Section Cut Through Passive House Showing Insulation

For many weeks now Alex and our Passive House Certified consultant Eric have been dredging through the 32 page Passive House spread sheet, a very sophisticated piece of software provided by the Passive House Institute U.S. to manage complex design issues.  With it we  analyze and determine if what we want to build will actually perform to the Passive House standard, the most rigorous energy-use standard in the World.  During this time we’ve considered a variety of building envelope methods and details including: Structural Insulated Panels (SIPs), framing with truss joist (TJI) members, standard framing with SIPs, and standard framing within standard framing (Double Wall).  In the end through analysis of cost and performance, we have come to a mixed solution.  Roof and Floor will be framed with TJIs and insulated with high-densitey, blown-in fiberglass, and the walls will be custom ordered from a SIP manufacturer.   The advantages for this are too convoluted to explain here, but, to put it simply, we’ve eliminated the most difficult-to-construct building system, the walls, and replaced it with one that meets our specification with a much higher degree of certainty on a few critical points.

The first advantage to choosing SIP walls is air tightness.  Compared to stick built walls to SIPs offer superior air tightness.  Two layers of OSB and many inches of foam combined with simplified construction, fewer joints, makes these walls the most likely option to bring air leakage down to the 0.6 air changes per hour when pressurized to 50 pascals  (ACH@50).  This is the minimum requirement for air tightness in any Passive House, strict when compared to a new,  ‘tight’ house which usually measures in around 5.0 ACH@50.  SIP homes have been built that seal to 0.1 ACH@50, so our choice of walls will allow us to put more effort into air barriers in the roof and floor that consist of OSB tongue and groove for an acceptable overall air tightness.

Air tightness in a house takes care of convection, but insulation is needed to minimize the other way to lose (or gain) heat through the envelope, conduction.  Measured in R-value, insulation blocks conduction.  Fiberglass is most common, and a passive house needs a lot of it.  This house has more than two feet of blown-in fiberglass throughout the roof system to give a combined R-value of more than 100, well over double the code requirement.  In the walls this is impractical and another good reason to go with SIP construction. The foam that fills the bulk of a SIP wall has a higher R-value per inch than fiberglass allowing us to build thinner walls giving back precious floor area as compared to framed walls filled with fiberglass.

The last benefit to our envelope choice is speed.  However thick, our floor and roof will frame quickly, but double stud walls would take longer.  The SIPs will arrive on a truck and will be fully erected three days later.   We have struck a compromise between cost, performance, and speed that will allow us to build an extremely efficient building, one that does not need a furnace, for not much over the local, average building cost per square foot, at least that’s what our budget says.  More updates to come as construction begins in earnest mid-March.

We have officially broken ground for our new Passive House at 515 Dayton St. in Yellow Springs.  The foundation has been dug and the concrete poured and the mason will be finishing up this week.

Alex is currently hard at work on the Passive House certification, which requires information and specifications for every possible nook and cranny of the building- right down to the placement and number of wall penetrations and the R-value for the window casements.

In the meantime, Andrew and his crew have been renovating a chiropractor’s office (it used to be an art gallery) and working on various energy retrofit jobs.

Check back soon for more details.

The site, with trench

Laying a geothermal ground loop for the ERV

We’re happy to report that we have two very exciting new additions to our team! The first is Alex Melamed, coming to us all the way from Florida with a Master’s Degree in Architecture.  He is now officially our “Design Director” and has recently finished rendering the building plans for our Passive House.  He brings a wealth of knowledge and expertise in design and shares our vision for building a more sustainable world.  Welcome Alex!

The second is actually a piece of land- the future site of our Passive House.  Situated on a busy street, we chose the property because the southern exposure is to the back, allowing the owner to maximize solar gain without compromising their privacy.  There are also a number of mature trees, which make it a very lovely spot indeed.

With the site chosen and the house designed, we will now start the arduous process of ensuring that it is up to the Passive House standard.  This entails picking windows with a sufficient R-value, managing air infiltration and finding energy efficient appliances- all while staying within our budget!

Check back soon to see what we’ve decided.

Passive House Site

Hi everyone,

Welcome to our blog!

Here at Green Generation Building Company we have two modest goals for the coming year: participate in the Thousand Home Challenge by completing a deep energy retrofit and build a house according to the Passive House standard.

What is a Passive House, you might ask?  A Passive House is a building standard, originally developed in Germany, that allows for an almost 90% reduction in energy use.  It does this by maximizing solar gain, creating air-tight insulation and paying meticulous attention to every possible place a house might lose heat (windows and doors being the main culprits).  Because buildings account for almost 50% of all greenhouse emissions in the United States, transforming our building practices is a crucial step towards sustainable living.  For more information, check out http://passivehouse.us/passiveHouse/PassiveHouseInfo.html

While the Passive House standard is a good place to start with new construction, it is not really feasible to apply it to existing housing stock.  This is where the Thousand Home Challenge (or THC) comes in.  The THC is an initiative of the Affordable Comfort Institute (www.affordablecomfort.org), and its goal is to organize an effort to reduce energy consumption by at least 70% in one thousand existing American and Canadian homes by 2012.  This will primarily be accomplished through “deep energy retrofits” in which all the different energy loads of a house are assessed and then made more efficient.  This generally includes things such as sealing up crawl spaces, adding more insulation and installing more energy efficient appliances.

We plan to use this blog as both a diary and a forum.  Since green and regenerative practices and technology are still relatively new and constantly evolving, there are a lot of questions and dilemmas about how best to accomplish our goals.  This includes everything from which materials to use for our building envelope to how to reach a wider audience and market.  As we run into these issues, we will discuss them here, in the hopes that you, our readers, will find the conversation informative and also contribute your own knowledge and expertise.

Cheers,

The GreenGen Team