Extra Attic Insulation in 1930's house

[PeachFuzzStacher]

Hey All,
It's been a cold two winters since I purchased my money pit that I'm learning to love.  I had a spray foam guy come in with a thermal camera and fill in some bad walls and the gaps by the sill beam.  That definitely helped.  I know that the attic should be first, but it actually has what looks like anywhere between 2-5 inches of some fiberglass batts and blown in cellulose all over the existing batts.  I stuck my tape measure through and got maybe 4 inches to the floor and even only 2 inches of lonely cellulose at times.

Looking at a bunch of DIY articles and videos, they all show someone really easily rolling out batts and crosslinking for extra r-value.  My climate zone is recommended for r-40+ in Northern NJ, but I'm guessing this attic has r19 tops.  I get ice dams too...

I'm thinking the original job was a fly by night blow-in, then when I had some mold remediation done before moving in, they probably threw some batts in the trash.

What's the recommended route?  Blow more cellulose over the existing?  Dig out the cellulose/batt mix and throw down some clean batts/spray foam?  What would you do?

[Greg]

If it were my place, I'd remove all the existing, then seal all wire/plumbing penetrations, install insulated ducting for any exhaust fans, install exhaust fans in the bathrooms, ensure proper roof ventilation at eaves and ridge/gables.  Then I'd install baffles to prevent insulation from blocking venting, then blow in R-49 shredded fiberglass.  But that's me, I'm a fussy builder.

[PeachFuzzStacher]

Curious, why blown fiberglass?  That seems like the least friendly material to me.

[CommonCents]

Check and see if you can get rebates from your energy company.  Some things they paid 100%.  Others, they paid 75% with a $2k for all (but people will just do work in different years to achieve it.

[Greg]

Curious, why blown fiberglass?  That seems like the least friendly material to me.

That's why I hire that out.  It gets around all the framing, plumbing and wiring ok.   If you use batts, you have lots of joints and gaps around framing etc. that reduce effectiveness.  If you plan to use the attic for storage etc., you may want to use batts, or at least in the areas you need to access.

[Jack]

Curious, why blown fiberglass?  That seems like the least friendly material to me.

That's why I hire that out.  It gets around all the framing, plumbing and wiring ok.   If you use batts, you have lots of joints and gaps around framing etc. that reduce effectiveness.  If you plan to use the attic for storage etc., you may want to use batts, or at least in the areas you need to access.

Why blown fiberglass instead of blown cellulose?

[PeachFuzzStacher]

I guess the unheard question here is, if blown-in insulation gets in all of the gaps, should I just add more cellulose?

[Vic99]

Definitely make sure that you get all the wire and piping penetrations sealed first.  Do the same for the crawl space and basement.  After that, focus on adding more insulation.  Fiberglass doesn't stop airflow too well.  If you notice dirty fiberglass, it is likely because air is flowing through, but dust is getting trapped.

[Greg]

The reason I prefer fiberglass over cellulose, especially here in the damp PNW, is that when wet, cellulose is mold food, fiberglass is not.

[PeachFuzzStacher]

Ok, bringing back this post with a followup question -

I found out that the room in the front of the house has a sadly attempted tongue-and-groove wood ceiling, where I can see the cross beams in some of the cracks.  I stuck a piece of wire through it and saw some cellulose dust come through.  I'm guessing that there is very little air ceiling in this room, since above is where the ice dams form.

I'm looking at one of two options, and am wondering what you all think.  Install rigid foam board and new drywall over the existing ceiling, or dig out the existing batts/cellulose and put the foam boards in the attic, hoping that there's a surface to do so. Any takers?

[zolotiyeruki]

Ok, bringing back this post with a followup question -

I found out that the room in the front of the house has a sadly attempted tongue-and-groove wood ceiling, where I can see the cross beams in some of the cracks.  I stuck a piece of wire through it and saw some cellulose dust come through.  I'm guessing that there is very little air ceiling in this room, since above is where the ice dams form.

I'm looking at one of two options, and am wondering what you all think.  Install rigid foam board and new drywall over the existing ceiling, or dig out the existing batts/cellulose and put the foam boards in the attic, hoping that there's a surface to do so. Any takers?

I'm of the "do it right the first time"/"if it's worth doing, it's worth doing right"/"buy once, cry once" mentality.  So I'd say dig out the insulation in the attic, seal it up, and pile on the insulation.  Whether you do the sealing  with foam board or just a plastic vapor barrier, I'd keep that stuff in the attic where it belongs.

And for cutting panels to put between the ceiling joists/trusses/rafters, I'd suggest you get the cheaper EPS styrofoam (the white stuff that looks like tiny balls of styrofoam stuck together) over XPS (pink).  It'll seal just as well.  Just cut the boards to 24" (or whatever the spacing is), lay them down between the trusses/joists, and seal all the edges with a can of expanding foam.

[Noahjoe]

I did something similar to what Zolo is describing. I live in Wisconsin in a house built in 1951. It has 2x6 rafters, 2x6 joists in the attic. The attic is also a HUGE storage area, and I didn't want to lose it to cellulose, so here's what I did. I took about 60+ hours of labor to go between 23 rafters on each side of the house (44 spaces total):

1. Removed all the old cellulose from the floor. 30 55 gallon garbage bags. By hand. In hindsight, I'd buy an electric leaf blower/vacuum, 100' of 4" corrugated tubing, and suck it outside into a dumpster. I've done this before and it works SO well. probably would have saved me 10 hours. Minimum.
2. Air sealed the wall plate with great stuff/foam scraps (I pre-cut my foam - read on to see).
3. bought 1x4'x8' foil faced foam (about 15 bucks a sheet at Home Depot). Inches are at a premium when insulating the rafters, so spend the extra on the good stuff. It also cuts/installs way more easily) I cut it to fit between my rafters (about 14.5"), then used cutting scraps to make 1" spacers.
4. Glued/calked/GENTLY nailed these into place between the RAFTERS (to save the floor space/make this a conditioned space - not it only works if you vent EAVE to ROOF vent/ridge vent). I foil taped the seams in the foam boards and used great stuff (which is closed cell foam) to air seal it.
   a. Make sure the foil is facing the roof. It'll direct heat up/out your ridge vent.
5. bought additional 2x6x12 foot lumber. Bought connection plates. Joined these to the rafters. This gave me about 9.5" of air space from the foam to the edge of the new board. I put some R-30 fiberglass in here. Total R-value: 36
6. took additional foam boards and sealed the top of the ridge (leaving about 6 inches of airspace).
7. Put foam board/great stuff on the gable ends. The attic is now air sealed.
8. Furred out the gable walls to also accept R-30 insulation.
9. Put another layer of foam board over everything to seal it from the inside. Foil facing INSIDE the house here. This will reflect heat or cold back into my living space. Aluminum tape EVERY joint. Now the attic is double air sealed, and R-42 total. I also have the entirety of the attic for storage. My wife likes to decorate for holidays so it makes it easy to store crap like that.

This has already cut my heating/cooling bills in half (I went from about R-19-23 to R-42/air sealed). It was running me 400/month or so to run either A/C in summer or heat in winter. I just did it in April so I can only tell you how it's affected the A/C but we've only had the air on for about 7 days so far this summer. The house temperature is much better regulated and not subject to huge midday or evening swings in temperature. And Wisconsin gets hot/humid here in the summer (Madison). This will pay for itself in about 6-9 months - it cost me about 1500 bucks, and took 60 hours, but I think I'll get a chunk of that back on my taxes and I'm already about 500-600 bucks toward the black with this investment.