It must feel great now that you have set the wheels in motion! If your goals are to enjoy some of the enviornmental and personal benefits of planting something green on the rooftop without investing in and maximizing all the horticultural and engineering standards of a self-sustaining living roof, then any growing medium you use for sedums would serve the purpose and may be even succeed for the long-term. However, instead of using a mix of coir and compost, a simple mix made of 75% inorganic (of what you already have) and 25% organic components (or less, 7%) may proof even more advantageous since similar growing medium recommendations (b/t 60-80% mineral materials) have been corroborated by various academic and commercial sources for growing rooftop sedums and/or building an Extensive Green Roof such as yours (with less than 6" of growing media) based on my cursory read. Your final choice of growing medium made of all/mostly coir and worm castings are all organic and thus will compact and shrink over time unable to deliver nutrients and provide the needed aeration, drainage, and plant support while leaving the roots of plants exposed and causing plant degeneration or death. Moreover, many sedums do better in poor sandy soil and don't do well in fertile soil. A few studies also showed a few specific varieties of sedums thriving and covering a given area faster comparatively when less or a certain fertilizer was used. Any potential discharge of N, P, and other metals from green roofs is likely to be reduced considerably by using the minimal amount of fertilizer needed to maintain plant health when growing succulents such as stonecrop. A few green roof studies (using specific modular or commercial systems) published by Michigan State and Southern Illinois University may be of interest to you. There is one more academic source with similar findings as SIU which I can't recall at the moment. You may also want to reference the only internationally recognized German FLL guidelines for building and maintaining green roofs when looking for answers or suppliers and contractors. How high up are you? Will wind and water retention be relevant challenges in securing either your grower and potting mix in any way? You may want to consider using some type of a biodegradable, one-quarter inch mesh to cover the surface of the flat in the first year (or recycle plastic mesh you may already have). This material functions similarly to mulching and plastic cover or landscape fabric I mentioned previously and will hold the growing medium and also serve to prevent loss of water through evaporation and enhance nighttime condensation during the initial growing season. BTW, SIU found pumice to be the top growing medium out of four other types tested for growing two varieties of sedums when using a brandname modular rooftop block. Hope to see you succeed at the top :)

Thank you for your fast reply! About our climate: - Extreme. Daily temp swings ~50 degrees between day and night. - Summers, though short, are intense reaching 100, - Winters below zero--last year we hit -38, which was not seen here for some time prior. - Snowfall ~20" annually and commonly swing (especially at the beginning and end of the season) between snow accumulation and melt cycles. - Not like the Rocky Mountains of CO where feet of snow pile up, but last year there were some pretty threatening icicles hanging from rooftops. - Its basically high desert--trees only grow along creeks. - Windy. Not constant or as extreme as say southern Wyoming or coastal hurricane regions, but it is a factor. The second vent space *is* being considered for the reason you state: to create a cold roof--an insurance policy, but perhaps overkill. Also, we already have the BCIs and sheathing for the roof so that part we're committed to. No other part am I dead-set on and very much appreciate input. Started this thread to identify any wrong-thinking on our part and gather now that: - insulation above the roof sheathing keeps that sheathing in the warm space, preventing condensation, otherwise a vapor barrier is required. That vapor barrier could be spray foam on the underside of sheathing, right? - 2 layers of underlayment for the 3:12 pitch south side. Thank you very much!!

Thanks again Renovator, Is that your house above...I love your cornices. I’ve been thinking about adding dentils and/or corbels and am definitely inspired. What are the approx. dimensions of the overhang, cornice and frieze? My overhang is 18" from the studs. (maybe 14" from the frieze). I like a prominent overhang but don't want to go Frank Lloyd Wright on a colonial. Following your suggestions, I dropped the rafters to sit on top of the wall and used a 2x12 joist which together just barely allows for a 8:12. Unfortunately I am now at 36' 6" above the lowest grade (4ft of exposed basement). I am calculating the average grade plane now as a first cut and will soon have my land surveyor's calc to see if am under 36’. I wouldn't mind a gable roof but am still confused on the 1/2 story calc. Based on my reading, it seems that they refer to the area under the 5ft and 7 ft planes and not just the width. If that is the case it would seem that a Gable roof would need a lower slope than a hip. I have a call into ISD to clarify. "a) Gross floor area shall include: ii. Any floor area above the second story, whether finished or unfinished, that meets all of the following criteria: 1. It lies below the area of a horizontal plane that is five (5) feet above it and which touches the side walls and/or the underside of the roof rafters; 2. Is at least seven (7) feet in any horizontal dimension, as measured within the area having a wall height of five feet or more; 3. Has a minimum ceiling height of seven (7) feet on at least 50 percent of its required floor area; and 4. Has a floor area of not less than 70 square feet as measured within the area having a wall height of five feet or more." From #1 and #3 is seems to say that the floor area is based on the 5ft area and not just the 7ft area. I hope I'm wrong though. I've heard that hydro-air is great (but expensive) and will look into it. A couple concerns about moving the insulation to the rafters is that I would have a large additional and unused space to condition and that I may have issues with excess moisture in the attic. I will need to do some more research on this. What is the next best option that doesn't require insulating the rafters. It seems most developers are putting ducts and a secondary HVAC system in an unconditioned attic and a primary HVAC in the basement. Obviously this is not so good as far as efficiency goes.

Ugh! Another bad house from a plan mill. 1149--two things immediately. Look at the toilet room in the master bath. Where will you stand as you open and close that door? There is no place for a person! Second--the kitchen (where you'll spend a lot of time) is in the middle of the house, with no windows. The dining room has lots of windows, but it's seldom used and mostly at night. Who wants to live like that? 1231 has the exact same kitchen/dining problem, with the additional kicker of 2 bedrooms flanking the front entrance and no bathroom access for BR4 unless you walk through the public spaces of the house. Good god. The metal roof is the least of your concerns.