Should we go from suck to blow?
November 11, 2011 4:23 PM   Subscribe

We just had an energy audit done for our 104 year old house and 3/4 of the heat loss was coming from the uninsulated walls. I was advised to get cellulose insulation. I've heard bad things about blowing insulation into old houses like mine, but the auditor said it would be densely packed and not be a problem. I've been reading up and haven't been able to find any definitive answers. Is it okay to have cellulose insulation blown in to my old house if it is densely packed?
posted by charred husk to Home & Garden (14 answers total) 1 user marked this as a favorite
You need to know if you have knob-and-tube wiring. The problem with it and blown-in insulation is that it can cause shorts. If your wiring is modern, you should have no problem.
posted by scolbath at 4:32 PM on November 11, 2011 [1 favorite]

what about using spray foam closed cell insulation. I believe it can be sprayed into a wall where it will expand and harden giving you quite decent r-values .
posted by 2manyusernames at 6:13 PM on November 11, 2011

According to the Secretary of the Interior's standards for historic preservation, blown insulation can cause a number of problems, specifically trapped moisture. The amount of damage that can be done by that trapped moisture in the blown insulation would cost you way more in the long run than high electricity bills. I would also be extremely hesitant about using spray foam because it is not removable, you would seriously have to destroy the walls to remove it.

Here's a link to some pointers from the National Trust for Historic Preservation. It's got some good advice. Sadly the NPS preservation brief on energy conservation is being revised right now so I can't give you more detailed information. You're best bet is to find a contractor in your area who is familiar with historic homes, and seek their advice. If you have a local historic district, they may have contacts and information for you, if not your state historic agency should be able to provide you with some pointers.

Good luck. Living in an older home is tricky, especially when it comes to weather proofing.
posted by teleri025 at 7:57 PM on November 11, 2011 [1 favorite]

The main thing is figuring out if you have knob-and-tube wiring.

Luckily, this is easy.

First, if you have access to the attic, go up and look. "knob and tube" means that the wiring is bare except for at the junctions. Look at the wiring you'll see in the attic. Are the wires bare except for at the bits that meet the joists? If so, you have knob-and-tube, which needs special attention.

If you don't have easy access, any contractor will be able to tell quickly if you have this old-style unfortunate wiring. Just ask them.
posted by Invoke at 8:53 PM on November 11, 2011

The wiring in the house is modern, so that should be okay.

teleri025 pointed out my primary concern, that blown in insulation would cause moisture issues. My quandary is that I've been told and read a few places that densely packed cellulose eliminates that problem, and other places say otherwise. For example:

This seems to indicate that it is okay to use on historical homes.
This seems to indicate otherwise.

I was really hoping someone might have had some experience to share. We just bought this house and we don't want to ruin it. At the same time, saving a few hundred bucks a month during the winter would really help.
posted by charred husk at 10:28 PM on November 11, 2011

I feel your pain. I also own a 105 year old house where none of the exterior walls were insulated, save for the living room that had the blown in cellulose insulation.

The blown in insulation was a nightmare in my particular case, primarily because of the moisture issues and the dry rot and mold ( mold!) that accompanied it. So I think your fears are well founded.

Now, my municipality does not have anywhere near a comprehensive historical or heritage policy so I've been given a pretty free hand at doing whatever I need to do to fix the issue. ( Just as an aside, before I started reinsulating my house, I was paying four times as much to heat my house as my neighbours with more modern dwellings. I now pay 30% less.)

So, I went room to room and started stripping plaster and lath and then reinsulating with an R-14 Roxul (Stone Fibre ) Insulating Batt and then the all important vapour barrier. And then I replastered. ( I could have put drywall up, but I like the way plaster sounds in room. There many days I wished I put drywall up. Your heritage code may not allow you to do that, though)

Replastering sucks.

Essentially, it makes parts of your house unlivable while the plaster cures ( for new plaster it is recommended to wait 30 days before priming and painting). But, it lets you also look inside your walls and fix wiring ( as I had to do, but doesn't seem to be an issue for you) or plumbing issues.

A word of caution, this is a big undertaking and , as I mentioned, it will make parts of your house uninhabitable for a time. On the plus side, you will have a warmer ( and quieter ) house at the end of it. Oh, also I calculated that I recouped my monetary investment in four years just on the savings I was seeing on my utility bills.

Good luck.
posted by Isosceles at 6:40 AM on November 12, 2011

The home improvement talk radio guy in my hometown (Tom Tynan) emphatically argues no! to blown in insulation. He claims it is an environmental hazard where you are inundating your home with particulate air transportable poison.

His website has a Q & A forum or you could call him on his radio show if you want his ideas clarified. I listen to him about once a month and I have learned a lot from him about other things so if I was insulating I would definitely look at this issue closely.
posted by bukvich at 9:22 AM on November 12, 2011

Depending on the house, it may be more economical to strip off the exterior and insulate from the outside in.
posted by gjc at 12:58 PM on November 12, 2011

I've heard bad things about blowing insulation into old houses like mine, but the auditor said it would be densely packed and not be a problem.

Does the auditor actually have any particular expertise regarding older houses? The auditor isn't going to take responsibility for long-term damage to your house. The current "default" advice tends to be based in newer construction, and even professionals can be pretty shockingly ignorant about differences in construction.
posted by desuetude at 4:13 PM on November 12, 2011

We have blown in cellulose insulation in our walls of our 105 year old house. We had it put in maybe 10 years ago. We haven't had any issues with moisture in the walls. We do have substantial eaves to keep rain out maybe that's why we haven't had problems.
posted by vespabelle at 7:56 PM on November 12, 2011

I asked a friend who does this kind of thing for a living (works here) if he had any thoughts:
The web link you pointed out has a whole lot of bad information. BSC's general position piece of cellulose insulation is here:

BSI-043: Don't Be Dense—Cellulose and Dense-Pack Insulation

However, you *can* definitely cause problems by insulating stud bay cavities in older houses--we have seen a bunch of those as well. They are primarily tied to a few things: lack of a drainage plane (e.g., tar paper) underneath the shingles/clapboard, and/or air leakage from inside.

>BSI-028: Energy Flow Across Enclosures

posted by spbmp at 1:25 PM on November 13, 2011

From the sounds of it, densely packed cellulose is a "maybe" where a lot of things can go wrong. What I'm taking away from this is, "find someone local with a knowledge of historical houses and have them take a look." I won't be jumping right into it, which is a shame since I have a chance to insulate a 2300 square foot house for $900 after rebates and the $400 gas bills are killing me.

Thanks for all the input, everyone.
posted by charred husk at 6:34 AM on November 14, 2011

Talked with Mrs.Husk, we decided it was just too risky, at least for this winter.
Thanks, everyone.
posted by charred husk at 1:57 PM on November 15, 2011

Well, at least you can scratch carbon monoxide or radon poisoning off the list of probable dangers. (No, really, we do take comfort in the fact that our drafty house at least doesn't allow for an easy buildup of toxic gases.)
posted by desuetude at 9:27 PM on November 17, 2011

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