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-   -   Attic Strategy (http://www.diychatroom.com/f103/attic-strategy-172019/)

shorehome 02-15-2013 03:05 PM

Attic Strategy
 
I have a large attic, with staircase access and an air handler up there.

Soon (year-ish), I want to convert this attic to living space.

The current situation in the attic is that it is poorly insulated under the floor due to contractors working under the subfloor and not replacing insulation. Also, the home is like swiss cheese with holes drilled all over the place and not sealed. The house definitely has insulation/air seal issues. The 2nd floor is cold in the winter for sure, almost to the point of being "drafty".

Anyway, I was looking some tips and would appreciate any feedback:

1) should I foam the roof, closed cell? --- I always wondered how to diagnose/fix future roof leaks if this path is taken. I have HVAC ducting in the rafter bays which is why I would prefer to use the thinner application of closed cell foam. Is it better to create space and also keep the roof vented?

2) should the floor remain insulated if the roof is insulated?

3) either way I assume I should close all holes/openings that result in a chimney effect or air movement between bays.

4) my 2nd floor recessed lights (accessible under the attic subfloor) all seem to indicate IC rating. Can/should I foam them up? - yes they are drafty

thanks again

joecaption 02-15-2013 04:13 PM

Yes all the lights, fans and any other holes where plumbing and wiring should have been air sealed long ago.
Before you get ahead of yourself you need to fiigure out if the joist will support a floor and wall.
What's the width, spacing and free spans?

DannyT 02-15-2013 04:26 PM

some attics i have been in only have 2x6 for joists while strong enough for a ceiling are not strong enough for a floor.

shorehome 02-15-2013 09:41 PM

yes, i may have to reinforce the floor system. I am looking at 2x8 16" oc with 13' spans. I was just thinking about an insulation and venting strategy :) but yes, the best way to reinforce the floor system if necessary - certainly a worthy topic. I am also seeing that my joists run perpendicular to my rafters.

i will have to get some input on the building code for live/dead loads and go from there. based on some quick chart reading, it looks like it will depend on wood species. not great - i would rather be overbuilt - would doubling all or every other of the 2x8s suffice?

Gary in WA 02-16-2013 09:29 PM

Check locally to verify; Zone 4 or 5: http://publicecodes.cyberregs.com/ic..._11_par002.htm

Page 71, read next to/map; http://www.buildingscience.com/docum...n-roof-venting

Any species listed of grade #2 will work for required 30# attic rooms; http://publicecodes.cyberregs.com/ic...002_par017.htm

Gary

shorehome 02-17-2013 06:54 AM

Gary,

Thanks for the links, very helpful and informative. I have to figure out what kind of wood that is - time to go hunting.

As for the roof, zone 4a - I like the idea of the ccspf under the roof, especially because I have poor seal at the floor and an air handler in the attic. I am not sure if the R38 is strictly applied to ccspf though - if it is, I will probably have to fur out the rafters to accommodate the insulation plus sadly the supply ducts that are running in many of them.

what is the current consensus on ccspf thickness under the roof? After 3" isnt it really no-gain? Is the air seal taken into account by inspectors these days?

dengle 02-17-2013 07:33 AM

If by township inspectors for permits, the one I had in monmouth county was extremely rudimentary in the examinations when I built a few finished rooms in my basement. He definitely had some points he checked thoroughly, but they were mostly basics such as wiring nailed properly, backflow preventer on the washer drain and a few other odds and ends. However, that could just have been my inspector, or I just did a pretty good job :thumbup:

As for home inspector for sale/purchase... It depends on the inspector, unfortunately. The few I've run into unfortunately did not do a good job for me. The last one missed several what should have been obvious issues which cost me $20k (and climbing) to fix.

Gary in WA 02-18-2013 09:35 PM

This explains it well: http://www.buildingscience.com/docum...rchterm=attic+

"Effect on shingle life"; expect a 10% reduction: http://www.buildingscience.com/docum...on?full_view=1

Gary

shorehome 02-20-2013 04:03 AM

Gary, once again thanks. Your links to those thoughtful articles have led my thought process in yet another direction.

So, I want to bring my attic into the conditioned living space. I have an air handler up there, supply ducts occupying half of my 2x8 rafter bays leaving little room for insulation, and a swiss chesse floor (thank you electrician and hvac guy). I am thinking that a good move may be to insulate above the roof sheathing with foam board under the shingle layer... per figure 7 in the second link you provided. this sucks because i have a new roof, but the roof is pretty basic and i think the cost would be comparable to an internal spray foam/fur out type of job.

honestly, my house has air leakage issues, top to bottom. i am not sure what to do lol.


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