To Insulate or Not

[Pastachio619]

Hoping to get some advice on my current situation.

I just had a 20' x 15' bedroom addition framed on the second floor of our home. The bedroom addition sits directly above the first floor den that has a Vermont Castings Encore 2240 that we use to heat our house in the winter. The framing and exterior is all done but I am holding off on moving forward on the inside because I cannot decide if I need to place insulation in the bedroom floor joist to prevent the room from over heating when the wood burner is running. Depending on who I ask I get a different answer. The goal would be to get some heat through the floor so that I can keep the bedroom door closed at night but not allow so much heat that the room is sitting around 72-74F and is uncomfortable to sleep in. Having the room over heat would be the worst scenario since it would mean we would not use the wood burner which we really enjoy, would rather not crack a window in the middle of winter. Below is more information incase it is helpful.

- bedroom will have R-19 walls and R40 ceiling
- bedroom has 12' ceilings with hvac that is set on fan mode when the wood burner is running, air return in the ceiling
- very little solar gain due to the location


I am pretty much open to any insulation method if it is necessary, R5 with spray foam around the edges, R10, R13 dosent matter to me as long as its the best option. But maybe I am overthinking it and insulating the floor is not necessary.

 

[stoveliker]

I don't know that anyone can give a solid answer unless they do a heat transfer calculation. Assume x F at the stove room ceiling, and 60 F or so upstairs. Calculate the heat loss from the room upstairs (outside wall area, windows, etc.) assuming 0 F? 20 F? Whatever you think is right. That'll give you a BTU need to keep temp constant.
Then Calculate the heat transfer through the floor construction and with different insulation levels in the floor for it to match the heat loss.

Basically a manual j calculation for the room.

 

[begreen]

I don't think any insulation in the floor will be necessary.

 

[fairtrout719]

Hoping to get some advice on my current situation.

I just had a 20' x 15' bedroom addition framed on the second floor of our home. The bedroom addition sits directly above the first floor den that has a Vermont Castings Encore 2240 that we use to heat our house in the winter. The framing and exterior is all done but I am holding off on moving forward on the inside because I cannot decide if I need to place insulation in the bedroom floor joist to prevent the room from over heating when the wood burner is running. Depending on who I ask I get a different answer. The goal would be to get some heat through the floor so that I can keep the bedroom door closed at night but not allow so much heat that the room is sitting around 72-74F and is uncomfortable to sleep in. Having the room over heat would be the worst scenario since it would mean we would not use the wood burner which we really enjoy, would rather not crack a window in the middle of winter. Below is more information incase it is helpful.

- bedroom will have R-19 walls and R40 ceiling
- bedroom has 12' ceilings with hvac that is set on fan mode when the wood burner is running, air return in the ceiling
- very little solar gain due to the location

I am pretty much open to any insulation method if it is necessary, R5 with spray foam around the edges, R10, R13 dosent matter to me as long as its the best option. But maybe I am overthinking it and insulating the floor is not necessary.

I'd insulate the joist bays, mostly for sound, then let the HVAC handle whatever heat makes it upstairs. Counting on floor leakage for bedroom heat seems like a recipe for never quite hitting the comfy spot.

 

[moresnow]

This thought as well ^

 

[begreen]

FWIW, we have a bedroom right over the stove room. It does not overheat and noise has not been an issue.

 

[Pastachio619]

begreen - How large is your stove room? What temperature does the bedroom above typically sit at when your are burning wood?

fairtrout719 - I am not sure if the hvac which is just the fan circulating air from the basement would be enough. Maybe it would. Basement typically sits around 64-66 when burning in the winter.


I guess my thinking was that if I insulated with R13 that if the room stays to cool I could always put a vent that is to code in the floor to let some of the heat from the fire room into the bedroom. But if I dont insulate and then the room gets to hot the only solution would be to rip up the wood floor and OSB and then insulate which would be terrible considering I havent even put the floor in yet!

I think the idea to insulate is coming from lurking on this forum over the years. I know I have read multiple times that people with wood burners in the basement usually get the first floor to 70-74 degrees and then the second floor is in the 60s. That made me think with my wood burner on the first floor that the bedroom above would sit around 70-74 and to me that is to hot to sleep.

 

[NN1]

Many variables can give totally different results, hence why nobody nor any AI can give you a precise answer. Maybe get a digital thermometer gun and do some measurements. Check the temp diff between floor and ceiling in the basement when unit is running. From my limited experience at least in my home the floor upstairs get most of the basement fireplace heat from the staircase well, not from the ceiling/floor separation where joists are.

So I agree that insulation against heat travelling in your new room is probably not needed. On the other hand, depending how hot the basement ceiling gets and what is it made of (closed in Gyprock, suspended tiles, etc.) then you might ensure to protect the electrical wiring and other stuff - if any - just above the stove. It might not be needed, but depending what you measure you might want to protect stuff from being gently cooked.

As a comparison - which is of course is a totally different situation than yours - my gas fireplace in the basement corner is in a chase. I insulated the chase cavity ceiling with Durock and hi temp alum tape etc, all about 15'' lower than the room ceiling. This way, the old joists and existing electric wires etc have extra protection from getting slowly baked. So you might not need insulation at all - it depends on the house config and temp readings while your unit is on since several hours.

 

[gthomas785]

How much airflow is there from first floor to second? Is there an open / vaulted ceiling connecting them or just a stairwell?

I'd expect convective heat transfer to be a much more important consideration than thru the floor.

Whether you insulate or not, I don't think that single factor would be the reason for your bedroom to get too warm.

 

[Pastachio619]

The only airflow from the first floor to the second is through the staircase. The new bedroom will be the first bedroom up the staircase to the left. All other bedrooms are down the hall on the right. My plan was to keep the new bedroom door closed at all times so that most of the heat from the burner will move through the second floor like it has in the past and will reach the 3 bedrooms down the hall.

Interesting that most people are saying insulation is not needed. The room with the wood burner is the same size as the bedroom and before it had a bedroom above it it use have R50 cellulose in the attic. The room would get to 80+ at the end of the day after burning all day. I just assumed alot of that heat would move up right into the bedroom and heat us out of the room.

 

[gthomas785]

Why do you let the stove room get so warm? Do you like it that way or need the heat in another part of the house or just have a hard time controlling the stove? I keep our kitchen with the stove around 70-75 and the surrounding rooms end up being around 67-70. Open doors, no interior insulation.

 

[EatenByLimestone]

I’d put some insulation in the floor. Maybe not a lot, say R12 fiberglass batt suitable for a 2x4. If not Kraft faced it’s not going to stop heat transfer, just slow it down.

I have a little insulation between my floors blown in before my attic was finished off. I’m happy it’s there. It’s 2-3” of settled cellulose. It’s not going to win any awards, but it does hold the heat downstairs for a little while longer before it heads upstairs and is held by the much better insulation up there.

Get your money out of the heat. Make it move as slow as you can.

 

[begreen]

begreen - How large is your stove room? What temperature does the bedroom above typically sit at when your are burning wood?

Our stove room is about 16 x 20 in an open floorplan. With the stove burning, it's typically in the 72-74º range. We bank down the stove overnight and the bedroom above may be around 70º at night dropping to around 68º by morning. There is no other heat or ductwork to this room.