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| A few things. I am still looking for complete studies on batts to ensure I have my ducks in a row.
The main reasons for me selecting glass is cost, appearance, modularity, and ROI. Also, I think some consider it tougher to install, and I am sure I will spend a little extra time BUT I really don't think people consider dimensional buildings. EVERY stud space should be the same if you built with care. Even not, go measure and have them precut. it will cost me 1/10 of a penny/sf to have mine precut and ready to go... They just feed the product out and chop.
As well, My methods of air gunning finish nails inside the stud spaces is HUGE! Reason is you get a piece up, then fight it keep it in place. With the finish nails, they lock the batt in place.
Glass is clean work. No big mess all over.
As far as costs, consider this. closed cell foam is at least 3x the cost but lets go with that. That is assuming the SAME R value. 2" foam roughly = 4" glass with vapor/air barrier. Assume 10k sf. Foam is $1/sf so that is $10k. that wound make glass $.33/sf so $3300. That is $6,700 more to insulate to the same rated R value. Now, where are you located? heating days? Around here, maybe 3mo of heating. Lets further assume the foam will drop your energy costs by $100/mo. That would be an ROI of over 20yrs!
I am willing to wager that within 20yrs, something new will come out.
Now, I am NOT saying foam is a poor choice! Just saying there are circumstances in which glass is still a good choice. The further reality is I can get R-19 walls for a 1/3 the cost of R-12 foam. So even if you have to derate the glass for convection losses, if there is a good air barrier on both sides, you may very well be able to perform on par with foam or better!
Obviously if you live way north with temps hovering 0F or less, foam becomes a better move!
What I have to consider is my radiant heating will run very affordably so cooling becomes the bigger question because electric will be needed for the geothermal heat pumps. However, I am working on some green tech that will use good old solar for cooling! | |
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