# broken window from fireplace heat?



## Runestone (Jan 7, 2007)

We have a masonry heater. The firebox is located about 8 1/2 feet from our bank of south facing windows. This is the first year we are using the heater as our main source of heat and burn two fires per day.
DH was home when he heard a cracking sound. One of our newly installed (summer 2011) large windows had cracked.
He says it has to do with the heat/cold etc. and I have no reason to doubt his explanation. HOWEVER, it seems to me that it shouldn't have happened and that the window glass was defective?
Any ideas....?


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## Cabin Fever (May 10, 2002)

In our cabin we have a woodstove about 16-inches from two windows on either side of it. The cabin has been ice cold - with outdoor temps of -20ÂºF and indoor temps of around 0ÂºF - when we've started a blazing fire in the stove. After several hours, the cabin will be 80Âº-plus and when its still -20ÂºF outside. The windows were fine.

I think you either got a defective window or your house settled/shifted which caused the window to crack.


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## commonsense (Jun 1, 2008)

I agree with Cabin Fever, probably something other than the masonry heater. We've had our woodburning stove situated under a window for years with no problems.

...off topic, sort of, how do you like your masonry heater?


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## Danaus29 (Sep 12, 2005)

No, the window shouldn't have broken. I hope you have a warranty on it. 
My guess would be that the window was never properly supported in the opening.


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## Runestone (Jan 7, 2007)

thanks...I didn't think it should have broken either. Since DH was the installer AND I know he is the world's most meticulous person, I'm suspecting a defect in the window.
I don't think we've had any settling since this is built on a slab that has been there for 2 years now but I suppose anything is possible!
CS...I LOVE the masonry heater. Until this year, we had convectair baseboard heating. I have found the even when the house is around 16C...(60F), it still feels comfortable. That was not the case with the electric heat.
Now, all I need to do is solve the breaking window


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## Danaus29 (Sep 12, 2005)

Oh how I know those meticulous laborers. Married to one myself. 
Defect in the window then. Heat would have had to be much higher and directly on the window in order to get it to break.


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## Evons hubby (Oct 3, 2005)

I am guessing the window was fit too close to the framework when installed. gotta leave a little room for expansion with temp variations and humidity changes.


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## gone-a-milkin (Mar 4, 2007)

Yvonne's hubby said:


> I am guessing the window was fit too close to the framework when installed. gotta leave a little room for expansion with temp variations and humidity changes.


This is my guess too. I have done the same thing. 
Windows need a bit of 'play'. Not much, but if they are super snug in dry weather the wood will swell in humidity.

Live and learn.


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## wharton (Oct 9, 2011)

Glass can be stressed by impact and relieve that stress at a later time. For instance you can have a kid run into a patio door glass unit, or have a large bird fly into a window and the window will at first appear undamaged. Then weeks, or months later it cracks or shatters. I worked in millwork sales in the past. Every so often a customerwould show up, clueless as to why their patio door just shattered as they sat around the table one night? I could often get the manufacturer to replace the damage under warranty, but it was done as a good will gesture, in reality the manufacturer had nothing to do with the issue. In the OP's case it is possible that the glass was physically stressed by impact, even if they never saw anything occur, and the heat of the fireplace added thermal stress to the mix, creating the crack. 
Who knows? This may have nothing to do with the situation, but the info. came from several window manufacturers I did business with.
OTOH, if the unit was home built, with a glass mounted in a frame built on site, there are two possible issues. First, as stated previously, it can't be too tight in the frame. Second, it needs to be installed on a pair of spacer blocks, which are small plastic blocks the are used to shim the glazing up off the sill. this allows the bottom to have some expansion clearance and prevents a bowed sill from stressing the glass.


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## Ross (May 9, 2002)

Certainly not the heat, unless you threw a bucket of hot water at it!  . Most likely it wasn't installed properly.


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## TnAndy (Sep 15, 2005)

Cabin Fever said:


> I think you either got a defective window or your house settled/shifted which caused the window to crack.


Yep.....I'd agree. Many times in the manufacture of windows, they get a small nick in the edge of the glass......nothing happens until it gets installed, and a slight pressure is applied from a very slight settle in the house, OR even a temperature difference between inside and outside ( that would never affect a normal piece of glass ). Think of a "star" ding in your car windshield....only appears to be a very small ding.....but often will turn into a crack all the way glass if you let it go unrepaired....that's WHY insurance companies will often pay the full cost of a guy to come out and repair the "ding", because it's a whole lot cheaper than replacing a windshield.


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## SteveO (Apr 14, 2009)

A couple of ??
Does the fireplace face this window
and what else has changed in the room You have added more window I am guessing.
How hot is your fire and how far off the floor is the window.
I am leaning toward the hot south sun and your hot fire being to much for the window.
don't know if the manufacturer would stand behind it or not being self installed
Where did it crack and did it go all the way across at first
And last but not least who was the manufacturer
Inquiring minds like to know
Stay warm anyhow
Steve


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## texican (Oct 4, 2003)

I've got a home built woodstove (piped for free natural gas) that sometimes get's cherry red. Three windows are three feet away max... they get hot, and have never cracked/broke, even when it was in the teens outside...

I'd say bad glass. Or ghosts. 

I'd replace the glass, and say some kind words to any house spirits you might be cohabitating with.


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## cowkeeper (Feb 17, 2007)

Hi Runstone, Another OT - Did you build your own masonry heater, and if so what brand of inner components? (I am also in Ontario) I would love to build one to replace the wood stove that is our sole heat source. Thanks.


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## Runestone (Jan 7, 2007)

Hi cowkeeper....we build our own masonry heater and we used Crossfire for the components. DH liked Crossfire for their customer service. It's a beautiful addition to the house...now I just might have to chat with the 'house spirits'  or perhaps the glass manufacturer!

SteveO - this is a new addition on the house so new slab, new south facing windows, and the fireplace faces bank of windows. The crack started part way up the window on one side and progressed upward. It has not gone across the window. We haven't had any sun for days...
the windows are manuafactured by Jeldwen in Canada.


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## SteveO (Apr 14, 2009)

I would suggest take some pictures and contact your supplier. They should want to send a Jelwen company rep out to look at it. Since these are new windows and new construction they should stand behind the replacment of the window. It doesnot sound like a stress crack from install to me.
I would pull the inside trim to confirm you didn't cause the issue by framing it to tight and send a picture of that also.
What did you put in the void between the window and the framing? Foam or fiberglass. PLease say fibergalss or they will say you didn't give the window enough room to expand and caused the problem your self.
I did a project with about 200 windows and had 3 crack getting them replaced was not an issue.
I would also use the term my contractor or my installer. Not that you are not qualified to install a window it helps to seperate you the home owner who suppied the windows for installation from a homeowner that shouldn't install a window
Start with the place you bought them then climb the food chain and call Jeldwen or as I do sometimes start at both ends so they are forced to talk to each other. But do it NOW and date and keep copies of it all
This is a slow time for them make the most of it.
Steve


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## NorthCountryWd (Oct 17, 2008)

Cabin Fever said:


> I think you either got a defective window or your house settled/shifted which caused the window to crack.


My money is on defective as well. We had a double paned window that lost it's seal and the interior window imploded on a really cold morning with the stove running. It was about 80 degrees in the house and -42 on the thermometer outside.

I was told at the building supply that the interior panes can't handle that kind of temp differential.


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## fordson major (Jul 12, 2003)

it is not fair not to show off the masonry heater Runestone!! (and i know i have to come see it someday!)


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## Runestone (Jan 7, 2007)

Okay....here's a couple of the masonry heater  All the stone was hand picked at a quarry near us and the brick is antique brick purchased from a masonry store. Also here's the windows


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## Ross (May 9, 2002)

Well I'm not a fan of Jeldwen windows but if I remember right they want continuous support on the bottom. It looks like they're shimmed at the corners for support.


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## Missy M (Mar 2, 2007)

Didn't read the entire post, so I hope I'm not repeating. I know a car windshield will crack like this from a heat change if it has a chip in it. My guess is with the others - the window was defective.


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## SteveO (Apr 14, 2009)

Any news from jeldwen? The install looks good to me.
Steve


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## Runestone (Jan 7, 2007)

The Jeldwen rep should be in our neck of the woods in a few weeks...I guess one rep covers thousands of square kms ...so it's a waiting game for them to show up. 

The crack starts part way up the window and is now making it's way upwards slowly through the centre of the window. We've taped it but it still keeps creeping when the weather changes. It's been really cold and for the past couple of days - sunshine.


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