Can you give us a bit more info about your house and where exactly you are putting this insulation.

I’m not familiar with the particular brands you mention but have worked with all three kinds of insulation. Spray foam costs a lot more but when applied to your roof deck puts your HVAC vent pipes in the building envelope if they run through your attic and provides an air seal.

Neither of the other provide an air seal. Fiberglass settles if you walk through it and blows around if you have vents blowing on it but if neither of those is a problem its a good product. I haven't seen cellulose turn to dust, its made of paper after all and there are some very old books around.

whichever way you go you will enjoy lower heating and cooling costs.

My house is somewhat old. It was built in the 80’s. It is 2 story with actually 4 attics, but really 2 main ones. The one in the garage doesn’t really count, although one of the vendors suggests putting more batts on the wall towards the house. And I have a very small attic that covers the front half of the master bedroom only. So I have two main attics, one downstairs and one upstairs. I have gas heat. I was told that makes for complications to do foam. Also, I know I will be needing a roof relatively soon and I imagine that might require some of the decking to be replaced if any of it is bad. So for those reasons, and because of cost, I have decided against foam.

Now, during last years freeze and broken pipes, the ceilings below the downstairs attic fell. When I replaced the ceiling, I thought I did not want foam on the rafters for the reasons I indicated. So I, aparantly mistakenly, had foam put on the bottom of the downstairs attic. But the foam vendor did a very poor job and many of the sections between rafters are less than half full of foam. Its a disaster. I actually had one vendor tell me that I needed to remove that foam and he quoted me $40,000 to remove the old foam and do foam on the rafters. Not doing that, for sure.

The other main attic which is upstairs came with blown in-insulation, but not well installed and lots of under coverage. So, what I did was is to scoop up some of the blown in and move it from one section to the next, leaving some sections completely uninsulated. Then put in R-19 batts in the spaces I cleared out. So, the upstairs attic is roughly R-19 all acrross with a mixture of batts and blown in.

When I first moved in, I had someone install radiant barrier. I now understand that radiant barrier is only relatively modest value. But still, it has value. But the original radiant barrier was cheap paper and it is falling down a lot. Since it has some value, I’m planning on getting the radiant barrier redone, but I know that the insulation itself is the most important.

So, for the downstairs attic with the poorly done foam, both the cellulose vendor and the fiberglass vendor suggest just piling the blown in on top of the foam I already have. seems to make sense to me.

For the upstairs, the cellulose vendor recommends just pouring the cellulose over the existing batts and blown-in. While the fiberglass vendor recommends removing the existing batts and blown-in, do a sanitization, and install all new insulation. For this reason, the fiberglass vendor quote is higher. Though he said he would do it without the removal for less money bringing the quotes closer together. But he said he didn’t recommend that.

Our main problem, besides paying too much for energy, is that during the winter, our downstairs is too cold, upstairs is too hot. We have a single AC/furnace for both upstairs and downstairs. When I put the foam in after the last freeze, I had hoped that would improve the situation. Instead, it was worse this winter, with a 25 degree difference between upstairs and downstairs on the nights it was near freezing. During the summer, we don’t really have that problem, but we do have high electric bills.