08-12-2005, 07:42 AM
Need help ASAP. Just had a small cabin built by our local Amish (wonderful people), 20x24 with 3/4 loft, full balconies on each end, plus large full deck on bottom front. Gambrel (barn) style roof extends over both balconies on ends. Question??? Roof is forest green metal, tar paper, wafer board, on 2x6 trusses. Interior ceiling in loft is all open (no attic space at all). No special venting was built in (ridge vent, etc), just the standard V cap over the peak of the metal roof. Will have ceiling fan in loft peak and downstairs. Lots of windows and 4 sliding glass doors, so can get good ventilation this way.

In looking to insulate the roof, however, we were told at the building center the trusses should have been 2x12 to allow for thicker, higher R-value insulation (Montana), and we didn't have enough space now. Asked about foam panels to allow air space to be left between insulation and roof deck. They said foam panels are more for garages, etc. Asked about spray in foam fill (VERY expensive here), they said leaves no air space and with metal roof would "cook" in summer (gets in 90's-100), could damage metal or be hard on it, plus hold heat inside loft area.... Was are your experiences/opinions re this??? (There is not room in the loft area with the sliding glass doors already installed to the balconies to bring the interior ceiling down any lower.) Could not really get a straight, direct answer. Don't know if they really knew the answer.

The place is already built, so we have to make due with what is there. It's a beautiful cabin and the quality seems to be very good, so it surprised me the roof was done this way.

Let me explain that I'm doing this all on my own, am a working single mother of 4, and am paying for the home as I go, rather than doing the standard 30-year mortgage plan, and working towards being debt free. At this point, I'm pretty well maxed budget-wise at the moment from the new bulding (just finished last wk). This will be a full-time residence for my family. So please bear with my "newbie" mistakes. I so appreciate all your input!

There is another adjoining 12x16 cabin with full covered/screened in porch used as bedroom. Appreciate the help! Trying to do-it-ourselves, but do not want mold problems, etc.. Thank you for reading all these details! lol I know old cabins, houses, etc, are redone all the time, so there has to be an affordable solution.

08-12-2005, 08:44 AM
reflectix is an aluminum insulation that can add R-value without any added weight/volume, but must be installed when insulation is going in. You may check on this at the building center.

Unfortunately, it doesn't sound like an easy fix. 6" of space is not enough to insulate to code in very many places. If rockengineer doesn't answer this thread try to PM him about this


08-12-2005, 09:00 AM
Cabin does NOT have to pass code (may be impossible to do at this point) as there are no covenants, building inspections, etc., on this property, and as there is no mortgage. (Would be of value if we ever wanted to sell. Presently have no intention of selling.) Mainly need something affordable and that will WORK without causing mold, etc., problems at this point. I will look up the insulin info you suggested on the internet for more info on it. I asked the building center guys about pretty much everything, and they couldn't seem to tell me much more. I believe I will go in and speak with the owner though. Thank you so much! I greatly appreciate it! D

08-12-2005, 09:18 AM
I've discovered something aobut building centers. Most of the locally owned ones are getting their lunch eaten by lowe's and home depot, and their prices are a little higher. But the locally owned places are WILLING AND ABLE to speak to you, in plain english, about what you need to do and will do everything short of installing it themselves to make your visit to their store is productive for you as well as them. If you are going to a lowes, or home depot, try a local do-it center or building supply store that deals with contractors as well as do it yourselfers. They will help you, you will help them, and you will help your local economy. I've discovered that one of my locally owned stores here in glasgow sells lumber and many other items cheaper than lowe's does, and will deliver for free (lowe's charges $60). You never know what you'll discover...

08-12-2005, 09:31 AM
and it is as you say. I have found items comparably priced to Lowe's and Home Depot, which are an hour and a half away from me. The service is far more friendly. I have my account with the local guys and do prefer to keep my money circulating in our little valley, as I so love this area. However, these are still the "guys" I'm talking about that cannot really give me an answer. I've spoken with three people there, but have not addressed the owner, which is probably what I should have done from the start. Supposadly one of the gentleman has worked there a very long time, has done remodeling in his own home, and did seem to know the most, but still could not decide what he should sell me. Unless one actually has experience with one of these open ceiling and the metal roof, it can be a little difficult for them to understand. And yes, I discovered delivery was FREE as you said. It has been a huge burden lifter and blessing to me, let me tell you, as I only have a midsized SUV that would not near haul all this stuff! Good info to pass on to everyone! We actually called to see if they even did deliveries and if so how much it was, only to find out deliveries are free for anything around $200. +.

08-12-2005, 11:16 AM
I'll quote back Ellsworth & Steve's info they teach in the log home building class because I agree with it from my experience and research.

If you are using Fiberglass insulation or some type of insulation that requires air to make it fluffy to get the insulation value, you need to ventilate above the insulation to keep down mold and sweating. If you are using solid insulation such as foam sheets or expanding foam, you do not need to ventilate. With your 2x6 trusses you can use 5-1/2" thick foam sheets cut to fit between the 2x6s and solid pack (no ventilation). The probablility is "very low" that you will get mold or sweating with this system. You will get a roof insulation R value between between 28 and 38 depending on the type of foam you buy. R values for the foam vary from about R5 to R7 per inch depending on whether you buy high density foam. If you end up with some openings around the insulation blocking use expanding foam to fill up all the little gaps. This should keep you warm in the winter and cool in the summer even in Montana. (I'm originally a SE Idaho boy myself).

The commercial item that supports this theory is the structural insulated panel (SIP) which has solid foam between two sheets of plywood or OSB. They are not ventilated and have a very good reputation for not molding or sweating. You need to seal all the holes in your end boards though because wasps and other burrowing insects think the foam makes a great home.

Good Luck. :lol:

08-12-2005, 11:32 AM
Yay! This is basically what I was asking the building center guys. I asked if I could stack foam board, if with that I still needed the air space or should have no air space, etc. They were pretty much recommending not to use it. I don't think they had the 5 1/2" thickness. I think they said they had 1 1/2 and 2.

Could thinner sheets be "layered" if that's all I can find locally?

I would so LOVE to take one of these cabin building classes! I just found out about them today (a little after the fact) when I found this forum.

I would really like to get started on the insulation this weekend, as it's what is holding up production right now. Have to see if I can find the right thickness now. But how you explained it (thank you for all the detail) makes perfect sense to me and coinsides with other bits and pieces I have read. Thank you so much for the very quick response! D D D

08-12-2005, 11:42 AM
Layered is fine. A little contact cement between the layers that is compatible with the foam may be a good idea just so it doesn't separate as easily. If you lack 1/4-1/2" of filling the whole cacity it shouldn't hurt to much either. Make sure the adhesive is compatible with the foam because some types will eat away at the foam and you don't want that.

My hat is off to you for your efforts as a single mother to provide for yourself and build your own home.

08-13-2005, 01:38 AM
Hi Rock, I spoke with the building center owner yesterday aftertoon. He said he had up to 2" foam, but could get anything I wanted. Only thing he disagreed with was closing up the air space. Said he would suggest using the 4" foam, leaving the airspace, and I would still get about a 32R value. Your thought re consequences of this? Would this allow moisture/mold, bug nests? (Another bldg center gentleman had said if we used the very expensive blow fill-in permanent foam we could have problems with no air flow in the house, holding summer heat inside the loft, overheating the metal roof on the outside, breaking down roofing materials, etc.) I've printed your responses to reference and take with me.

By the way, Basil, just had another problem creep up yesterday afternoon, last minute (4 p.m. on a Friday), and our building center guys swung in to action, fixed it, and showed up out here out of town with a delivery truck at the last minute. I did speak with the owner, who actually handled it, a benefit of living in a smaller town. Awesome service!!! We would not have gotten this from the city building centers. (I called Lowe's the other day trying to get transfered to return dept, and was transfered back to a different receptionist 3 TIMES! Finally the third one took the info. Never did make it to the correct dept. lol ) Local guys are GREAT to work with! We're going to bring them a cookie plate!

Thanks guys! D

08-13-2005, 06:37 AM
Reflectix is great stuff but won't work for the roof.
Poly-iso board or VIP's (vacuum insulated panels
might be your best choices.


08-13-2005, 07:00 AM
You can't go wrong ventilating the insulation space but if you leave an air gap you need to make sure there is an air flow (eve vents and ridge vent). Air gap with no air flow can be a problem from the information I have read.

I don't claim to be an expert on all areas of home building. I'm just an engineer who likes to make sure log homes stand up and it pays better than flipping burgers at McDonalds. I have done a little research and tried to apply common sense. There are definitely strong and differing opinions when it comes to insulation and ventilation. You will have to make the decision in the end based on the information you have been given. Either way you go now you at least have some warnings of what to do and what not to do. If you take those warnings you should have no problems either way. It sounds like a cop out but it isn't. Both ways work if you take the proper precautions for each method.

Good Luck. Enjoy Life. Don't be a workaholic like me.

08-13-2005, 06:54 PM
you could use this product made by owens corning http://sweets.construction.com/mfg/20855/E715704.jpg

it's called Raft-R-Mate®** attic rafter vents

The site located at http://www.owenscorning.com/around/ventilation/raftrmate_attic.asp

08-13-2005, 07:18 PM
Thanks, Rock. I think I'll stick with the solid foam, no air space, as you suggested. I specifically asked the bldg center owner if any special venting was needed and he said no. We worked all day today doing wall insulation. I checked the roof out well from outside inside lower floor, and upper loft. I just don't see a good air flow the way it is without adding a lot of venting. I think I'd be asking for problems. There is a LOT of Gambrel ceiling coverage. I really do NOT want to put it up, only to tear it down to tackle a mold problem. (Actually had this experience before. It wasn't pretty.) Thank you SO much! D We'll probably be tackling the roof insulin this next weekend. If you have any other tidbit suggestions, let me know before then! ) I'll let you know how it goes. Made a LOT of progress just last night and today. It's so exciting. Going to be a very cozy little place! ) Thank you, again, endless thanks! Really, really, really!

08-15-2005, 03:33 AM
I used RMAX poly-iso sheets in my home.They are 2 1/2 in thick.That gets you a R15.30. I just doubled it up for a total of 5in. thick to meet my R30 reQ. here in washington state. Atlas roofing is another brand

08-15-2005, 03:40 AM
Thank you. What type of ceiling do you have? Open, cathetral, Gambrel style, etc? With air space and venting, or filled all solid airspace and cracks as Rock suggested? How long have you had it this way? Are you really happy with it, no problems? Thanks for the brand names. Our building center owner is supposed to be calling this morning for prices for me. Thanks! D

08-17-2005, 10:05 AM
Hey Rock,
Haven't received the foam insulation board yet. Read up on the foil type insulation while waiting (Insulation 4 Less web site).

Question on possibility...
On the waferboard roof decking (tin roof, tar paper, then waferboard decking), on underside interior ceiling area could we do something like VAPOR BARRIOR PAINT TO SEAL THE WOOD, THEN FOIL INSULATION (HIGH R (FFMF) FOIL FOAM FOIL - INSTALLING IT FLAT AGAINST THE ROOF DECKING TO SEAL. THEN add 5" solid foamboard FLAT up against the foil to fill the air space, then seal all cracks? Or do you think this work better than if we used only the foamboard by itself?

I keep reading while there is still time. I found a couple other internet posts from people with similar situations.

EMAILED INSULATION 4 LESS with basically this same question to see what they would say. See their responses below

Yes apply per your fist method Apply Prodex High R underside of interior ceiling VAPOR BARRIOR PAINT TO SEAL IT, THEN FOIL INSULATION (HIGH R (FFMF) FOIL FOAM FOIL. Make sure you have ¾??? or more air-space for optimal performance. Tape seams with metal tape. For additional install ideas click http//www.insulation4less.com/install_methods.asp and http//www.insulation4less.com/quick_installation.asp and http//www.insulation4less.com/installation.asp.

Thank you for the quick reply. I need it as I need to get some of this ordered asap IF it will work. HOWEVER, please make sure you have read carefully and understand before selling me anything.

I did read your website (including all of the links you sent me) prior to emailing you. My BIG question and dilemma is I will NOT have VENTED air space. There are no eave vents. And if the interior ceiling is done this way there is room to leave air space, but it will be DEAD AIR SPACE. Plus you are saying to use this foil as a stand alone and DO NOT add the solid foamboard below it? I am in Montana right up by the Canadian border and our ceiling R-values are usually in the 30's.

If you do not know the specifics of this, PLEASE be sure to forward it to someone who does. I really want to do this correctly PRIOR to the ceiling being all closed up! ) ) ) It will have a finished ceiling over it.

Not able to give more specifics. We aren???t installers. All the advice we have is posted on website. If you don???t see it on the web, than we don???t know it. We would never state to not use additional insulation. That will always be a personal call. If it???s a residence we would suggest you contact your code official or local contractor.

08-17-2005, 05:09 PM
I don't know anything about the foil beariers. I know a couple people who have used them but I haven't heard good or bad. The manufacturer's data and the salemens statements are good but I tend to be a skeptic when it comes to salesmen.

I have shared with you all my limited knowledge on roofing and insulation. Any information I might share beyond this point would be pure conjecture. Sorry I'm not much more help. I know it is frustrating.

I don't think the foil can hurt your situation but that is just a wild guess. In Engineering terms it is a WAG (Wild Ass Guess) not even a SWAG (Scientific Wild Ass Guess).

Good Luck.

08-17-2005, 05:12 PM
Is it really possible for this Prodex insulation to really have an R-value of 14.5 per 1/4 inch layer? That sounds ridiculously high for the thickness. Maybe it could be for radiant energy, but seems hard to believe it could insulate thermal transfer.


01-01-2013, 11:49 AM
2 x 6 rafter spaces are clearly not sufficient amount of space for the adequet amount of insulation needed for your area. But theres nothing much you can do now that the metal roofing is installed. You need to have the roofing people come back and install a vented ridge cap to help or at least make an attempt to move some air out of the confined 2 x 6 spaces.