I am in zone 7 (Northern Minnesota). Looking at building timber frame structure without SIPs. I love the idea of using Roxul Comfortboard 80 for exterior insulation. I want to…
Solar panel prices You can get brand new solar panels for $1.20/watt. This is the cheapest I have ever seen them and they are the polycrystal glass faced ones made by Kyocera, not some Chinese brand. This does not include any other balance of system components but since I am simply adding onto an existing system and installing myself the price is not much more then that. Warranties are for 20 years and some are for 25 years.
Posted: 07:31 am on August 20th 2012
Martin, Northern Arizona Wind Martin, Northern Arizona Wind and Sun has the 315 watt panels currently selling for $378 a panel.
Posted: 06:34 pm on August 20th 2012
Missing at least one more Use Case You mentioned only 2 use cases. Either sell your power back to the grid or be "off-grid". You are missing at least one other user case. Some inverters have the capability to sell back to the grid, be off-grid, and act as a UPS. I have an Outback GTFX3648 inverter with an optional battery bank. This inverter allows me to have any circuit(s) in my house powered by either the battery bank/PV array or the utility power. With a remote controller hanging on a wall I can press a button to switch to either power source. Using this setup easily allows you to start out "small", learn about the system, and continue to add PV capacity over the years as funds allow. When you do acquire more PV panels you can switch more circuits over from the service entrance panel to the inverter panel allowing them to be powered by either source. This system also acts as a UPS. If I do not have the remote set to use RE power and the grid goes down, the system instantly switches to RE power to keep all the circuits connected to it powered. Using this setup might be a better setup if you still want power when the grid goes down, want to start small, and/or want to use both grid and RE power without going through the red tape of selling back to the utility company.
Posted: 10:52 am on August 27th 2012
Solar hot water statement The statement: "If you also use solar hot water, you’re going to need at least 4 more kilowatts of PV." does not make sense. This statement was made to make installation as simple as possible. You generally should not design a system to use a PV array to heat hot water. A solar thermal panel(s) can heat water at around 80% efficiency compared to less then 20% for PV. So you would need at least 4 times the roof space with PVs to heat hot water compared to using solar thermal panels. Solar thermal panels would also not be affected nearly as much by partial shading/snow cover.
Posted: 11:06 am on August 27th 2012
Kathryn, please update if you are able to find something that gets approved. I have also looked in the past and unable to find a halogen free romex type cable. I am actually surprised a manufacturer has not produced this considering the lengths to which many people will try to make their homes as green as possible. Just because you should be away from the location if it does catch on fire does not mean we shouldn't look for products that are inherently greener.
Posted: 08:05 pm on July 4th 2017
Just priced Comfortboard 80 from Home Depot in upper Midwest. Pallet of 3" thick R12 2ft. x 4ft. sheets (66 on a pallet) was $954 or $14.55 a sheet, $1.81 sq. ft., ~$0.15 sq.ft per R1 value. For 3" thick R12 3ft. x 4ft (32 on pallet) it was $699 or $21.85 a sheet, $1.82 sq. ft., ~0.15 sq.ft per R1 value. XPS: 1" thick R5 4ft. x 8ft. $12.32 a sheet, ~$0.39 sq.ft., ~$0.077 sq. ft. per R1 value. EPS: 2" thick R8 4ft. x 8ft. $11.25 a sheet, ~$0.35 sq. ft., $0.044 sq. ft. per R1 value Summary of $ per sq. ft. per R1 value from my local Home Depot: XPS: ~$0.077 EPS: ~$0.044 CB80: ~$0.15 Of course each has advantages/disadvantages which make these price comparisons not completely fair. The comfortboard being basically fireproof is a big one.
Posted: 10:54 am on March 1st 2018
Martin, Thank you for that link! I find it somewhat difficult searching on their website. Edit: After reviewing that doc I see they then reference another doc for fastening that I had to google: https://static.rockwool.com/globalassets/rockwool-na/downloads/technical-guides/residential/fasteners_guide_techguide_en.pdf
Posted: 04:46 pm on March 8th 2018
Found another excellent reference from the 15th Canadian Conference on Building Science and Technology in a paper titled "STRUCTURAL TESTING OF SCREWS THROUGH THICK EXTERIOR INSULATION" https://buildingsciencelabs.com/wp-content/uploads/2017/11/CCBST-2017-Structural-Testing-Screws-through-Thick-Exterior-Insulation.pdf. The primary objective of the study was to evaluate the vertical load resistance of long screws through insulation as a cladding attachment technique with specific focus on relatively thick insulation layers of mineral wool (equivalent of Comfortboard 80 and 110). They found that with a typical cladding load of 25 lb per fastener the deflection was less then 0.025" which is likely insignificant considering a one story wood-frame structure is expected to potentially have moisture shrinkage of 3/8". Some key findings I noticed: - deflection difference between 6" of XPS and 6" of mineral wool was 0.005". Basically no difference. - the difference in deflection between using 6" of mineral wool and 12" of mineral wool was 0.007" - when fasteners were installed into 3/4" plywood sheathing only it provided similar load deflection response to fasteners installed minimum 1" into stud framing. This gives me confidence that even 9" of Comfortboard 80 will not be an issue, especially when using a Heco Topix screw.
Posted: 09:57 pm on March 8th 2018
Thick Insulation Test To cross-post from another thread with information that is relevant to this one.. See this study released late last year: https://buildingsciencelabs.com/wp-content/uploads/2017/11/CCBST-2017-Structural-Testing-Screws-through-Thick-Exterior-Insulation.pdf Basically showing that even at 12" of Comfortboard 80 there was not an issue with deflection using 8mm screws.
Posted: 07:49 am on March 9th 2018
Word of caution with the GreenFiber cellulose. There are several different variations of GreenFiber cellulose. The version our local Home Depot carries is the one in the green bags (INS541LD Blended blow in). This version has up to 11% Ammonium Sulfate and up to 10% Boric Acid. The All Borate Treated blow in version (INS765LD) is special order and has up to 15% Boric Acid, up to 7.5% Sodium Polyborate, and up to 7.5% Sodium Tetraborate Pentahydrate. I would not want the ammonium sulfate version in my house. If it got wet it becomes a respiratory ailment and stinks.
Posted: 11:09 pm on August 8th 2018