Insulating an insert, how much difference does it make

[Tracks74]

I have discussed this a bit in the past and sitting at the same crossroads in a decision.

We have a late 1960’s brick single story home (1800 sf) with a masonry fireplace. The backside of the masonry fireplace is our uninsulated garage. FWIW, I live in WI.

We have a Vermont Castings Montpelier insert in the fireplace. When temperatures are around 30 degrees or warmer, the insert heats the entire home. Any colder and we have to turn on our furnace.

My question is, how much of a difference will insulating and installing a block off plate make?

A friend of mine has a VC defiant and when you walk in his house, you FEEL the heat. For our setup, you need to be 2-3 feet in front of the insert. If you are 7-8 feet away, you don’t feel the heat at all.

I feel I have 3 options:
1. Install insulation / block plate
2. Option 1 with a larger insert
3. Install a wood stove

Comments?



Sent from my iPhone using Tapatalk

 

[Easy Livin’ 3000]

I have discussed this a bit in the past and sitting at the same crossroads in a decision.

We have a late 1960’s brick single story home (1800 sf) with a masonry fireplace. The backside of the masonry fireplace is our uninsulated garage. FWIW, I live in WI.

We have a Vermont Castings Montpelier insert in the fireplace. When temperatures are around 30 degrees or warmer, the insert heats the entire home. Any colder and we have to turn on our furnace.

My question is, how much of a difference will insulating and installing a block off plate make?

A friend of mine has a VC defiant and when you walk in his house, you FEEL the heat. For our setup, you need to be 2-3 feet in front of the insert. If you are 7-8 feet away, you don’t feel the heat at all.

I feel I have 3 options:
1. Install insulation / block plate
2. Option 1 with a larger insert
3. Install a wood stove

Comments?



Sent from my iPhone using Tapatalk

Yep, all three are good options to feel more heat. I like option 1 to start, much cheaper and easier. If it doesn't work well enough for you, then you can go to option 2 or 3.

3 is the best, wish I could do it. I'm stuck with option 1. Every time we add insulation or plug an air leak somewhere, it gets better and better. I'd try that along with option 1, you might find yourself set with that.

 

[begreen]

Insulating behind the insert and installing an insulated block-off plate makes a notable increase in heat output into the room. I don't recall anyone putting instrumentation on an insert to measure the difference, but there are several people that have reported it made the difference between considering replacing the insert to satisfaction with having adequate heat.

If you choose to do this, can you measure the air temperature coming out of the insert's convection vent before and after? That might be helpful information to the next person with this question.

 

[jetsam]

You can do insulation and a block off plate for about $50.

The block off plate is a big deal for exterior chimneys, and significant for interior ones. It helps the stove a little because cold air isn't whooshing past the outside of the liner and drawing conducted heat from the stove.

It helps the house a lot because your warm house air isn't blowing up the chimney around the outside of the liner.

Obviously you'll get better heating from a freestanding wood stove than a similar insert, but given the low cost of making a block off plate, I'd suggest doing that first to see how much it helps.

 

[Tracks74]

When I priced out Roxul and micore boards it was close to $300 via Menards or Home Depot. Any other products or source recommendations?


Sent from my iPhone using Tapatalk

 

[begreen]

When I priced out Roxul and micore boards it was close to $300 via Menards or Home Depot. Any other products or source recommendations?

If there is room behind the insert, roxul batt insulation is fine and much less expensive. It's also good for stuffing around the liner on top of the block-off plate. Micore can also sometimes be salvaged from office cubicle dividers. It's used as sound proofing.

 

[jetsam]

When I priced out Roxul and micore boards it was close to $300 via Menards or Home Depot. Any other products or source recommendations?


Sent from my iPhone using Tapatalk

A batt of Roxul should run you about $40. I got mine for $20 by buying a damaged one. If you want to wall it in, Durock is $10 for a 3x5 board. The blockoff plate can be a piece of sheet metal and a little furnace cement, both of which should be in the $5-$10 range.

 

[SculptureOfSound]

Tracks74 did you try this? I've got almost the exact same setup (1650sf house in central Wisconsin, exterior masonry fireplace) and am considering the Montpelier primarily because it is one of the only inserts that would fit our fireplace while still allowing enough room for Roxul on the sides and back.

Considering how cold inside bricks get in winter I am thinking the Roxul would make a big difference in heat output and as mentioned is one of the main reasons I am considering the Montpelier rather than larger inserts. I don't need overnight burns as we have ng furnace too.

I did put Roxul in our fireplace in the meantime as we aren't using it and it really made a difference. Curious how that would translate to an insert, so hoping you tried it!

 

[begreen]

If the insulation thickness is constraining insert choice consider using 1" micore insulation board instead.

 

[mellow]

Micore is good, Cement board is good, and if you can Cement board / Micore + Roxul would be the best. You will notice a difference.

 

[Tracks74]

I have not installed the insulation yet, I think at this point I will wait till the season is over and do it then unless I find a free weekend soon


Sent from my iPhone using Tapatalk

 

[nola mike]

It seems fairly obvious in retrospect, but I had a block off plate installed that I removed on my F602 so that I could have easier access to a pipe joint/flue damper. I had used thermix pour in insulation, which seems to work just fine to limit air flow up the chimney. I also haven't seen a ton of discussion about where to place the block off plate (it's assumed that it's at the bottom of the chimney), but I'm not sure why a plate at the top wouldn't work just as well.

 

[Rickb]

It seems fairly obvious in retrospect, but I had a block off plate installed that I removed on my F602 so that I could have easier access to a pipe joint/flue damper. I had used thermix pour in insulation, which seems to work just fine to limit air flow up the chimney. I also haven't seen a ton of discussion about where to place the block off plate (it's assumed that it's at the bottom of the chimney), but I'm not sure why a plate at the top wouldn't work just as well.

You have a large area of air between the top plate on your chimney and the top of the stove, heat rises and when that happens the cooler air up in the chimney will fall and cool the whole setup. A insulated block off plate keeps this from happening.

 

[nola mike]

You have a large area of air between the top plate on your chimney and the top of the stove, heat rises and when that happens the cooler air up in the chimney will fall and cool the whole setup. A insulated block off plate keeps this from happening.

Well, I guess the extent of that effect depends on the chimney, existing insulation, etc. The block off plate at the top would still prevent airflow, which is the main purpose.

 

[Hogwildz]

Well, I guess the extent of that effect depends on the chimney, existing insulation, etc. The block off plate at the top would still prevent airflow, which is the main purpose.

It won't prevent the heat that migrates up, from being transferred through the masonry.

 

[nola mike]

It won't prevent the heat that migrates up, from being transferred through the masonry.

No, it won't. Nor will the block off plate by itself. Needs insulation for that. A block off plate at either end should slow the convective transfer though. I'm sure the plate at the bottom is better, but I bet an insulated chimney + plate at the top is still probably pretty good.

 

[nola mike]

As an amusing/annoying aside, when I installed the insert I initially tried to insulate the chimney with perlite. Well, it doesn't take much of a gap in the blockoff plate to end up with a perlite avalanche behind the insert. I removed the insert and vacuumed (not fun) and swept (also not fun) every little pellet. Should have just left it back there...

 

[Easy Livin’ 3000]

As an amusing/annoying aside, when I installed the insert I initially tried to insulate the chimney with perlite. Well, it doesn't take much of a gap in the blockoff plate to end up with a perlite avalanche behind the insert. I removed the insert and vacuumed (not fun) and swept (also not fun) every little pellet. Should have just left it back there...

Actually a really useful post. I'm sure others have considered doing that with perlite, in concept it's a decent idea. In practice, doesn't sound great. Maybe you'll help someone else avoid a big mess.