🌲Passive House Design Basics

Five Tenets of Passive House

Introduction to Passive House Design

Like Steve Jobs--the mastermind behind the infectious gadgets, architects are inventors. At its core, the everyday practice of architecture is about devising solutions and enhancing existing techniques to improve human habitats. The trick is, how to create spaces that also reach into our beings and affect the intangible portions of our human experience. Buildings should function with the ease of an iPad, looks cool, and simply works well. What we are talking about isn’t rocket science but a subtle craft that outperforms current industry codes and standards. It’s about achieving Passive House standards—super-insulated and ventilated right, with each and every design.

How this is done, requires little more than applying fundamentals of basic shelter, adding some simple objectives and software. It’s about using the software as a tool in our arsenal to develop buildings that improve the quality of life by quantifying comfort and personal health.

The primary software is called the Passive House Planning Package – PHPP for short, and it does a miraculous job of quantifying the once thought unquantifiable. Take for example a comparison between PHPP, and the likes of, say RESCheck – the current standard for code compliance + 2013 IECC requirement interface (Michigan Residential Code 2015). In the specific category for envelope inputs, RESCheck requires only the R-value and gross area of the surface being defined. Let’s stop at R values for a second - PHPP breaks down R-value into 3 categories:

  1. Surface Film Resistance values

  2. Individual R-value per inch properties separated by material (many assemblies have over 5 materials)

  3. Percentage of framing or structural material that effectively discounts the R-value for each individual material.

What you end up with is a conservatively planned building design with defined values for exactly what is in a wall and roof assembly when modeling for a Passive House. To finish the comparison, for the area requirement with PHPP wall envelope assemblies require gross dimensions in addition to net dimensions taking into account the interior volume of air for mechanical performance. A complete description of PHPP would take hours. What can be learned from this short comparison is that this level of detail and quantifying severely cuts down on error in the energy model approach to design and construction – allowing for a truly quantifiable, 90% better-than-code performance that Passive House is known for – both proven theoretically in the modeled simulation and actual after construction performance.

This software is used to analyze the thermal comfort and physical performance of the building envelope. This is nothing new, but its employment in the design and construction of buildings is where we cross over from the tangible to the ethereal, where personal comfort and health are the essential components of our everyday. This is supported by the mixing of the shelf components in a calculated combination to achieve truly great buildings.

If we are to meet the ambitious requirements of AIA’s 2030 Commitment, we need to start pushing past the bar of our current energy codes, let’s face it, they are not anywhere near on track to meet Net Zero Energy by 2030 – Passive House is going to be the closest, at 80% of the way when referencing the goals for 2030 Challenge. Therefore we need to take it upon ourselves to be the leaders of the built environment, once again, and with the types of technology explained in this article, we have the ability to do so.

AIA’s 2030 Commitment does vary slightly from the Global 2030 Challenge. It does not require firms to meet net zero by 2030, it is more of an open-source database of how our designs are performing, a tool to encourage architects and clients to continue to improve our built environment.

In the ever-advancing society that lives in, we as architects, cannot do everything. Nor do we need to. With new delivery models like integrated project delivery, architects can build diversely talented teams that work together to develop excellent high-performing buildings at every scale, much like a conductor guides an orchestra to create beautiful symphonies. For the design shown in this article, our office has worked very closely with a Certified Passive House Consultant (CPHC), to develop the design without sacrificing performance. Without this collaborative process, the project at a minimum would suffer from a drawn-out timeline and risk not meeting the stringent standards of US Passive House.

Our design team has brought a design from concept to building permit within a few months. After six years the project has completed construction and has achieved rigorous certification and can use the label of, Michigan’s first Passive House certified under Passive House Institute United States (PHIUS). While this is a fact that we can be very proud of, the more important notion to us is that, by using PHPP to inform our design, we can confidently assure the client that their project is not only one of the highest-performing homes in the country, but it also meets all of their space and comfort needs. This is our utmost goal, to provide the client with an excellent building that will last many generations.

Four Principles of Passive House Design

1-Solar Orientation

Each design starts with a site plan that accurately orients the main elevation of the building directly south for maximum solar gain potential. By harnessing the sun’s energy in the winter and managing it in the summer, Passive Houses can take advantage of the free and natural resources. Each Passive House is designed for its specific climate region.

2-Super-Insulated Envelope

By increasing the amount of insulation all around a Passive House, we can control temperature differentials through all four seasons maintaining a comfortable indoor environment 365 days a year. By using blown cellulose insulation a Passive House dramatically reduces the embodied energy compared to batt insulation or spray foam.

3-High-Performance Windows

In addition to a well-insulated exterior envelope (walls, roof, and floor) a good passive house also maximizes thermal comfort with carefully chosen windows and doors that are thermally insulated from the exterior. These windows are also triple-pane windows that have a higher R-value to reduce excess heat loss in the winter and heat gain in the summer. Window size and placement are also very important. In the Northern Hemisphere, it is ideal to have the largest windows facing directly south and smaller and fewer windows facing north for optimized building performance.

4-Air-Tight Construction

In concert with the insulation, the envelope of a Passive House is carefully constructed to minimize cracks and thermal bridges where air can infiltrate through the house. By dramatically reducing air leakage, a Passive House saves on energy costs that standard construction spends on reheating draft homes. The air-tight layer of a Passive House acts like a balloon filled with water, eliminating leaks.

5-Fresh Air Ventilation

With all four of the above methods accomplished, the final step is to ventilate the Passive House efficiently. The best way to do this is with Heat Recovery Ventilation. This system takes 100% fresh air from the outside and preheats it with the exhaust stale air from the inside of the house. This quiet system replaces traditional fossil fuel-burning forced air furnaces.

Additional Resources

Phoenix Haus - Michigan’s First PHIUS Certified Passive House (Project Architect - Designed at Sedgewick + Ferweda Architects)

Satori Haus - Project Architect - Designed using Passive House Principles at Sedgewick + Ferweda Architects

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