As you all know that the D.C. region experienced a lengthy power outage last week. This really got me and I am sure, other local energy geeks to think about backup power. The traditional backup power is a generator that burns either gas or diesel. Generators pollute and frequently lead to combustion gas poisoning (Some people are really that dumb). People who have off-grid photovotaics (PVs) do not need to worry about outages but in the D.C. area most of us grid-tied folks will still experience loss of power even if we had PVs; the power company won’t let you charge up the lines when they are down for safety reasons.
Well, one elegant solution that is already available combines PVs, electric vehicles (EV) and ideally, a Passivhaus. Imagine, Arlington Passivhaus with a PV array that wipes out its electric loads, so, a net zero energy home. The garage also comes equipped with an electric car charger and the owners drive EVs or Plug-in Hybrids.
Under normal circumstances, the PVs will generate enough juice to power the house and charge the cars. Whatever electrons left over go into the grid and the neighbors get to use and owners get to net-meter. In a power outage situation, even though the PVs stop generating, the car batteries are already fully charged to power at least the most essential part of the house. In a prolong outage like what we had recently, the batteries will eventually be depleted, at that point, if you have a Plug-in Hybrid, you can take it out for a long spin to charge the battery, then you have some juice again to power the house.
Now, let’s take this one step further. Imagine if entire neighborhoods, towns, cities have this, we would’ve achieve a level of energy security that no oil, gas, coal or nuclear company can promise. Utility companies will continue to play a very important role, they can focus their efforts on supplying power to the biggest consumers of energy, i.e. manufacturing, data centers, etc. Utility companies really should be the ones building this network of home-generated power and the ones that maintain it. Economic development is inevitable, energy consumption can only continue to grow, so, the utility companies need not worry about having enough customers.
I think of the War of Currents in the late 1880s between Thomas Edison and Nikola Tesla needs to be revisited. Perhaps instead of battling over whose current was superior, the two geniuses should have married their technologies.
We’ve been monitoring the temperature and humidity in the Arlington Passivhaus for about a week now. As part of a long stretch of heat wave a storm hit (they haven’t come up with a name yet, but let’s just call it the Big One for now), along with the PH, more than 1.5 million homes in VA/MD/DC area lost power, some areas are still recovering from a multi-day outage without air-conditioning. This actually provided us with an unique opportunity to monitor and report what happens in this situation.
Let’s start with monitoring.
Here are a few constants:
MiniSplit setting: cool 67 F
ERV: Low (approximately 75 CFM)
Transfer Fans: ON
Thermo/Hygrometer
A note on humidity: we noticed the indoor humidity has been consistently high (60s), since we’ve been monitoring. We attribute this largely to the moisture still in the building materials, especially that giant basement slab and seasonal factors. However, we also noticed the relative humidity level has about a 7% swings if several windows or doors are open and it is humid outside. This let us to consult the Bethesda Passive House team (David and Brandon JR.) since they probably experienced something similar. The advice they gave us was to turn the ERV down while the house is “drying out”. Because while the ERV dehuminifies the air that comes into the home, it does not take all the moisture out, so in effect, operating an ERV makes the humidity problem worse. See http://www.greenbuildingadvisor.com/book/export/html/15970 for more explanation on this. By turning down the ERV, we’ve been able to consistently drop the relative humidity levels a few percentage points a day from high 60% to mid-50%. It still likes to go back up on very humid days though…
Temperature Results:
On a Normal Summer Day
We don’t have a large enough data set yet but we can report our observations so far.
We’ve observed the following on a typical summer day (June 27, 2012 Outdoor Temp: 62-89F, Humidity: 23-40%)
At 12 pm when the outdoor temp was 88 F, the indoor temps were: 68F/70F/70F (Basement/1st Floor/2nd Floor)
At 3pm when the outdoor temp was 94 F, the indoor temps were: 68F/70F/72F (Basement/1st Floor/ 2nd Floor)
Two Degree Temperature Differences Between Floors
This experience was consistent with other days with similar levels of humidity and temperature. The temperature differences are typically about 2 degrees. Heat rises up so, the 2nd floor usually is the warmest.
Effects of Solar Screens
We have motorized solar screens on the 1st floor south-facing windows. This picture was taken around noon time and it is illustrative of the need to shade first floor south-facing glazings, the sun hits directly on it, while the 3ft roof overhang protects the 2nd floor windows from the sun. By the way, shading needs to be on the outside of the windows, or they just become radiant heaters!
Solar Screens
One day, we wanted to see the effects of not shading, the result is that initially, the 1st floor becomes warmer than 2nd floor, then a few hours later, both 1st floor and 2nd floor are 2 degrees warmer than they would normally be. This makes sense because the lack of shading makes the 1st floor 2 degrees warmer, then as heat rises, the 2nd floor eventually gets 2 degrees warmer too. The basement is most consistent, the lack of shading on the 1st floor has no noticeable effect on the basement temperature. However, not shading creates a temperature difference of 3-4 degrees between basement and 1st floor.
On an Extra Hot and Humid Day (Outdoor Temp 71-103 F, Humidity: 50-66%)
At 12 pm when the outdoor temp was 95 F, the indoor temps were: 68F/70F/72F (Basement/1st Floor/2nd Floor)
At 3pm when the outdoor temp was 103 F, the indoor temps were: 70F/75F/77F (Basement/1st Floor/ 2nd Floor)
As you see, at 95 F, the indoor temperatures are still able to keep a nice two degree temperature difference between floors. However, when it hit above 100F, temperature differences widen between basement and first floor to 5 degrees. However, the difference between first and second maintains 2 degrees. Also keep in mind, conditions are never perfect. On this day, we had workers opening and leaving doors open all day long bringing in large amounts of hot and humid air.
Solar screen close-up
3ft Overhang
After the Storm
The storm devastated Northern Virginia, Mayland and D.C. Here’s a picture of what we are seeing around town.
Crews restoring power
After the storm, the heat wave continued to rage on. We were curious how Arlington Passivhaus performs in a heat wave with no active cooling. Here’s what we observed on after 40 hours of power loss on another scorcher day:
While the outdoor temperature was 92 degrees, the basement was a comfortable 73 degrees. First floor was a warm but not unpleasant 81 degrees. Second floor was 79 degrees.
This tells me two things:
Insulation Really Works
First, all the insulation in the walls and roof is effectively isolating the indoor environment from the outdoor elements, slowing down the effects of extreme outdoor temperature changes, i.e. after 40 hours of power loss, the first floor only warmed up by 6 degrees (75F -81F) and second floor by 2 degrees (77F-79F).
Shading is Crucial
I think the 6 degree increase in temperature on the first floor can also be attributed partially to the lack of shading on the French door on the middle of the wall (see first picture above), which explains why the second floor only increased by 2 degrees.
We still have no power…
We anxiously await the power to return. This would be an opportunity to monitor how quickly a system like this recovers to desired indoor temperature and relative humidity level.
Hopefully, the next time we post, there will be power and interesting observations to report.
This past Sunday, we had the great honor to host the Arlington Green Home Choice Program’s annual awards ceremony at OUR house! It was an awesome success. Arlington County uses this opportunity every year to recognize the home owners, builders and the homes that voluntarily participate in the program to build and retrofit homes to a high performing level that is “healthy, comfortable, cost efficient and reduces energy and water usage and protects the environment.” Helen, the manager of the Green Home Choice Program works tirelessly to engage builders through the entire process from design, construction to commissioning. She certainly kept us going through the hard times with her encouragement and her frequent site visits tell us how serious she and the county are about promoting green homes.
We really like the program because of its prerequisite that the home be Energy Star qualified. Even though Energy Star isn’t the most stringent standard out there, it is a great starting point and more importantly, it is performance based. This also means a Green Home Choice building will perform significantly better than a conventional home. Additionally, as Energy Star continues to tighten its standard, Green Home Choice homes will also improve in energy performance. Modeled after the EarthCraft program, Green Home Choice uses a score card to determine other sustainability features of a home, such as water use, site design, etc. Here’s the 72 page score sheet. http://freshaireva.us/wp-content/uploads/2012/01/Arlington-Green-Home-Choice-Guidance-Manual-1-01-12.pdf It’s also good to look for ideas in during the design process.
For this year (2011-2012), twelve homes were certified in the Arlington Green Home Choice program. Out of which 6 received”Certified”, 3 “Silver” and 3 “Gold” awards. This is the first year, Arlington has given out the “Gold” awards.
GHC Certified Homes
Here’s our gold!
Matt Fine and Jake (Zavos Architecture and Design), me, Jay Fisette (Arlington County Board Member), Charlie Byrd (Intellistructures), Ricardo Leon (Leon Home Improvement), Helen Reinecke-Wilt (Manager of GHC)
Special thanks to Helen Reinecke-Wilt, Joan Kelsch for organizing this successful event. To Jay Fisette for his support and commitment to a sustainable energy future. Congratulations to all the other Green Home Choice participants.
Stay tuned and be sure to come visit us on June 3rd for the 10th Annual Arlington Green Home and Garden Tour. For more information, click below.
Andy from Elysian Energy came out to do our final blower door test. We knew that we had a 1 ACH 50 from John’s test at the Meetup event with 30 people walking around and playing with the windows and doors. After taking some significant measures to air-sealing the windows and joints, Jim and Andy came for a second test which had a result that I thought was too good to be true but we felt comfortable enough to proceed with drywall and everything else. I think there was a discrepancy in how the total air volume was calculated…
Last Friday, Andy did our final testing the ACH at a number of different pressure levels and our final number was 0.52 ACH 50! The number is not 0.33 but we think it is a very respectable one for our first attempt at Passivhaus.
Final Blower Door Test
Air-tightness really is a difficult thing to achieve if you do not plan ahead. I think to get the air infiltration number even lower, air sealing must be done in conjunction with construction, i.e. tape as you build. I know of a builder that tapes up each nail hole right after the nail is hammered in so as to not miss any. It is obsessive but I am not sure if that effort is really excessive. Air-tightness is a quality of construction issue. We’ll never get to a 0 ACH 50 unless you build a house with a balloon but we can certainly get darn close…
The Importance of Air-Tight Construction
I know this is a huge topic but in an effort to share information and help me articulate the issue I must dip into the importance of air-tight construction. We had previously talked about this but we only talked about what we need to achieve but never explained why. Here are some of the “why”.
1. Energy conservation: Did you know that you can have all the insulation in the world and the build can still perform poorly? A leaky building envelope means “uncontrolled ventilation”. This means conditioned air can leak out and hot/cold air can leak in; thus decreasing the effectiveness of the insulation.
As you can see, air can leak in and out at a variety of places. This is “uncontrolled ventilation” or what some typical builders talk about when they say, “You don’t want a tight house, your house needs to breath.” Our retort is, “Your house does not need to breath, you do!”
2. Indoor Air Quality: Air can carry pollutants, moisture, odor and other undesirables into the building through these leaks. If you cannot tell where the air is leaking in from, you have no idea what pollutants are being carried into the indoor environment. As I like to say, “you are breathing like a frog.” I love Kermit the Frog but we are mammals, so let’s have a tight skin (air-tight building envelope) and breath through a dedicated respiratory system (an Energy Recovery Ventilator or Heat Recovery Ventilator) that brings in fresh air through a controlled path and filters it before we consume it.
Do you want to breath the air that passes through this window?
3. Vapor Penetration
Air carries a large amount of vapor or moisture. Each air leak has potential to cause water intrusion which in turn causes mold and structural damage if the moisture does not dry out. In well insulated buildings, this problem can get worse because there is so much material that can trap moisture. Therefore, air-tightness becomes even more important as building envelopes get tighter to keep water out in the first place.
This image from Building Science Corporation paper RR-0412: Insulations, Sheathings and Vapor Retarders http://www.buildingscience.com/documents/reports/rr-0412-insulations-sheathings-and-vapor-retardersgives us a dramatic visual of how moisture laden air behaves with air-tight building envelopes and leaky building envelopes. Over just one heating season in a cold climate, 30 quarts of water enters into a 1in sq hole in a building envelope whereas in an air-tight building envelope, only 1/3 quart of water enters into the envelope through diffusion.
Water is the biggest enemy of buildings, keep it out. By building an air-tight envelope, water intrusion becomes water diffusion.
So, we’ve concluded that a house does not need to breath and does not need to drink water either.
Never thought about that until I saw a picture tonight.
We really like green roofs. They provide a range of benefits.
1. Reduce Stormwater Runoff:
Simple, when rain hits a regular roof, it flows where gravity takes it, taking with it, all the debris, nutrients, etc. with it and go into the storm drains and into the waterways it goes. When it hits a vegetative roof, it gets absorbed into the growing medium, the vegetation grows. A typical green roof system retains from 70-90% of every inch of rainfall and you don’t need to water the plants. It saves water.
2. Extends Roof Life: The green roof sits on top of the actual roof membrane, shielding the roof membrane from UV radiation and temperature swings, extending the life of the roof membrane by 2-4 times. It saves money.
3. Mitigates “Heat Island Effect”: When the sun hits buildings heat is retained making the surrounding space warm, then the heat re-radiates back when the surrounding space cools, basically, a negative thermal mass effect. When you have a green roof, it insulates the roof from the sun and through the evapotranspiration (cool word for plants sweating), it also cools the space surrounding the roof. It cools.
4. Green Space: Instead of a boring old deck, you get a garden! It Beautifies.
5. Reduce Heating and Cooling Loads: Essentially, you the green roof is insulation or as I like to call it, “outsulation”.
Here are a couple of cool ones:
Chicago City Hall
Photo courtesy of courtesy of DOE/NREL I Photographer: Katrin Scholz-Barth
We don’t plan to start a goat farm but we plan to have a nice outdoor space above the garage (as much as I love it. Maybe on my own house:)
What we decided to do was to strategically place about sixty 2′x2′ green roof trays above the roof terrace. We believe the effect will be pretty awesome. Stay tuned.
I personally am extremely glad that such a platform exists now for PH designers, architects, engineers, builders… on the ground just doing their work. Passive House/Passivhaus no matter how you spell it and no matter how you measure it (metric or imperial) it, is something that needs to be nurtured. If PH is to become the mainstream building standard as it has become in Europe, people involved in PH in the U.S. and internationally need to work really hard and in solidarity to make it happen.
“The Americans will always do the right thing… after they’ve exhausted all the alternatives.” — Winston Churchill
We simply cannot and do not have time to waste on the alternatives.
I am sure many others feel the same way I do about the break up. We were the children of two divorcing parents who continue to be aggressive against each other. The good thing is we really should not feel the need to choose sides, in fact, it probably benefits us the most if we continue to talk to both sides. More importantly, we have each other. I benefit loads everyday from all the PH individuals I correspond with. It a great community of people who share knowledge and experience freely, so let’s continue to share as generously as possible with each other. It’s a movement that should not be slowed down because of petty disagreements.
For those who are just getting into PH and not familiar with the breakup, don’t bother. Just skip ahead and know that there are people out there building homes/schools/apartments for the future and join our efforts. I did not know about APHN until about two weeks ago but I am really psyched!
I think a visual of why PH folks are such an obsessed, fanatical lot is helpful here. This is a trailer to Charlie Hoxie’s Passive Passion, the official selection from the 2011 NY Architecture and Design Film Festival: http://vimeo.com/17874239 check it out! You should really buy the movie for the full effect. I did.
A simple fact about real estate is that its value is dramatically impacted by the condition of the immediate area where the property is located. This is especially true in the case of the Arlington Passivhaus. This whole journey started with Eric and I driving around in Arlington neighborhoods looking at properties listed for sale. We came to this neighborhood to look at another piece of property a block down. We were not familiar with the neighborhood at all except that it “felt like a nice place”. We decided to drive around every block hoping to learn a little more about the area. That’s when I chanced to turn my head and saw a small hand-written sign inside of a dusty window of a house stating, “For Sale.”
That “it felt like a nice place” sensation has a lot to do everything in the neighborhood. We are not from Arlington and will not pretend to be Barcrofters. We can’t help but appreciate the beauty of the neighborhood. 8th Street is a relatively wide (for Arlington), tree-lined street with cute, distinct and largely well-maintained historical homes.
Our neighbor and award-winning landscape designer Scott’s home has the most amazing masonry walls and of course one of the most elegant gardens I’ve seen. I don’t think you can get someone to build walls like that anymore.
Scott's Masonry walls
Scott's Front Yard
Scott's Front Entrance
Half a block down sits the Barcroft Community House, which dates back to 1908, a building designated in the National Register of Historical Places. I love the Gothic windows! The Community House is currently undergoing restoration. I can’t wait to see it when the work is complete.
Columbia Pike is the main drag in the area. For the last decade exciting developments have been coming down the Pike. Other than the glitzy new condo/apartment buildings, there are several high-impact developments in progress.
I think the three most exciting developments are
1. Wakefield High School:
Rendering of the new building from Arlington Public School website
The $91 Million school broke ground last June. The building is to be completed in 2014 to boast 403,940 gross sqft on four floors, enough to accommodate 1900 students. The building will be going after LEED Silver. Although we are are not huge fans of LEED, we like some of the features being included at the school.
This $24 Million project broke ground last August. It is expected to be completed early 2013 to feature a 5-story main building (57,000 sqf), an attached Gym (8,700 sqf), a public plaza and two levels of underground parking.
This is a 5 mile modern street car project to connect Pentagon City, Arlington to Bailey’s Cross Road, Fairfax. This five mile long corridor was slow to develop because it isn’t metro accessible. With so much development going on on Columbia Pike, the Pike Transit will transform Columbia Pike from a car based growth to a much more sustainable public transportation based one.
I envy the folks who live in Barcroft, with so many positive things going on just a stone’s throw away.
Here is an Emmy nominated video created by the Columbia Pike Documentary Project (http://cpdpcolumbiapike.blogspot.com/) that captures the diverse heritage of the Pike and the changes happening.
Well, that is not to say you should go and blow it all on stupid stuff. What we are saying is that you can really save a lot of energy and money if your home has a tighter thermal envelope.
This is why the Energy Efficiency section in newer editions of the International Residential Code (IRC) are gradually getting more stringent. This made me wonder how tight existing single family homes are. According to a 1998 study “Air-Tightnedd of U.S. Dwellings” published by the Lawrence Berkeley Laboratory http://epb.lbl.gov/publications/lbl-35700.pdf, the average SFH in the U.S. has a 1.72 NL(Normalized Leakage) or 29.7 ACH50 (Air Change per Hour at 50 Pascal). I won’t bore you with the relationship between the two but basically the ratio is 1:17.5 with a 13% standard deviation. 29.7 ACH50 is quite leaky. The study also showed that there are a few significant factors that causes some homes to be tighter than others.
Number of Stories: multi-story homes (31.5 ACH50) were about 11% leakiers than single-story homes (28 ACH50) . This makes sense, more stories means more joints, penetrations to seal and more places for failure.
Floor/Basement Type: homes with crawl spaces and unconditioned basements (30.6 Ach50) are 5% leakier than homes with slab-on-grade or fully conditioned basements (28.7 Ach50). This means a lot of heat loss occurs through floor leakages and highlights the importance of insulating slabs, foundation walls and air sealing all the critical joints in the foundation.
Age of construction: Homes built prior to 1980 were about twice as leaky as ones built after. The data also shows that from 1980 t0 1998, there was very little improvement in air-tightness. This maybe the reason for the increasingly stringent air-tightness standards in recent editions of the IRC.
Duct System: Homes without a duct system (15.75 ACH50) were reported to be leakier than the homes with one (12.25 ACH50). Another interesting result is HVAC duct systems account for just under 30% of the overall air leakages of a home. This explains the need to build air-tight duct systems in homes.
Retrofits: Homes that undergo energy retrofits on average were 25% tighter than prior to retrofit. This shows that retrofits do work, but I think 25% is probably too low a number. If you are gonna do it, you might as well go deep!
This is an old study but it explains why IRC seeks to reduce air-leakages of new constructions. The 2009 IRC N1102.4 which is just beginning to be enforced in Virginia provides builders with two options: Either to comply with a checklist of visual inspections by an inspector or show a blower door test result of 7ACH50. Here are two interesting articles analyzing this new code provision.
As Martin Holladay pointed out in his analysis, the code writers made a mistake by not explicitly specifying “who” is to perform this blower door test. This creates a significant loophole which I hope jurisdictions will close before they adopt them. In any case, at 7 ACH50, this air-tightness standard is still considered leaky but it will probably force builders to start thinking about the issue.
Fast forward three more years, hopefully by then the already published 2012 edition will start to be adopted. The 2012 edition eliminates the visual inspection option, instead requires 5 ACH50 in Zone 1 and 2 (really deep south), and requires 3 ACH50 in Zone 3 through 8 (the rest of the U.S.). This standard will force builders to come up with an air-tightness strategy. However, this new edition still leaves the “who” in doubt. It states, “Where required by the building official, testing shall be conducted by an approved third party.” This is unfortunate, not only does it leave the question of who is to perform the blower door test to individual jurisdictions, if the state code is silent on the issue, it actually leaves it to the “building official”, i.e. the plan reviewer, field inspector, etc. to decide whether to require the test be done by an “approved third party”. I can see various compliance problems ranging from uneven enforcement to corruption issues.
All this legal analysis aside (I set that aside four years ago…), how does one actually tighten a building envelope?
We are by no means experts in this field (in fact, we are newbies) but we do have expert/supplier friends at Four Seven Five Performance Building Supply and Small Plant Workshop and all the Passive House designers who give us advice. Here’s what we’ve done so far to try to reach our goal of 0.6 ACH50. If you have a suggestion, feel free to comment.
SIPs Joints taped with Rapid Cell tape
This is a vapor-open tape sold by 475. The adhesion is very good but because SIPs edges and corners can get a little rough, it’s very important to clean up the OSB a little bit before applying the tape.
Floor Joints Caulked
Ideally, we would have taped these joints above and below the plate too. But because the joists were already there, taping it would have been very labor intensive. Here we opted for a good sealing caulk. The lesson here was to do air-sealing as we build the structure instead of air-sealing after the build. But then I guess we will need to ensure the work is not exposed to rain.
Basement to SIPs Joint
Here, the the joint between the SIPs and plate, we caulked. Between the plate the Superiorwall is a larger gap, which we caulked and sprayed foam. For the larger cavities, we used high expansion foam.
Windows installed with Tremco ExoAir Trio
For the windows and doors, we installed them using Tremco ExoAir Trio (you can get it from Small Plant Workshop). I think it is a good product for installing windows. I hope it will eliminate having to come back with a can of Great Stuff to go over the gaps (Only the blower door test/Thermal imaging will give us the answer). It’s also important to caulk the corners prior to installation as an insurance policy. I have my reservations about it when it comes to installing doors, especially at the threshold. Because it is expansion foam, it can potentially push up the threshold if the opening is large, like in a French door, causing the doors to not operate properly. Additionally, don’t trust it be weather tight as the literature claims. When we noticed our French door threshold bulging, we pulled the trio out from under the threshold and the Trio was soaking wet. Basically, we don’t recommend it where water can potentially accumulate.
ERV Pentration Sealed
For the exhaust and supply points of the ERV, first, we made 10″ diameter round holes for the 8″ ducts. We sleeved the ducts through a Roflex 200 Gasket, using Tesco No.1 tape to tape the connection and taped the gasket to the SIP panel. Finally, we made sure the duct is positioned in the center of the penetration (not touching the sides), then sprayed foam from the outside. This is my favorite seal! I must be a real geek to have one…
Plumbing Penetration Sealed
For all plumbing penetrations, we made sure the penetrations are larger than the pipes, position the pipes in the center of penetration and sealed around them. We will most likely trim off the foam, caulk and then tape around the pipes to ensure the seal holds over time.
MiniSplit line set sealed
The MiniSplit line set is basically sealed the same way as the plumbing pipes except with the insulated coolant line. We cut back the black insulation for the portion that is in the wall and sprayed around the line set.
SIPs Chases Filled
This is less of an Air-tightness but more of a insulation issue. Our SIPs (except for the roof panels) came with electrical and plumbing chases. These chases cut into the insulation value of the walls. We weren’t sure at the time we ordered the panels whether we would need to use them. In the end, we did not use even one of them. We basically drilled holes along the chases every foot and filled each hole with 2-part foam. The work is not difficult but unnecessary if we had ordered roof panels for the entire house. So, we learned our lesson. Also, don’t believe it if anyone tells you the chases have a negligible impact on the overall performance, we emptied at least 6 tanks of foam into the walls.
Oh, if you survived reading this post, check out our video, it’s a lot more fun
The 6th North American Passive House Conference was held in Silver Spring, MD (about 20 mins from downtown DC). This was my first and I thought it was worthwhile just hearing some of the cool experiments people are doing all over the U.S. and Canada. I am sure PHIUS will upload conference materials shortly on their site but here’re some of things I found interesting from the sessions I attended.
Sam Rashkin talked about how to move PH from early adopters to mainstream consumers. Having grown the Energy Star for Homes program from nothing to nearly 30% market penetration in 15 years, I wanted to hear how he proposes to move PH to the mainstream. In short, he offers a gradual process of improving building standards in the mainstream building market until they reach the “aspiration goal” of passive house. I am not sure how I feel about that. This seems to be the Microsoft method of putting out an acceptable product then putting out an incrementally improved version every few years. I think there are enough people who know how to put out a product that is drastically better (i.e. a Passive House) that it doesn’t seem to make sense to do this gradually. However, perhaps the problem is that the vast majority of consumers do not know about Passive House and do not demand to live in one. Production builders will not make improvements on their homes unless they perceive a strong demand.
Jason Morosko explained how the ERV does/doesn’t dehumidify. I am still a little confused… What I took away was that ERVs slow down the humidification of a home on a humid day but it cannot take humidity out of a house unless the humidity level is lower outside. Also that minisplits will do enough dehumidification in most climates except in some very humid areas, where additional dehumidification strategies will be necessary. I think the D.C. area is safe… But I should probably research on this more.
Prudence Ferreria spoke about the reasoning behind Passive House’s 0.6 ACH standard. Something that has always puzzled me every time I try to explain that standard to people. I understand it as a qualitative measure of construction and that is the number that ensures safe moisture migration, but why 0.6 and not 0.65? She said that tests are being done to determine the significance of 0.6 ACH and whether that number should be more climate specific. The results of which will be presented during next year’s conference. I am a believer of building a nearly air-tight house but I am glad someone is looking into the significance of this number. Perhaps this is an opportunity that has opened up since the big split, that PHIUS can now freely question those assumptions.
My favorite lecture was one given by Thorsten Chlupp of Fairbanks, Alaska. Over the years, he built many homes in an extremely cold climate. He wanted to stop using foam due to the high embodied energy of foam production. He presented the SunRise house which is his home and personal lab (Man, I would love to have one). One of the most intriguing parts about this home is the wall assembly, which was built with CDX plywood with 22 inches of cellulose outsulation (remote wall). The cool thing is that the cellulose is wrapped in a vapor permeable membrane with no OSB or plywood holding it back on the outside. This design ensures that the wall has no vapor barrier and moisture can escape from both sides. The difficulty of implementation is off the hook!
The SunRise house uses no fossil-fuel heat sources. Instead, it uses a combination of solar thermal, thermal mass (with a massive 8 million btu storage), and a stone masonry heater. Thorsten said the last time he lit a fire was back in February. I was floored! To read more about this house check out these two articles:
Finally, Sunday was the local Passive House tour, which consisted of the Bethesda Passive House and our own Arlington Passive House. I hope people enjoyed visiting my project. I was seriously intimidated to talk about our project in front of an entire busload of experts!
Eric and I went to take a look at a few more houses at the decathlon yesterday. Unfortunately, the open house hours ended at 2pm. Seems kinda early. Well, we’ll try again later. We were able to get some pictures of houses and look leisurely at some exterior elements.
CHIP
I love the exterior of the CHIP. It’s outsulation really makes me rethink the skin of buildings. And did you know that this is completely student-built? There are only four out of the 19 that were actually student-built. I wonder if they get extra credit for that. They really should!
Tailgate Party at CHIP
Unit 6 by Team Tidewater
Nice mix of traditional materials in a modern style
Shades at Unit 6
Solar Homestead by Appalachian State
Lot of regional character.
Natural Tree Bark Sidings at the Solar Homestead
Tree bark protect trees when they are alive, so why shouldn’t it protect dead trees? This makes intuitive sense.
More Bark
Enjoy House by New Jersey
Pre-cast concrete. The only masonry structure here. I believe the concrete panels are built using thermalmass system, i.e. Rigid foam sandwiched by two sides of concrete.
E-Cube by Team Belgium
Clean lines but seems a little boring.
E-Cube with Shades
Watershed by University of Maryland
A beautiful house house by Maryland. Heavy on water conservation. Butterfly roof with PVs and a green roof.
Watershed in Action
Here’s a real watershed moment. Wonder if they measured how much water they collected.
Living Light by University of Tennessee
I really like the Living Light’s modern look. I think everything just kind of “fits”. Beautiful design!
Tesla!!!
Speaking of beautiful, we parked our little Prius behind this guy. The funny thing was across the street was the display of the Nissan Leaf and a Ford Escape Plug-in Hybrid. I wanted to tell the visitors to go across the street and see the real deal.
