An observation, and a question

[drewmo]

The observation:
It's 10-20 degrees below 0, and it's a struggle to keep the house warm. Hovers mid-50s to 60 upstairs with the stove downstairs. Now, at 20-30 above, we're toasty and cruising in the mid to upper 60s upstairs. Even the young kids ask why it is so warm.

The question:
Why does the interior temp rise only +/- 10 degrees inside when the outside temp rises 40-50 degrees?

It kind of makes sense for some reason, but I just can't seem to explain it

 

[JA600L]

Were you pushing the stove harder when it was colder?

 

[DougA]

All stoves generate a maximum amount of heat, measured in BTU's (British Thermal Units) A BTU is the amount of energy needed to cool or heat one pound of water by one degree Fahrenheit. So, the stove when fully loaded can heat the same amount, whether it is 30 or -20 outside. The colder it is outside, the colder it gets inside, based on your house insulation and air leakage.

Same problem when it's -20 outside and no wind or -20 outside and a gale force wind. The wind is forced into the house - actually, the air in the house is sucked out of the house by the vacuum effect on the leeward side - and the warm inside air gets replaced by cold outside air.

I bet you skipped a lot of physics classes.

I only got a 53 in physics because I spent most of my time making and firing spitballs at people in the class.

 

[Mag Craft]

Well when I was in school, wood burning stoves and how they relate to physics was the last thing on my mind.

Now when I had to make a living then things changed.

Good explanation on the wind. I have to be careful on windy days opening the wrong door or window will suck the fire right out of my stove.

 

[Rearscreen]

Insulation in reverse? Like if you took a cold beer out of an insulated cooler then closed it up, the air inside would stay cold for a while.

 

[drewmo]

I bet you skipped a lot of physics classes.

That I did and is an apology for this thread. I understand the thermal envelope and how insulation, air sealing and air pressure play on the dynamics of this drafty house. My simple thinking is that if it is 30 degrees warmer outside from a day earlier, it should be damn near 30 degrees warmer in my house if I'm introducing the same amount of heat from the stove. Simple being the operative word. The difference here is the temperature of the air infiltrating into the house at -20 or +20 is huge, yet it marginally affects the interior temperature.

 

[Oldman47]

Think about it this way and maybe it will make sense. Your stove can only add x amount of heat to the building so that is a fixed number, whatever it is, except that it is based on how hot the stove is compared to inside air temperature. The building only loses heat based on how much temperature difference there is across any insulation and how good the insulation is. The bigger the difference inside to outside the faster you will lose heat but, don't forget, that stove is still providing the same heat into the system more or less. As the inside to outside temperature difference increases, you lose heat faster but remember the stove is using maybe a 500ºF surface to feed a 65ºF environment. The huge temperature difference between the stove and the house doesn't change much so the heat supplied to the home doesn't change much but the inside to outside temperature difference has changed a lot so the heat loss part of the equation has really changed a lot. Until the heat loss and heat supplied are equal, the temperature will be changing and the house will be cooling.

 

[Sawset]

The stack effect can create a lot of infiltration, more on cold days, less on warmer days. Add up all the cracks and holes and it's like trying to heat with a window open. An energy audit with a blower door test could catch some of that.