# Chimney through basement window opening?



## Badfish740 (Oct 15, 2008)

I am planning on installing an Englander 28-3500 add on furnace and I'm lucky enough to have what I think is an ideal layout in my basement.  On the west wall of my house there is a basement window which is not far (about 8 feet) from my oil burner.  The window is a standard basement window size (about 32" x 19" give or take) and would provide plenty of room to bring the chimney pipe through.  The construction of the opening is such that the foundation wall (cinder block) makes up the bottom and sides of the window, but the top edge is actually the sill plate of the house.  So basically the top is combustible and the bottom and sides are not.  Given that, what's the best way to bring the chimney through the wall?  I'm not all that familiar with how thimbles are properly used, etc...but basically it looks to me like the chimney pipe passes through the thimble, which simply acts as a spacer to provide an air gap-is that correct?  If so, would it be ok to simply mount the thimble (the correct size for 6" Class A double wall pipe) in the opening with the thimble resting on the bottom (non-combustible) edge of the window opening, and closing in the rest of the opening with bricks and mortar?  This way the layers of protection for the combustible wood sill plate above the pipe would be as follows:

-Insulation layer inside chimney pipe
-Air gap inside thimble
-Approximately 10" of non-combustible materials (bricks/mortar)

And now a follow up question-once the thimble is installed in the wall and the chimney pipe is passed through, then what?  Is a tee simply attached to the outside (with a proper support brace on the bottom), redirecting the chimney upward at that point?  Now to the inside-do I simply connect black stove pipe to the Class A sticking out of the thimble with an elbow and connect that to the stove itself?  Sorry for all of the convoluted questions, but I'm trying to get an idea of what I need to buy.  I have a source for my chimney pipe and related pieces (bottom support, wall bands, cap, etc...), so if all I need is a thimble, some bricks, and a bag of mortar mix, I don't need the $350 Duravent kit from Home Depot right?

*EDIT*

I just realized that I posted this in the boiler room when it should probably have gone in the hearth room-mods, please move it if it should be moved.


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## begreen (Oct 15, 2008)

In essesence you have it correct. The window would cease to be an openable window. An area would get framed in for the 12"x12" thimble. That will establish a safe sleeve for the class A pipe. You could still have glass in the remaining part of the window if you want some light, or you could brick or board it up. Class A clearance is 2" so you needed worry as much about it as about the interior connecting pipe clearances. I'd consider using double wall pipe on the interior unless you have 18" clear in all directions for the single wall pipe. From the sounds of things, the floor joists will be less than 18". With an exterior chimney already cooling the flue gases, I think you would benefit from using Simpson DVL (double-wall) on the interior run. If that run is horizontal, be sure it has at least a 1/4"/ft rise towards the exterior chimney. With the DVL pipe you will still need 8" clearance above it and 6" clearance to the side wall.

Simpson has a great installation manual online that I think will help you a lot. It has good illustrations. Look for DuraTech 5-8" in the second popup menu (installation instructions PDF) http://www.duravent.com/?page=ts.php

Edit: No problem, that was me that moved the post to the boiler room for better coverage on future hot-air furnace questions. This is a better forum for whole house wood heating questions and advice. There's good folks hanging out here.


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## Badfish740 (Oct 15, 2008)

BeGreen said:
			
		

> In essesence you have it correct. The window would cease to be an openable window. An area would get framed in for the 12"x12" thimble. That will establish a safe sleeve for the class A pipe. You could still have glass in the remaining part of the window if you want some light, or you could brick or board it up. I'd consider using double wall pipe on the interior unless you have 18" clear in all directions for the single wall pipe. From the sounds of things, the floor joists will be less than 18". With an exterior chimney already cooling the flue gases, I think you would benefit from using Simpson DVL (double-wall) on the interior run. If that run is horizontal, be sure it has at least a 1/4"/ft rise towards the exterior chimney. With the DVL pipe you will still need 8" clearance above it and 6" clearance to the side wall.
> 
> Simpson has a great installation manual online that I think will help you a lot. It has good illustrations. Look for DuraTech 5-8" in the second popup menu (installation instructions PDF) http://www.duravent.com/?page=ts.php



Thanks!  I was hoping my post wasn't too confusing to follow.  I will definitely use double wall pipe on the inside as well because the inside horizontal run will probably be within 12-14" of the floor joists.  I'll simply block up the window with masonry as that seems to be the most hassle free way to go.


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## Eric Johnson (Oct 15, 2008)

I see many of those in my travels.


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## begreen (Oct 15, 2008)

Here's a basic diagram. I've shown it with the thimble right at the bottom of the window in case clearances are very tight. But normally you would carry the bottom window (wood) plate all the way across if clearances are ok. 

Get the Simpson DuraVent catalog and the DuraTech installation guide and you'll be off to a good start.


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## Tony H (Oct 15, 2008)

If the wall is cinder block it would not take much to core a hole. I rented a drill and bit to make 2 holes in my foundation the one thru 8" of reinforced concrete took 6 hours to core the one in cinder block took 10 minutes. If you are ok with rough edges you don't even need a drill you can use a "star bit" and hammer to make a hole we used them all the time when running cable thru block walls.


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