduce carbon emissions. Still, when it comes to interior materials, we draw the line. If we are to guarantee excellent indoor air quality, only truly can be used for all surfaces exposed to indoor air.
It would seem reasonable to assume that this strategy is already common practice in the modern world of building. That would be a potentially dangerous mistake. Many commercial paints and finishes, trim materials, and even furniture and baby clothes (not to mention foods!) contain substances known to be toxic to humans. Our strategy is to start with local wood, stone, and earth for interior assemblies. We then utilize either site-made earthen plasters and paints or natural finishes manufactured by Earthpaint, an incredible non-toxic sustainable finish manufacturer located in our area. Here’s a blurb from their website:
Our biodegradable green finishes contain non-toxic, native ingredients derived from plants, vegetables, trees, minerals and elements. Nearly all of these components are gathered locally (within a day’s drive of Asheville, NC). We do not use anything that gets shipped in from overseas.
In an industry dominated by an overuse of dangerous petrochemicals, Earthpaint instead practices only responsible, limited use of these materials and has proven that there are better, kinder alternatives. We do not use any toxic petrochemical solvents. We do not use any mineral spirits, naphtha, toluene, xylene, formaldehyde or benzene. At present, 30% of our containers are recycled. Our goal is to use 100% recycled containers within 2 years. more
Ultimately, you can’t have good indoor air without good outdoor air. There are many flavors of air pollution. Most of them originate with the act of combustion, basically the act of burning. Combustion not only consumes natural resources, but releases polluting particulates and CO2, the main culprit in our present global climate change woes. We burn fuels to manufacture pretty much everything, from concrete, lime, and steel to the plastic packaging on your organic lettuce. Burning is also the source of energy for most of our electricity production. Of course, our cars and trucks are propelled by the “internal combustion engine”…more burning. The Nauhaus approach reduces combustion and therefore helps clean the air in the following ways:
- The conventional approach to heating, cooling, and electrifying our homes is combustion based. For most of us, a light or TV at home is made possible by a coal-fired smoke stack. The Nauhaus passively reduces energy use, and therefore associated polluting combustion, by 70 – 90% over the norm. With the addition of renewable energy systems, a Nauhaus can be combustion neutral, or even combustion negative if it produces more power than it uses.
- Cutting energy use during the life of the building is a huge step, but what about the energy required to make the materials we use. The sum of the energy used to harvest, process, and transport a material to the building site is called “embodied energy”. The Nauhaus system focuses as much as possible on site-harvested, local, and natural materials because they cause the least pollution and resource depletion in their manufacture. Examples of each are:
- Site-harvested. Compressed earth blocks and earth plasters
- Local. Rough milled timber and trim materials, stone, and finishes from Earthpaint
- Natural. Straw, purchased earth materials, cellulosic products (recycled newspaper insulation, Tradical® Hemcrete®.