Insulation, Radiant and Vapor Barriers - Success with blow-in cellulose

Hello All,

In case someone ever comes searching on "cellulose insulation," I wanted to share an account of the best money I have spent on my house in some time. I live in a 95 year old two story 4 bedroom stone house in Philadelphia. All the houses here are made of a local stone called Wissahickon Shist. Though my stone walls are 18-20 inches thick, there is virtually nothing between those stones and the plaster lathe except a few inches of air. In addition there are these strange boxy columns at the corners that act like a cold air chimney.

This house is an energy pig and was always freezing in the winter and frying in the summer. Especially upstairs. I did a lot of winterizing on my own and it made a big difference, so never doubt the small stuff. However, the blow-in cellulose insulation was very dramatic. I had it put in my attic where I have both a pitched roof and a flat roof. The flat roof had never had insulation while the pitched roof had a layer of fiberglass batting - they just blew the cellulose right over it. In addition, we are fixing up a few bedrooms - lots of cracked plaster walls - so I had them pump some in to the walls of these bedrooms which also face the most wind and weather. This required drilling 2.5 inch holes between each joist. Given this, this is not the kind of thing you want to do in a nice painted room!

The very night they put in the insulation the difference was unbelievable. It used to be that when you walked upstairs you could feel the temperature difference right on the stairs. I even measured it and on cold days it was 5 degrees colder. Now it is 2 degrees warmer. The furnace barely goes on and is on for much less when it does go on. The house is really retaining the heat. All in all it made a house that cost too much yet was still cold a place that will, I am sure, cost less and be livable. In fact, it is downright pleasant now. I hope the change in summer heat is equally noticeable.

You will read that foam insulation is superior, but it has a superior price - probably 5 times as much as cellulose. Best vs. better is not really an issue here. I paid $1600, but the attic alone - which I think makes the biggest difference - would have been about $700. Can you do this yourself with a rental machine? Sure, but you need a truck to carry not just the machine, but many bags of insulation. My house took just over 50 bags! For a DIY project this one was worth paying someone to do it. They filled every hole with a plug and a thin coat of mud, plus they were great about the clean up.

Any way, sorry if I sound like an infomercial or something, but I just had to pass on the news. Many people here have helped me and I know it can be tough sorting out what to do to a house when there are many choices. I hope this helps anyone considering insulating their house.

Best of luck!

Thanks for sharing deke!

Congrats! Will you be doing the rest of your walls eventually?

Thanks for sharing deke!

Congrats! Will you be doing the rest of your walls eventually?

Hi jganyard. I think this will be it for a while. I'm sure the walls helped, but the attic was, I think, the real payoff. New windows are somewhere on the horizon. Funny, but the 95 year old windows aren't nearly as bad as some of the 1970s windows that were put in!

Great job. Now you're gonna have to buy a smaller furnace and a/c system. :D

I think I hold off on the new furnace until fate makes it something I have to do! :-) Did I just jinx myself?

I found the benefits of insulation to be astounding. We had cellulose blown in the attic to R-49 over the old beat up R-13. This was in December 2004.

We have gas heat, electric air conditioning. The difference was noticeable from the first. The house was quieter and the furnace ran less. The next winter, gas prices rose, so it was hard to tell if the heating cost was less or not. The measurable difference was in the summer.

The electric company has us on level billing. We received a notice that the level billing amount was being reduced $10 per month. Nice. Saving $120 per year on electricity. The next summer we received another notice that the cost was being cut $10 per month. Now saving $240 per year. The heat has not run much this year, so the cost is not measurable, but the comfort is so. The furnace runs less often. Overall, the cost of electricity is down $240 per year. I paid $500 to have the insulation blown. At this rate, it will pay for itself in about three years.

Of course, there are the small things that I have done: caulking, weatherstripping, and such. The attic insulation is the most remarkable change.

As far as having a contractor blow the cellulose is concerned, I found that I could have the contractor perform the work, turnkey, for less than I could buy the materials. This is one DIY job that I was glad I farmed out.

Hi Chris, it sounds like we have similar situations and I am looking forward to what the summer may bring. As far as the winter I hope I end up paying less for gas heat, but unlike past years at least now I am paying for heat that I can actually feel and stays in the house for a while!

Like you, I also did a ton of caulking and other things and yet I was really dumb about it. I waited (procrastinated) for two years to do all this thinking it wouldn't really make a difference. How wrong I was. If I added up all the little cracks and seams I filled up it would probably add up to a square foot or two of space that used to just let the cold air flow right in. When you think about it, that is equal to leaving a window open all winter long! Any way, thanks for the post. It is nice to know how things worked out for you. Me, I am still on a high over all this. Perhaps I need to "get a life" but this really is/was my favorite of all home improvements this year and I did a lot!

Thanks for the post. I've got to do something about my uninsulated walls and am trying to gather info on both foam and cellulose. Currently, I'm leaning toward foam in the walls and cellulose blown on top of my fiberglass batts in the attic.

Thanks for sharing your experience -- sounds like money very well spent.

I'll add my own experience here...

This weekend I set out to blow in cellulose to the exterior walls of my 1939 Cape Code in Virginia. I rented the machine a Lowes (20 bucks a day - free with 20 bag purchase). I found the job to be very easy, here's how my wife and I did it.

We drilled 2 1/8" holes in the exterior of the house using a hole saw. I had two saws, so I would alternate between the two, allowing my wife to clear the plug from the other saw while I kept working. This made the drilling go much quicker, which was by far the most time-consuming part of the job. Next, we filled the cavities with the cellulose. This went very quickly, taking maybe 1-2 minutes per cavity. I have read in several places that you should drill two holes, one near the top plate (as I did) and one five feet down. Given that my house is nowhere near airtight, I was skeptical of the need for the second hole. I experimented by blowing in the cellulose with only one hole, and then opening up a second hole below to see if it had packed properly. I was pleased to see on several occasions that it did, so I did the remainder of the house with only one hole. What I found, was that the additional holes up top I had drilled in adjacent stud bays provided enough relief pressure to allow the cellulose to fill. This was evidenced by a lot of air/dust pouring out the adjacent holes as I filled.

After the bays were filled, I sprayed "great stuff" type foam ("minimally expanding" vice the 2x or 3x expanding stuff) in the holes, then replaced the sheathing plugs (1x material, in my case), sprayed more foam and replaced the siding plug. I plan to reside my house soon, but will caulk/sand/paint the plugs in the meantime.

Anyhow, it's too warm to tell if this will make any difference, but I feel relatively confident that it was applied correctly. The house is certainly quieter now, much harder to hear things outside. In particular, based on the square footage coverage information on the bag for 2x4 walls, I expected to use 10.5 bags, but ended up needing 14.5, so I am fairly sure I got the appropriated density/coverage levels. No idea if I did it correctly or even well, but I figured I'd share my experience. Just under $200 all tolled for the blower rental, 15 bags, foam and misc. About 14 hours of work for two people (700 square foot house). Not bad if you ask me - we'll see how it does if it ever gets colder.

This is a pretty messy job, however - the stuff just gets everywhere. If you are considering doing it yourself, and are on the fence as to whether to do it inside or out, I would certainly recommend taking the outdoor approach.