(Visited 10 times, 1 visits today)FacebookTwitterPinterestSave分享0 Data from the Curiosity rover’s RAD instrument seem to indicate astronauts could survive radiation reaching the surface.The data are preliminary, but a press release from the Mars Science Laboratory (MSL) team at Jet Propulsion Laboratory graphed measurements from the Radiation Assessment Detector (RAD) on Curiosity and found a cyclic variation over 5 sols (Martian days) corresponding to atmospheric pressure cycles. The radiation environment appears similar to that endured by astronauts on the International Space Station.Live Science quoted the principal investigator for RAD saying, “Absolutely, astronauts can live in this environment.” He stressed, though, that the data are preliminary, with Curiosity only 3 months into its planned multi-year mission. The article said, “He and his team have not yet put hard numbers on the Martian radiation levels, though they plan to do so soon.”The real issue for future exploration, the article continued, “is determining how much of a radation dose any future astronauts would accumulate throughout an entire Mars mission — during the cruise to the Red Planet, the time on the surface and the journey home.” The cruise part, with no atmosphere, may prove to be the biggest obstacle for human travel.There’s nothing like “ground truth” to constrain speculation. Earlier radiation estimates we reported were more pessimistic (e.g., 9/14/2000, 5/02/2001, 5/18/2005, 9/23/2006), so it’s good to see that radiation may not rule out human exploration some distant future day when the world’s governments learn how not to bankrupt themselves.More data are needed, though, to keep the dream alive. How often do solar flares and high-energy cosmic rays hit the ground on Mars? While it’s comforting to learn that the thin Martian atmosphere can dissipate some of the radiation, Mars lacks a global magnetic field and associated Van Allen belts, and has no ozone layer, so it has far less protection than does Earth. Then there is still the issue of getting astronauts to Mars on a nearly two-year round trip with no protection from the sun’s shooting gallery on the way. In addition, the types of radiation (UV, charged particles, cosmic rays) have to be accounted for separately and in sum.As for probabilities for life on Mars, don’t get your hopes up. Does fewer bullets in a computer room mean better chances for survival? Millions of years of bombardment, even if lighter than previously estimated, is not conducive to the growth of hopeful monsters.
What comes first: insulation or vapor barrier?Meyer’s plan to encapsulate the crawl space will include both insulation for the walls and a vapor barrier to seal the floor. Which comes first?“Most people install polyethylene on the floor and walls before insulating the walls, but frankly, it doesn’t matter very much,” Holladay tells him. “If you insulate the walls first, with either rigid foam or closed-cell spray foam (and no polyethylene on the walls), everything will still be OK. You can do the floor last if you want.”If Meyer chooses polyiso foam insulation for the walls, however, Dorsett suggests it would be better to lap the ground vapor barrier up the foundation at least a foot before installing the insulation to prevent the cut edge of the insulation from touching soil directly.“Holding the polyiso in place with 1×4 furring through-screwed to the foundation puts a few minor holes in the vapor barrier,” he says, “but on the walls that doesn’t matter.” A gas appliance will probably be too bigDana Dorsett sees trouble ahead if Meyer goes forward with his plan of installing a gas-fired furnace in the house, particularly if he puts the furnace in the attic as the HVAC installer wants to do.“Almost any gas-burner is going to be ridiculously oversized for a 1150-square-foot rambler in Fall City, especially after tightening it up a bit,” Dorsett says. “That would be mistake #1. Putting it in the attic rather than in [an] insulated, conditioned crawl space would be mistake #2.”With an outside design temperature of between 20° and 22°F, and assuming Meyer performs some air-sealing work, the heating load is likely to be less than 15,000 Btu per hour — and that puts him within range of a 1.5-ton ducted minisplit.There are two models that might work, Dorsett says: the Mitsubishi MVZ-A18AA and the Fujitsu AOU/ARU-18RLFCD. “With either of them you have the benefit of modulated ultra-quiet output (more so with the 18RLFCD than with the A18AA), and at your average wintertime temps you would beat their HSPF efficiency numbers if the ducts are all extremely short, and inside a conditioned insulated crawl space,” Dorsett says.Under the right conditions, a 1.25-ton or 1.5-ton ductless minisplit also might do the job, and cost less to install, he adds. There might even be local rebates available to help pay for the conversion from electric baseboard to a heat pump.“Even the smallest gas furnaces are likely to be 2x oversized for your actual loads,” Dorsett says. “If you’re committed to going with natural gas, a condensing gas water heater and a suitably sized hydro-air handler is probably a better solution than an oversized gas furnace + water heater.” RELATED ARTICLES The house is currently heated with electric baseboard heaters, but Meyer is considering a switch to a gas-fired forced-air system. If he locates the furnace in the crawl space, it would heat the space and the ductwork would not have to be insulated. Is that a better option than putting the furnace into the attic and running a duct to the crawl space? Or heating the crawl space by placing an exhaust fan in one of the crawl space vents and opening a floor register between it and the house? Would the exhaust fan be enough to mitigate radon hazards?Meyer’s questions are the starting point for this Q&A Spotlight. What if the house got bigger?Meyer replies that he plans to expand the house into part or all of the garage in the next year, enlarging the house to a total of about 1,600 square feet.“We are in the process of converting to natural gas for cooking, water heating (tankless gas water heater), space heating (forced-air furnace), and possibly clothes drying,” Meyer says. “The baseboard heat and the old electric tank water heater are costing us a fortune. The house is not too open, and has 4 bedrooms and 2 baths (‘1.75 bath’ in realtor speak).”Even so, Dorsett says, the design heat load will be less than 25,000 Btu/hour, making only the very smallest gas furnace a reasonable option.“Replacing the electric baseboard with hydronic baseboard, running off a condensing tank hot water heater would allow you to micro-zone with impunity, and never have to suffer the limitations of a tankless water heater,” Dorsett says. “It’s a lot easier to find places to route pipes than it is to route ducts (which is how ducts all too often end up outside of conditioned space). The 50-gallon all-stainless HTP Phoenix Light Duty is a good candidate for this type of combi-system, but there are others.”A ducted HVAC system would only make sense if Meyer were planning on central air conditioning, Dorsett says, “in which case heat pumps (ducted minisplit or traditional) make a lot of sense.” Insulate the exposed footing, tooThe photo Meyer has provided of the crawl space (see the image at the top of the page) shows that some of the concrete footing has been exposed. Holladay suggests that Meyer insulate the exposed areas with closed-cell spray foam, available in a two-part kit.Meyer seems concerned about cost of adding a required thermal barrier over the two-part foam, but Dorsett says painting it with an intumescent paint would be enough in most jurisdictions.Alternately, Meyer wonders whether he could use rigid foam to cover the exposed parts of the footing.“There’s nothing wrong with your plan to cover the horizontal and vertical parts of the exposed concrete footing with rigid foam,” Holladay tells him. “And, as Dana Dorsett pointed out, there’s less heat loss through concrete components that are well below grade than through concrete components that are near grade. So you’re fine. “ You don’t need to heat the spaceDon’t worry about the heat, GBA senior editor Martin Holladay advises, because you don’t really need it.“A sealed, unvented crawl space in your climate will not require any heat to stay warm,” Holladay writes. “Once you have sealed the air leaks and insulated the walls, it will never freeze.”Many crawl spaces do incorporate an exhaust fan and a register in the floor above, he adds, but those features have nothing to do with heating the space. They are included to control moisture.Holladay adds that Meyer could install a register from his forced-air heating system to the crawl space. In that case, he should keep the floor grille, but not bother with an exhaust fan.Here, too, the object is not to heat the crawl space but to provide humidity control.As for radon control, he adds, start with a radon test to determine whether it’s a problem that must be dealt with. If so, Meyer will need to do more than rely on a crawl space exhaust fan alone. Building an Unvented Crawl SpaceFive Ways to Deal with Crawl Space Air CAD Details from the GBA Library: Building Plans for Conditioned Crawl SpacesThermal Barriers and Ignition Barriers for Spray FoamFrom Fine Homebuilding: Sealing a Crawl SpaceHow to Insulate a Basement WallAll About RadonAn Open Discussion on Closed Crawl Spaces David Meyer’s Seattle-area home is built over a crawl space, and after stripping out the old insulation and vapor barrier he is ready to re-insulate and seal the area. After looking into his options, Meyer is leaning toward “encapsulation,” meaning the crawl space would be sealed (unvented), with the insulation on the walls, not between the floor joists.He’ll have 18 inches of clearance to work with. The floor framing consists of what he calls the “old style post and pier construction method” with 4×6 joists on 48-inch centers, followed by 2×6 tongue-and-groove subflooring, and hardwood finish flooring on top of that.“After cleaning up the crawl space I started doing research into how to insulate the area, and found the encapsulation method,” Meyer writes in a Q&A post at GreenBuildingAdvisor. “I like the method due to not having to run insulation in the floor joists, giving me more space to work down there, and also in keeping the area cleaner for rodent inspection purposes and for when I do plumbing or other type of work.”There are, however, a few details yet to be worked out. Our expert’s opinionGBA technical director Peter Yost added these thoughts:On the West coast, it sure seems that there’s a preference for venting crawl spaces and placing the air and thermal barriers or control layers on the underside of the first-floor assembly. I have found it really hard to get continuity of the air and thermal control layers there, so I have a strong preference for installing them on the crawl space perimeter. It does mean you are conditioning or semi-conditioning an extra volume, but that penalty is overcome by what you gain in energy efficiency and moisture control by placing your crawl space firmly inside your building.You should check with local HVAC folks about the 18-inch clearance in your crawl space, but getting a furnace into this space, much less getting it well installed, seems highly unlikely to me. I’m betting that the space is just too tight.When in comes to testing for radon, of course you test at the lowest inhabited level of the house. But when do you test? If you test before your work is complete, there is some uncertainty concerning whether you will improve or worsen radon levels on the first floor. And don’t rely on just what your neighbors might say or know; research has shown there is very little correlation of radon levels in buildings that are right next to each other.Another question is: What type of radon testing do you do? The most accurate radon test is the alpha tracker test, but to get useful numbers you need to test for up to three months when the building is closed up, as it would be during the winter. I have found that the Siren Pro Series 3 electronic meters correlate pretty well with alpha track testing, and they give results in just three days (although testing over longer periods is much more valuable). I like the fact these meters can be set for short-term testing (three-day averages that after three days drop the first data and add in new — a running average) and set for long-term cumulative data collection.In the photo provided, there is evidence of water wicking up the concrete piling on the right, but also what appears to be a sheet capillary break between the concrete and the wood post. Make sure that you indeed have a capillary break underneath each post.Finally, on the question of whether you need a thermal barrier or ignition barrier to protect spray foam in crawl spaces: The model building codes allow for spray foam thermal barrier exceptions in attics and crawl spaces where entry is limited to repairs or maintenance. So in this type of crawl space you can use one of these ignition barriers prescribed by the codes:Mineral fiber insulation, 1 1/2 inches thick.Wood structural panels, 1/4 inch thick.Particle board, 3/8 inch thick.Hardboard, 1/4 inch thick.Gypsum board, 3/8 inch thick.Corrosion-resistant steel, 0.016 inches thick.Alternative ignition barriers — such as intumescent paints or coatings — can be approved by code officials based on testing that follows ICC-ES Acceptance Criteria 377, Appendix X. Be careful: even if someone claims a material qualifies as an alternative ignition barrier, you should really insist on the appropriate test information.Finally, you may be able to leave spray polyurethane foam (SPF) exposed, so long as the SPF has been tested and approved per AC 377 Appendix X or ASTM E 970. (For more information on this topic, see Thermal Barriers and Ignition Barriers for Spray Foam.)
Going into Week 9, the No. 1 slot in our Elo ratings had been the exclusive province all season long of last year’s Super Bowl participants, the Seattle Seahawks and Denver Broncos. In fact, the last time a team other than Denver or Seattle ranked first in Elo was Week 19 of last season, when the San Francisco 49ers owned first place after beating the Carolina Panthers on the road in the NFC divisional playoffs. (They would cede that ranking to Seattle the very next week.)This week, though, the New England Patriots have finally broken the Denver-Seattle duopoly on No. 1 after the Patriots crushed the Broncos 43-21 Sunday afternoon. How unusual was the Seahawks’ and Broncos’ long stranglehold on the top slot? Going back to the advent of the 16-game schedule in 1978, it’s the eighth-longest span into a season it’s taken for a third No. 1-ranked team to emerge. Last season, it took seven weeks for Seattle to wrest No. 1 away from a Denver/New England duumvirate.For the Patriots, it’s a long-awaited return to a familiar spot. New England occupied No. 1 in 27 (!) consecutive editions of the Elo rankings between Week 19 of the 2011 season and Week 2 of the 2013 season. And since 2000, they’ve spent more weeks at No. 1 (102) than the next three most frequently top-ranked teams (the Indianapolis Colts, Green Bay Packers and St. Louis Rams) combined.But of all teams, the Patriots should know that a No. 1 Elo ranking midway through the season is no Super Bowl guarantee. They sat atop the league through the first nine weeks of both the 2012 and 2007 seasons but failed to hoist the Vince Lombardi Trophy either season. (Since 1978, the top-ranked team through Week 9 has gone on to win the Super Bowl at a 41.7 percent clip.)New England also faces a difficult schedule. It has a bye this week, but after the break it will have to travel to Indianapolis to face the fifth-ranked Colts. Then, following a home date against the 17th-ranked Detroit Lions, the Patriots must go on the road against the No. 12 Packers and the No. 14 San Diego Chargers in back-to-back weeks, with the surging No. 16 Miami Dolphins waiting in the wings after that. An average (1500 Elo rating) NFL team would be expected to win only 46.6 percent of the Patriots’ remaining games, which means they have the seventh-hardest remaining schedule of any team in the league.Our Elo-based simulations give the Patriots just a 16 percent probability of winning the Super Bowl, which is well below the aforementioned historical average for top-ranked teams through nine weeks. Part of that is simply an artifact of league and playoff expansion. Since the NFL adopted its current size and divisional format in 2002, the top-ranked team through Week 9 has won the Super Bowl 25 percent of the time, a rate more in line with New England’s simulated odds. But 2014 has also been a strange year in terms of the distribution of ratings across the league’s 32 teams. The Patriots’ 1677 Elo rating at No. 1 is 21 points below the average for that slot through Week 9 from 2002 to 2013, while 18 of the next 22 highest-rated teams have better Elo ratings than the average for their ranking from the previous 12 NFL seasons.In other words, New England isn’t as strong as the typical No. 1, and there is an unusual number of solid teams out there for the Pats to tangle with en route to the Super Bowl. That lends credence to the growing talk of 2014 being a banner season for parity in the NFL.Meanwhile, the league’s nine worst teams by Elo are far worse than usual, culminating with the Jacksonville Jaguars and Oakland Raiders each falling more than 50 points behind the typical ratings of the NFL’s two worst teams through nine weeks. It will be worth monitoring whether this year’s atypical dispersion of Elo ratings is a one-year quirk or part of a larger trend.Here are the current playoff and Super Bowl odds for all teams:I mentioned that San Francisco had defeated Carolina (who ranked fifth in Elo at the time) to briefly claim the No. 1 ranking during last season’s playoffs. This year, however, neither team has enjoyed the same kind of success, going a combined 7-9-1. And there’s a 55 percent chance that both will be shut out of a return trip to the postseason.After starting the season 1-2, the 49ers had regained some measure of playoff probability with three straight wins over the Philadelphia Eagles, Chiefs and Rams in Weeks 4 through 6. Going into Week 7, they even had an NFC West-leading 65 percent probability of making the playoffs, as well as the division’s best projected end-of-season win total in our Elo simulations. But a pair of losses sandwiched around a bye week have left San Francisco on the verge of missing the playoffs entirely. Its current playoff probability stands at 32 percent after taking into account their mediocre record (4-4), the difficulty of their remaining schedule (ninth-hardest), and the strength of the teams they’d have to beat out for a wild card (as their hopes of winning the NFC West have been all but extinguished).Carolina’s chances of returning to the playoffs look even worse. Despite failing to win five of its previous six games (it lost four and tied one), Carolina still had a 44 percent probability of qualifying for the postseason before its game against the New Orleans Saints — but our weekly playoff implications article also identified Panthers-Saints as one of the most crucial matchups of Week 9. Sure enough, New Orleans’ 28-10 victory dropped Carolina’s playoff probability by 25 percentage points, leaving it with less than a 1-in-5 chance of making the playoffs.In addition to the Panthers and 49ers, the other teams who lost the most from their playoff odds in Week 9 were the Baltimore Ravens and the Chargers in the AFC.The cause for Baltimore’s decline was all about the division odds — predictably, its head-to-head loss against the Pittsburgh Steelers on Monday night had huge ramifications for the AFC North race. Going into the game, the Ravens had a 33 percent chance of winning the division, with the Steelers sitting at 28 percent; after the game, Pittsburgh’s chances had increased to 45 percent and Baltimore’s had dropped to 13 percent. (Neither team’s wild card odds really budged at all.)San Diego’s dip, on the other hand, had little to do with a division race. The Broncos are rated so much higher than their AFC West competitors that our simulations see little chance they don’t win the division. That leaves the wild card as the only real viable path to the playoffs for the Chargers and Chiefs, both of whom are in a dogfight with each other — as well as the losers of the AFC East and North — for one of those two slots. (The AFC South loser is unlikely to make much of a wild card push.) Miami’s 37-0 pasting of San Diego on Sunday had direct consequences in that regard, boosting the Dolphins’ wild card probability by 17 percentage points as the Chargers’ chances dropped by 19 (with scarcely a change to either team’s division odds).Elo point spreadsRecord against point spread: 64-62-3 (7-5 in Week 9)Straight-up record: 94-39-1 (9-4 in Week 9)Although the Elo ratings are performing better against the spread in recent weeks, we still would strongly advise you not to take them to Vegas as a betting tool. Even so, it is always interesting to see how they differ from the spreads offered by the major sportsbooks.This week’s biggest disparity is in the Dallas Cowboys-Jaguars game, which is not only taking place in London, but adds the wrinkle of Dallas quarterback Tony Romo’s availability being in question. With the possibility that the Cowboys will once again have to start backup QB Brandon Weeden, who oversaw the team’s Week 9 defeat to the Cardinals, the oddsmakers have dropped Dallas to a mere 6-point favorite against the lowly Jaguars, rather than the 10.5-point favorite the Elo ratings would suggest.Aside from that change, the other big discrepancies against Vegas this week involve the Cardinals and Rams (the books have been comparatively down on Arizona all season, relative to Elo) and the Cincinnati Bengals and Cleveland Browns (Elo rates Cincinnati slightly higher — and Cleveland slightly lower — than Vegas’s power ratings would value the two teams). But in the Detroit-Miami tilt, which may go down as the biggest game of the week from a playoff-implications perspective, both Vegas and Elo agree: The hosting Lions should be favored by about a field goal.CORRECTION (Nov. 6, 11:56 a.m.): A previous version of this article incorrectly said that Elo is 62-44-3 against the point spread. It is 64-62-3.(Nov. 6, 2:04 p.m.): A previous version of this article said the Dallas Cowboys had a 75 percent chance of defeating the Jacksonville Jaguars on Sunday. Dallas should have an 82 percent win probability, because it has an Elo difference of +259 and there is no home-field effect in either direction.
July 31, 2017Conviviality – a chance for the August workshop participants to meet Arcosanti residents. (photo and text lvb)A barbecue potluck to welcome the new workshop is organized in the Vault. Cyo, one of the residents, is vegetarian: bean burger for him.Thanks Charlie for taking care of the barbecue and thanks to everyone who prepared something for the potluck or simply joined it. Welcome to Dominik, Miles, Richard, Taylor, Camilo and Irene.