# Heat loss to cinderblock?



## Black Jaque Janaviac

I've got a stove in the basement.  It seems like I've received a lot of advice that the cinder block would soak up heat like I wouldn't believe, and maybe that's so.  

The fact that the stove my stove room is blazing hot while the rest of the house could use a five degree lift leads me to suspect that my problem is moving the heat about, not loss to the concrete foundation.  Am I correct?

I'm trying to figure out where to aim my efforts first - installing floor grates? or insulating foundation walls?


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## realstihl

The hotter the walls get the more heat loss you get. My vote is on insulation first.


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## Hardrockmaple

Insulate. I tried for years to heat my main level with a woodstove burning in an uninsulated basement. Could never get it to happen. A few years back I insulated the basement walls, now I can heat the main level with just the basement stove throughout the fall shoulder season.

Insulate.


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## PLAYS WITH FIRE

I say insulate which will cost some coin! But the time and effort you save from keeping more heat in will be saved by using less wood. Then spend 20 bux and buy a box fan, point it down stairs into the stove room until you save enough money to do some clever ducting like I have planned tis summer!


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## nate379

Cinder block without no insulation is something around an R2.  I'd insulate at least the section that is above the dirt level.


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## daveswoodhauler

Put 1" rigid insulation on my basement walls for the kids playroom. With the IR gun, the temps are about 10 degrees warmer with the R5 vs just the concrete foundation walls. Basically, if I take a reading on the interior wall above grade in the basement, the non insulated wall will read 48-49 degrees vs the insulated wall at 58-60 degrees at the same height. I don't have heat down in the basement yet, but think it would be a good idea for you to at first insulate, then look at something to move the air (grates, fans etc...)
The 2 X 8 X 1" sheets I got were like $8 a piece and easy to install/cut as they were tounge in groove


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## Black Jaque Janaviac

> Iâ€™d insulate at least the section that is above the dirt level.



I would imagine this is done by insulating on the outside.  This could be tricky as much of the perimeter is surrounded by garage and/or raised cement patio or porch.  I suppose it just wouldn't get done along these sections.

Can you recommend type of insulation?

How to install it (painted block)?

How to cover it?  (it sounds like I could put up foam, fasten metal lath somehow, then shmear drywall mud over all)


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## realstihl

NATE379 said:
			
		

> Cinder block without no insulation is something around an R2.  I'd insulate at least the section that is above the dirt level.



It'll still soak the heat like a sponge. Best way is to frame walls out then insulate. Firring strips will work also.


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## Black Jaque Janaviac

> Best way is to frame walls out then insulate. Firring strips will work also.



What's the difference between framing out and firring strips?


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## Black Jaque Janaviac

Oh yeah.  Instead of floor jacks my basement has interior cinder block walls.  I can't imagine those would need to be insulated but I figure I'd best check first.


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## Hardrockmaple

Inside of exterior walls. You'll find a huge difference.


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## Locust Post

Black Jaque Janaviac said:
			
		

> Best way is to frame walls out then insulate. Firring strips will work also.
> 
> 
> 
> 
> What's the difference between framing out and firring strips?
Click to expand...


Firring strips aren't as thick as framing with 2x4s. Depends on how thick of insulation you want and if you intend on drywalling later.


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## Battenkiller

NATE379 said:
			
		

> Cinder block without no insulation is something around an R2.  I'd insulate at least the section that is above the dirt level.



I agree. It's not that the blocks themselves act as heat robbers, it's the fact that they have basically no insulating value and heat is lost to the above-grade portions of the basement perimeter.  

Heat flow increases as the temperature differential increases. The ground below the basement floor in my area is around 55Â° year round, but the outside air surrounding the above-grade portion of the foundation may get down to 25 below.  That's more than a 100Â° temperature differential if you're running that stove like most basement burners do.  Heat is just pouring through those blocks in those conditions. 

To make matters worse, the parts of the foundation exposed to the outside air have no heat storage capacity.  While the below-grade portions of the basement store more and more heat as the heating season progresses, the heat that passes through the upper portion conducts through the foundation walls and is instantly whisked away by the outside air. 

Short version: get the upper 4' of the basement walls insulated to at least R-15 and you will see a big reduction in heat loss.


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## smmm

http://www.familyhandyman.com/DIY-P...w-to-finish-a-basement-framing-and-insulating

Hope you can get to this link... I am finishing my basement and trying to follow this as close as possible.

Click on the step by step methods and you'll find some pretty detailed steps...


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## Ehouse

Here's an easy fix that worked for me.  Depending on how and where your stove is situated, build a three sided plenum (box) with the open side facing the stairwell.  Allow plenty of clearance from the stove on all sides and line it with a reflective material ( I used some old 4' square highway signs at first).  A large percentage of the heat lost to the block is from radiation.  If your stove is close to a corner, you only need to put up one side of the box.  Reflectix (that bubble wrap stuff) works great as it provides the required 1/2"  to block radiation, but remember it is flammable so give it clearance and fasten it securely to the inside of the plenum walls.  

Ehouse


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## PLAYS WITH FIRE

A useful heat loss calculation I use frequently is:

Btu=U*A*(T1-T2) where "U" is the reciprocal of the "R" value and "A" is the area of the wall. T1 and T2 are the change in temp from inside to outside.

This will give you heat loass per hour from the wall. The nice thing is you can see what will happen when you add the insulation just how much you have saved. I know there are calculators for this but this is the simple equation and I like to sometimes do it the hardway!


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## Wood Duck

smmm said:
			
		

> http://www.familyhandyman.com/DIY-Projects/Indoor-Projects/Basement/Basement-Finishing/how-to-finish-a-basement-framing-and-insulating
> 
> Hope you can get to this link... I am finishing my basement and trying to follow this as close as possible.
> 
> Click on the step by step methods and you'll find some pretty detailed steps...



one nice thing about the method shown in this link is that the first step - glueing foam insulation to the cinder black wall - is pretty easy and quick, and you'll make a big difference in the heat loss just by doing that first step.


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## peakbagger

One advantage of a conrete block wall is that you dont need to shovel snow around the house as it melts rapidly. My mother used to grow roses up in Maine (which was a challenge due to cold weather). Her graden was up against the house and the heat from the woodstove kept the roses warm int he winter and they bloomed right up int he spring . 

Whatever you do dont get convinced to drill and foam the interior of the blocks, its a waste of money that would be far better spent on proper insulation.

One caveat is that if you are in wet area with clay soils, there is remote chance that if you do too good of a job at insulating the foundation that you could have some issues with the clay freezing and pushing in the blocks. This usually occurs when the foundation wasnt backfilled properly with gravel and lacks drainage. Year ago I had a house in Wisconsin that had been repaired from a similiar situation. It wasnt just my place, the entire neighborhood had the same issues and repair.


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## Butcher

I've found just the oppisite effect in our home. It may have to do with the stove being in the center of the basement close to the stairs or the heat ducts being almost right above the stove or it may be in the way our house is constructed. I've found that as the basement cools alott of times the temp upstairs will actually rise.


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## Black Jaque Janaviac

> Btu=U*A*(T1-T2) where â€œUâ€ is the reciprocal of the â€œRâ€ value and â€œAâ€ is the area of the wall. T1 and T2 are the change in temp from inside to outside.



Interesting I calculated the heat loss for the top two block that are exposed to the atmosphere and for the lower 5'8" which would be covered w/ soil.  Assuming R-5 and the outside temp was 10* and the room temp 80* the top two blocks were losing 440 BTUs/hr.  The portion below ground was losing 680 BTUs per hour using the same R value but increasing the area of course and reducing the gradient by assuming outside temp of 55*.  

So the top 24% of the basement wall was losing 65% of the heat!  So to maximize the heat savings per dollar spent it would seem to make the most sense to insulate on the outside by just digging down a bit and slapping up foam board insulation and parging over that.  I realize the weakness would be the assumption that all 5'8" of buried wall is exposed to 55* soil temps.  Frost does penetrate.  

Interestingly there is not much of my basement wall that is actually exposed to the outside air.  Probably 1/2 to 2/3's of the perimeter is covered by either heated breezeway or concrete porch/patio.  So to insulate the outside actually would not involve too much work.


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## PLAYS WITH FIRE

If I understand corectly what you did you are losing more heat from the area below grade? That should be the opposite as the area below grade should have less of a temp change and the btu loss is less. I would say anything exposed to direct elements is going to lose more and anything below grade (ignoring frost line) should lose less.

If 100 sqft BELOW GRADE and r=4, inside temp =80, 50 being below grade temp:

1/5=.2

.2*100*(80-50)=600btu/hr

then:

100 sqft ABOVE GRADE and r=4, inside temp =80, 10 being above grade temp:

.2*100*(80-10)=1400btu/hr

Unless we are saying the same thing and I can't read real well.......


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## Seasoned Oak

I recently read that an uninsulated block wall Basement can lose as much as 1 million Btus per day.
That would be ALL the heat from a stove putting out 50000 Btus per hour for 20 hours.


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## PLAYS WITH FIRE

Ahhhhh, I read more better you increased the area below! Sorry!


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## peakbagger

I usually assume cinder block is a lot lower than R -5.


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## ozzy73

Insulation is the key here. We went from bare block walls to R24 insulation on the walls ( 2" Rigid insulation R10 + R14 bats ) and R28 in the headers.
I could not believe the difference the first winter.


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## smmm

If you put the insulation outside your are exposing it to many things that can damage it.  (animals, insects) Insulate inside and go from top to bottom.  Better to be safe than to do it again


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## begreen

And uninsulated basement can suck out 25-35% of the heat through the walls. Insulation is good. It can be done on the exterior if properly attached, flashed and protected, but often inside is easier.


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## Butcher

I'm gonna buck the status quo here and say that those blocks holding up your house are a sorce of stored heat. That has been proven through centuries of building with stone and concrete. While the R value may be low as to keeping the cold out on a cinder block it is a great heat storage unit which will hold and release its heat over time. I may be biased in my opin but having worked for years with stone and concrete products here in the midwest I am sold on what I have seen, felt, and lived with. Do a search of thermal mass and concrete on the internet and there are all kinds of studies that will say the same. But like I said, I'm kinda biased. Grew up reading the 3 little piggies to much maybe.


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## PLAYS WITH FIRE

Thermal mass for sure Frank Lloyd Wright designed some of his homes with this very much in mind. But there needs to be a thermal break....otherwise it's sucking up the heat that it can't hold.


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## begreen

Exactly. It can act as a conductor just as well. With an outer insulation jacket, it would have the potential as thermal storage. As long as you didn't let it cool down too much. If you do ,the time to recover may exceed your patience.


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## Black Jaque Janaviac

Plays With Fire,

Yep.  In my house only the top two rows of cinder blocks are exposed to atmosphere.  So that portion accounts for only 25% of the wall area.  That's the only reason the lower portion loses more heat is because it is so huge.  From a cost-benefit standpoint, a dollar spent on insulating the top two rows of blocks is worth almost two bucks spent insulating the lower part of the wall.

*Is there anyone here who only insulated the exposed part of the foundation?  What has your experience been?  Did it make a noticeable difference or do you wish you insulated top to bottom?*


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## Ehouse

If you don't want to excavate below the exposed part of the foundation,  you can insulate horizontally ( moderate slope away from the wall) a few inches down.  Use flashing at the vert. to horiz. transition.  I think it's an Alaskan slab detail but should be an improvement from just insulating the above grade portion.

Ehouse


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## Yagminas Masonry and Wood-heat

If given the choice, always insulate and leak-proof the exterior. The heat storage and moderating effect is well worth it. Kinda like living inside a masonry heater.
Kev


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## tecumseh

I have found the perfect product and would just love to use it.  Great rvalue, soundproofing, moisture prevention and even a bit of bug repellent.  It is called Core fill500 and/or Tripolymer and because my entire house and basement (on a hill) are concrete block with just a 1.5 inch of wood and insulation behind the dry wall it would be awesome.  The foam injection takes the average r-1 of the block to to almost r30 in the block and evened out over a normal wall gives r20.  However, because of this absurdly warm weather my gas bills are almost nothing because my smallish stove is heating my house like a champ.  Convincing my wife to spend 6K on it for a small savings in winter and summer cooling is tough right now.   The salesperson says most people can get payback in 2-4 years.  However with the wood stove, low gas prices and cheap electric in NW Ohio convincing the financial wizard of the house will take some doing.   The company I called mostly does this type of insulation for commercial buildings but were willing to come to my home and do it.  

I despaired that I couldn't ever find something that would insulate my house.  This if it does what they says would be great and since I have to paint the walls any way in a year or two the 3/4 inch holes they need to drill and patch would get covered anyways.

Just thought I would pass on the product and see if it makes sense for anyone or is even available in your area.  If you order it tell them Tim from Ohio sent you, maybe they will give me a credit!  lol

Tim


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## StuckInTheMuck

Might be worth taking a look into this product to get you started on the exterior of the house.  http://styro.net/FoundationInsulationPanel.htm  Seems to be more durable and better looking than standard foam board.  Can't seem to find a price anywhere online.


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## Black Jaque Janaviac

I thought I remember reading somewhere that there was some synthetic stucco that was applied over these foam boards that was giving the practice of stuccoing over insulation a bad reputation.  In other words, if you put up the foam board, cover with metal lath, then a healthy layer of stucco that is actually fairly resistant to weed whackers.


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## StuckInTheMuck

I guess I should have said, that I know nothing about the above product..  Just saw it when I was looking for a solution for my house.  I ended up using the 2" foil backed foam insulation on the interior of my foundation walls..  Don't know the best way to handle insulating on the exterior, but I think I would have preferred to be able to do that..


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## sesmith

Black Jaque Janaviac said:
			
		

> The fact that the stove my stove room is blazing hot while the rest of the house could use a five degree lift leads me to suspect that my problem is moving the heat about, not loss to the concrete foundation.  Am I correct?



You are correct.  If you insulate and don't find a way to move the hot air upstairs, your cellar will be even warmer and your  upstairs will still be cold.  I heated many years with my stove in an uninsulated cellar.  It isn't the most efficient way to do things, but the key is in moving the air upstairs.  I laid up an unmortared short block wall around 3 sides of my stove to help keep it from just radiating the heat at the cellar walls and act as more mass for the stove.  The 1st course were set on their sides to allow air to flow up between the stove and the wall.  I wasn't using the oil furnace most of the time, so I left the blower box open for cold air return.  The hot air went up the stairwell and also up via a duct fan and vent through the floor.  This setup wasn't ideal, but it worked.  Close up the furnace blower door or shut the door at the top of the stairs and it didn't work very well at all.  Insulation will certainly help with heat loss, but it won't fix the air circulation problem.

FWIW, before you insulate, try air sealing the rim joists first.  That will probably be a bigger bang for the buck to start with.  Depending on how leaky they are, it may also help in getting the air flow upstairs.  I used to have a problem moving the air up through my house in a strong south wind, due to leakage and air pressure from the leaks.


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## DickRussell

tecumseh said:
			
		

> I have found the perfect product and would just love to use it.  Great rvalue, soundproofing, moisture prevention and even a bit of bug repellent.  It is called Core fill500....
> 
> Tim



While filling the voids of concrete block with a foam insulation undoubtedly would improve the R value of the whole wall some, I doubt that it would be the hoped for great improvement. The inner and outer faces of the block remain exposed to the inside air and outside air or soil, and these faces still would be connected by highly conductive webs of concrete. The heat loss through those webs of concrete still would dominate the heat transfer (thermal bridging). Even with the block voids not filled with foam, the mostly dead air cavities still have insulating value, much like the air space between an old double hung window and an exterior storm window. Improving the R value of a part of the assembly that isn't contributing much to heat loss in the first place won't help the whole wall R value too much.

It's no surprise that building highly insulated wall structures requires near elimination of thermal bridging of wood framing. This is can be done by using double frame walls, applying a continuous layer of rigid foam on the inside or outside of the wood, or using structural insulated panels (SIP, a sandwich of foam between inner and outer skins of OSB). In the case of a foundation wall, about the only way to insulate it well is to apply a continuous layer of insulation on one side of it.

Insulating on the outside lets the foundation mass be a heat storage device, which would release heat long after the fire has died. However that mass will soak up a lot of heat for a while when the fire is started, resulting in a delay of availability of heat for the rest of the house. Insulating on the inside doesn't provide the thermal storage of the concrete mass, but it does mean a faster heatup of the basement space and earlier availability of heat for the rest of the house. Then it's just a matter of leaving the basement door open or providing other means of moving air between basement and the rest of the house.


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## Black Jaque Janaviac

Sesmith,

Thanks.  I couldn't quite understand how not insulating the basement was causing the basement to be 80+ degrees while the next floor up could barely push 65 when the outside temps were in the 20's.

I think I have decided to insulate the top part of the foundation in the summer when I can dig down a bit.

In the mean time I will work on small-dollar projects to help move the air around.  Floor vents are easy.  I'm also tearing down the tongue-and-groove ceiling tiles to expose the heat directly to the floor-boards of the next floor.  In removing these tiles, I learned that for the entire portion of the tiled ceiling the previous owners never insulated that part where the joists rest on top of the cinder blocks (what do you call that?).  So $30 worth of 6" batting is going up there.


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## jimbom

DickRussell said:
			
		

> tecumseh said:
> 
> 
> 
> 
> I have found the perfect product and would just love to use it.  Great rvalue, soundproofing, moisture prevention and even a bit of bug repellent.  It is called Core fill500....
> 
> Tim
> 
> 
> 
> 
> While filling the voids of concrete block with a foam insulation undoubtedly would improve the R value of the whole wall some, I doubt that it would be the hoped for great improvement. The inner and outer faces of the block remain exposed to the inside air and outside air or soil, and these faces still would be connected by highly conductive webs of concrete. The heat loss through those webs of concrete still would dominate the heat transfer (thermal bridging). Even with the block voids not filled with foam, the mostly dead air cavities still have insulating value, much like the air space between an old double hung window and an exterior storm window. Improving the R value of a part of the assembly that isn't contributing much to heat loss in the first place won't help the whole wall R value too much.
> 
> It's no surprise that building highly insulated wall structures requires near elimination of thermal bridging of wood framing. This is can be done by using double frame walls, applying a continuous layer of rigid foam on the inside or outside of the wood, or using structural insulated panels (SIP, a sandwich of foam between inner and outer skins of OSB). In the case of a foundation wall, about the only way to insulate it well is to apply a continuous layer of insulation on one side of it.
> 
> Insulating on the outside lets the foundation mass be a heat storage device, which would release heat long after the fire has died. However that mass will soak up a lot of heat for a while when the fire is started, resulting in a delay of availability of heat for the rest of the house. Insulating on the inside doesn't provide the thermal storage of the concrete mass, but it does mean a faster heatup of the basement space and earlier availability of heat for the rest of the house. Then it's just a matter of leaving the basement door open or providing other means of moving air between basement and the rest of the house.
Click to expand...

+++1  Absolutely correct in my opinion.  Standard engineering knowledge for decades.


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## DickRussell

Black Jaque Janaviac said:
			
		

> ......
> In the mean time I will work on small-dollar projects to help move the air around.  Floor vents are easy.  I'm also tearing down the tongue-and-groove ceiling tiles to expose the heat directly to the floor-boards of the next floor.  In removing these tiles, I learned that for the entire portion of the tiled ceiling the previous owners never insulated that part where the joists rest on top of the cinder blocks (what do you call that?).  So $30 worth of 6" batting is going up there.



The sill (aka mudsill) rests on the foundation wall, and the floor joists rest on that. There also is a rim joist perpendicular to the floor joists and also resting on the sill, the purpose of which is to hold the floor joists vertical. Yes, in some houses, the rim was not insulated, and it's a big heat loss. There also can be significant air leakage both between the sill and the foundation and between the sill and the rim board. Stuffing a 6" FG insulation batt up against the rim board isn't really the right way to insulate the rim. FG insulation won't prevent diffusion of interior humidity through it to the rim, but it will provide insulation, resulting in a cold rim surface. That can lead to condensation on the rim and thus mold. One good way to insulate the rim is with the use of a couple of inches of spray foam. Another is to cut pieces of rigid foam to fit up against the rim sections between the joists, and then seal those pieces to the wood all around using can foam. FG batt insulation could be applied over the rigid foam for additional insulation. This latter option is an easy DYI project and not all that expensive for materials.


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## sesmith

Black Jaque Janaviac said:
			
		

> Sesmith,
> 
> Thanks.  I couldn't quite understand how not insulating the basement was causing the basement to be 80+ degrees while the next floor up could barely push 65 when the outside temps were in the 20's.
> 
> I think I have decided to insulate the top part of the foundation in the summer when I can dig down a bit.
> 
> In the mean time I will work on small-dollar projects to help move the air around.  Floor vents are easy.  I'm also tearing down the tongue-and-groove ceiling tiles to expose the heat directly to the floor-boards of the next floor.  In removing these tiles, I learned that for the entire portion of the tiled ceiling the previous owners never insulated that part where the joists rest on top of the cinder blocks (what do you call that?).  So $30 worth of 6" batting is going up there.



Do what Dick Russel suggested on your rim joists.  I used 2" xps on mine, cut pieces to fit in each rim area, and sealed the edges with can spray foam (great stuff).  It made a huge difference.  Also seal any other leaks to the outside you find (like plumbing and electrical entrances, and weatherstrip doors, etc.

One thing about cutting direct floor vents into the cellar is it isn't code (fire could spread more easily from cellar to the upstairs).  I believe you can get duct doors that close in the event of a fire.  You might check into that.


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## Black Jaque Janaviac

I could not find anything in the building code that would outlaw a floor vent.  There are required fireblocks that must go into concealed spaces which can have the effect of outlawing laundry chutes.  But these floor vents are not in a concealed space.

Do you have a reference to a code that you can point me to?

From a practical standpoint I don't think such floor vent pose any more hazard than open stairways.


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## sesmith

Black Jaque Janaviac said:
			
		

> I could not find anything in the building code that would outlaw a floor vent.  There are required fireblocks that must go into concealed spaces which can have the effect of outlawing laundry chutes.  But these floor vents are not in a concealed space.
> 
> Do you have a reference to a code that you can point me to?
> 
> From a practical standpoint I don't think such floor vent pose any more hazard than open stairways.



this should do it:

http://publicecodes.citation.com/st/ny/st/b400v10/st_ny_st_b400v10_6_sec002_par017.htm

#4 pretty much covers it, I think (this is the code in NY, though).  I'm not sure if it's the only place this sort of thing shows up, but I'm pretty sure a building inspector wouldn't allow through floor venting (at least in new construction or a remodel).  There's also mention of mechanical system ducting having to be done so that it satisfies the fire block rules I linked to above.


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## Black Jaque Janaviac

That wording is similar to Wisconsin's.  The way I read it #4 states that the openings around the vents must be sealed.  This is not supposed to prevent vents in the first place.  So maybe I'd have to goop around the floor vent with fireblock foam.

And again the entire code on fireblocks is in reference to "concealed" passages.  Without that word "concealed" in the code this section effectively outlaws stairways.

Of course that's just my interpretation but I'm not an expert either.


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## Butcher

Do you have any duct work close to your stove? If so an inline fan like this would be very easy to intall.
http://www.homedepot.com/Building-M...splay?catalogId=10053&langId=-1&storeId=10051
You would of coarse have to put a vent in the pipe to suck the warm air from your basement cieling into the exsisting heat runs. With a little imagination a themostate and a reostate could be wired in to controlle its operation. I actually did try this with our old stove but it put out so little heat it didnt work. Now that I have this Oslo huffin and puffin away I may try it again as it gets to damned hot in the basement after 3 loads.
Just a thought.


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## Black Jaque Janaviac

Butcher,

No duct work.  House has hot water baseboard.  

Yesterday evening the temps were in the teens.  Had both the NC-30 going in the basement and the Montpelier in the living room going house was comfortable to me.  74* in living room 60s in the upstairs bedroom.  Wife seemed a bit dissappointed though.


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