Author: Katie Henry

What is Passive House?

Passive House or PassivHaus – The Comfort of Energy Efficiency

Passive House (or PassivHaus in Europe) is an energy efficiency standard that was developed in Germany but has its foundation in North America. The goal of Passive House is to reduce the energy required to heat a building by 70-80%, relative to current code-built buildings. The same goes for reducing cooling energy use in a cooling climate like Phoenix, AZ. Three primary design considerations and several secondary principles are critical. Also, it is important to highlight that in addition to energy savings, Passive House Buildings offer a healthier, quieter and much more durable and comfortable building. In commercial buildings, let’s not forget how all these things convert into a productivity factor, which effectively contributes to the ROI. The Passive House approach is rigorous yet very feasible with the right attention to detail from design through construction. PassivHaus buildings in Europe and increasingly in North America are being certified every day. Parts of Europe have and will be making PassivHaus the required building code, as are parts of North America.

In the 1970s, Wolfgang Feist traveled to the US and Canada to learn about various buildings that were being constructed in response to the energy crisis. Some had Passive Solar Design approaches. Others were highly insulated and some included double stud wall construction. Still others, like the Saskatchewan Conservation House, had many of the principals found in today’s Passive House buildings. However, the Passive Solar Design approach often suffers from overheating even in the winter. Many of the super insulated and double stud homes had issues related to moisture, such as rot and mold in the walls. From his studies and the practical application of what he learned, Dr. Feist eventually developed the PassivHaus standard and built the first PassivHaus in 1991. The standard has two primary objectives. The first is heating loads must meet 4.75 kBTU/sf/yr. Most existing and even some new homes are 40 to 70 kBTU/sf/yr. The second is air tightness must be below 0.60 ACH50. Most existing homes are 4.0 to 15.0 ACH50 and even worse.

The three primary design considerations are SuperInsulation, low air infiltration and minimizing thermal bridging. The insulation levels are generally based on the specific climate for the project and can vary due to many circumstances. It is not unusual to have below grade foundation and slab and above grade wall insulation in the r-40 to r-60 range. Roof/ceiling insulation can often vary from r-65 to over r-100. Air infiltration rates are a standard and are tested or commissioned at 0.60 ACH 50. This is very tight and very achievable with proper attention to detail. Finally, thermal bridging often requires eliminating or reconfiguring cantilevers, insulating footers and rethinking some of the designs like balconies and bump outs that we see in many North American homes.

For several years, AE Building Systems (AE) has been bringing this mindset to a wider audience. Basic principles such as increased thermal performance, reduced air infiltration, and reduction of thermal bridging are keys to providing efficiency and comfort. AE has brought together separate building envelope components into a cohesive system that can meet these efficiency requirements and provide comfortable, durable and healthy buildings.

Most people do not understand why they are uncomfortable. We know we are cold or hot but not entirely why. There are several reasons and following are a couple examples. A standard window with a u-value of 0.30 is considered energy efficient. However, on a 7-degree F day, the indoor surface temperature on the u-0.30 window will likely be below 60 F. With a cold surface, our bodies are literally robbed of its heat due to radiation. Heat travels to cold and our bodies radiate heat to the cold surface making us feel cold. In addition, cold windows and walls often create convection currents within the building to include our living rooms and bedrooms. Air next to a cold wall or window drops and warm air in the space rises creating a very local convection current or microclimate that most believe are drafts. A similar condition is stack effect where warm air rises to the upper levels in a building while cold air drops to the lower levels. In some homes, there is often a 10 to 15 degree temperature variance between lower and upper levels. Higher performance windows and walls will increase the interior surface temperatures to levels that reduce the potential of the walls and windows to literally “suck” the heat off your body. At the same time, improving the interior surface temperatures will reduce the potential for convection currents and stack affect or microclimates within the building.

Several secondary considerations are important. First, high performance windows are crucial. Windows are the weak spot in our building envelopes. Windows with u-values as low as u-0.11 (r-9) are often necessary for achieving the Passive House standard. Passive Solar or solar heat gain is important, but it is also important to optimize and not maximize south facing glazing – to minimize the potential for over-heating. Also, it is critical to incorporate mechanical ventilation. Most leaky homes get fresh air through the cracks and holes in the walls. This is not where you want to get fresh air. Energy Recovery Ventilation (ERV) systems bring in fresh air and transfer the heat to the incoming fresh air effectively keeping the heat where it belongs while filtering the air. Also, a shoebox design is often incorporated with Passive House. Bump outs and corners invite thermal bridging and air infiltration. These feature, while they have aesthetic benefits, do not contribute to energy efficiency and comfort. Moisture management is also critical. Moisture most often enters walls in the form of vapor or humidity in the air. When the walls are cold, the vapor condenses on the interior of the wall. While Passive House buildings are largely air tight and have minimal thermal bridging, it is important to pay attention to how walls might have condensation and more importantly how they will dry. Also, “House” is a literal translation of Haus. Haus in German means “place of inhabitation” and Passive House applies to schools, office buildings, etc. Existing buildings are not excluded and passive house applies to retrofitting buildings. The retro-fit requirements are not as stringent, but achieving them can be quite rigorous depending on the building conditions. Finally, spec homes or homes built to be sold can pay off. Having a realtor who knows how to market this type of special building is extremely beneficial.

AE Building Systems has been delighted to have had the opportunity to provide products to several Passive House projects as well as other standards or objectives, including Zero Energy buildings. There are several important considerations, and we do our best to help our clients through the process.

The Quality of Air

The focus of AE Building Systems over the years has been the building envelope. We have concentrated on this specific part of the building with the conviction that most issues related to green building start with a well designed and executed wall assembly. In fact AE has predicated its entire business on this basic idea. While most of our focus has been energy efficiency and comfort, the idea that a building should be healthy has always been assumed. Recently, a couple of events have brought this very important issue to the fore of AE’s thinking. Specifically the idea that occupant comfort is not just related to air temperature, but also the specific content of the air they breathe and the indoor air quality.

The Virtue of Health

A few months ago Jackie Burnett contacted AE, because of her interest in building a Passive House. She was moving from Vermont to Fort Collins and was searching for some land on which to build. In meeting with Jackie it became apparent that her goals of this project were slightly different than the majority of our customers. While energy efficiency and longevity were important, the healthiness of this new home was of most importance. Jackie, like many people, suffers from the debilitating effects of toxic environments. Mold, mildew, high VOC contents, all contribute to symptoms that can leave her bedridden. Jackie’s home not only needs to be free of these poisons, but needs to remain so for the life of the building. Jackie came to AE with very specific needs. She wanted factory produced wall assemblies, products that had little to no VOC content, and systems that provided a healthy indoor air quality. Jackie has helped educate the whole AE staff on the virtues of a healthy building and their effects on occupants. Fortunately AE is in a position to help and we are looking forward to continuing this journey with Jackie.

The Healthy Air Equation

Jackie Burnett feels the real effects of poor indoor air quality and came to AE primarily because of her interest in the CERV (Conditioning Energy Recovery Ventilator). Recently, AE invited Ty Newell from Build Equinox to give a presentation on the CERV. Ty specifically spoke about the benefits of good IAQ. As we build tighter and more energy efficient “a critical shift in thinking from a goal of indoor environments that are acceptable to the occupants to those that are truly healthy and productive” must take place. (Bill Bahnfleth 2013-14 ASHRAE President). We have spent many years researching and perfecting wall assemblies that are air tight, with high insulation values, but can also dry to the outside. This was the obvious solution to homes that were failing do to moisture penetration, resulting in the development of mold and decay. Not only were our construction techniques resulting in short building life cycles, they were also placing building occupants at risk. Tightening a building helps reduce the amount of VOC content allowed to infiltrate a building. Increasing insulation levels help to reduce energy loss and increase comfort. But, without a way to continuously eliminate VOC build up and manage moisture, we are setting a course for continued building failure and risking the long term health of our clients.

The goal of the CERV is to manage these these risks in an energy efficient manner. The CERV continuously monitors indoor air for both CO2 and VOC content. Through it’s interface occupants can set both levels to meet their desired comfort. Taking a hourly sample, the CERV will only bring in fresh air when one or the other of these levels is exceeded. It can’t be overstated the importance of appropriate CO2 levels. Recently, Berkley Labs conducted a study on elevated indoor CO2 levels. They discovered that contrary to previous thought, decision making impairment can start as low as 1,000 PPM of CO2, with significant impairment beginning at 2500 PPM.

The primary source of indoor CO2 is humans. With the adverse effects of CO2 becoming clear and the increased air tightness of buildings being mandated, designing an efficient mechanical fresh air system is now critical to any building plan. Likewise, with VOCs, a precise plan must be made. VOCs can range from smells produced in a home from cooking and other activities, to off gassing of building materials, furniture and even humans. Keeping these toxins at an appropriate level is key to a healthy indoor environment.

The building industry has understood for a while that keeping the humidity levels between 35 and 50% was optimal for building performance. As it it turns out is is also optimal for occupant health. Humidity levels below 25% lead to drying of the mucous membranes and chapping of the skin. Higher humidity levels increase the development of mold and fungi. The CERV maintains humidity levels at those 35 to 50% levels all year around as seen by the graph below.

A healthy building starts with good design and product selection. Making your building tight and with high insulation levels is a good start. In order to maintain the health of the building and the health of the occupants a good fresh air system is critical for the long term functionality of the building. Selecting base building materials and furnishings with low VOC content and low levels of toxins is also a critical point in providing a healthy indoor environment.

AE Building Systems is now providing a variety of mechanical fresh air products that meet the standards discussed above. We are actively researching products to round out our current offerings and expect to offer design services in the near future. By providing a complete Indoor Air Quality package, along with our other products, AE can offer an energy efficient and healthy building envelope. Contact AE Building Systems for more information.

The Independant Power of Elon Musk

Just last week Elon Musk announced that Tesla would be producing the next great advancement in battery storage. Until now, battery storage for Photovoltaic Systems were costly, unreliable and required a large amount of space. That has all changed with the Powerwall. For only $3500 anyone can now purchase a 10kw storage system that will allow off grid operation of a home or building. As Musk stated in his announcement, this could be as revolutionary as the cell phone and as ubiquitous as the smart phone. We will no longer need wires to bring power to the world, and we will no longer rely on fossil fuels for our power sources.

What exactly does this have to do with high performance building? Generally, we building science geeks tend to focus on ways in which we can eliminate waste and reduce the amount of energy required to operate a building. We design and construct building envelopes that reduce air infiltration, and manage our heat with high levels of insulation. Squeezing out every last BTU in our designs until we can comfortably heat with a blow dryer. These are all noble goals and once critical mass is met will help significantly reduce the amount of fossil fuels we consume. Ultimately, however, no matter how efficient we become, we are consumers. In order for a Passive building or a near Passive building to be net zero energy it must produce power. Combining the two technologies would be a powerful force that could literally convert the world to only renewable energy production.

In Musk’s presentation he pointed out several astounding facts that make the previous statement more real than we might think. Musk explained the the surface area required to power the United States completely using solar was equivalent to a square the size of the northern Texas handle and that the area of battery required to mange this production was a tiny dot in the middle of it all. The United States would need 160 million 100kw Powerpacks, (Tesla’s utility grade battery system), to transition entirely to renewable energy. While this is quite impressive there is a key variable that gets ignored in Musk’s presentation that would make this transition faster. Status quo ruled Tesla’s assumptions as it related to the worlds energy consumption. As we all know the majority of the that energy is consumed by buildings. What if we combined Tesla’s world vision with the continued proliferation of Passive House?

Passive House seeks to reduce the total required energy to run a facility by up to 90%. This type of construction is becoming more prevalent and in some cases required throughout the United States and the World. This reduction in energy consumption would make adding renewables more obtainable. Individual buildings would require significantly less PV and fewer batteries in order to operate entirely off the grid. Less money spent on the renewable side of the equation would mean more money for energy efficient strategies and materials. Combined with more aggressive governmental policies reducing carbon use, like we see in Fort Collins, flattening the Keeling Curve becomes more realistic.

AE Building Systems is proud to be part of a global movement to be better stewards of our planet. Make no mistake, that while we tout the personal benefits of building more efficient, we have a clear vision of making the world a better place. Leaving a cleaner environment for our children. By providing education and product that reduce building energy consumption we approach the problem from the opposite side of Tesla. Soon we hope to meet in the middle.

Bringing it all together

AE Building started out with the simple idea of filling a void in the building industry by providing high performance, energy efficient building products. Since that time we have expanded our reach by becoming building envelope experts, consulting with our clients on the many decisions required to develop a high performance wall assembly. We have seen a maturation in the market where owners are increasingly demanding better performance and architects and builders are responding. AE Building has responded as well. We have been ahead of the curve with many of the products and technologies that we promote and have found it necessary to provide appropriate training to many of our customers and installers. A more recent example of this type of collaboration is with our excellent installation partners Efficiency Matters. AE has always been impressed with their attention to detail and fine craftsmanship, but wanted to be sure they understood the intricacies of a Alpen window installation using SIGA air sealing products. AE partnered with Nicholus Holbus from SIGA and Riley Dennig from Alpen to develop a joint workshop. Efficiency Matters crews received hands on training in regards to the application of SIGA tapes and membranes as they relate to window installation. Riley then walked them through a best practices training on an Alpen window install as well as making appropriate adjustments to the windows for optimal operation. They finished with an Alpen factory tour. This type of training ensures that AE and Efficiency Matters can continue to service their clients in the very best way possible.

A good example of how this training helped with a customer comes from Matt Bruckner of Bruckner Construction. Matt couldn’t be happier with the products and service he received from both AE and Efficiency Matters. AE put together a wall assembly for Matt for the McNaughton residence that included air sealing, windows, and exterior insulation in an integrated package. AE also suggested that Efficiency Matters would be an excellent choice for installing the systems. When we spoke with Matt he was excited to point out how seamless each component of the system worked together and the attention to detail that Efficiency Matters displayed in installing the system. Not only does the finish product look fantastic, but we know that the owners will be pleased with the resulting comfort and energy savings.

AE is continually looking for opportunities to collaborate in this manner with owners, architects and builders. Recently we participated in the Energy Smart Contractors Expo speaking on deep energy retrofits. We are working with several architects, helping them to develop new “go to” wall assemblies. When is comes to wall assemblies we will go anywhere and speak to anyone that is interested.