Peabody Fine Architects

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  • Open House at Fairfax Net Zero Home on March 25

    The Fairfax zero energy home will be complete within the month, and the garage is expected to be complete by mid-May. Our will be opening the house on the 24th to Fairfax County officials, and have generously allowed us to follow up that tour with two open houses on Saturday the 25th. The morning tour is booked but the afternoon still has some openings, so please write to David  (david@greenhaus.org) if you would like to join us.  While the work is not complete, all systems except solar pv and batteries are now in place.

    West facade IMG_4644 IMG_4631

     

  • The Fairfax Zero Energy House: Mechanical system overview

    The mechanical system for the Fairfax house  differs from our earlier houses in several ways. We have zoned the house differently; we have taken a different approach to the heating and cooling equipment; and we have changed the ERV equipment.

    This house is zoned from side to side rather than up and down. This decision had to do with the very different window configurations on the north and south sides as well as the room arrangement in the house.

    The Rockville and Bethesda houses have a multi-zone heat pump with two ducted mini-split units: one for the top two floors and one for the bottom two floors. This house has three independent and very small (9000 btu) ducted mini split heat pumps. One unit handles the north half of the house; a second unit handles the south half of the house; and a third unit handles the basement space. We could have gotten away without the third basement unit, but there will be a computer room in the basement with multiple work stations, as well as large groups of people from time to time. The basement unit won’t run much, but when it does it will definitely be needed. This approach was a little more expensive than the multi-zone unit approach but it made sense in light of the fact that this will be a zero energy home. The efficiency of the independent 1:1 minisplits (23 SEER) is far superior to the multi-zone approach (16 SEER). The lower energy demand translates directly to fewer solar panels on the roof.

    In the Rockville and Bethesda houses we used Zehnder energy recovery ventilator (ERV) units. In this house we are using the more economical CERV unit by BuildEquinox. A CERV (conditioned energy recovery ventilator) is basically an ERV with a small heat pump inside it. In addition to exchanging heat and humidity from the incoming and outgoing air streams, it conditions the incoming air. While a standard ERV may have 90% efficiency in the temperature exchange, the fresh air coming into the room will still be colder than the room air in the winter and hotter in the summer. With the CERV, the incoming air is at exactly the right room temperature. The other advantage the CERV offers is that it doesn’t run all the time the way an ERV does. BuildEquinox likes to call the CERV “an ERV with a brain.” Built-in software that can be accessed from an IPad monitors VOC’s, CO2 and CO, and turns on the fans when needed, saving further energy. Peter Schneider has had  success with this equipment in his VerMod homes and we are following his lead here.

  • Our Team Wins Project for 8 Zero Energy Ready Homes in Fairmount Heights

    The Prince George’s County Department of Housing and Community Development has just announced The Housing Initiatives Partnership (HIP) the winner in a competition to develop eight abandoned home sites. Seven of those sites are in the town of Fairmount Heights; one is in Capitol Heights. HIP, a non-profit affordable housing developer in Prince George’s County, was our partner in the development of the prototype modular Passive House just completed last year in Fairmount Heights. We plan to adapt that prototype to these sites, building upon what we have learned.

    What makes the project particularly interesting is that six of the houses will be on contiguous lots, each with prime solar orientation. This presents an ideal situation for a case study hybrid direct current microgrid (HDCM). Much has been written about the potential for residential dc nanogrids and microgrids (including my own post last month). They are expected to transform the enegy grid from a centralized, vulnerable, top-down system to a distributed, transactive energy system within the next ten years, yet no residential HDCM’s have yet beeen built in the real world.  As a HDCM the six homes will essentially become their own power plant, sharing site-generated solar energy among themselves and selling the surplus energy back to the grid. During power outages, they will continue to produce and store power. During peak energy demand periods when rates rise, they will go offline, using their own energy stored in batteries if they need more energy than they are producing on-site.

    The key to creating an affordable HDCM is to reduce energy demand to the absolute minimum so that a minimal investment in photovoltaics and batteries is required. Passive House construction techniques and new generation high performance variable refrigerant flow (VRF) heat pumps reduce heating, cooling and hot water energy demand by 85% below standard homes. But they do nothing to reduce the electrical demand of lights, appliances, TV’s, computers, etc. This is where switching the house over from alternating current to direct current comes into play, with the potential to electrical energy demand a further 50% by some estimates. My previous post goes into why this is, so I won’t repeat myself here.

    With the help of Dave Geary of Power Analytics, Terry Hill, who sits on both the PHIUS and EMerge Alliance boards, and Stephen Pantano, of CLASP, we will now begin the process of assembling products, expertise and funding for the case study microgrid design and implementation.

    Our team for the construction effort is:

    Housing Initiatives Partnership, Developer
    OMF,  Builder
    Pando Alliance, Third Party Testing and Energy Certification
    Subcontractors have not been determined at this point.

    Construction is anticipated to begin on the first three homes in the summer of 2017.

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  • Takeways from the 2016 North American Passive House Conference

    We just got back from the PHIUS national conference in Philadelphia. It was quite well attended, with a broad array of topics covered.  These conferences are no longer focused simply upon how to do build one, but have become much more specialized and look at all the various aspects of what goes into a Passive House. They are also looking at other building types that are now employing Passive House design principles – multifamily housing, office buildings, schools, and even high rises. We have come a long way!

    Takeaway 1: The biggest takeaway, I have to say, is Izumi’s: she went through the day-long training for the new PHIUS WUFI+ energy modeling software. Quite rigorous. She has immediately put it to work on a current project in the office. Matt learned this software when he did his PHIUS training. So that leaves me as only one who hasn’t made the shift to the new WUFI+.

    Takeaway 2: Spray foams aren’t as bad as we thought. Several years ago Alec Wilson of BuildingGreen published an article positing that the global warming potential of the gases in the blowing agents far out outweighs the savings in CO2 emissions that these products give you. Bailes examined the assumptions of Wilson’s calculations and made a strong case that the issue is not quite so black and white. His argument is that the EPS and XPS foams’ savings in emissions actually exceed the environmental cost of the gases in the blowing agents when you apply it in thicknesses of roughly R-20 or less. This is based upon the declining increase in R-value with each extra inch you add. He did not address other issues around the foams: the lethal gases produced if they catch fire, and the fact that they are fossil fuel based. The takeaway for me:  yes, it is ok to use these products in small amounts where there is not another alternative insulation system that would work (such as some retrofit situations). The exception is XPS insulation (extruded polystyrene–eg: Styrofoam) for which one can always substitute the more benign EPS (expanded polystyrene) insulation. To learn more, read Allison Bailes’ article, which also references the Alex Wilson study.

    Takeaway 3: … and cellulose insulation isn’t as perfect as we thought. Prudence Ferreira gave a very detailed review of the performance of different insulation types in various climates with regard to mold and wood rot. Her studies taught her that cellulose insulation—either loose or densepacked—tends to hold moisture longer than other insulations. This can become a problem at the outside edge of your insulation cavity where moisture can accumulate and remain if the surface bounding the outside face of the insulation (usually the building sheathing) gets cold enough. What it tells me for our climate is that we always need to have rigid insulation on the outside face of our sheathing to keep it from getting too cold and causing these problems. Luckily, that has been our practice to date. A wall that would not work well in our climate, for example, would be a double stud wall with nothing outside it. Even though the wall might be 10” thick and achieve tremendous R-values, it could develop moisture problems at the interior face of the sheathing.

    Takeaway 4:Hybrid AC-DC microgrids are coming. Terry Hill, who sits on the board of both PHIUS and the non-profit EMerge Alliance, moderated a very interesting panel including  Brian Patterson, the founder of the the EMerge Alliance and Tim Martinsson, CEO of Power Analytics a leading firm in microgrid design. We learned of the latest  developments in microgrid technology and products and their application to individual buildings. We are working with both of these groups in trying to develop a case study project for a home powered by a hybrid microgrid. I’ll be blogging more on this later.

  • Matt and David to Lead Class at 2016 North American Passive House Conference

    Matt and David have been asked to give a half day seminar on the special issues related to construction of Passive Houses in our climate zone. We will be talking about building envelope strategies we have used and the evolution of our thinking regarding heating and cooling and ventilation in this climate.

  • Second floor walls going up on the Net Zero home in Fairfax.

    IMG_4032There are big changes to see since my last report. The rains finally ended, and O’Neill Development wasted no time in getting underway on the framing. This is an exciting time for both the owner and the architect, finally seeing the form of the building take place so quickly after months and months of planning. Here are some pictures from the last few weeks, the most recent being this morning…

    DSCF5048 The two steel beams carrying the first floor. The one on the left is a 28′ span, which will allow the rec room to be clear of posts. That was heavy — a W16x67, almost a ton!

    DSCF5073DSCF5074 First floor decking and framing waiting for the rains to let up.

    DSCF5071 Basement walls completely buttoned up with insulation and drain board.

    DSCF5051 The haunches that will carry the front entry slab.

    IMG_4038 The site this morning. They had just tilted up the two second floor walls before I arrived. This is the front entry facade.

    IMG_4034 Those walls are all braced frames, meaning all the nailing and blocking are completely installed before it goes up. Took six men two tries to get this one in place.

    IMG_4039 The recess at the front entry door. We are using standard 2×6 framing on this house. We will insulate those walls with cellulose and then add the extra insulation we need to the exterior using an EIFS system. More on that later.

    IMG_4040 Post and beam at the front entry.

    IMG_4041 Looking from living area toward kitchen area. First floor ceilings are 9′.

    IMG_4043 Preparing to tilt up one of the second walls.

    Here is a film clip of the general scene this morning..

    IMG_4054

    and here is one of them tilting up the wall in the picture above…

    IMG_4055

     

     

     

     

     

     

  • Groundbreaking this week on the first Net Zero house in Fairfax City

    Front elevation-cropped

    The bulldozers are on the site, and barring rain, they will begin excavation on Fairfax City’s first net zero home. The house was designed using Passive House principles, and the owner is anticipating that the 20 kw solar array planned for the garage and main roofs will power both the cars and the home. We will be blogging about the project as it moves forward.

  • Preparing the site for our modular Passive House

    Sitework began in mid-July. Everything is now ready for the arrival of the modules on August 11.

    One of the ways we controlled costs on the project was to eliminate the conditioned crawl space, which on a passive house can be a very large expense, with the insulation of walls and footings just as is required in a passive house basement. As described in the previous blog, we opted to make the first floor framing the edge of our building envelope so everything below that is of standard construction.

    One issue we ran into in the design phase was the confict between the Building Science Corporation’s recommendations for an insulated floor first floor assembly over a crawl space, the building code’s requirements for crawl spaces, and passive house requirements. The issue is warm moist air in summertime getting into the floor assembly and condensing when in contact with the relatively cold floor structure.
    BSC would prefer we have a completely closed crawl space protected from below by a sturdy vapor barrier. This would keep moist summer air out of the crawl. They then recommend completely insulating and sealing the underside of the joists to remove any chance of condensation there. They also recommend monitoring the sealed crawl space for moisture and having a dehumidifier located there in case of any moisture build up.
    All fine, but the building code requires sealed crawl spaces to be ventilated with air from the interior of the house. That of course would completely erase all the airtightness we are struggling to achieve.
    What we decided to do was follow BSC recommendations completely, but to create a “ventilated crawl space” as defined by code, placing the minimum number of ventilation louvers in the exterior walls of the crawl space. Since we are allowed to make these louvers operable, we will simply keep them closed up, making the crawl effectively a sealed crawl space.

    Here are some pictures of the progress…

     

    The day work began
    The day work began
    Some of the brush we had to remove
    Some of the brush we had to remove
    Site cleared and ready for digging for footings
    Site cleared and ready for digging for footings
    Formwork in place
    Formwork in place
    Formwork in place - view from front
    Formwork in place – view from front

     

    Formwork in place - the south wall
    Formwork in place – the south wall
    Top plate and termite guard in place
    Top plate and termite guard in place; plumbing waste lines run, and ready for gravel fill
    Gravel fill in place
    Gravel fill in place
    Vapor barrier in place; waterproofing in place; backfill beginning
    Vapor barrier in place;
    waterproofing in place;
    backfill beginning
    passive house crawl space
    Vapor barrier in place, joints taped. The pile of insulation will be applied to the bottom surface of first floor joists after the house is set in place and joists cavities are filled with insulation.
    backfilling
    backfilling
    Crawl space vent open
    Crawl space vent open
    Crawl space vent closed
    Crawl space vent closed

  • The mechanical system at the modular Passive House

    Yesterday Michael Bonsby of Michael Bonsby Heating and Air Conditioning and his crew drove over to Greenwood to rough in the mechanical system. Similar to our Rockville Passive House, we are using a Mitsubishi mini-split heat pump system and a Zehnder ERV system.

    Installing parts of the systems in the factory and parts on-site make the logistics a bit more complicated, and took some planning, but the overall design is quite simple. We were fortunate that Michael was willing to take his crew over to do all the rough-in work for the Mitsubishis. This eliminates the chance things falling through the cracks had we had a Greenwood mechanical subcontractor to do this work.

    Because of the open plan of the first floor, heating and cooling of that level will be handled by a single minisplit cassette mounted in the ceiling of the kitchen. This central location allows it to blow air to the living room in the front and the dining room in the rear. Because the second floor is divided up into bedrooms, a centrally located cassette was not an option. We are therefore installing a ducted minisplit in a closet upstairs, with short duct runs to each of the spaces.

    Ventilation will be handled by the Zehnder Comfoair 200, located in the mechanical closet on the first floor. Instead of a standard metal duct system we have used in the past, we are using the Zehnder Comfotube system. This allows us to sneak the 3” flexible ducts throughout the first and second floor. To facilitate this even more we designed a large chase running between the floors adjacent to the mechanical room and we are framing the second floor with open web wood truss joists. This allows running pipes and ducts “across the grain” without the need for dropped ceilings for anything running below the joists. An added benefit of the Comfotubes for modular construction is that anyone can install them — you don’t need sheet metal workers– so Beracah can do all the duct insulation work onsite with their regular crew.

    Because the house is built over a crawl space, the first floor framing system is sealed and insulated and no ducts can run through that framing. We are therefore placing all the ERV supply and return ducts for both floors in the second floor framing cavity. For a more in-depth look at the installation of a Comfotube system, you might want to check out Zehnder’s video of the process for installing their Comfotube system.

    Below are some photos of the rough-in work going on yesterday. Today they uncrated the windows and may try to install the first one tomorrow.

    Bonsby 5The ceiling mounted Mitsubishi mini-split roughed into first floor ceiling. No ducts to worry about, just freon lines.

    Bonsby 2A ceiling mounted diffuser box for the ERV system with Comfotubes already hooked up.

    Bonsby 4Comfotubing about to go in.

    Bonsby 3Comfotubing hanging in the mechanical room. All the tubing is run to the mechanical room ceiling and left loose like this. When the first and second floor modules are married at the site, the first and second floor portions of tubing will be field connected, the Zehnder unit will be installed, and all these tubes will be hooked up to it.

  • Our modular Passive House is under construction

    This week Beracah Homes in Greenwood, Delaware began construction of our — and their — first modular Passive House. The house is sponsored by the Housing Initiative Partnership(HIP), a Maryland non-profit organization committed to providing affordable housing. HIP had seen the Habitat Passive House at the last DC Solar Decathalon and had toured our Bethesda Passive House, and procured a grant to build their first one. We teamed up with O’Neill Development, our partner on the Bethesda project and Beracah to offer a modular Passive House. The factory construction will be complete in two weeks, and site installation and finishing work will begin immediately.

    Our approach to the project was simple: let a good modular builder do what he does best, building as much of the house as we can in his shop. Then add additional insulation, complete air sealing, and add the HVAC system in the field.

    Beracah was already doing Energy Star certified homes, using densepack fiberglass for wall insulation, the Huber Zipwall system for an air/water membrane, and committed to upping their game in the modular market. Their enthusiasm for taking on the house was in marked contrast to the attitude of most modular manufacturers we spoke with.

    The project has involved a lot of careful planning. We had to learn the rules of the road in their construction system — very different from the site-built and panelized construction we are used to. And they had to learn about all the specialized requirements for thermal bridging, air sealing and ventiliation that go with Passive House construction.

    From the beginning we have worked with their senior construction specialist, John Meredith, who has tirelessly stuck with us to iron out the myriad construction issues. And now the rubber meets the road.

    To keep things as simple as possible (remember this is our first!) and to keep costs under control, we decided at the very start to build the house as two modules that would be stacked on top of each other. Field work joining modules together adds time and money and the potential for greater air infiltration, so the fewer the modules the fewer the problems. We designed the house (1600 sf, 3 bedroom/2-1/2 baths) with all public spaces in a rather open-plan first floor, and all private spaces on the second floor. Making that happen within the 18′ maximum allowable exterior dimension was the challenge.

    Framing was completed on both modules last week. Next week will be devoted to roughing in plumbing, electrial, and mechanicals. Below are some pictures of the progress this week.

    Beracah front facadeBeracah’s headquarters in Greenwood Delaware.

    Beracah shop exteriorOut back where the work gets done.

    modular passive house The first floor module – note Huber Zipwll system at exterior, standard with Beracah Homes.

    Modular passive house framingFirst floor module interior. Note taping of subfloor (Profil’s Tescon Vanna tape).

    Modular passive houseInterior corner — note double wall construction and space left at corner to allow densepacking there. The 2×6 ceiling framing is standard with modular construction, holding the module together during shipment and providing extra space for running conduit and pipes. Note the header at the left — headers generally have 2x’s at interior and exterior with the interior filled solid with rigid foam.

    modular passive house constructionSecond floor platform. Ready for construction of exterior walls, which happens right on top of it.

    Modular passive house exterior wall constructionTaping of the second floor walls using Huber Zipwall system.

    Modular passive houseDetail of second floor wall and platform before tilt-up of wall. Sill sealer is not necessary, as our air barrier is at the exterior wall sheathing.

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    Tilting up the wall!

    IMG_3610Framing up interior partition walls of second floor module.