Residential energy use accounts for a whopping 20% of yearly greenhouse gas emissions in the United States. Luckily, there’s a solution that can consume up to 90% less energy than the standard home. It’s known as the Passivhaus standard and it’s used to create passive houses, or passive buildings. According to the Passivhaus Institute a “Passive House is not a brand name, but a tried and true construction concept that can be applied by anyone, anywhere.” So, what is a passive house? And how can you get one of your very own?
What is a Passivhaus?
Passivhaus, which literally means “passive house” in English, is a high-efficiency, low-emission construction standard originally developed in Germany. A building made using Passivhaus standards is designed to maintain a comfortable interior temperature no matter the weather with little or no heating or air conditioning.
Passivhaus Goes Beyond the House
Don’t be fooled by the name, passive houses can be any building really. Schools, churches, office buildings, apartments, grocery stores, factories and more can all be made using the passive house standard.
Check out this affordable housing project made using passive house certified construction standards.
In order to truly be a passive house, you must get your project certified. Currently there are two passive house standards that offer certification; The International Passivhaus Standard for Germany and much of Europe and The Passive House Institute – US Standard (PHIUS) in the USA. Although their certification requirements vary, both are based on similar principles: continuous insulation, airtight construction, optimized windows, thermal bridge free construction, and balanced ventilation.
Anatomy of a Passivhaus: 5 Principles of a Passive House
One of the most important aspects of a passive house is its ability to insulate itself from the elements.Think of a warm winter jacket. Like your warm coat, passive houses typically need continuous insulation that extends around the entire structure. This means that they usually require around double the amount of insulation of a standard building. However, energy savings in the long run will likely pay for the added cost of materials. Plus, eco alternatives to standard insulation like sheep’s wool insulation are increasingly available.
Air sealing technology
Passive houses not only require insulation from outside elements, they also need to seal ideal temperatures inside. That’s why passive houses require stringent air sealing measures. Doors, windows, skylights, electrical outlets on exterior walls, sill plates, and even hose bibs and the edges of recessed lights should be properly sealed. Essentially, any area that could leak air, should be sealed. These seals not only prevent heat and cooling loss, they also seal out damaging moisture.
Window and building orientation
More comfortable indoor temperatures start with the optimal building orientation. Passive houses are designed to take advantage of the sun or shade depending on the climate. Similarly, windows are designed to be oriented in the best possible position to maintain heating or cooling. To do this, windows are placed on southern facing walls to welcome morning light in the winter. Overhangs fitted to the exterior of the windows are installed to prevent the high, hot summer sun. These windows are often double or even triple-paned to trap optimal temperatures.
Free from thermal bridges
In a house, a thermal bridge is essentially a place that has weaker insulation that allows air to leak out. This area acts as a bridge where warm air will try to stream out to the cooler outside air. For passive houses, these areas should be sought out and well-insulated. Some places where thermal bridges can often be found are where a window is attached to the wall, where a wall meets a balcony, and where walls meet at corners. The first defense against these types of thermal bridges is to reduce their likelihood in the first place. You can do this by “using self-supported decks and canopies for low-rise buildings or reducing the number of cantilevered balconies and articulating architecture (lots of corners) on larger buildings.” The second line of defense is to add additional insulation around problem areas or using materials like thermal breaks on the area.
Of course, with all that sealing, a passive house will need to have a way to filter in fresh, healthy air. Passive houses require a ventilation system to rid the home of stale air, C02, odors, and other pollutants. In the winter this usually results in releasing warm air out and pulling cool air in. This makes it so the system has to heat up the cool air, upping the energy output. However, passive house ventilation systems use a heat recovery ventilator (HRV) to continuously remove old air and bring in fresh air. “During this process, it extracts heat from the exhaust air and puts it into the incoming air without directly mixing the airstreams together.” This reduces the amount of heat that needs to be recovered by about 15%. In the summer, passive house-certified ventilation systems can bring in and circulate fresh air without generating unwanted heat.
FAQ about Passive Houses
Do Passive houses cost a lot?
According to PHIUS, a small passive house can cost between 3-5% more to build than your standard home. Larger projects typically cost less, only 0-3% more than standard buildings. Of course, in the long run, passive houses can also save “up to 85% on heating and cooling and up to 60% on total energy use compared to conventional construction.”
Can you open the windows?
Yes, the windows and doors can be opened just like any other house! Although you may not feel the need to as often as a standard home due to the passive house’s advanced air filtration systems.
What about mold?!
While the airtight nature of passive houses inherently prevent mold growth, it’s still paramount to do everything to prevent dangerous mold growth. This means paying special attention to ensuring the HRV (Heat Recovery Ventilation) or ERV (Energy Recovery Ventilation) systems are working properly. In order to prevent mold growth, the HRV system must be balanced, with equal parts fresh air coming in and stale air flowing out. ERV’s can be utilized in damper climates as they prevent moisture accumulation which can promote mold growth fast.
What about the design? Do all passive houses look the same?
Nope! Passive houses can be designed many different ways in many different styles. However, they will still have defining features like thick walls, triple paned windows and other common features.
How can I get my own passive house?
Passivhaus is, at its core, a green building certification. Like LEED and EnergyStar certifications, Passivhaus aims to help construction companies and individuals create their more environmentally friendly buildings. The first step to building your dream passive house is to find a certified passive house designer or consultant. In the USA, you can find a consultant directly from PHIUS’s website. Similarly, Passivhaus Institute in Germany has some suggestions for designers on their website. Next, you’ll have to decide your certification goals. For example, PHIUS has a couple different certification goals ranging from low to zero emissions. Then, it’s time to get building! You’ll work with your designer or consultant who will help you during designing and construction. The final step is, of course, to get your house certified. For PHIUS, the certification process involves submissions at the design, construction, and finished stages.
For homeowners, developers, and construction professionals looking for a smart, low emission building method, passive house standards may be the perfect solution. With their simple, healthy, and truly green principles, passive houses might just be the next big thing in environmentally friendly design.