Rockwool insulation and an insert

[karl]

I had the surround off my insert to look at how I was going to insulate around it. Then it got cold and I needed a quick fire to take the chill off.

With the stove at about 425 and the blower running. The metal part of the heat-a-lator that the insert seats in was at 120 or so on the sides and 170 on the top.

This sets in a cinder block chimney chase. All the heat the goes to the cinder block goes up and out of the house due to a pretty sizable air gap between the heat-a-lator.

Assuming the metal is R-1. That's probably accurate. And assuming the temperature of the block is 40. A guess but probably pretty accurate. That's a delta of between 80 and 130

Say 15 square feet exposed. That's 1200 to 2000 btu's an hour wasted.

 

[Fod01]

Similar set up here. I think my insert gets its secondary air from the sides, so I'd have to be careful to clog up any inlets. Other than that, I can't think of any reason not to insulate that space. Perhaps there would now be a chance of the unit overfiring if the power went out? I'll check my manual for any precautions. Hopefully the guru's will chime in with helpful info.

Question for you... I always wondered if I should block the convection inlets/ outlets on the old fireplace. Did you fill yours with anything?

Gabe


***** EDIT ***** I found your thread on this from August. There were solid arguments not to wrap the insert, so I'll be leaving mine alone.

 

[stejus]

There's been plenty of discussion earlier on this. Do not wrap the insert at all. They were not engineered to be wrapped. As for heat loss to the concrete surrounding the insert and the chimney, yes there are solutions for this.

First thing is a block off plate where the liner goes through the chimney flue. Most sweep installers will not do this. They cap the top and say that's all that is needed. If left open, your stove will cool down much quicker because of radiant heat loss from the stove and room heat finding it's way up the chimney.

Second thing is insulate the liner all the way to the top. You can wrap the liner (too late if you didn't) or drop in insulation.

Third thing is to insulate the firebox. Some out here insulated the firebox with some sort of hard board insulation. I think this is what you are looking for and it may be difficult to do with the insert installed at this point. I'm not sure how much heat loss there is with this one. The hottest part of any stove is the top. Inserts are designed to move that heat off the top through the blower. So, in theory if most of the heat is being exhausted out the front through the blower, there can't be much left around the stove (external sides and back) to radiate outwards.

 

[EJL923]

I am also looking at upgrading my insulation inside the fireplace for my insert. My installer did put in a block off plate, but there is still a very small gap around the plate / liner junction. This is always expanding and contracting so furnace cement is out as it will crack and break off. I am going to wrap some roxul around the liner, tight up against the plate. Not a perfect seal but better than it was. I am also going to add a second block off plate. In between the two plates i am going have some more insulation. I had thought about just laying a piece of Roxul insulation on the very top of the insert as an experiment, only the top. I will closely monitor the temps during this period. My thermometer is on the stove top where the air from the blowers comes out, so i will be able to watch the temps very closely. As others have said, stove makers did not design the stoves to be insulated. You could overfire the stove if not careful.