It’s “Haus” for a Reason

courtesy of Brian Curran Construction

In architecture, fashion, and pretty much everything besides sports, we cannot seem to avoid looking to Europe for inspiration and guidance. Relatively recently I’ve noticed builders adopting the concept of “Passiv Haus” as a form of sustainable building. While I won’t mention names or locations, through my experience with this concept here in the States, I find myself ever more opposed to its adaptation to fit with our typical construction style.

The majority of the residential buildings in the United States are constructed in a “stick built” manner, where individual pieces of lumber are joined to form a frame, the frame covered in wood sheathing, insulated with organic or synthetic materials, and then clad in any number of ways. Essentially our homes are a chaotic mélange of material that works fairly well when assembled correctly. In Europe, builders use masonry construction to create a relatively homogenous structure at a much higher rate. When left alone our different techniques do not create a problem, and why should they?  Even in the States we employ various systems and methods depending on the climate, or at least we should. These regional approaches do not affect home prices or aesthetics and in fact can contribute greatly to an area. The issue appears when we try to adopt an idea based on one system and adapt it to a radically different method. Here’s where “Passiv Haus” comes in.

The main concept I’ve seen taken from “Passiv Haus” and applied to new home construction is that of the super sealed envelope. I know of others but for clarity and brevity, I’ll only discuss this one. In theory and in practice, with the proper materials, the super sealed envelope reduces electrical consumption to almost absurd levels because the ”building is primarily heated by passive solar gain and by internal gains from people, electrical equipment, etc.”[1] Though eliminating nearly all air leaks, heating and cooling bills drop significantly, and by providing appropriately sized – and placed – windows, good air circulation is ensured during temperate seasons. In order to provide enough air changes during the rest of the year, as the envelope no longer “breathes” as we are accustomed, a heat recovery ventilator or energy recovery ventilator is installed. This super efficient appliance tempers the fresh air entering the home by transferring the heat or chill from the expelled air to the replacement air. Again, by not having to heat or cool as much, the appliance uses less electricity.  Sounds fabulous right?  Yeah, sure, as long as the power doesn’t go out, and you clean the filters, and you don’t have some sort of malfunction.

Now, with concrete or other masonry construction, the sealing of the envelope need only occur at openings or penetrations, essentially. With stick built construction, where a single wall will have many seams at all layers, the sealing must occur over and over and over again. I’ve been onsite where countless tubes of caulk, rolls of gasketing, and hours of labor have fallen prey to the sealing machine. This extremely tight envelope prevents air from getting through – the goal – but it also prevents air from circulating within which can quickly lead to mold and rot if any water makes its way into the wall.  The first question of the FAQ on the US Passive House website actually responds to this dilemma by stating, “Unlike most other new construction, the passive house employs an appropriate vapor barrier and then a mechanical, balanced ventilation system with heat recovery…moisture is safely removed, as well as other potentially unhealthy pollutants.”[2] One thing we’ve found over and over again is that no matter how right you think you are doing something, mistakes will be made, especially the first 2, 3, or 20 times. So even if under ideal conditions this should be the result, rarely will this occur in practice because of infinite other factors out of our control as the architect or contractor. This is the point of tolerances, of over-engineering, of getting that little wiggle factor that allows for some error on the part of anyone involved, and without it, conditions can go from bad to worse very quickly. Once water spurs organic growth within the wall, it is hard stop and generally requires the replacement of any affected material. If the owner attempts a sustainable demo and tries to recycle any “clean” elements removed, s/he would still be left with lumber covered in caulk, glues, and coatings. At some s/he involved would lose interest in any recovery because of the tedium it would require.

I’m just not sold on the fact that a reduced electrical bill offsets these other factors relative to sustainability. To be truly sustainable we need to accept our habitat’s quirks and temperature ranges, allowing for more extreme interior environments. Reduce the winter heating bill by dressing more warmly, embrace the oppressive summer heat, and rejoice in the few months between when everything is perfect. We as a people have lived for thousands of years in mostly unconditioned space. Only recently have we felt it convenient, and occasionally vital, to remain at 72 degrees all year long. And unless we want to start using mortar to adhere 2x4s or try and nail concrete blocks together, we need to stop applying masonry tactics to wood framed structures. If the concepts behind “Passive Haus” really work, we should look at the benefits they create and then find a way to get those same results using methods that work with, not against, our typical materials.

[100% of the projects featured on the US Passive House website are wood framed or of mixed construction materials (wood, masonry, etc). 52% of the projects featured on the European Passiv Haus website are wood framed or of mixed construction materials, while 48% are solid masonry.]

For more information visit: www.passivehouse.us and www.passivehausprojekte.de


[1] Passive House Institute US, (2010). Retrieved from www.passivehouse.us/passiveHouse/PassiveHouseInfo.html

[2] Passive House Institute US, (2010). Retrieved from www.passivehouse.us/passiveHouse/FAQ.html

Article Info
Posted by: Stefanie Dirks
Thinking About: Architecture / Building / Strategy / Sustainability / Technology
Location: New York City
Website: http://www.stefaniedirks.com
Twitter:
Add A comment
*
*