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Old 11-22-2009, 10:21 PM   #1
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attic observation questions


Am trying to airseal my attic before blowing in insulation. A couple observations I'd appreciate feedback from the willing:

1.) I found an empty cavity behind the chimney. Where the actual chimney tapers, the framing goes straight up. As a result, in the attic there is a gaping hole alongside the attic. I assume the cheapest way to insulate this is to go over the top of this hole... Should I cover it with drywall? pinkboard?

2.) In trying to put baffles into the rafters, I'm having to crawl out to the edges of the house where the roof tapers down to the ceiling. This is being made much harder because of railings that are nailed into my joists. When laying down to towards the edges of the roof - these railings (a 2/6 nailed standing upright) are right on my thighs (or worse)... Anybody know the purpose of these painful railes (1952 ranch)? Removable?
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Old 11-23-2009, 07:53 AM   #2
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attic observation questions


Judging from the amount of insulation originally put up there and the amount of fibreglass insulation added afterwards, I imagine you are in a relatively cold zone...whereabouts?

By "air-sealing" the attic, you are using foam cans and tape, even plastic sheets to try and reduce the air movement from inside your house towards the outside, known as the chimney effect of rising warm air, and the natural tendency of warmth to go to cold. You are, in fact, supplementing the existing vapour barrier that is there...I don't see one (again depends where you are located) but this may just be the paint on the inside of your room ceilings. That has nothing really to do with "insulation"...

However, it looks like someone has added more insulation - and that's great. More insulation retards the transmission of warmth to cold and is related to the air movement that's happening up there.

So the overall effect of both air-sealing and insulation makes the inside of the house warmer - which is what you're looking for, after all; so by keeping more warmth inside the house, it means that your attic is now a colder zone - compared to the house. As such it is more susceptible to freezing and condensation effects due to the cold air. Hence the need for more air movement to dilute the air up there and keep mould and mildew in check. That's why you put the baffles to help outside air get in and out again thereby creating air movement i.e. you protect the soffits by putting baffles along the roof underside to create a free channel for air to come in.

However, more air 'in' means more air has to go 'out'; do you have vents at the top of the roof somewhere?

IMO there is no need to seal off or insulate that area above the chimney. It is a cold zone anyway and you need more air movement to prevent condensation on the brick, so keep that open and let cold air circulate.

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Old 11-23-2009, 07:54 AM   #3
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attic observation questions


1. yes, cover the hole with plywood or osb, then insulate.
2. don't remove anything structural in the attic. The flat board is a tie for the joists, and moubnting the 2x4 vertically adds a bit of strength. Probably not needed, but leave it.
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Old 11-23-2009, 08:02 AM   #4
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attic observation questions


If you have soffit vents you should be adding rafter vents
You also don't want blown insulation to go down into the soffit area

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Old 11-23-2009, 08:24 AM   #5
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attic observation questions


The "railings" are "strongbacks" supporting the ceiling below:



You should not remove them unless some other method of support is provided - as it is, it appears to me that the strongback in the bottom picture is currently deflecting 3/4'-1", a 2x8" or even 2x10" would likely have been a better choice there.

I don't like the those struts' connection to the purlins, either - would not pass inspection in my area. A lot of that reinforcement looks like a ad-hoc retrofit, what are the struts bearing on at their base?

Also, that appliance/fan exhaust line hose should be a well-supported a direct run to the exterior with no low spots, likely it would be better if metal, and it should be insulated if that attic is in a cold climate.
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Last edited by Michael Thomas; 11-23-2009 at 08:49 AM.
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Old 11-23-2009, 09:04 PM   #6
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attic observation questions


The purlins (3x4)? and struts (2x4 angle braces) are fine if original, which they look (old) because of the roof sheeting (1x8 boards). I would replace the flex ducting with straight metal and elbows for better air flow (15%) and less condensation (1/2 as much), wrapping with insulation and a vapor barrier.(As Michael said).

The chimney should be fire-stopped at the top of ceiling with metal and unfaced fiberglass batts or fire foam. This is minimum fire code- {1001.16}. And don't use OSB or wood unless it's 12" from the inside flue liner--- {1001.15x3} Page #4: http://www.codecheck.com/cc/images/CC5thEdSample.pdf

Build an attic access door: http://apps1.eere.energy.gov/consume.../mytopic=11400

I would sister a 8' joist next to the split/broken one (second one from gable).

Be safe, Gary
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Last edited by Gary in WA; 11-23-2009 at 09:06 PM.
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Old 11-24-2009, 06:54 AM   #7
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attic observation questions


Gary,

My concern is the attachment of the struts to the purlins if there is significant wind lift, resulting in subsequent weakening of their (likely toe-nailed) attachment.
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Old 11-24-2009, 12:54 PM   #8
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attic observation questions


Great responses all around.

carlisle - the cavity is actually alongside the chimney, not above it. I took that picture in landscape format, but forgot to rotate it.

Scuba_Dave: I have no soffit vents. But, the crack between the fascia and the external wall provides a little gap that air can go thru. So, I am going to put baffles in place to maintain the minimal air flow that produces. I plan on dealing with that minimal air flow with a gable vent fan and possibly smartvents inserted when I put on a new roof (12-18 months from now).

Michael: The drawing you posted looks to be exactly what those boards are - "strongbacks". Thanks for that reference, I'll leave them untouched and just wear a cup and thigh pads when working towards the edges. PS, agree on the exhaust. I plan on getting to that... the prior owner ran about 30 feet of plastic flex-hose to vent a bath fan to a gable vent. Pretty unwise move on their part.

Gary: Pulins and struts are original. So, are they OK because the 1x8 roof sheeting is light? Your fire-stopping sounds wise - are there any pictures of that on the web? I don't think there is 12" between the flue liner and that spot. Good eyes spotting the split joist in the background of that picture - also on my to do list.

Michael: I wonder if wind-lift is reduced by the fact that the roof has no overhang from the exterior wall. There is no eave/awning/soffit on the roof at all.
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Old 11-24-2009, 02:30 PM   #9
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attic observation questions


"So, are they OK because the 1x8 roof sheeting is light?" -----Not the 1x8's, but the nails. I see two toenails on one side, one on the other in the pictures of the purlins. Old houses used heavier and longer nails than today's. 20d and 8d were common then. If those are 20d or 16d, they (3) have 277# uplift shear or more at each connection. http://books.google.com/books?id=_CP...age&q=&f=false
Granted, the purlin is supposed to be the same depth as the rafters and rafters should have metal connections against uplift, per today's codes. If in a high wind area as the Gulf or Eastern Coast or Alaska, then I would for sure add metal where needed. With no overhang or soffits, you could add venting on the roof: http://www.cor-a-vent.com/in-vent.cfm

"Your fire-stopping sounds wise - are there any pictures of that on the web?" ----- In that site I stated on page #4 of the fireplace chimney on code check.
Be safe, Gary

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