Clean Windows = Warmer House?

[iod0816]

Interesting observation... I've been lazy sometimes, not cleaning the three bay windows on the Quad 4100i well because its cold out and cleaning a hot window doesn't work well.

But every time I do clean it, I get so much more heat outta the sucker than before. I know ash is an insulator but I didn't figure clean windows did anything but make it look better. But WOW there is a noticeable difference clean vs not clean.

Anyone else already know this or experience this? I wish they had put something in the manual, like CLEAN WINDOW = MORE HEAT DUMMY!

 

[NH_Wood]

Me thinks you are seeing a better light show and psychologically experiencing warmer temps! Cheers!

 

[Intheswamp]

I can't comment one way or the other on this but I do have a question...

Do the windows have an ash film on them that simply wipes off or is it more of a creosote-like film that requires a little scrubbing?

It does seem that you might lose some radiant heat from the flames if there is something blocking the wavelengths from exiting through the glass. To what degree (no pun intended ) this will impact heat output I have no idea.

Best wishes (and waiting for some input from some of the experienced burners),
Ed

Edit: I guess I did comment, didn't I?

 

[Wood Duck]

Does radiant heat actually pass through the glass? I would guess no, it doesn't pass through as electromagnetic waves. Visible light passes through but doesn't have very much energy compared to longer wavelengths. My first thought about this subject was that the ash on the glass blocks radiant heat transfer through the glass, but now I am not so sure. I think the way heat transfer through the glass works is the fire radiates heat to the glass, the glass absorbs the heat and gets hot, then the glass re-radiates heat into the room. Maybe the ash layer makes the glass reflect more of the radiant heat rather than absorb it, so the glass stays cooler and thus radiates less heat into the room.

 

[snowleopard]

My first thought when reading the title of this post was that you were talking about south-facing house windows--and my thought was "Well, duh! Of course! Why didn't I think of that?" Made me feel ambitious about getting out there and washing the windows when the weather warms up. (I can be a little slow on the uptake, seeing as how this is the Hearth Room . . . :roll: ). But still, an epiphany is an epiphany, and I'll take it. Stands to reason that even a thin layer of dust is reflecting heat, whether solar or wood. You've given me a reason to get busy and get that done on a regular basis.

And thanks for the rationale. I give my stove glass a wipe several times a week, because I like looking at the fire. Now I can tell myself and any critics that it's because it's more efficient.

 

[DonNC]

Wood stoves have ceramic glass

Radiant heat passes through ceramic glass. You are correct in your observation

http://www.vetrotech.com/us/download/Heat transfer and fire.pdf

A good article that speaks directly about wood stove glass. Copy and past the URL. The forum removes the percent symbols that should be in the gaps in the url

 

[woodgeek]

But the ceramic glass has a coating on it to intentionally block radiant energy output (for more eff combustion). How much leaks through is a complicated question. If the OP is seeing a real effect, it should be accompanied by a change in burn profile/duration/temp, etc. Was it?

 

[amellefson]

I have the same stove and just cleaned my glass before reading this thread. Sorry, I can't say one way or the other. Hot is Hot. I will say the only build up that I get is thin ash in the corners and side lights.

 

[pen]

Does radiant heat actually pass through the glass? I would guess no

Yep, it does. If the glass were completely black, then it would be blocked. Well not completely blocked but the visible spectrum and some others wood be.

pen

pen

 

[cptoneleg]

I thought it was like washing your car ( clean car seems to run better) About 3 times this season I shut it down and detail it out, and yes it runs better :exclaim:

 

[NH_Wood]

Are we really thinking that cleaning the glass is resulting in noticeable heat output in the home??!! I'd have to see some real good numbers to buy this one. Cheers!

 

[DonNC]

Are we really thinking that cleaning the glass is resulting in noticeable heat output in the home??!! I'd have to see some real good numbers to buy this one. Cheers!

Easy enough. Find something suitable to hide the glass after you have a good fire going. Now sit on the floor 4' in front of you heater and feel the warmth on you body/face. Now get up and remove the object from in front of the glass and instantly feel the heat on you.

If it was heat being inducted through the air or by convection then it would still be there.

Put a fan to blow cross ways between you and the heater. It will remove any inducted or convected heat from coming your way. Do you feel the heat on your face now? thats radiant heat.

 

[NH_Wood]

Are we really thinking that cleaning the glass is resulting in noticeable heat output in the home??!! I'd have to see some real good numbers to buy this one. Cheers!

Easy enough. Find something suitable to hide the glass after you have a good fire going. Now sit on the floor 4' in front of you heater and feel the warmth on you body/face. Now get up and remove the object from in front of the glass and instantly feel the heat on you.

If it was heat being inducted through the air or by convection then it would still be there.

Put a fan to blow cross ways between you and the heater. It will remove any inducted or convected heat from coming your way. Do you feel the heat on your face now? thats radiant heat.

I'm with you on the above. But, wouldn't the radiant heat hitting the object in front of the glass warm the object and the object would then radiate that heat back into the room? Wouldn't this be the same for the dirty glass? The heat energy isn't magically disappearing when the glass is dirty. If the window were completely replaced with more cast or steel, would the heat output in the home drop dramatically? Again, what I'm saying is could cleaning the glass contribute to noticeable heat increase in the home? Still don't buy it. I need BK to run some numbers! :cheese:

code

 

[DonNC]

The gist of the question is..

How much more heat comes through the window vs steel.

In searching for info on this thread I came across a video showing two different glass barriers.. one of them ceramic and one glazed.. and how they held up to a raging fire on the other side of the glass. (fire safety video) The results were dramatic. Im not sure how you would measure it statistically though.

The original question was, does heat radiate through the glass. The poster thought he detected a difference and he was correct. It was noticeable. If every drop in the bucket counts, then clean those windows

 

[pen]

Anything that is hot will radiate infrared (thermal) energy. Glass can also transmit the visible spectrum and uv.

pen

 

[iod0816]

I mean whether this is a "prove-able" theory or not, I'm sitting here in front of the stove, clean sparkling window and it just feels warmer. Yes feelings are relative but it was just a noticeable thing because well I did notice it after I cleaned it. Same consistent temps in the good ol state of MA, same types of wood I'm burning, same levels of air input that made me notice this...

I'm not saying just carbon dirty glass either, I'm saying not cleaned for a week (s), ash covered class because of how well ash is an insulator. I've got coals enough to start a fire 12+ hours later after a burn, air all the way out so I think it would make sense, no? Oh well, I'm convinced and will make more of an effort to keep clean!

Thanks for the responses and good discussion!

 

[LLigetfa]

My guess is that it's not just the glass that is getting a good cleaning. I get much more heat from my stove when I remove all the ashes. I burn dry wood so my glass stays relatively clean.

 

[DiscoInferno]

I often feel like I'm seeing the same - clean the ash off the glass and get more radiant heat out the front, with the Ultima. There's no question the ash blocks visible wavelengths, so presumably it blocks some of the infrared also. Not sure if it seems to be more total heat though, or just a different distribution.

 

[Pagey]

I just cleaned every window in the house. And though I personally feel warmer from the activity, the house feels the same. :lol:

 

[woodgeek]

Dude, give me a break. If you think the radiant energy from the fire goes through the window, then the expt is to compare radiant heat with the doors open and closed! And I think we all know the radiant flux we feel is WAY higher with the doors open than closed. The radiant heat you feel sitting in front of the window is b/c the window itself is hot, so it radiates too. To a first approximation, if you put steel plate in place of your windows, you would feel pretty much the same thing.

Along the same lines, point an IR therm at the doors when closed, and then at the fire with the doors open. Then point the IR through the hot, open window at a cold wall. Does it now read the temp of the wall, or the same hot window temp? The huge diff in readings will suggest that the radiation the IR thermo measures sure doesn't get through. Of course, the stove puts out energy at different wavelengths that the IR therm reads as well, but basically, the window blocks radiant energy, and is engineered to do that.

 

[DonNC]

Dude, give me a break. If you think the radiant energy from the fire goes through the window, then the expt is to compare radiant heat with the doors open and closed! And I think we all know the radiant flux we feel is WAY higher with the doors open than closed. The radiant heat you feel sitting in front of the window is b/c the window itself is hot, so it radiates too. To a first approximation, if you put steel plate in place of your windows, you would feel pretty much the same thing.

Along the same lines, point an IR therm at the doors when closed, and then at the fire with the doors open. Then point the IR through the hot, open window at a cold wall. Does it now read the temp of the wall, or the same hot window temp? The huge diff in readings will suggest that the radiation the IR thermo measures sure doesn't get through. Of course, the stove puts out energy at different wavelengths that the IR therm reads as well, but basically, the window blocks radiant energy, and is engineered to do that.

So then, ... Woodpeek, your saying adiant heat does not pass through ceramic glass?

 

[CountryBoy19]

I'm with you on the above. But, wouldn't the radiant heat hitting the object in front of the glass warm the object and the object would then radiate that heat back into the room? Wouldn't this be the same for the dirty glass? The heat energy isn't magically disappearing when the glass is dirty. If the window were completely replaced with more cast or steel, would the heat output in the home drop dramatically? Again, what I'm saying is could cleaning the glass contribute to noticeable heat increase in the home? Still don't buy it. I need BK to run some numbers! :cheese:

code

Radiant heat hitting the object then be re-radiated would be greatly diminished because that heat would also be radiating back into the fire as well so it's really not a direct comparison.

Dude, give me a break. If you think the radiant energy from the fire goes through the window, then the expt is to compare radiant heat with the doors open and closed! And I think we all know the radiant flux we feel is WAY higher with the doors open than closed. The radiant heat you feel sitting in front of the window is b/c the window itself is hot, so it radiates too. To a first approximation, if you put steel plate in place of your windows, you would feel pretty much the same thing.

Along the same lines, point an IR therm at the doors when closed, and then at the fire with the doors open. Then point the IR through the hot, open window at a cold wall. Does it now read the temp of the wall, or the same hot window temp? The huge diff in readings will suggest that the radiation the IR thermo measures sure doesn't get through. Of course, the stove puts out energy at different wavelengths that the IR therm reads as well, but basically, the window blocks radiant energy, and is engineered to do that.

Absolutely nothing that you have suggested is logical or proper in determining if the glass is allowing radiation to pass.

It is absolutely not possible for any glass to pass 100% radiation. If glass passed 100% radiation then it wouldn't ever heat up from radiation hitting it. If you have a stove with an air-wash to keep hot convective currents off the glass then this means your glass will never get hot.But guess what, even with the air wash the glass gets hot. So we have now established that the glass at least partially absorbs radiant heat. However, with suggestion #1 above you illogical concluded that bc your glass absorbs some radiant heat it must absorb it all.

Did it occur to you that maybe it is only absorbing some radiant heat? When I shoot the temp of my glass it normally shows around 1000 degrees. Do you think my glass is really that hot or do you think maybe there is also some radiation passing through and throwing off the temp? I think the temp and/or radiant feeling you get is a combination of both.

next you illogically concluded that because your IR thermo says the fire is hotter than the doors that they aren't passing radiation is along the same lines. It doesn't at all prove that no radiation is coming through the doors, it just proves that not all of it is coming through.

Lastly we come to the final very, very wrong conclusion that when the IR thermo is pointed through the door at a cold wall the radiation doesn't pass if the temp doesn't read similar to the cold wall. If you think that will tell you anything then you clealry don't understand radiation. The IR thermo is basically just "adding up" all the radiation it is seeing. The hot door is still radiating heat itself, the radiation of the wall is so small compared to the door that you will, in all reality, just be "seeing" the door.

A better comparison to determine if you're seeing any radiation through the glass is to point the IR thermo at the closed, hot door with a good, hot fire going, note the reading. Then open the door and point the IR thermo through the door at a cool wall. If the second reading is any lower than the first then you are, in fact, seeing radiation through the glass.

No need to let me know your results, I already know the answer.

BTW, to the OP, yes, I also notice an increase in radiant heat after cleaning the glass.

 

[Milton Findley]

Back in the dark ages I was a tech weenie for a company that makes infrared dryers for paper machines. We used a highly polished quartz plate to pass the IR and visible light to the paper as it passed under the dryer. We paid a lot of money for the highly polished quartz plates. The manufacturer wanted to sell use frosted quartz, as it would decrease our costs and his time to manufacture. I hired a physicist to answer the question for us.

There was a decrease in the IR radiation through the frosted glass, but it was less than 3% as measured in a laboratory.

Perception of temperature is a combination of tactile and visual and expectations based on our experiences. If you perceive that the radiant output of the stove has increased, it indeed feels warmer.

Now, having studied neuropsychology for a couple of decades, I will venture to say that nobody is so finely calibrated that they can tell a 3% difference in the radiant output as it is a change that is insufficient to register to our analogue nervous system. Our expectations are the difference here, and there is no use arguing over it.

Having said all of that, my IR gun says that dirty spots on my glass are 5 degrees warmer that clean glass. Now, that is way less than 3% of the temp indicated. Like .05%.

 

[Milton Findley]

Does radiant heat actually pass through the glass? I would guess no, it doesn't pass through as electromagnetic waves. Visible light passes through but doesn't have very much energy compared to longer wavelengths. My first thought about this subject was that the ash on the glass blocks radiant heat transfer through the glass, but now I am not so sure. I think the way heat transfer through the glass works is the fire radiates heat to the glass, the glass absorbs the heat and gets hot, then the glass re-radiates heat into the room. Maybe the ash layer makes the glass reflect more of the radiant heat rather than absorb it, so the glass stays cooler and thus radiates less heat into the room.

Radiant heat is photonic, radio is electromagnetic. Stoves ain't radios. Not all photons are moving fast enough to be visible.

 

[woodsmaster]

My guess is that it's not just the glass that is getting a good cleaning. I get much more heat from my stove when I remove all the ashes. I burn dry wood so my glass stays relatively clean.

+ 1