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Old 08-15-2010, 02:04 PM   #1
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Order of operation


Hi All,
I'm going to be improving the performance of my attic by blowing in insulation and replacing the old wooden soffits with perforated soffit.
I know that I will need to prevent the insulation from blocking the air flow from the soffit, so I have those foam soffit chutes.

One issue that I'll have to deal with, is that I have a rather low slope on my roof, and thus, very little room to move around in the attic. And making it hard or impossible to get to the edge of the attic from the inside.

My question is about the order of operation....in what order should I do things?

Because of the slope of the roof, I don't know if I can put the chutes in from the attic side, so I may have to take down the old soffit and insert them from the outside. But should this be done before or after the insulation gets blown in?

If I put the chutes in first, I may have to staple them up to the underside of the roof and they may get clogged with insulation, although I could probably blow the chutes clear with air afterward.

And if I blow the insulation in first, I might be able to insert the chutes from the outside, pushing the insulation out of the way and the chutes might be OK to just rest on the insulation.

I'm also concerned that with the low slope, one 4' chute may not give me enough length to clear the depth of insulation I need to get to R50. I could put in two chutes, end to end, but I don't want to do that if I don't have to.

So if anyone can give me some insight, I'd really appreciate it. I'm apprehensive about doing in wrong, because once I blow that insulation in, I probably won't be able to do anything up there afterward. (Which is why I'm also putting in a new bathroom fan first).


Last edited by Photo Mike; 08-15-2010 at 02:06 PM.
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Old 08-15-2010, 03:01 PM   #2
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The air baffles go in first. Low roof slope...sucks to be you Installing from the inside, a few boards or sheet of scrap ply will help you lay on your belly to get out to the edge. It's gonna suck, I won't sugar coat it.

How low of a slope we talking about? Is it a ranch? 5/12 pitch I'm guessing. R-50...that's beefy.

One thing you have to remember is that the baffles are made to allow an air gap of 1". This means that you will have to block the rest of the gap to keep the insulation from blowing out into the soffit area when they are installing. This means 2 steps for you. The baffle, then the block. Some of the baffles have the ability to be bent at the bottom to be dual purpose, like the cardboard ones.

I would think a rigid insulation would work well, but expensive. Also, the length of your baffle will be an issue since it may interfere with your fascia board. Depending on your overhangs and the flexibility of your baffles.

Have you talked with the insulation contractor about doing this for you?

If you are thinking of doing this yourself, take the time and check with an insulation company. Around here, their final material and install price is lower than what I can purchase the material for. I would hate to install insulation myself if I didn't have to. This may be one of those times, hint hint

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Old 08-15-2010, 03:19 PM   #3
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Thanks for the reply.

I am 95% committed to doing this myself. I've already got the insulation and the baffles (rigid foam). I just need to rent the blower and buy the materials for doing the soffit. I've talked to a few people already, and they say that I should be able to insert the chutes/baffles from the outside, once the soffit is off. Although I'd still need to staple them up from the inside if I do them before the insulation. Also, I was thinking that I wouldn't install the new soffit until after the insulation has been blown in, that way, I can ensure that it's not blocked.

I'm going to go measure the slope today...but there really isn't any room to get near the eves from the inside. I'd guess that at 6 feet from the wall (not the eve), there is only 6" or less between the top of the ceiling beams and the underside of the roof rafters.

And yes, R50 is quite a bit, but it gets darn cold up here in Edmonton. Plus, I'll get a much bigger energy rebate if I get to R50.
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Old 08-15-2010, 03:50 PM   #4
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Oooh....damn, that sounds like 3/12 or 4/12 depending on your structure. Screwed nonetheless. Your baffles may indeed not be long enough. Put one up and then take the measurements and see how much you get.

Leaving the soffits open, that's a good idea.

I wish you all the fun you are going to have! Let us know how it went.
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Old 08-15-2010, 07:04 PM   #5
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1 Air seal the attic first to prevent ice dams: http://bct.nrc.umass.edu/index.php/p...ting-ice-dams/
http://www.rd.com/how-to-seal-attic-...icle18158.html

2. Install two or more baffles with the required 1” gap at ends. Install foam board vertically or use a baffle with the flap to protect from wind-washing of the insulation: http://www.bergerbuildingproducts.co...sAccuvent.html
Use a plastic or foam baffle that won’t feed mold from the water vapor depositing there.

3. Use foam board over the exterior wall and a few feet in to get the required R-value in that limited space. R-50 in the attic---- R-19 over the walls with fiberglass, vs. R-30 for rigid foam. http://www.homeenergy.org/archive/he...96/961110.html

4. Don’t shoot the messenger…Due to the convective loops, the R-50 may decrease to R-25 or 35, as you lose 30-50% of value at 60-70* with blow-in fiberglass: http://www.homeenergy.org/archive/he...92/920510.html

There are much better options, rock wool, cellulose, etc. bottom of the list is fiberglass: http://michaelbluejay.com/electricity/insulation.html

5. Install continuous soffit venting near the fascia board for optimum air flow without snow/rain entry: http://www.airvent.com/homeowner/pro...it-specs.shtml

Be safe, Gary
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Old 08-16-2010, 10:33 PM   #6
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Turns out I have to put the vents in from the top and bottom (inside/outside). After taking down the old wood soffit, I can slide one 4' vent in, but that doesn't go far enough into the attic...so I'll need to put two vent chutes in, end to end. The hardest part is getting close enough to staple the top of the first vent. It would be a lot easier if the rafters were 24 centres...but mine are 16" and it's a tight fit.

I measured the slope, (without a level, so it's not all that accurate) but it's 12:2 or less. So you can guess just how hard it is work in that attic.

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