diy blown in insulation question for first timer. 100+ year old home.

Submitted by jjax2003 t3_y24y52 in DIY

i have a quick question about the project i am working on. I have framed in an attic / loft space and put r22 rockwool insulation in the walls and ceiling. i want to blow in to achieve r50 in the attic/ceiling.

this old house only has 2 vents to the outside in the attic (gable ends), no vents from the soffits or anything like that. on the loped portion on the attic ceiling there is a air gap behind the insulation.

When I blow the insulation is it okay to blue all the way to the edges? If i do that on the sloped sides I will be essentially trapped air in there that has no way out. hopefully this makes sense.

dos the air behind the sloped walls/ceiling ned to be able to get to the top of the attic to vent out? or can i simply blow insulation and cover the entire flat portion of the attic?

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TheTemplarSaint t1_is13cbn wrote

Post this in r/centuryhomes. Insulating homes that weren’t constructed for it really really has to be done right or you’ll introduce issues and cause damage. Marrying old and new building technologies isn’t super straightforward. Also check out greenbuildingadvisor for expert info.

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never___nude t1_is31wqr wrote

You are correct. My building science guy is warning against too much insulation on my double brick home. Still have not decided how to do it.

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Aquarius265 t1_is3kwtb wrote

Wouldn’t the R value on that be pretty good?

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never___nude t1_is3n6ie wrote

No it’s not but it is very efficient on its design because of all the air pockets help keep it cool in the summer and it’s very slow to fluctuate with temperature swings. I have been advised against making it too efficient because the brick is meant to stay ‘warm’ in the winter. With huge temperature fluctuations (summer and winter) and an airtight house with too much insulation, it will lead to too much thermal expansion and contraction on the bricks and mortar.

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anally_ExpressUrself t1_isgxx4j wrote

Is your interior warming up the exterior brick in winter? If that's making a serious contribution to the exterior brick warmth, you must spend a fortune in heating!

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never___nude t1_isizru0 wrote

Less efficient was poor choice on my part for words, it’s still efficient, just not a high r value to allow for some heat transfer that inevitably happens anyway. My air barrier is beyond what most do, so even though my r value isn’t really high overall, it’s enough to keep us toasty warm without being expensive - it is technically lower than 2x6 construction, but it’s more energy efficient because of sealing and no thermal breaks. The house originally relied on just fir strips, plaster and paint as the barrier and insulation. What most contractors wanted to do was either go with more r value and get there with sprayfoam pretty much, which was the worst thing we could do for the brick. So our method goes like this from outside to inside — regular brick, air pocket, 9x9 structural clay tiles with webbing and air pockets within, render, air pocket, 1” foam board with foil barrier and finally rockwool insulation and then drywall. The foam board doubles as a reverse barrier in the summer when the house is cooler than outside. The fear of over insulation was a concern because lots of new data suggests that allowing that inner brick to be ‘warmer’ in the winter is how it’s meant to work and why it lasts so long, the same research is showing that allowing the masonry house to breathe is another reason it will last so long. Anyway, in the end, there was way more insulation talk and planning than anyone one of us would of liked but it did save us from spray-foaming everything.

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Elmore420 t1_is33yd2 wrote

Boy, you’ve got that straight, upgrading old houses is complicated because you can build in a mold problem that requires burning the house down to get rid of. I was an insurance adjuster on mold abatement issues for a couple years, saw a lot of problems from blocking airflow, burned down more than a few houses in that time.

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jaxreddit t1_is3icyc wrote

Very much this. Doing this kind of work incorrectly could cause serious problems with moisture retention leading to rotting wood and eventual failure of critical members.

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betcher73 t1_is0w1oa wrote

I just did blown in insulation and my contractor installed small vents in my soffit (I think that’s the right word) so that air flow could come in

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Akanan t1_is16fcu wrote

If you do add small soffit vents, make sure to protect them before to blow in your insulation. There are rafter vent sold for pretty cheap, honestly a pain to install tho.

u/jjax2003

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gladiwokeupthismorn t1_is2yhuc wrote

Best to just replace the soffit with continuous venting and install baffles at the point. How much of a pain in the ass it is depends on the pitch of the roof.

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hertzzogg t1_is0wlto wrote

I'm sure it's location based, but I can get an insulation company to do the job cheaper than diy'ing. That includes the free rental of the blower.

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Akanan t1_is1641i wrote

I saved more than 50% diy, that includes the government rebates i'd get hiring a contractor. It was still no making the cut.

Surely location based...

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brewchimp t1_is1rqp3 wrote

Yep what I saw too. Quotes I got are in the $4k range for new construction. I can do it myself for well under $2k. I just need to figure out how to get my kids to feed the blower without losing limbs in the process.

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Akanan t1_is1s50k wrote

I called a friend to feed the machine who is... clueless about everything else than playing chess and microwave hotdog... and he did a great job.

The machine I rent had a remote control to start and stop the machine. I didn't need much communication with the feeder.

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apocalypticboredom t1_is28rro wrote

When I did this last week, we didn't even have a remote, so we used walkie talkies to communicate and it worked great - and for sure anyone can do the loading part!

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neil470 t1_is10mvm wrote

I think OP is asking if it's okay to blow insulation all the way to the edges so it is in contact with the roof sheathing. They said there are no soffit vents, so it's not about venting, but about moisture being trapped against the sheathing.

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jjax2003 OP t1_is19bbo wrote

Correct, thank you.

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neil470 t1_is19suz wrote

You're probably better off keeping the insulation from touching the roof sheathing.

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SpartanBlockchain t1_is17brh wrote

I'd recommend cutting vents in your soffits and installing vent baffles to keep the airflow going. Additionally I'd recommend air gap sealing as many cavasses down to the house, walls, pipes, etc with spray foam. Its a little extra work but well worth it.

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nikdahl t1_is210gu wrote

Don't skip your air sealing step. You want to seal off any recessed lights, seams between walls, etc. Watch some youtube videos on "air seal attic before insulation" for some more info.

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chopsleyyouidiot t1_is2g53b wrote

This really depends on where you're located and what type of 100-year-old house you have.

Do not listen to anyone who hasn't worked on the same type of old houses in your location, or at least in a similar climate. You can absolutely destroy a 100-year-old house by retrofitting it with modern materials and/or using modern building methods. You can also cause serious damage by using methods and materials that work really well in a different climate.

Tons of houses in New Orleans were destroyed within a decade after hurricane Katrina, when contractors came from all over the US to cash in. They used methods that are perfect for modern houses in Phoenix or Dallas or old houses in Philadelphia or Buffallo, but they resulted in all kinds of rot and termite problems here.

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zoinkability t1_is1bvp5 wrote

Ideally you'd put vents into the soffits and use baffles like this: https://www.doityourself.com/stry/installing-attic-insulation-baffles

If you can't or won't put in vents, it's still best to install baffles to ensure that the insulation does not touch the underside of the roof decking.

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GeoffdeRuiter t1_is1hxw9 wrote

u/jjax2003 You definitely want to put in the baffles like in the picture above. You will have mad condensation issues if you don't and water will condense on your roof sheathing and drip down and saturate your insulation and eventually moisturize your ceiling in the house = mold. You can never have too much ventilation in an attic, but you can have too little. :)

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madcaesar t1_is31559 wrote

Do baffles go between EVERY stud or do you just need a few in each side of the house?

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zoinkability t1_is34e1l wrote

Every stud, ideally. Any area between two rafters without a baffle is a spot where the insulation can trap warm air and moisture against the underside of the roof decking. If your insulation isn’t deep enough to touch the underside of the decking it’s not as much of a concern.

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ReignAndFire t1_is11lrn wrote

Where I am, attic rafter vents are stapled to the roof sheathing, and batts are installed at the edges. The rafter vents allow air flow and the batts stop the blown in from filling the soffits.

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[deleted] t1_is13upo wrote

[deleted]

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jjax2003 OP t1_is19flg wrote

Thanks

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datredditaccountdoe t1_is1vna0 wrote

What you need is attic insulation stops. They can be bought in foldable cardboard or pre-moulded styrofoam sheets. You staple them around the perimeter of the attic.

Wether you can physically reach that space through the attic is another problem. Most old homes do not have much space between the wall and roof for a human to fit there and work. Even in new homes they are a bitch to install after the home is built. They are installed when the house in being framed in a new build.

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shaking_the_trees t1_is1xh3d wrote

You might as well go with R-60, or 20 inches of insulation. The incremental cost won’t be much, and you are up there anyways…

Is air sealing in century old homes just as important in newer homes?

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rededelk t1_is18pj5 wrote

Ya don't block air flow. I bought 20 bales to do some spaces, blower was free for the weekend, it was easy, had my X feeding the hopper from outside below and communicating with walkie talkies. I just drank beer and pointed the hose. Money well spent

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Iamdanno t1_is2qvpo wrote

You need a product called rafter mates in (usually every second rafter cavity. If it were me, I'd add soffit vents around the perimeter as well. Also, gable vents are only good if they are in the top 1/3 of the attic space, ideally at the very top.

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Elmore420 t1_is33eu8 wrote

You want to maintain airflow between the soffits and vents to prevent ice damming issues.

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villagewinery t1_is2oc4x wrote

I suggest you talk to an insulation contractor. If you're not foaming gaps/holes before insulating you are not optimizing the results.

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usV5them t1_is32umm wrote

My neighbor was just told she has termites and nothing can be done about them due to blown in insulation added a few years back. Apparently not even tenting the entire home will help.

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Eirikur_da_Czech t1_is0ua0b wrote

Why not cellulose?

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jjax2003 OP t1_is0vm1m wrote

thats what i wantd to do. i thought cellulose was blown in. maybe i am confused. its a small space, i would have a very hard time fitting up there to do any manual work. so i wanted to blow everything in as it would make it way easier

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Sluisifer t1_is5xybg wrote

> very hard time fitting up there to do any manual work

You still want to get up in there to seal any air gaps. It's a lot of work, but if you don't do this, all the insulation in the world will only get you so far.

Blown in is a good option, but sealing is very important.

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Tito_Mojito t1_is0uzat wrote

Do not cover the eaves or vents or you will quickly get mold.

Personally I hate blown in insulation. It’s messy, makes great animal nest material, and creates holes in walls, etc.

Why not lay down attic insulation? The kind that pops up a foot or so?

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jjax2003 OP t1_is0vt8f wrote

there is perpendicular boards in the attic and suck which woul make laying another layer on top not sit flat with the existing layer leaving an air gas between both layers of insulation. i thought that was bad.

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Tito_Mojito t1_is0ws0t wrote

You could lay insulation between the gaps to fill then layer on top?

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jjax2003 OP t1_is0y0b7 wrote

i guess your right, i could just use some r 28 rock wool batts and make it work, alot cleaner install just a bit more labor. that would bring me to r50

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Tito_Mojito t1_is12ug0 wrote

R50 is HUGE! Do you live north of the attic circle? Ha!

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MrMonopolysBrokeSon t1_is19ses wrote

R49 is now code minimum all the way down to climate zone 2. For zone 5A (OP's location) it's R60

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slayez06 t1_is1cvwt wrote

Don't do it! My house has blown insulation and I want to kill the guy who did it. You can't do any attic or ceiling work with out making a huge mess. The attic gets hot as hell like 140+ and is just awful.

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