Attic insulation??

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Posts: 29
Joined: Fri Feb 21, 2014 6:20 am

Sat Oct 03, 2015 4:37 pm

I have an opportunity to inspect and add blown in fiberglass insulation with a the new ridge vent system I'm having installed. I will blow in from the center peak opening before being covered.

Home is a 14X70 with joisted attic and shingled roof. I believe it's 3 or 4/12 pitch. FLAT interior ceiling throughout the home. (A full flat attic space) NO soffit venting at all. 2 big gable vents and a full ridge vent.

From a previous inspection through the hole for the bathroom fan, I realized that the insulation levels are between R13 and R19 and not consistent. I see some pulled back in the distance and it worries me that it's not right.

Anyway I know that the insulation must be on the attic floor and should not touch the bottom of the roof decking, but that is nearly impossible to not touch when adding blown in fiberglass to the edges of the roof. There is so little space at the edges Since there is NO soffit venting anyway, what is the concern with some insulation touching the decking? No soffit to clog!(The insulation touches the metal on metal/flat roof mobile homes. What is the difference in my case)? There are many old stick built homes with no soffit vents and insulation touching the decking at the edge of the roof, why would a mobile home be different? It would seem to me that, added insulation would help keep more moist heat from getting to the roof to condense.

Could someone tell me just how much and where to add blown fiberglass in my case whilw I have full access. Opinions are appreciated!!

Thanks, Todd

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Mon Oct 12, 2015 10:29 am

I think you will find varying opinions on the question of how much contact is "OK". You are correct that even very old homes with minimum insulation still reach a choke point at the wall end of the trusses. So with an R13 or less, we may be talking about less than a foot of contact at the wall. With an actual R19 or more so R30, this contact would be considerably larger, which would create some restriction to air flow. The best solution would be an insulated roof product, but that is very costly. A verifiable answer to your question would probably require an engineering report. I have always recommended to my customers to stay with the original factory plan, which did come with the report in question.

Adding blow in insulation can be done easily through gable vents at each end and side of the home. If you don't have these vents, it would probably be a good idea to add them, if you are adding to the insulation height. More air flow.
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Posts: 29
Joined: Fri Feb 21, 2014 6:20 am

Mon Jun 13, 2016 7:12 pm

attic2.jpg (105.34 KiB) Viewed 2650 times
Did not get to this insulation project last fall, but will be doing the attic strictly from the gable ends. (I already had the full ridge vent installed last fall). It's a 4/12 roof, trusses 16" apart. Anybody with additional insight? I recently read that some people "FILL" the entire attic cavity! I think that would be crazy. I'm thinking I can crawl through the rafters/trusses and control the flow with my partner running the machine below. I have to control the flow around the furnace vent in particular. If I can even get an additional 3-4" installed, I feel that will make a big difference.