Blowing in more insulation project - questions

[secondcor521]

Hi all,

16 year old house.  I'm getting ready to blow in some more insulation in my attic.  It already has blown in fiberglass to about 12", I'm going to blow in more - probably up to about 24".

First question:

I've crawled up there and looked around.  There are some insulation baffles / vents in place already, but I'm going to add more.  My main concern is that I have about a 15" soffit with soffit vents but there is currently nothing in the way of sheathing - see the vertical board marked sheathing in the first picture here:

http://bradyroofing.com/how-to-maintain-proper-venilation-while-insulating-your-attic-using-baffles/?no_redirect=true

Without that sheathing, I'm concerned that when I blow in the insulation, there will be nothing to prevent it from either being blow over or spilling over on top of the soffit vents, thus blocking the air flow.

I also don't have anything like a band joist in the above picture.  The trusses have diagonal supporting members, but they're not vertical and they don't align with the exterior walls.

I'd rather not try to cut and install plywood sheathing vertically between the trusses.  That's difficult and also I think is overkill.  What I have read is that some people seem to install the baffles / vents then cut squares of fiberglass batt insulation and stuff/wedge those vertically between the trusses, exterior wall, and bottom of the baffle / vent.

My trusses are 24" OC and the vertical space at the exterior wall is maybe 12" - 16".

Are there better solutions?  Tips?  Tricks?

Second question:

In one of the kid bedrooms, there is an attic access hole.  That room has always been cold, and I finally discovered why tonight.  On top of the attic access cover is about 12" thick batt insulation.  The blown in insulation is all around that, but there is a noticeable wedge-shaped gap between the batt and the blown in all the way around the access hole perimeter.

I think I can fix the "cold" problem in that bedroom by just blowing insulation into the wedge-shaped gap.  But since I'll also be adding more insulation, I know I'd be tempted to just blow it all over the top of the access cover batt insulation and bury it all in another foot of blown in.

Of course, that is unkind to anyone who might use that attic access hole in the future (which probably won't be me as I've never used it).  What's the right thing to do here?  I could add 12" more batt insulation on top of the access door.  I almost feel like I would need to build a little plywood box around the access hole to keep the blown in insulation from pouring in if someone ever opened that access hole from below.

Thanks.

[Jon Bon]

Ok a few things.

1. Don't cut your trusses, your house will fall down, I am not kidding.
2. You can blow in fiberglass or cellulose. Sounds like you have fiberglass so I would probably still with the same product if you add more.
3. Soffits, generally its hard to cover your soffits with blwon in just to the nature of the sloping roof line. The material quickly loses its forward momentum and floats down. So most of the time it will hit the roof decking and settle there rather then filling the soffit. If you tried and got the perfect angle you can fill your soffit but it kind of naturally tries to not do that. I am saying this poorly but its not like water from a hose that you can direct nearly perfectly. The distance you can spray this is relatively short.

Also you can buy baffles for these. You will also need a stable hammer to install.
https://www.homedepot.com/p/Owens-Corning-Raft-R-Mate-22-1-2-in-x-4-ft-Attic-Insulation-Rafter-Baffle-Proper-Vents-70-Pieces-70RM/204853491

For the attic access Build yourself a custom cap with rigid foam. Cut it with a wood hand saw. I would not do loose fill as it would not work and just make a mess. There are also lots of reasons the room might be cold. Is it furthest from the furnace? Lots of windows? Your insulation guy might have done a poor job on that room etc. A $10 temp gun is a great investment. I have mine and found and fixed tons of hot/cold spots.

[Paper Chaser]

Do you know how the current baffles are installed?

Many of the baffles can be folded easily to create a dam that will wall off most of your soffit (like the center option in the following pic


You can do the same thing with cardboard and some staples if you have any.

[secondcor521]

Thanks for the replies.  Will respond in order.

@Jon Bon:

Sorry for the confusion, but I'm not going to cut my trusses, LOL.  Yes, that would be very bad.  What I meant was cutting ~22"x12" plywood squares to fit vertically in between the trusses left/right and roof/exterior wall, essentially recreating the bottom half of the fancy baffle you linked to.  I think it'll be easier and better just to find and acquire the fancy baffles.

I do have a hammer stapler, which sounds like the same thing but will google your term to confirm.

Yes, I have blown fiberglass already, and was planning on just keeping with that for simplicity's sake.

As far as avoiding filling the soffits, since I'm going to be adding insulation up to 20-24", I was hoping to have it end up where the 24" depth was even above the entire living space.  Currently, even with just 12" or so, near the edges the insulation just sort of tapers down like the side of a dirt pile.  In ASCII art cross-section:

What I have:

..:![][][][]!:..

What I want:

[][][][][][][][]

But getting the fancy baffles and installing them should do the trick.

I'll look into building a cap.  If I did, I would just put it over the existing access panel and batt insulation, then cover it with blown in from above?  I'm also thinking of just extending the frame vertically with four thin pieces of plywood cut to fit into a rectangular open box.

@PaperChaser:

There are a few (like 3 or 4) of the basic Durovents - like the one on the left side of that pic you included - installed.  But they broke them in half and installed them in the centers of the spaces between the trusses, and it looks to me like they may have installed them up from the fascia a bit leaving a gap at the bottom.  I can buy more basic Durovents, but I think they're made of styrofoam and don't bend in the middle.  What I need is something like that middle option, but I am not sure if the vertical length is long enough to where the bottom part of the baffle would hit the soffit on the house side of the soffit vents.

As an aside, I tried to link a picture of my soffits but it was too big.  My soffit vents are about 6"x12" metal plated things sorta like this:  https://www.lowes.com/pd/Air-Vent-8-in-L-White-Aluminum-Soffit-Vent/1000515457.  They're installed in the middle of my soffits/eaves on the underside, like the first picture here:  https://www.ezpzroofing.com/ventilation/soffit-vent/

[Jon Bon]

Thanks for the replies.  Will respond in order.

@Jon Bon:

Sorry for the confusion, but I'm not going to cut my trusses, LOL.  Yes, that would be very bad.  What I meant was cutting ~22"x12" plywood squares to fit vertically in between the trusses left/right and roof/exterior wall, essentially recreating the bottom half of the fancy baffle you linked to.  I think it'll be easier and better just to find and acquire the fancy baffles.

I do have a hammer stapler, which sounds like the same thing but will google your term to confirm.

Yes, I have blown fiberglass already, and was planning on just keeping with that for simplicity's sake.

As far as avoiding filling the soffits, since I'm going to be adding insulation up to 20-24", I was hoping to have it end up where the 24" depth was even above the entire living space.  Currently, even with just 12" or so, near the edges the insulation just sort of tapers down like the side of a dirt pile.  In ASCII art cross-section:

What I have:

..:![][][][]!:..

What I want:

[][][][][][][][]

But getting the fancy baffles and installing them should do the trick.

I'll look into building a cap.  If I did, I would just put it over the existing access panel and batt insulation, then cover it with blown in from above?  I'm also thinking of just extending the frame vertically with four thin pieces of plywood cut to fit into a rectangular open box.

@PaperChaser:

There are a few (like 3 or 4) of the basic Durovents - like the one on the left side of that pic you included - installed.  But they broke them in half and installed them in the centers of the spaces between the trusses, and it looks to me like they may have installed them up from the fascia a bit leaving a gap at the bottom.  I can buy more basic Durovents, but I think they're made of styrofoam and don't bend in the middle.  What I need is something like that middle option, but I am not sure if the vertical length is long enough to where the bottom part of the baffle would hit the soffit on the house side of the soffit vents.

As an aside, I tried to link a picture of my soffits but it was too big.  My soffit vents are about 6"x12" metal plated things sorta like this:  https://www.lowes.com/pd/Air-Vent-8-in-L-White-Aluminum-Soffit-Vent/1000515457.  They're installed in the middle of my soffits/eaves on the underside, like the first picture here:  https://www.ezpzroofing.com/ventilation/soffit-vent/

You are approaching over thinking levels.

Keep the air moving is really all that needs to happen. IT does not have to be pretty just effective. As long as the air has an unobstructed path from soffit to ridge you are fine.  Lots of the baffels have built in bends so they can tightly fit. Your house is newer so these products should fit perfectly.

[Fishindude]

You are approaching over thinking levels.

Keep the air moving is really all that needs to happen. IT does not have to be pretty just effective. As long as the air has an unobstructed path from soffit to ridge you are fine.  Lots of the baffels have built in bends so they can tightly fit. Your house is newer so these products should fit perfectly.

Agreed, this is being overanalyzed.
Our old farm house is built in a manner that installing soffit vents would have been a very difficult option.   We put in gable end vents and ridge vents and that moves enough air so that we've not had problems.

[vector]

Those foam baffles can also be stapled, no hammer needed in that usually cramped corner.

IMO blocking the rest of the space with fiberglass bats is the easiest way to go. All it has to do is to stop the blown-in stuff from falling in the soffit. The only time this is not enough is when the roof slope is very low and the amount of insulation on the edge is not enough for your needs. If so you may want to spray-foam a band 2-3 feet wide to ensure a proper R-value and in this case sheathing could be worth it. But based on your description this is likely overkill for you.

Regarding the access hatch, I would do the right thing and build a plywood box around it. Nothing fancy, just to keep the insulation from falling in the room when you open it. Preferably sturdy enough to not break the first time you lean on it while entering the attic . I built a box out of 2x12 wood and screwed it on top of the frame because I have to lift myself on it in order to get in the attic. Don't forget to add insulation on the top of the hatch, foamboard is the easiest option to get the same R value as the rest of the attic. Finally, make sure to seal the hatch. If you don't use it much there is some easy-peel caulk that comes off easily and cleanly when you need to remove it.


Worth mentioning that the insulation is usually only part of the fix, the other important part is air sealing at the ceiling level. If you care about it, do the sealing while you have better access before adding insulation. I taped the vapour barrier where it was overlapping and spray-foamed all the obvious cracks I could find. The biggest issues were around the flue (don't use spray foam there, just sheet metal and fire-resistant caulk) and the drain venting stack. Also where the brick wall met the wood structure - the wood warps and leaves a gap.

V

[uniwelder]

I haven't liked blown fiberglass and would opt for blown cellulose. In 2 houses with blown fiberglass vs 3 with cellulose, it seems the fiberglass leaves more air gaps due to its fluffy nature and longer strands/clumps.

If you put cellulose over top, it might help to compress it a bit and trap an air layer. Wherever they're a penetration such as ceiling fan or recessed light with the fiberglass in my houses, there's a significant amount of darkened/dirty insulation, indicating to me that quite a bit of air has been infiltrating the attic space.  You might want to push some of the insulation around a little to uncover some electrical boxes/vent pipes and see how yours is doing in that regard.  Also might be worthwhile to have a can of spray foam to seal as you go.

Also, it sounds like you plan on doing the blowing yourself, though I don't think you've explicitly said that.  I was with the crew when fiberglass went in at one house, and it was horrendous.  Airborne fiberglass dust is much less than fun than cellulose.  Also, I've not seen DIY fiberglass, so perhaps you do intend to have a contractor come.  I live in a very LCOL area, and it ended up being the same cost for me to buy insulation myself vs having a professional do the job.  Doing the prep work (baffles, sealing, etc) yourself makes sense regardless. 

Something to add--- one of the times cellulose went in, the guy running the equipment turned the water sprayer on slightly to dampen as the insulation was being blown.  This virtually eliminated any dust.  It wasn't enough moisture to get it to stick, like the way cellulose gets sprayed onto open wall cavities, but just enough to knock back 95% of the airborne particles.

[secondcor521]

@vector, the hatch panel currently just has a really thick (maybe 9-12") piece of batt insulation on top of it.  And yes, I found that caulk stuff when I opened the hatch the other day; I'll pick some up and reseal it with that after I'm done with that part of the job - right now having that access on that side of the house is helpful.

I've looked into air sealing.  I did a survey of my attic and checked several likely spots for air leaks and didn't find any.  I also don't have any discolored insulation.  So I'm probably going to skip it unless I have an extra day or two and extra motivation before blowing in the insulation.

@uniwelder, yes, I do plan on doing the insulation myself.  I have a friend who also wants to add some insulation in his house, so we're buying enough together to get the 30% off at Lowe's and a free blower rental.  This way we can man the blower for each other.

I'll use an N-95 mask and protective eyewear.  I was up there crawling around for an hour last night and my skin wasn't even itchy, so maybe it depends on the specific brand / type of insulation.

Good point about a water sprayer.  I'll try to remember to see if the rental unit we get has a feature like that.

[uniwelder]

What's your cost going to be?  When I had R-30 cellulose blown a year ago, it was $0.90 per sq ft in the attic of a very small house.  The guys were gone in less than 2 hours.

Update--- I think I just answered my question.  It looks like you might be at around half my cost.  Looking at pricing when I said they ended up the same, I had actually been comparing fiberglass batts.

[secondcor521]

What's your cost going to be?  When I had R-30 cellulose blown a year ago, it was $0.90 per sq ft in the attic of a very small house.  The guys were gone in less than 2 hours.

Update--- I think I just answered my question.  It looks like you might be at around half my cost.  Looking at pricing when I said they ended up the same, I had actually been comparing fiberglass batts.

It's $30.44 a bag for DIY.  I can only determine cost per square foot after the fact.  I have about 1500 square feet to do and I plan to cover to a depth of 24" or so, but what I already have up there varies quite a bit in depth.

I think I was quoted about a 50% above that for someone else to do it.

[StashingAway]

!!AIR SEAL FIRST!!

As someone above me pointed out, you likely have lots of penetrations going into your attic. It is best to address these before you put in (more) insulation.

Air sealing is more important than insulation for HVAC control. If you pump your house full of expensive, filtered, heated/cooled air, and then let it all leak out, then you're wasting money and creating a less healthy interior space. Air sealing is more important at the top and bottom of the house due to the stack effect, so before you do anything to your attic, spend more time air sealing than with insulation.

Insulating without air sealing is like buying a bigger winter jacket but not zipping it up. It will help, but ultimately isn't as effective against wind or moisture or just general homogeneous control. For example, your bedroom with an attic access could be cold because the cap is leaky. You should try to make sure the interior air is contained before addressing other problems.

If you never never use the attic hatch in the other room, you may even want to drywall it over. But if not, build a cap like was said. Something like this: http://www.renovation-headquarters.com/images6/attic%20access%20panel%20-%20insulated%20cr.jpg
Note the foam weather stripping on that drawing. That's for air sealing! I also typically build up a dam around the cap with plywood or foam or something to keep the blown insulation from falling in (where the "rafters" are labeled in the image)

In brief, if your house is heated or cooled, it has a different pressure than the outside. Because of this, air will want to equalize pressure by moving air in or out. This is exasperated if it is windy or there is humidity differences as well. This air comes through all of your penetrations, but particularly at the base of your house and your attic. Anywhere there is a light or conduit or sometimes even load bearing wall there is a hole from your unconditioned attic to your conditioned house. The way to fix this is to seal all of those holes up. I've found quite large holes in many spots of houses where no attention was paid to this. Most contractors drill a 1"hole for 1/2" conduit, etc. That's typically dozens of little spots where air is moving freely (insulation does not stop this). It ends up being a large square footage of what is effectively a big hole in your roof.

To fix this, you grab a good mask and some longs sleeve shirt and gloves and methodically work from one end of your attic to the other, removing the existing insulation and spraying foam along all of the holes or using rigid foam to cover the bigger ones. Then replace the insulation. This is why it's better to do before you blow another 12" of insulation in there. Or hire someone to do it.

The benefit is that you also have better control of the filtration and humidity within your house. It is not a glamorous or exciting job. It's even less appealing than insulation. But it is higher on the list of priorities in most cases for creating a more functional building envelope.

[jpdx]

Speaking of air sealing, do yourself a favor and get a dispensing gun like this cheap one:

https://smile.amazon.com/MANGZ-Expanding-Dispensing-Application-Applicator/dp/B07J5NTGJ3/ref=sr_1_6?dchild=1&keywords=expanding+foam+gun&qid=1602305227&sr=8-6

The expanding foam cans without the gun just makes a huge, sticky mess and is difficult to control and difficult to start/stop. The gun lets you adjust the bead size and start/stop the flow without any residual foam oozing out. You'll find its so much fun to use that you'll be air sealing every nook and cranny you can find.

[Endo1030]

There are also likely to be air gaps along the intersection of interior walls and the ceiling.  Air from the conditioned space enters the wall at electrical outlets and underneath the baseboard which usually isn't caulked to the floor. From there it can rise straight up to the attic unless someone had the foresight to put a continuous air barrier along the entire ceiling before interior walls went up.