Energy Revolution in a Brooklyn Townhome
We have been going back and forth for a couple months now, debating which backup gas heating system we should use for the solar hot water. What is set is using the Heliodyne flat plate collectors with the Heliopak heat exchanger. The collectors will be (3) 4’x6′ units that we have to line up on the roof laying at a roughly 20 degree angle but unconventionally with the long side against the roof. We have Landmark visual clearance issues from the street behind the building. The tank size we have assumed is 120 gallons and the system is roughly sized for 75-80% of the hot water annual demand for the 2 families. Therefore, it will cover close to 100% of the summer demand and probably 60% of the winter demand. For this reason, a backup heat source is necessary. We have been looking at the Phoenix Solar tank with a gas burner attached. It is a condensing direct vent burner which means that we can side vent rather than go up the chimney to the roof. This is good because we do not have confidence in the fire-proofing of the old brick and mortar chimney after seeing some of the areas exposed on upper floors.
However, the cost of the Phoenix is quite steep at around $6,500 after tax and shipping, so we checked into many other tank-less and condensing burners to supplement a water storage tank. While these will be cheaper in materials, the plumbing costs will increase and we will have more external parts to maintain. Something that I learned while researching the Navien and Bosch condensing tank-less burners (I think it applies to all of the tankless) is that they start their operation based on flow rate and not temperature. Why does this matter? If you are not using a solar thermal system to pre-heat your water, it doesn’t, because you always have 55-60% water coming from the city supply and for one faucet of hot water demand will need at least the lowest level of modulation on the burner for heat. If you have the water preheated to 100 degrees or even 120 degrees at your set point and the flow rate turns on the tankless burner, then you will get the base modulation for heat output (Navien is 15,000 BTU) that will bring your water higher than your set point. You will then have to have your mixing valve introduce more cold water to lower the temperature and you will have effectively reduced the efficiency of the system. We figured out a plumbing bypass to this problem which would be a separate temperature regulated zone valve, and while that would work it would add complexity to the system.
This week we are making the final decision, but it looks like we are going to push ahead with the Phoenix, do to the compact design and simplicity of operation. I will let you know if it changes and why.
Over the past several weeks, a lot of energy went towards getting the ductwork for our energy system ‘just right’ in efficiency. The passive house consultant and HVAC contractor had multiple conversation to specify even the smallest of details. For instance, one specification is to have the ducts lined with foam pads in lieu of the industry standard fiberglass. (FIBERGLASS? In the ducts that supply the air we breath? Not in this house!) With that detail and many others sorted out, the installation finally began today.
Also this week, the carpenters are installing framing for the windows. We’re days away from our window order and have our specifications ready. Since window openings are big holes in our air barrier, the framing and connections between the windows are super important. Any square inch left uncovered will compromise our barrier – allowing “ungoverned’ air flow into and out of the house.
We also anticipate a plumbing inspection this week and expect the solar hot water equipment to be ordered. Our cellar slab pour has been delayed awaiting an inspection because the sewer and storm lines will run below the slab. We initially dug down 12″ inches so that a proper drainage detail can be incorporated into the new slab and a layer of foam can be sprayed below it. As part of our sustainable practices we specify that 20% of Fly ash be incorporated into the concrete mix. Fly ash is a byproduct from the coal industry that has been proven to strengthen concrete when added. It’s essentially coal ash that would otherwise be dumped in landfills.
Stay tuned as we begin to close up walls and conduct blower door tests.
Stained glass windows:
We have 3 stained glass windows for this house that are in need of restoration. They have been sent to a local stained glass shop called Stain Glass Store on 5th Ave. in Park Slope. The windows are in such bad shape – broken pieces, bent all out of shape, etc., that it will take four weeks to fix. To wait the four weeks will delay our window manufacturing too much, so we are having a template made of the glass without the frame and sending that to Germany this week. Once the stained glass is fixed, it will be crated and shipped directly to Germany to be fitted onto the Optiwin windows. The stained glass will be siliconed onto the front frame of the windows, sealing them in place and allowing their full beauty to be visible from the outside (and meeting landmark requirements).
We have two skylights that we are replacing on the top floor. We did a search all around the country for skylights that would meet Passive House standards and could not find any that would be close. All of the window companies like Serious Windows, Thermotech, and even the German companies shipping windows to the US don’t make skylights, so we were out of luck there. We then contacted Wasco Skylights out of Maine since they are one of the larger North American skylight producers. I was connected to Alan Kinne from their Engineering division and I explained the tough requirements that we had to comply with. He said that they had recently tested and gotten approval for U-0.29 skylights for Energy Star, but didn’t have anything close to the U-0.14 that we are looking for. This was disappointing.
However, what was exciting and refreshing about talking to Alan was his immediate willingness to try to come up with a product that could satisfy our needs. He called me back the next day and said that he had located a triple-paned tempered glass from a Canadian company that would meet our U-value requirements and for the frame he thought that they could get a better U-value than they normally did by injecting their standard pvc frame with their nanogel technology. They are going to make and test the skylights in January and then we will see how close to Passive House standards they were able to get. Even if their skylight could not make Passive House Certification levels, based on a U-value in the 0.20’s we should be fine for our building certification because we have low enough loads in the rest of the building.
Yes, even more discussion about spray foam! When we are using spray foam as our air barrier and not just for insulation, the quality of installation becomes that much more important. The company that we are using is doing a good job working with us to come back and do multiple stages of spraying so that we can move forward on testing our side walls for infiltration while we wait the 3 months for the windows to come in, but their initial pass was not very careful in terms of coverage or depth.
The areas to look for when reviewing a spray foam job are:
- Rim joists: Were they all covered or are there gaps? In this case the rim joist in the entire house were missed on the first pass.
- Overall depth of spray: If you have purchased 3″ of spray foam at $1.50 per in/sq ft, then you want to make sure that you get what you paid for. Spray foam is difficult to “eye” how consistent the depth is, so we use a simple method. We purchase small bamboo skewers (sold for grilling), cut them to the 3″ and then stick them every couple of feet or where the spray looks low to determine the depth. The good thing about the bamboo, vs. using a nail is that the bamboo does not act as a thermal bridge and can be left in place for the next pass of the spray foam to go right over.
- Wall intersections interrupting foam: When I was inspecting the property after the initial spray, I noticed some areas where a partition wall ran perpendicular into the exterior wall framing, creating an area of a lot of wood and no spray foam. We remedied this by removing those studs and after the spray foam is filled in, we can put back a nailer for our drywall.
The common thread that I have seen with the four spray foam companies that we have used in the past is that they will not do quality control on their own. They tell their guys to spray and wait for you to either accept the work or make a complaint. While this is frustrating and not how their companies should operate – we expect it now and can work to get a good quality product regardless.
Passive House BKLYN is featured in the November 13th Daily News Article, The Passive House: European energy- (and money-) saving building standard catches on in New York. Check it out!
We have spray foam – the first phase of it anyway! Most of the front and back walls, as well as 3 feet of the party walls on either side, were covered with 3.25 inches of foam yielding a 23.4 R-value. After 3 months, that R-value will drop to 21.5. An R-value of 21 is the specification set by the passive house consultant. The windows cavities were left un-sprayed for now. We will have a second phase of spray foam when the frames for the windows are installed. Every opening of our 23 windows are a different size, some by as little as an 1/8 inch, so it is best to wait until the windows are in before adding the foam to those areas.
We found a nifty, inexpensive way to deal with airsealing the electrical boxes in a retrofit capacity – Lessco boxes. We simply cut out the sheetrock around the box location and install the Lessco box – into which the electrical box can be installed. Any penetrations made through the box can be caulked before the sheetrock is replaced, and if there is still some leakage after everything is put back together, this box can be filled with spray foam right through the sheetrock.
More to come in the next 2 weeks as the windows are ordered, the solar hot water system is installed, the ventilation system is installed, the plumbing inspection completed and a blower door test to indicate how well the house is sealed thus far. After these elements are complete, we can begin closing up walls and moving forward with the finish elements of the house.
We have created a Passive House Meetup group because we are interested in raising awareness in the Passive House movement. We believe that the ideas behind Passive House can revolutionize the way we build in NYC. Are you interested in renovations, building, or the “green” movement?…You should join!
Go to www.meetup.com
Register or Sign in if you are already a member (it is free) and then look for our Meetup Group – Passive House NYC.
This week, we put a lot of focus in preparation for the spray foam installation. There is no turning back after this phase. Anything in the way of the foam as it expands will either move or be buried, so special attention was given to protecting our framed walls. The carpenters installed a lot of bracing on the studs of the framed walls to keep them from moving out of plumb and or level during the foam expansion.
The roof (new, durable SBS membrane) was installed this week (minus the new skylights.) The roofers removed many attic ducts intended for venting the interior space. This concept of attic venting is outdated and contrary to the passive house concept. Since we will have mechanical ventilating systems in place, we will be able to control exactly how much fresh air enters the home. Open holes in our air barrier aren’t needed and are avoided at all costs. We can now move forward with our solar panels installation for the hot water system.
Early next week, while we continue to work out the particulars on the ventilating system and windows, the house will be cleared of the contractors so the spray foam can be installed.
Currently, a lot of our effort is being put into sizing the windows just right to place the order. Since the frames of our new triple pane windows are much thicker then the old ones, many details need to be worked out so that the old interior window shutters and casements can be re applied appropriately. A number of dimensions can’t be compromised so that our landmark and insulation requirements can be maintained.
Much of the plumbing sewer and supply lines are in place and we should be ready for an inspection in another week.
However, in order for a plumbing inspection to pass, tubs need to be installed, which will block access to walls that need spray foam. To avoid a delay we are forced to phase the insulation application. In the approaching week, we will be preparing for this. Key areas will be sprayed now, leaving out the window areas for a second phase after installation.
This week, we will also prepare for duct work installation. The ducts are currently being fabricated at the shop. Our Heat Recovery Ventilators (HRVs) are en route from Europe, and we want to have everything ready so they can be installed as soon as they arrive. An area of this passive house construction that differs from conventional construction are the soffits around the duct work. The carpenters will need to pay special attention to the way the soffits are sealed so they don’t become chambers for air movement. This means that the walls within the soffits need to be finished and air sealed, the ducts can then be placed and the soffits built. Duct work tests will need to be conducted after installation making sure the ducts are air tight. We will likely have to cover the seams with mastic several times to pass these tests.
This past weekend, (before my Landmark board presentation), I presented Passive House BKLYN at the 4th Annual Passive House Conference in Urbana, Illinois. It was great to get feedback on our efforts and to hear about the growing passive house movement.
Now, you might be wondering, “Why Urbana?” Urbana is where 4 of the fewer than 10 U.S. passive houses are located and is home of the Passive House Institute US – thanks to the pioneering work of Katrin Klingenberg and Mike Kernagis (and the staff at the Passive House Institute and Eco Lab).
If you are interested in exploring more about Passive House – check out http://www.passivehouse.us/passiveHouse/PHIUSHome.html and even consider attending next year’s event – it is worth it!