Don, about your PV Just wondering why you went with the microinverters. Don't get me wrong--they have their place, primarily for systems experiencing shade issues in which it is more beneficial to directly harness the AC power, and possibly for spit pitches and orientations. Other than that, I question the advantages over a traditional string inverter. The maintenance and troubleshooting has both pros and cons---sure, if a string inverter is down, you lose all your revenue grade power, vs losing only the power of one module. The cons are, however, that the microinverters can be really fun to get to (under the modules, on the roof) if need be, and their reliability has no track record...I'm not sure how I feel about having my inverter in the sunny heat, under a solar panel, exposed to the elements, with big clusters of wires, for 25 years, vs a readily accessible string inverter. Also, they're expensive--at over $150 each, plus those bulky connectors, gets expensive quickly. Next, I would be very cautious about purchasing an inverter with a 20-25 year warranty. Most, if not all, solar modules guarantee a performance of 90% of their nameplate rating (given -0%tolerance) over the first 10 years of service. The remaining 10-15 years of service are guaranteed at a 80% tolerance. In other words, the inverter must be able to produce power from a solar module performing at only 80% of its nameplate value, which means that it dumps the extra power for the first 10 years. For example, it is often suggested to have a 235W DC input to produce only 190W AC out. If it were 210-215, even 220W, maybe.....Once again, it depends on your circumstances. I'm only offering something to consider. Also generalizing, but $28K for a 5kW system is almost $1/watt more than installed systems cost today (at least here in south NJ), unless you're using Sanyo modules, FatSpaniel monitoring....or microinverters....
Posted: 10:06 pm on February 28th 2012
Ted, Energy Saving Features Solar PV isn't an energy saving feature. It has nothing to do with conserving energy. It is simply a supplemental source of energy, regardless of how much you use or save. If you are tied to the grid, the solar production is the amount of energy you are not purchasing from the local utility. If you are off grid, it is the total available energy for use, whether or not you are frugal or wasteful...
Posted: 10:17 pm on February 28th 2012
Brian, Response to comment #30 I am confused about the "divide by 2" ... I believe in accurate site surveys and proper installations. The electronic "computer" on your roof was probably a Solmetric SunEye, although there are others out there. Knowing how to do the math comes in handy when the need to make field adjustments happens. Converting real to solar time, for example, magnetic declanation, determining exact azimuth, etc...The surveyor should know how to do a proper survey without the "shortcut" tools, and use them as a supplementary data collection tool only. They are convenient in terms of having a built in fish eye camera, but the electronic compass on the newer model is very sensitive and not always accurate. Power lines above, even a belt buckle, cause interference with the orientation reading. I always carry a marine grade magnetic compass to compare notes. Normally, however, the differences and inaccuracies aren't a big deal. Next, and even more critical, are the points in which the shade analysis data is taken. For example, suppose your roof will have 3 rows of 8 modules each in portrait (approx 16' x 22'). There is some early morning and late afternoon shading for purpose of this example. If you took pictures of each corner and averaged the production estimate of each picture, you will determine an overall system production estimate. Now, if you used the same four corners, but also took pictures of the sunnier middle section of the array and averaged them in with the corner pictures, the result will be greater annual production. This is a big point because the sunny portion of a string does not count if even a small portion of the string is shaded, and I don't think this crosses everybody's mind. I've seen too many systems performing 5-15% below their predicted output. I think the problem is that people are trying to sell, and forget the simple rule of thumb--conservative predictions often result in pleasant surprises---. I'd rather expect less and get more than vice versa. My next point is about the installation and materials as well. 240W modules are not necessarily the same. You must also consider the power tolerances. Each batch of silicone is basically 240W, but not always EXACTLY 240W. For example, many modules have a -0%+5% rating. This means that the actual 240W module will perform at a minimum of 240W and possibly as much as 252W. Another 240W module may have a power tolerance of -5%+10%. This means that the module may not actually be putting out 240W. It could be generating as little as 228W or as much as 264W---a BIG difference. So just based on this power tolerance, our example system of 24 modules has a large range of power production. Also, installation can affect power. For example, if the inverter is installed on the sunny side of the house with no shade protection, the heat will cause greater inefficiency in terms of DC to AC energy conversion, which adds up over the course of the year. Another example is the space between the roof and the module. A 4" minimum airspace should be achieved. Any less and you're compromising the airflow underneath the modules, causing heat build up. The hotter the modules, the more inefficient they are. Voltage drop from long wire runs will lose power, as will wire in conduit attached directly to the roof. I always suggest raising the conduit off the roof, even if it's only by 1/2". It makes a huge difference in terms of the heat potential within that conduit. There are several other things to think about, but these are the biggees...
Posted: 11:01 pm on February 28th 2012
Responses to Martin, Don Martin, About microinverter performance: I understand that today's sine wave inverters combined with MPPT tracking are 95% efficient and up...when they are "converting" energy. What I am saying is that given the same amount of DC input power, the AC output power is less with microinverters than is with string inverters. There's also the factors that contribute to the high efficiencies. As far as string inverters go, generally speaking of course, there is a "sweet spot" of highest efficiency close to, but not quite at its maximum input power. I feel that this characteristic allows the system to squeeze out a bit more power than its microinverter counterpart. I am far from an engineer and am only speculating, but the facts are that I have seen a higher DC(STC) to AC conversion ratio than with microinverter systems. Don, I couldn't agree with you more about solar PV---it isn't just about the payback. Solar PV was so heavily marketed here in NJ as a 2 year payback, 20 year money making venture, bla bla bla, and sold by people who knew or cared nothing more than signing lease or financing contracts...The real environmental benefits, while somewhat obvious, were treated as politically correct finishing touches. Everybody sure saw green(backs), but nothing more. As a result, the rat race was on, solar contractors (who I wouldn't even trust to caulk around my kitchen sink, let alone install 350V on a roof they just made 48 penetrations through) sprouted everywhere, and I mean everywhere...Now that the financial incentives are winding down, the whole buzz seems to be disappearing with it, except for the not yet emerging solar installations repair industry---you watch, those 5 yr installer warranties should be expiring soon ... Nobody really cares about environmental benefits, or the substantial benefits of solar. ..and it's a shame. However, these "green" conscious people still play video games and use their $700 facebook machines all day and night, blow leaves instead of rake, sit down lawn mow instead of blade'n push, drive to the local store (less than 1/4 mile away), etc....It's all about CONSERVATION, not production.... Getting back on track: I do think PV is a no brainer for new construction---for $25-40K added to a mortgage ($150-200/month)---I'd rather pay a higher mortgage and own a solar PV system than pay a lower mortgage and higher utility bills. I wasn't trying to get you all worked up when I mentioned that I felt over $5/watt was high. I don't know your neck of the woods, nor do I know exactly what system you went with. Sure, a crappy inverter with cheap racking components and inferior grounding lugs, etc, will be cheaper than an above and beyond system. I was only trying to offer outside sources of information, namely that a well installed system of medium grade components is around $4.50/watt installed,period, regardless of incentives, SREC's, and other paybacks. Next, I must agree and disagree with you as far as the maintenance issues go. Once again, I don't know your situation--you may live 5 minutes from readily available parts, and have a 1 story rancher with a 6/12 pitch roof. What I do know is that the "years of performance" part of your bathtub curve statement are missing from the live world experience of microinverters, and that it can be quite time consuming to A) troubleshoot & determine the problem, and B) to physically isolate and remedy it...Dealing with a slate 12/12 pitch roof 37 feet up is not easy or fun to deal with. I'd rather there be 1-3 inverters READILY ACCESSIBLE. When comparing micro to string inverters side by side, I was offering my opinion as to why I would choose string. Once again, microinverters have their place when used properly, but I would still question the use of one instead of a string inverter in most general situations without shade issues.
Posted: 10:57 pm on March 2nd 2012
I think the LEED program I think the LEED program should be weighted accordingly to the geographic/demographic region its in...In other words, the point values would change region to region (but still always add up to 136 or whatever the new total is).. Like in coastal southern NJ, which is mainly a marshland surrounded by Pine Barrens, and a very, very shallow aquifer, I think water management (conservation and pollutant management) is way more important than having a building located within 1/2 a mile from shopping, public transportation, etc. However, in a more urban area which is already developed and populated, it may be more important to deal with reduction of atmospheric pollutants, which should result in higher points being assessed in this department. Next, the recycleable thing: I was never big on the embodied energy nonsense. Steel is green (comes from the earth, goes back to the earth, can be recycled indefinitely), natural concrete is green (made from limestone, rocks, sand, etc...) Plastic is NOT green (It is made from petroleum and chemicals) Foam is NOT green (made from unnatural chemicals and does not break down into natural form) Talking countertop material choice, nobody is going to tell me corian is more environmentally sound than granite, yet the corian gets the point. Time to just forget about the 'what's politically correct b.s. category'.
Posted: 10:25 pm on March 6th 2012
Strive for perfection, work Strive for perfection, work with what you actually wind up with---the pretty good house in my opinion...as long as we don't mess with ideas that have NO leeway, or ZERO error tolerance, success is in the works. Let's face it, nobody can build a perfectly airtight house (except maybe NASA in a clean lab somewhere), and even if it were to be done, sizing the exactly right air and pressure exchanges would be just as challenging. So, we may as well learn to build a close-enough to airtight house with escape passages for moisture and vapors. Building the pretty good house is the way to go, as it's all we as human contractors and skilled builders can do. To first understand how and why a perfect building could be, then to understand the inevitable failures and weaknesses, and finally to design a building which encompasses all this will ultimately be the best of all worlds---a cost effective building that serves the need it was intended to .....the sweet spot on the curve between the most cost effective and the most high performing building.....
Posted: 08:25 pm on March 7th 2012
Initial construction costs also have weight. How much did the Beaton's house cost? I wouldn't be surprised if it cashed in around $350/ft--a huge investment for, in my opinion, not much more than status and conversation. I can't see the payback being worth it... Given that the Montague house is basically a double 2x4 home with great attention to insulation detail, ornamented with renewable energy and fiberglass windows, the $174/foot is still a high cost (not by much, but still high) in my opinion. Kudos to the Montagues for conservative energy use practices, but I think that getting a home in the $125/ft range is do-able. At about $50/ft more than traditional energy star home building, I can see payback, but not for a while... I'm building a 3400 sq ft --a pretty good house (attention to insulation, but not dedicated to it-....R-10 below basement slab, R-30 walls, R 45 roof in southern NJ)--home using icf, concrete, steel, for just under $50/ft...Granted, I'm doing 85% solo, but still doing it....Careful shopping, doing the research & design yourself, and flexible plans are a big part of the secret. I think it's more important to compare the performance of the house to its cost per ft because that's pretty much the bottom line. Energy consumption can always be offset by energy production, but the cost of energy efficiency must be able to realistically be pay for itself in savings within a reasonable amount of time (in my opinion, no more than 7 yrs).
Posted: 10:12 pm on March 10th 2012
nice vertical cuts--you made nice vertical cuts--you made that look a heck of alot easier than it really is...about the scabbing deal--i guess you don't need hurricane clips as the scabbed on eaves/rakes are 'detachable' like a lizard's tail....how do you exactly "scab" the boards on? long stainless decking screws through the rafter end?
Posted: 10:37 pm on April 9th 2012
thanks martin Thanks Martin, that's pretty cool.
Posted: 10:45 am on April 11th 2012
How do you get rid of it How do you get rid of it without replacing the mold with chemicals? I've been building a house for just about 3 years, and am just now beginning to sheath my roof. It's hard enough to come up with $$ to survive, let alone build a house out of pocket. Needless to say, the house --full basement (half above grade), 1st, and 2nd floors, have been exposed since its birth in 2009. The good news is that with the exception of the roof, the entire building is icf, concrete floors, and steel joists/decking. The bad news is that my house resembles an abandoned structure, musty, damp in the basement and first floor with basically permanent water (from rainfall having no way to completely dry). I also used an ICF with mineral wool inserts, which I know have some mold issues. There is no way to get to the mineral wool, as it is an internal component of my concrete filled walls. I could not afford another concrete deck (the original roof plan), so I broke down and decided the only way I could finish the envelope was to use wood. The roof sheathing was bought used, and my rafter lumber was bought at auction. In both cases, the material had been exposed to an undetermined amount of weather. There is definitely visible mold on a small, but decent portion of my material, and virtually all of it is wet , even slimy, between boards; however, I have no choice but to use these materials. I was planning on an unvented cathedral ceiling, 2-3 inches of closed cell spray foam on the underside, and 4 inches of rigid xps between 2 layers of 5/8 CDX on the roof. I have been wondering about how I will get internal moisture out of my house if not through the roof. Also, I am assuming that I will be trapping mold and whatever moisture content is in the lumber forever between the exterior and interior closed cell insulations. Any thoughts in terms of cleaning the musty, wet, moldy building, and dealing with my roof?
Posted: 10:33 pm on May 12th 2012