We had a kick-off meeting with our MEP consultant Benjamin Klein and I will try to summarize (before I forget everything which was discussed!):
- Heating / Cooling: Each apartment has its own ducted air handler (12,000BTU Mitsubishi), but we might have a combined 6 ton condensing unit on the roof. Each apartment can have its own temperature setting, but we’ll have one shared bill which we’ll have to subdivide by apartment size (judged by square footage). The main reason for this solution is that one big condenser is a great deal more efficient at low temperatures, which translates into an even lower heating bill. It’s also simpler to maintain one unit vs 7 or 8 units. We would probably be fine with less than 12k BTU, but that’s as small as they get. Additionally, the pump runs with variable speeds so it is able to scale down it’s heating/cooling output without losing efficiency.
- Fresh air: Each apartment will get its own Energy Recovery Ventilator (Zehnder ComfoAir200), which will be independent from the ducted air handler to keep things simple and to avoid negative interaction between the individual fans. One simple solution for avoiding double ducts would be to have the air handler supply in the living area and the ERV supply in the bedroom. ERV return in the bathroom, and AH return just outside the bathroom. The supply air out of the ERV is a couple of degrees colder than the design temperature, but this might even be welcome because it’s a bedroom. Both units are hidden in the ceiling above the bathroom but accessible.
- Fresh air UPDATE: We will have two ComfoAirs550 in the unconditioned basement supplying the apartments with fresh air. There are some advantages to this simpler approach: it’s less expensive, the filters are accessible from a common area and can be serviced by 1 person, there is less room for human error due to the wrong settings of the HRV (download the user manual here to see that they are quite complex to operate) and we have almost no duct losses.
- Domestic Hot Water: Considering HAUS has no natural gas connection we will try to supplement our electric heat pump water heaters with an array of flat plate or vacuum tube collectors. (Stiebel Eltron or Viessmann). A quick modeling in PHPP looks promising!
If you like to see more about our Haus here is the link…
Mechanical System
We started working on the conversion of a good ol’ Brooklyn warehouse into a single family Passive House residence. The existing structure was built in the 1960s and is a commercial building in the residential part of Williamsburg. The design concept is quite simple: We propose to create a courtyard to bring in natural light and also serve as a divider between the living area and the work studio. The small roof extension houses the bedrooms and bathrooms. We were careful to keep the addition low in order to bring sunlight into the courtyard year-round, particularly the low winter sun for, you know, solar gain…
The challenges ahead:
- How to insulate the existing CMU structure to PH standards. We can’t add more than a couple of inches on the exterior because it is a lot line.
- We would like to keep the street-facing brick exposed, so we will need interior insulation in this area at least.
- We would like to leave the existing wood joists exposed, so how will we air seal the roof area?
- The existing parapets will have to be extended because of the increased thickness (min 8″ insulation and min 6″ for the green roof). To avoid a thermal bridge we will probably use Autoclave Aerated Concrete.
(this list will continue to grow…!)
It took us a while to decide which structural system we should use for our new building. In the end, we went with an “Insulated Concrete Form“ which is made out of cement-bonded wood fiber. Wood fiber, instead of polystyrene! The product is called Durisol -it’s a Dutch invention from 1932 and was widely used to rebuild European cities after WWII.
We were delighted to find out that there is a plant that makes it in Hamilton,Ontario.
Here’s is a list of reasons why we went this way and did not use regular polystyrene ICF’s:
* Most common ICF’s are out of Expanded PolyStyrene. While we have a few concerns about the durability of the foam, we just don’t like the fact that with a regular ICF we have 50% petroleum-based foam in the interior of the building.
* The symmetrical build-up of the insulation of regular ICF’s creates a thermal bridge by tying the floor-slabs structurally into the concrete core. Durisol forms have the majority of the insulation on the exterior where it should be.
* The company claims an R value up to 28 for the 14″ thickness with 5″ mineral wool in the cavities which is sufficient. (Conservative PHPP modeling came closer to 25, but that’s still good enough for this Passive House.)
* The interior surface of Durisol doesn’t have to be covered with a layer of Sheetrock–it can be stuccoed with clay, which should help balancing humidity levels.
* The higher weight compared to EPS blocks seem to help to prevent blow-outs during pouring of the concrete.
Our building has a simple envelope of 51′ long by 25′ wide, and it’s only 4 stories or 40′ in height. Normally this shouldn’t not pose any serious construction challenges but we building a Passiv Haus so certain areas need special attention. Here a (not yet) complete list:
* The cellar is outside the treated envelope but we still need to verify if it is enough to insulate the foundation walls or we still need to add a couple of inches of high-density, insulation-like foam glass under the footings.
* The two parts of the forms are connected by wood fibers and while this is great to avoid thermal bridging we still have to find a solution for applying the air-tight layer on the exterior, which is particularly difficult at the side-lot lines where we have existing buildings. So far, we are leaning towards a liquid applied membrane.
* Balconies built by cantilevering floor slabs are massive thermal bridges and so we are looking into a steel frame with wooden decking solution hung from the exterior walls with aircraft cables and stainless steel anchors.
* Roof parapets should not be filled entirely with concrete but foamed out in the last 4-6 inches (another thermal bridge).
After talking to very helpful person at the company we even came up with an estimated price for the exterior wall of $40,000 including delivery to Brooklyn. Here is a link to the Canadian Durisol website which has detailed technical information.
PS: it seems that this simple building requires some creative solutions from our structural consultants (especially the interior stair) so a loud Thank You to them!
Today we were surprised (and very pleased!) to learn that we won TreeHugger’s Best of Green Readers’ Choice Award in the category “Best Young Architect.” Thank you, TreeHugger — for appreciating our work, and for including us in such esteemed company as the other two firms nominated, and most especially for being staunch advocates of Passiv Haus.
A big thank you to all the people who voted for us and especially to Lloyd Alter for nominating and voting for us too. We are now officially a one award winning firm! : )
We just got some interior photos of the freshly cleaned interior all bright and sunny…
Q: So why are there these exposed ducts everywhere?
A: We like them, but they also serve a purpose… read on!
Three photos from our new Passiv Haus retrofit project in Fort Greene: on the left, 1940 with no cars; in the middle, 1980 with gigantic cars; and, on the right, 2011 with no cornice. Our two main goals are restoring the beauty of this landmarked building by bringing back the cornice and bay windows, and the full renovation of the interior to meet PH standards. More to come…
We started working on a new ground-up project in one of our favorite neighborhoods, Greenpoint Brooklyn. It will be a 7-unit Passive House apartment building called Haus, and will be built on a typical Brooklyn-sized 25′x100′ lot. Each of the floor-through spaces is ~700sqf; the 1st floor unit has a private rear garden and all others have a generous balcony; everybody shares the roof.
The major design challenge of this project is to prove that a PassivHaus in NYC can be built for comparatively little money — even more so than our existing PH projects, which have very reasonable construction costs but the owners opted to invest in high-end fixtures and appliances. Haus will instead be a true Every Man experiment, and a good gauge of how reasonable it is to expect that even people with very modest budgets can build a Passive House.
Let’s see how it will all work out. We are very excited!
You can find more drawings and details here!
No Passive House in the Northeast is really warm enough to exist without at least a small heat source, and humans need fresh air to breathe in an airtight structure, too, so we tried to combine these 2 elements into 1 system…
thank you PowerAir for all your work and patience and ZehnderAmerica for the ventilation system
If you are wondering why our project at 174 Grand St does not have orange glowing windows like it’s neighbors please stop by February 1st at 6pm for an Open Passive House.
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… from Austria is available here in the US. Cembra, located upstate NY started to import Rieder Windows from Tyrol. They make a variety of tilt_and _turn wood windows with different glazing options and also a full blown Passive House certified window. The frame is aluminum clad on the exterior for low maintenance and has a graphite enhanced layer of EPS sandwiched to a wood frame. So they can achieve a an U-frame of 0.74 W/(m2K). (which translates to an R-value of 7.67) It sounds like they are able to offer quite aggressive pricing…
Cembra website is here.
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One of the requirements of the PassiveHouse Planning Package is to calculate the Treated Floor Area and all the areas of the building envelope. While this can be done by overlaying regular CAD floor plans, elevations and sections, it’s easier to work with a 3D model so as not to forget any building elements. We use Sketchup for our 3d needs because it’s easy to use.
Here is one approach:
- Start out with an empty Sketchup file. Purge any components and materials.
You can also start with this file here, as it has the layers already organized by PHPP’s building element group, such as”Exterior Wall – Ambient” ect…
- Import a section and an elevation file from your CAD program into SU. Delete all layers and have SU place them on the default Layer 0. Group the section and the floor plan, etc, and lock them too.
- Create a simple outer shell model using the imported CAD as a template. By redrawing the volume you have better control over the geometry you create. Don’t worry about creating only one closed volume for your whole project: SU has a simple way to extract individual faces from a volume.
- When you are finished, hide the imported plans, sections and elevations.
- Double-click on each face of your building and group it. After you have grouped each face with its surrounding edges, put it in the appropriate PHPP layer in SU. Turn on “color by layer” so that you have a visual feedback of what you are doing.
- After you have finished with the walls, slabs and roof, draw your windows. While the attributes command also works with groups, it can save you some time to create window face components. Don’t cut out the windows from your walls as PHPP does the subtraction for you. Name the windows appropriately and put them in the right South, North etc layer. ( I moved the windows 1″ in front of the walls so that the graphic output looks nicer)
- Now comes the trick: Open the “component attributes” window under Tools. After grouping each face you can add a component attribute to it even though it’s just a group. Click on the + icon in the window and call it “A” for area. (so that you don’t have to type the whole word for every face)
Hit enter.
Click on the empty rectangle to the right of “A” and type:
= (FACEAREA()/2)/144
Hit enter again.
The reason for this is that SU counts both sides of a face (hence a division by 2) and calculates in inches, so for your output to be in square feet you must divide by 12*12=144. Of course you have to type the command only once; for the other grouped faces just paste your copied FACEAREA command.
- Go to an orthogonal side view and select each floor and group it too. This ensures your final data output is nicely ordered by floor.
Select file/generate report and pick CSV and save it.
- Import the CSV file in Excel or Google Docs. The last column shows you the area in SqFt of each element of the outer building shell of your project, which you can link to your Area Calculations sheet in PHPP.
Use the saved time to redesign the building and start again…
Enjoy!
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We opened the container yesterday and unwrapped them…They look great…frameless, triple insulated glass and elegant rectangular wood frames… photos coming next week!
What you see in this photo is the Concrete Masonry Structure with the 7″ thick EPS insulation. Thick walls!
We started working on the design of a new building which is again somewhere on Pacific Street. Again we are using our exterior circulation concept, but this time we are making the attempt to build a Passive House! Above is the first exterior sketch. More to follow…
While we won’t disclose yet where we found them, as the deal is not completely worked out, we can’t resist to show off the stylish windows we found. And to make it even more interesting please look at the performance data for a casement window (test size ~48″ x 58″):
- Uglass = 0.6 W/(m2K) or an R-value of 9.46 (hr.sqft.F/BTU)
- Uframe = 1.38 W/(m2K) or an R-value of 4.11 (hr.sqft.F/BTU)
- Uwindow = 0.83 W/(m2K) or an R-value of 6.84 (hr.sqft.F/BTU)
- SHGC = 0.48
Not too bad, isn’t it? ; )
photo credit coming soon.
What looks a bit like a racing stripe running horizontally around the top of the building is actually not decorative; instead it addresses a problem that we, and i guess many others, completely overlooked: a C.M.U. parapet wall is a massive thermal bridge!
What normally happens: The structure of the building is constructed of concrete, and the walls and roof are insulated on the exterior. This is absolutely a good thing, as exterior insulation is far superior to cavity insulation of the interior stud walls. What has been historically overlooked, however, is the fact that by not wrapping insulation all around the 42″ high parapet (NYC building code) we create a huge cooling rip for the building. As you can see in this Therm model (heat transfer modeling software), the upper corner is much cooler than the other interior surfaces and so condensation is more likely to occur here (grey: concrete, yellow: EPS, blue: XPS).
One way to solve this problem is to use a different concrete-based material which has a similar fire rating to CMU but is a much better thermal insulator: A.A.C or Autoclave Aerated Concrete! AAC has an R-value of up to 1.25 per inch, compared to 0.07 (hr*ft2*F / BTU*in). This is quite easy to see in the different isotherms:
Here’s a last close-up shot how CMU and AAC come together. The metal strip you see in the photo is the flashing detail which will terminate the roof membrane later…
