Have you had rodents in your attic?

Hi Elmer. For sure the previous owners did at some point because there are droppings up there. We had a pest control company out months ago (soon after fumigation but back in Oct/Nov) and said the droppings he saw looked older but he also didn't seem to look very thoroughly - but again, this was a while back and who knows if anything could have gotten up there since.... The first attic cleaning guy who came out last week and gave me the ridiculously high quote kept pressing and insisting that the droppings he saw were from recent and new activity (I honestly think this was a scare tactic to try to get me to cave and sign with him the other day). The attic guy today said the droppings look older. I placed some cameras up there a few days ago and didn't pick anything up but that doesn't mean there aren't any. We haven't really heard the trademark scratching noises either. While I was up there though, I definitely saw the various entry points as well as the gaps with outside light coming through that they were suggesting to seal off.

It's pretty easy to blow cellulose insulation yourself - I did 1000 pounds in 4 hours. Very dusty, need two people - one filling the hopper, one blowing - like a vacuum in reverse. Cost ~$500. Lots of youtube videos on this. HomeDepot has a free one-day blower rental if you buy a bunch of cellulose insulation - they'll deliver a palette free. Plus rodents won't get into cellulose. Also an attic needs to breathe - not sure you want an air seal but just rodent-proof.

@Alan Strassberg yea it doesn't seem to difficult. Just messy. I'm more concerned about cleaning the space up there, rodent proofing and air sealing gaps honestly - the rodent proofing would probably be the most difficult thing to address out of everything. My HVAC contractor was saying that we should consider a different type of insulation though because of how dusty the cellulose is (I think his concern relates to the stuff getting into our home or worse into the air ducts - theoretically this should never happen if everything is sealed off... I think it's more one of those "over time" types of deals though). Are there good alternatives that perhaps won't leave behind as dusty of a mess? Like blown in fiberglass insulation? Also, if I wanted to save some $, would it be fine just blowing in insulation over the existing fiberglass batts? I think the only concern is the old rodent droppings that are on the existing batts etc. Unless none of that's a big deal...

For air sealing, it's more so sealing the gaps around existing light fixtures, fans and small gaps. Aren't the soffit and gable vents primarily how the attic "breathes"?

Yes, soffit vents are for the attic breathing. Yes, you can blow cellulose over the fiberglass. Yes, it's dusty but that settles. Air ducts in the attic? Not familiar with these. I just covered my furnace while blowing. The harder part is not blocking the vents. There are barriers you can buy but problematic installing depending on the roof slope. I blew them back from the outside after. Cellulose has a better R-factor than fiberglass and rodent-proof unlike fiberglass. Either product will work fine. I'd clean up the rodent droppings with a shop vac as best as you can (or farm this part out) but wouldn't be overly concerned unless there's a smell. If I recall it's the borate treated cellulose I used. In my case I only sealed a few "low-hanging-fruit" fixtures and such. Depends on your climate how good a seal you want. Ask on a place like nextdoor.com for local installers if you decide to have it done - your quotes are all over the board.

Yea, the first guy who quoted me $12k is on another planet. The guy who quoted around $2k seems to think it's not as a big deal (and it was concerning when he said the insulation we have up there is adequate enough... he seemed to want to do bare minimum work and maximize profits that way). The other guys who gave me quotes online seem to be most straightforward with what I should actually expect all of this to cost. So I'll most likely end up going with one of them if I outsource this. Someone else was suggesting that we consider professional spray foam (2-3") of it then supplementing with blown-in cellulose or fiberglass, etc. This way we could take care of the air sealing at the same time and probably more efficiently. It may cost more but might be worth considering depending on how much...

Historical construction techniques that left many air gaps (especially with electrical work) from the living space through walls and attics are well known and conscientious builders today use products and approaches to minimize them. And test for air tightness. I think you're overthinking the matter. You're in coastal Southern California, winters are not like Minnesota and summers are not like Florida. The problems if any are not so extreme as to warrant much action, I think you'll have little or no perceived benefit. If you have single pane door sliders and windows and an old front door with old weather stripping, you're losing a substantial amount of indoor air at those points, maybe more than through electrical openings.

If there is no evidence of current rodent activity, I'm not sure what your heightened concern is. I think you can probably seal obvious entry points on your own (or hire a pest control service to spend a few hours doing it). As for insulation, lay down another layer of batts if you want (or pay an insulation contractor to do it) and call it a day.

Old rat excrement in the attic of an older home is kind of like external asbestos wrap on things like water heater or furnace exhaust pipes. I have both in my house. If you leave such stuff undisturbed and cover it (with the appropriate kind of wrap for pipes and more batts in the attic for the rat poop), it can remain where it is and present no danger.

Wondering if the OP did the DIY treatment and hoping they didn’t end up another victim of Great Stuff?

I bought great stuff but didn't use any except for around the attic hatch lol. I found some foam board from a neighbor who was getting rid of it. I didn't buy any new insulation. At this point I probably won't end up doing anything or if I do it will be a very slow process. The main reason I got the supplies was to qualify for a rebate on energy efficiency but it sounds like it's probably not worth the return on effort