# Thread: How cold does it have to get for pipes to freeze?

1. Member
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Nov 2007
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Originally Posted by Rich Engelhardt
We have a ..situation...
We're having a dispute with one of our tenants.
Our lawyer has advised us not to enter the property for the next ten days.

We're concerned that the tenant is going to shut off the heat.

Temperatures are supposed to be in the low 30's as a high during the next four days and lows in the upper 20's over that period.

The house is insulated - but - not as well as a newer house. It was built in the 1950's.

According to the long range forecast, the tempertures are suppossed to be 30's to low 40's in the day and upper 20's to low 30's at night - through next Thursday.

I'm thinking that it should be ok but - you never know.
I'm a bit bored.
Assume they turn off the heat. Let's use math to waste some time

Heat loss in BTUs/hr is
HL = U-value * Area of wall (sq ft) * temperature difference
U-value = 1/ <sum of r values of layers>

(U-value is actually standardized to certain conditions, but it's all we've got :P)

A 2x4 stud wall with 3.5 inches of fiberglass is about R-15 (and a U value of 1/15)

IE the wall is 8x20, you would lose (1600*temp difference/15) BTUs an hour through that wall.

How many BTU it takes to raise or lower the air in your house one degree depends on the volume, but it's roughly 0.02 BTU to raise 1 cubic foot of air 1 degree.

Basically, as it gets closer to the outside temperature, the rate of cooling will slow down.
Worst case, assuming you have a 1600 sq ft home (which was average in 1950), and it was only walls (this is the worst case), and it was 35 feet tall (a lot of zoning codes in the country allow 35 feet from top to bottom), and it was square (40 * 40 ft), you have 40 * 35 feet of wall space on each of the 4 walls, or 5600 sq ft of wall space. Assuming it started out at 68, it will initially lose 14187 btu/h through the walls when the outside temp is 30 degrees (and the btu/h will decrease quickly as you lose temperature in the house).

You would have roughly 56000 cubic ft of air in this house (40*40*35), and it will take 56000*0.02 = 1120 btu to effect a 1 degree change in air temperature.
So over the first hour, it will lose 12.6 degrees.
The second hour, we start out at 68-12.6=55.4 and if it was still 30 degrees outside, it would lose 9482 btu that hour, or 9 degrees, roughly.
So the third hour, we are down to 46. If it was still 30 degrees outside, we'd lose 5973 btu that hour, or 5 degrees, roughly.
So the fourth hour, we are down to 41. If it was still 30 degrees outside, we'd lose 4100 btu that hour, or 4 degrees, roughly
So the fifth hour, we are down to 36. If it was still 30 dgrees outside, we'd lose 2240 btu that hour, or 2 degrees
So the sixth hour, we are down to 34. If it was still 30 degrees outside, we'd lose 1490 btu that hour, or 1.something degrees

etc
Again, remember these calculations are very much overestimating the temperature loss because it changes every instant as the temp difference goes down. I don't have mathematica to do this properly and am too lazy to do it by hand.

But basically, after the first day, inside your house is going to pretty closely follow the outside temperature, lagging behind by a few hours.

For the pipe containing your water, copper pipe heat loss for fluid inside 3/4 pipe with a 40 degree temp difference is 29 BTU/hr per foot. So it will take slower to follow the temperature, but there is less of it.
Water takes about 143 btu per lb to convert to ice (this is pure water).

Multiplying it all out, this theoretical house may actually have water freezing after the first day, at night, but its going to be close.
There are other things at play. If it's city water, it will tend to have a lower freezing point due to impurities. Additionally, once you hit back to the line you are sharing with your neighbors, , the heat from that water (at 40 degrees) is going to diffuse through the rest of the pipe/water over time. Same with all the other water that may get over 30 degrees.

All this said, i'd say
1. Its going to be close as to whether anything freezes. If it gets into the low 20's for more than a few hours, i'd be worried. If it stayed 30 degrees the whole time, i wouldn't be worried.
2. I have successfully used math to waste time.

2. Originally Posted by Daniel Berlin
I'm a bit bored.
Assume they turn off the heat. Let's use math to waste some time

Heat loss in BTUs/hr is
HL = U-value * Area of wall (sq ft) * temperature difference
U-value = 1/ <sum of r values of layers>

(U-value is actually standardized to certain conditions, but it's all we've got :P)

A 2x4 stud wall with 3.5 inches of fiberglass is about R-15 (and a U value of 1/15)

IE the wall is 8x20, you would lose (1600*temp difference/15) BTUs an hour through that wall.

How many BTU it takes to raise or lower the air in your house one degree depends on the volume, but it's roughly 0.02 BTU to raise 1 cubic foot of air 1 degree.

Basically, as it gets closer to the outside temperature, the rate of cooling will slow down.
Worst case, assuming you have a 1600 sq ft home (which was average in 1950), and it was only walls (this is the worst case), and it was 35 feet tall (a lot of zoning codes in the country allow 35 feet from top to bottom), and it was square (40 * 40 ft), you have 40 * 35 feet of wall space on each of the 4 walls, or 5600 sq ft of wall space. Assuming it started out at 68, it will initially lose 14187 btu/h through the walls when the outside temp is 30 degrees (and the btu/h will decrease quickly as you lose temperature in the house).

You would have roughly 56000 cubic ft of air in this house (40*40*35), and it will take 56000*0.02 = 1120 btu to effect a 1 degree change in air temperature.
So over the first hour, it will lose 12.6 degrees.
The second hour, we start out at 68-12.6=55.4 and if it was still 30 degrees outside, it would lose 9482 btu that hour, or 9 degrees, roughly.
So the third hour, we are down to 46. If it was still 30 degrees outside, we'd lose 5973 btu that hour, or 5 degrees, roughly.
So the fourth hour, we are down to 41. If it was still 30 degrees outside, we'd lose 4100 btu that hour, or 4 degrees, roughly
So the fifth hour, we are down to 36. If it was still 30 dgrees outside, we'd lose 2240 btu that hour, or 2 degrees
So the sixth hour, we are down to 34. If it was still 30 degrees outside, we'd lose 1490 btu that hour, or 1.something degrees

etc
Again, remember these calculations are very much overestimating the temperature loss because it changes every instant as the temp difference goes down. I don't have mathematica to do this properly and am too lazy to do it by hand.

But basically, after the first day, inside your house is going to pretty closely follow the outside temperature, lagging behind by a few hours.

For the pipe containing your water, copper pipe heat loss for fluid inside 3/4 pipe with a 40 degree temp difference is 29 BTU/hr per foot. So it will take slower to follow the temperature, but there is less of it.
Water takes about 143 btu per lb to convert to ice (this is pure water).

Multiplying it all out, this theoretical house may actually have water freezing after the first day, at night, but its going to be close.
There are other things at play. If it's city water, it will tend to have a lower freezing point due to impurities. Additionally, once you hit back to the line you are sharing with your neighbors, , the heat from that water (at 40 degrees) is going to diffuse through the rest of the pipe/water over time. Same with all the other water that may get over 30 degrees.

All this said, i'd say
1. Its going to be close as to whether anything freezes. If it gets into the low 20's for more than a few hours, i'd be worried. If it stayed 30 degrees the whole time, i wouldn't be worried.
2. I have successfully used math to waste time.
Take into consideration the thermal transfer of windows. Yes, they do lose heat, but they also gain heat during the daylight hours and create a "greenhouse" effect on the interior temperature. Also, the inside of an insulated/ unheated structure doesn't normally fall to the same temperature as the outside air.

3. Originally Posted by Brian Elfert
Minnesota has a law that does not allow utilities to turn off gas/electric during the cold months. I think plenty of people take advantage of the law and simply don't pay their bill until absolutely forced to. Service can be disconnected in the spring unless a payment plan is established.
From my understanding if a person were behind on their utility bills, they have to set up and stick to a reasonable payment plan. If they fail to do this then they can be disconnected even if it is winter.

4. Originally Posted by Brian Elfert
Minnesota has a law that does not allow utilities to turn off gas/electric during the cold months. I think plenty of people take advantage of the law and simply don't pay their bill until absolutely forced to. Service can be disconnected in the spring unless a payment plan is established.

I can assure you that people DO take advantage of this. Many of those cases that I'm aware of, they HAVE the money to pay their bill. However they want to spend that money on something else, and will claim they can't pay it right up to the moment before disconnection, then pay it to keep their lights on. I really wish I could elaborate more on this, you'd be amazed.

It's sad really, cause it makes it nearly impossible to help out those who truly need it/deserve it, without the rest taking advantage and working the system to the fullest.

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Kevin I know of some people like you speak of. They and their friends have figured out how to game the system. They know the right things to say to achieve their desired result. Pride and self respect? What a quaint old fashioned notion.

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could you enter the premises with a police escort? there must be a way to have access to prevent possible major damage to this dwelling.

7. Assuming you have Natural Gas, is there an outside meter that you can read and check to see if fuel is being used?

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Originally Posted by Daniel BerlinI'm a bit bored.
LOL! Yeah - Christmas Day afternoon can get like that! I had some "down time" around noon yesterday right before we headed out for the Christmas dinner w/the wife's side.
Thanks for the calculations! BTW the house is listed on the county auditors website as being just under 900 sq feet.

Re: utilites.
We open ourselves to criminal charges if we shut off any of the utilites.

Re: access.
We're currently looking into gaining access to the property. Since it's a civil matter andinvolves real porperty, I believe the county sherriff has jurisdiction, not the police.
We have a call into our lawyer to see how we should proceed.
Due to the circumstances, even setting foot on the property is trickey.
Thank God we're having a warm spell. That's been the only thing keeping my wife and I sane the last few days.

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you will need to call the sheriff dept and ask if they are the person in charge if the paperwork do not say whom office issued it, I were evict once and also give up a house because of a tenant that refuse to pay his rent

10. Member
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Originally Posted by David Larsen
Take into consideration the thermal transfer of windows. Yes, they do lose heat, but they also gain heat during the daylight hours and create a "greenhouse" effect on the interior temperature. Also, the inside of an insulated/ unheated structure doesn't normally fall to the same temperature as the outside air.
It would in fact fall to the same temperature, given enough time. Unless the laws of physics are broken, the temperatures will eventually equalize.

However at some point, depending on the level of insulation, the amount of BTU you lose per hour is so small as to be eaten by local temperature differences outside, and by then the temperature outside starts increasing again.
Additionally, there are other weird impacts you have to take into account that don't normally matter. For example, your water/chairs/tables/etc have some heat capacity, and when the ambient air around them gets to a high enough temperature difference, the BTU they transfer into the air will matter (particularly because water holds 62 btu per lb (or something like that) and air only 0.02, so 1 pound of water can heat a lot of air :P. Wood is similar )

11. [OP] Contributor
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First off - thanks to everyone!

We finally gained access to the property yesterday. Just in time as the temperatures dropped under 20* last night and look to be staying there all week long.
The tenant had contacted the utility companies last week and had them shut off the services.
Nice huh? Lock us out & then have the gas and electric shut off - in the dead of Winter. :|

I can't say any more on that subject though since it's possible criminal charges may be forthcoming.

12. Pipes on an outside wall are more likely to freeze than ones on an inside wall. I bet you will be ok if all of the pipes are on inside walls.

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Rich I hope there was no major plumbing or water damage. I wonder if if would be possible to set something up with utility companies where if they receive a disconnect request on a rental property, they notify the owner of record? That doesn't seem like it'd infringe on anyone's rights or privacy and might possibly save an expensive mess. Of course someone with ill will could simply turn the heat off (and open the windows).

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Curt,
The utilities are supposed to verify ownership prior to shutting off service.
People lie though and sometimes the utilities take their word for it, apparently without checking first to see who the owner is.

Thankfully, we got to it when the temperatures were high enough.

15. Yeah, but you don't always want to be the "owner"... if you are, it means you are ultimately responsible for any charges the tenant racks up. This varies from locale to locale, but one notable story was on Holmes on Homes a couple of years back. The house was in CA (Canada, not the home of San Francisco), and the tenants had burrowed through the basement wall to get to the electrical contacts before the meter... to steal the electricity for all of their grow lights, turning the entire house into a marijuana nursery. The electric company wanted \$40k+, but luckily the house owner made the tenant get the electricity bill in their name, and therefore the tenant is (properly) stuck for it... if they can ever find/arrest them.

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