Author Topic: Blown-in versus batt insulation in attic  (Read 1014 times)

ysette9

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Blown-in versus batt insulation in attic
« on: September 28, 2017, 10:30:05 AM »
We are having our entire house insulated, inside and out. The contractor is on contract and is starting soon. The only open question is how to insulate the attic. Most unfortunately there is not enough space up there for the spray foam insulation I had dearly wanted. The options are blown-in or fiberglass batts.

Our general contractor is concerned about blown-in because of the possibility of it getting sucked around and blown out the vents via the attic fan and/or passive venting system in place. He also warns us that once in place, we won't be able to see the ceiling joists and moving up in the attic and doing any kind of future work would be greatly inhibited. On the plus side, blown-in fills all gaps completely.

The fiberglass batts stay more or less in place and allow future work in the attic to take place more easily. They do have to be cut and fit exactly right to not leave air gaps.

Our research online on the pros and cons of each seem to focus on the pitfalls encountered by DIY folks. Since this will be professionally installed either way, that is not a concern. The price differential is minor (~10% of that line item). I am leaning towards the batts since our contractor has proven himself to be knowledgeable and trustworthy in everything else so far. Does anyone will more knowledge have a different opinion?

bacchi

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Re: Blown-in versus batt insulation in attic
« Reply #1 on: September 28, 2017, 10:33:05 AM »
Have the crew lay the batts and then go to a Big Box store and rent a blower yourself to fill in any gaps.

ysette9

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Re: Blown-in versus batt insulation in attic
« Reply #2 on: September 28, 2017, 10:56:34 AM »
With a toddler and a preemie newborn at home, DIY is not an option at this point. I am hoping for help distinguishing the pros and cons of one versus the other for efficacy and impact to any future attic access. Thanks.

Bourbon

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Re: Blown-in versus batt insulation in attic
« Reply #3 on: September 28, 2017, 11:19:46 AM »
Depends greatly on what your attic looks like, I see some disconnect between not having enough room to do spray foam, and the negative point on blown in about being able to move around in the attic to do work in the future.

Our first house was a cape cod style, and I went with blown in as best as I could, DIY.  In the eaves where we had attic access, I added 2x4's on top of the joists so that I could blow in a full 8", and then put plywood down on top of the 2x4's so that I could have storage and move around the attic easily.

GuitarStv

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Re: Blown-in versus batt insulation in attic
« Reply #4 on: September 28, 2017, 11:27:49 AM »
Our general contractor is concerned about blown-in because of the possibility of it getting sucked around and blown out the vents via the attic fan and/or passive venting system in place. He also warns us that once in place, we won't be able to see the ceiling joists and moving up in the attic and doing any kind of future work would be greatly inhibited. On the plus side, blown-in fills all gaps completely.

When you say attic fan, you don't mean that any of the bathroom fans vent into the attic do you?  If so, fix it so they vent outside!  Venting the bathroom into the attic is a recipe for mold.

It is a pain in the ass moving around in your attic after blowing in insulation, but it can be done.  Batts only insulate between the joists, so don't have this problem.  That also means that batts tend to have a significantly lower insulation value and don't work as well.

ysette9

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Re: Blown-in versus batt insulation in attic
« Reply #5 on: September 28, 2017, 11:30:25 AM »
Our roof is not very pitched so the attic space is rather short/tight. I haven't been physically up to see it myself due to pregnancy/recovering-from-pregnancy, but I am told that where the roof rafters meet the walls it comes down to a pinch point that is too low to allow access for spray foam insulation, since you have to get up pretty close to each section that gets insulated in order to spray it in.

I could have been more clear when I talked about future access. We have installed can lights, we are installing skylights, and have upgraded the electrical. We are also upgrading the HVAC ducting. Due to all of that we SHOULD have a low probability of needing to crawl up in the attic to do other work, but it seems like planning to never have to crawl around up there isn't the wisest decision. The general contractor's concern with the blown-in is that it will completely cover the joists and then some, so you won't know where to put a foot or hand when crawling around.

Has anyone heard of issues with blown in getting airborne due to an attic fan and then venting out the attic vents in the roof? To anser GuitarStv, yes, I mean a true ttic fan and not a bathroom fan venting into the attic. :)

Bourbon

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Re: Blown-in versus batt insulation in attic
« Reply #6 on: September 28, 2017, 11:45:36 AM »
Our roof is not very pitched so the attic space is rather short/tight. I haven't been physically up to see it myself due to pregnancy/recovering-from-pregnancy, but I am told that where the roof rafters meet the walls it comes down to a pinch point that is too low to allow access for spray foam insulation, since you have to get up pretty close to each section that gets insulated in order to spray it in.

I could have been more clear when I talked about future access. We have installed can lights, we are installing skylights, and have upgraded the electrical. We are also upgrading the HVAC ducting. Due to all of that we SHOULD have a low probability of needing to crawl up in the attic to do other work, but it seems like planning to never have to crawl around up there isn't the wisest decision. The general contractor's concern with the blown-in is that it will completely cover the joists and then some, so you won't know where to put a foot or hand when crawling around.

Has anyone heard of issues with blown in getting airborne due to an attic fan and then venting out the attic vents in the roof? To anser GuitarStv, yes, I mean a true ttic fan and not a bathroom fan venting into the attic. :)


Got it.  I wouldn't be too worried about covering the joists. Pretty common these days, and it sounds like you won't be going out there anyway.  Any contractor you bring in should be able to put a foot down and know that the rest are 16" away.


ysette9

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Re: Blown-in versus batt insulation in attic
« Reply #7 on: September 28, 2017, 11:49:26 AM »
Quote
Pretty common these days, and it sounds like you won't be going out there anyway.  Any contractor you bring in should be able to put a foot down and know that the rest are 16" away.

That is helpful. Thanks for the input.