A couple of years ago we renovated an abandoned pasta factory in Oakland into affordable housing. This is part of a larger project for the Oakland Housing Authority called Tassafaronga Village - www.dbarchitect.com/Tassafaronga.
It had a beautiful wooden floor that had to be removed to install a shear diaphragm. The contractor removed the flooring and gave us some which we put into storage.
The floor has to be carefully sorted before being diagonal nailed down. The goal is to finish it in a minimal way so that it shows some of the evidence of it’s history.
The view of the Zero Cottage site as of July 24th, 2011. The foundation and underground utilities are in but we’ve been stalled for a month sourcing the FSC (Forest Stewardship Council) certified framing material. Our goal is to use 100% salvage from the site, recycled, or FSC wood. This has been a challenge because of the lack of availability more than the cost. We’re hoping to have delivery in the next two weeks.
The first day of construction was on March 1, and just in the last three days, Jon Blandin and his Falcon Five crew have managed to build a bridge and walkway to protect the breezeway, move the contents of the existing shop, and scrape up all of the gravel and stone throughout the breezeway. Things are looking quite good and orderly.
Jon came up with a fantastic idea to reuse some of the wood we had on hand to make these really nice boxes. He will be creating a series of these boxes to hold all of the earth that will be dug out during the trenching of the breezeway. The boxes provide a really area efficient way for holding all of this material while we have the open trench.
Jon and crew built this extremely handy bridge to cover the area of low ground between the breezeway and the old shop which is getting deconstructed. This bridge has proven extremely valuable for moving all of the large equipment in the old shop. Again, it’s made from recycled material on hand.
For all of you who remember the old shop, tomorrow will be its demise. But, get excited for the new more awesome, but smaller shop that will be open in November if all goes perfectly.
There are a number of factors that we’ve taken into consideration to design our hot water system:
We want to heat the water with as little fossil fuel as possible. To us, heating the water efficiently means that the sun heats the water as much as possible. In San Francisco, this is easy since it’s sunny in the Mission District 300 days per year. Still, any solar hot water heater (SHW) will not be able to provide necessary hot water all year, so we need another more traditional heater in the system.
We don’t want any pumps or tanks to have to maintain. The way to eliminate the tanks and pumps in the equation is by choosing a passive solar hot water heater which requires no pumps or tanks and works completely with thermal mass and hydrostatic pressure. The heater looks like a big box which is angled to the same degree as your latitude or angled at a steeper degree if you want more hot water in the morning. Inside the SHW box are huge copper tubes where the water is stored and sun absorbing materials that help the huge thermal mass of the water heat up. Next in the system is a tankless water heater which gets the water heated up to an optimal temperature of 115 F on those cold winter mornings. Voila! No tanks or pumps!
We don’t want any unnecessary exhausting that might allow air infiltration. If you are trying to do a passive house as we are, you don’t want any exhaust pipes to create an easy way for cold air to come in.This is best achieved with an electric tankless heater. Using electric, of course, means no exhausting like you would do for natural gas, thus no holes in the exterior. Electric also has the advantages of eliminating all the additional gas infrastructure normally needed, and electricity can be fully generated in-house, as in our project.
As it turns out, there are some pitfalls in every system. Here are a number of things to be aware of:
The passive solar hot water heater can overheat. Be sure that there is some sort of mechanism that allows for pressure release.
Not all tankless hot water heaters can accept preheated water. What that means is most tankless hot water heaters such as those from Bosch do not detect what the incoming water temperature is. Thus, they heat the water again. This is a huge waste and you might as well not have a solar hot water heater. The heaters from Stiebel Eltron, however, do detect the incoming water temperature which means if it’s hot then the system just passes water through without reheating.
Size your tankless hot water heater as if there was NO solar hot water heater. You cannot depend on your solar hot water in the winter mornings and therefore will depend on the electric tankless to supply 100% of your hot water.
We’ve recently been drawing away on framing plans, framing elevations, and cut lists to get the most efficient framing we can possibly get. We also get Leed for Homes Points MR1.2 and MR1.3 for generating this information. We use a program called Revit to generate 3D models that show us where every piece of lumber on the whole project is, and exactly how long that lumber needs to be.
We also want to get the wood FSC Certified for a number of wood components in the building. FSC Certification, simply put, is an assurance that the forests from where our wood came from will be around a long time from now through sustainable management.
FSC Certification is important. But another aspect of lumber that is often overlooked is the lumber waste stream. Let’s say I buy FSC Lumber and I get the lumber pre-cut and packaged for the job site. Very cool. So, there’s no lumber waste on the site. But, we’ve just moved the cutting from the site to the factory. What does the factory do with this scrap lumber?
Most likely, the scrap lumber from a pre-cut framing package is no more likely to be properly reused than it would be at the job site. This was a bit shocking for me to learn from a 30 year veteran of the industry. There are “good” lumber mills, however.
The good mills will reuse the scrap wood by burning it in a co-generation plant to create a portion of its energy requirements, or it will reuse scrap to make another product, or both. The worst case scenario is all the scrap is sent to the landfill without any thought being put into what happens to the waste.
Still, pre-cut packages offer the best waste stream efficiencies available because the cuts are computer calculated to create the fewest amount of boards needed. Just be asking these questions of your supplier and don’t be discouraged if they laugh at you.
Our firm is committed to achieving a number of major efficiency certifications, most difficult of which is the German standard called PassiveHaus. There are so many things you could say about PassivHaus, but essentially the idea is to use an extremely small amount of energy to heat your house through three measures: 1. super-insulation 2.eliminate air infiltration 3. heat the house with solar heat gain and ambient heat from people, lights, ect.
One of the major components for controlling these three factors are windows and doors because these are the weakest points of the system in terms of insulation value and air infiltration as well as the strongest points for gaining some solar heat. So, what do we look for in windows for the design of a passivhaus?
The windows should have at least two gaskets and a mechanism that firmly engage these gaskets when the window is closed. These gaskets insure quality air infiltration resistance by sealing the opening not unlike a door on a washing machine.
The windows should have as high an insulation value as possible in both the frame and the glazing. The highest quality window has a U value of .12 to .15 or R value of 8.33 (American Standard). This insulation value, of course, is used to keep the temperature extremes of the outside environment on the outside. Without buying German windows and glazing, the absolute best “normal” window can only render a .24 U value. What it takes to make this insulation value is pretty amazing. The glazing sandwich is three layers of glass covered with a specialized film and separated by two layers of a noble gas such as argon or krypton.
Windows should be thermally broken. Windows achieve a thermal break as much as they can in a couple of ways. First, insulation covers up the window frame as much as possible lowering the effects of external temperature. Second, there is a physical break with an insulative material between the inside frame and outside frame.
Windows should be reasonably priced. When I say reasonably priced, this is a relative decision. I think in many ways that quality (but inexpensive) vinyl windows, if given a chance, could meet PassivHaus standards in the overall system. For example, we have a window that is a casement window mulled to a fixed glazed panel. It’s a fairly big window. Initially, we had an estimate from Pazen which came in at about, say, $2,500 plus shipping. Optiwin, arguably the best window made, we didn’t even price. We priced an American equivalent called Jeld-Wen which is beautiful and high performing. It came in at 30-40% less than the Pazen. Now we’re talking! Next, we priced the mid range Sorpetaler, a German window, which has somewhat better performance than the Jeld-Wen. The price came in 50% below the Pazen not including shipping. If you include shipping, then the Jeld-Wen is arguably the better choice for an American Market.
Windows should be locally sourced. If energy consumption is an issue, then it should definitely be better to source locally, right? Possibly not. Why? According to Bronwyn Barry, a PassivHaus window expert at Quantum Builders in Berkeley, CA, because Sorpetaler are shipped by rail and ship to where we are in San Francisco, the carbon footprint is almost as low as shipping from Oregon by truck (Oregon is where Jeld-Wen windows are made). I think this debate will be up in the air for some time, but Ms. Barry has some pretty compelling data to back this up.