In the PHPP 2007 manual there is a section called “First Steps”. This is designed to give you an idea of the basic inputs that are required to calculate the heat demand which is the primary target of Passive Houses.
In order to do this simple calculation and see how your project is projected to form in this one area, you only need to complete the worksheets that feed the Annual Heat Demand worksheet – the U-Values, Areas, Windows, and Ventilation wprksheets. Since my project is not located in the default European climate area, I also added information to the Climate Data sheet so that it would consider all inputs from a Seattle perspective.
At this time I am still designing the Passive Bunkhouse so I just used the loosest of information to begin looking at how it would work. I know I want to use vacuum panel insulation but I am also adding some additional mineral wool in the void. Because of the humidity factor at my location and the weight issues, I tried using metal studs with an aerogel strip to break the thermal bridge. I have temporarily selected fiberglass for the exterior but am still investigating recycled plastic as a material source. I know I want to use the Lunos E2 ventilation system that the guys at 475 sell. Windows and doors I plugged in from the Optiwin line. At this point I am using what can be expected to be high quality Passive House options just to see what happens with the PHPP. I haven't considered cost.
Fortunately for me the view on my property is to the South and my plan minimizes the North facing wall while maximizing the glazing to the South. The climate here is fairly mild – we rarely get below zero or above one hundred degrees. My lot has significant shade but is cleared enough that there is also good periods of direct sunlight. I am hopefully optimistic that the PHPP will like my idea.
I entered the information in the few worksheets required for this basic exercise and….. it failed. Miserably. I knew this would most likely happen because there is what some call the small building penalty for having a small building volume to area ratio. If my trailer were two stories tall, it would perform better. We’ll look into the science of that further in my next blog installment. For now I felt like the guys from the show Mythbusters – only in reverse. Instead of blowing something up, I was going to change window sizes, and throw insulation at it until it met the PH requirements. After many iterations it finally did with way too much insulation to be practical.
I know that small is hard but that small has been done in Passive House. I need to go back to the drawing board and see where my plan differs from those who have successfully designed and built small Passive House projects.
Up Next – What is this so called small building penalty?