What is the coldest temperature that humans could live in, and still have our homes heated with current technology?

I don’t think the heating would be too much of a challenge, down to some incredibly cold temperatures. I think the support systems would start to fail first, the transportation networks, the utilities, etc. Most cars are winterized to -35F around here. I did see it get that cold once. With some adaptions we could go lower, but things start to get brittle in that kind of cold.

We can certainly survive anywhere. We have an installation at the South Pole, and people have lived near the North Pole for extended periods. But it would be hard to maintain even a shadow of what we know as society under those conditions. We’d spend a lot of our time indoors, or underground.

I don’t know if you’re familiar with this, but a large portion of Montreal’s downtown core is interconnected by tunnels that we use all the time. You can go from shopping mall to bank to train station to university campus to a thousand other places without ever putting a coat on in extreme winter weather. But… living that way permanently would be hard, I think. You’d miss having sun and fresh air on a daily basis.

@glacial: Yes, I’ve been to those malls in Montreal. They’re great.

Boston has something similar, except they’re above ground, but the malls and hubs are connected by tunnels over the streets, so you never have to step outside, and therefore, can do without a coat if you want to.

@jca Yup, in Calgary they’re called ”+ 15s”, bizarrely.

Interesting.
I agree with @Adirondackwannabe that we’d be dependent on the infrastructure and that it would be the end of us. Few of us still have gravity furnaces, which means we’re dependent on electricity. If the temperature drop was fairly sudden, not allowing for increased insulation, then even a short break in service would probably mean death. The temp in my area has dropped from about 40° recently to the current <0°. Although my furnace setting hasn’t changed it’s freaking COLD in here!

Humans give themselves the illusion if being in control. I leave my butter out year-round in a cover glass container near the outside wall in the kitchen. Although the thermostat is set within 7 degrees summer and winter, the butter separates summer, is hard as a rock winter. Yeah, my house is ‘climate controlled’!

I would think insulation and the psychical structure of the building would play a larger role when it comes to keeping out the colder temperatures.

(Hand up waving around) Oooo!!! Oooo!!! I know!!! Pick me! Pick me!

Back when I was working in the auto industry we designed systems for different manufacturers. Every OEM had their own cold start spec. For example: “At -28F the car must start within 5 seconds. At -40F a “No start” is acceptable. With no engine block heater.” Below that, temperature a block heater is specified.
In general American cars had the lower temperature specs than “foreign” by about 5 F.

As for your house, the factors depend upon your insulation and the capacity of your heating plant. My oil furnace is 80,000 BTU per hour. The design temperature for my region is -4F. For my home at the design temp, I need 50,000 BTU / hr to maintain 65F. That means my furnace will keep my house warm to about -45 F!
I also have 2 wood burning stoves at 35,000 BTU/hr and 45,000 BTU/hr. Yesterday I was able to heat my home with only wood when it was -4 F outdoors with both stoves running about ½ to ⅔ wide open. I used no oil! Nice.

Almost forgot. The cold start tests had to be run with the batteries at a specified state of charge. The American OEM specified the batteries be at 50% of capacity. Most of the ‘foreign’ companies were similar but one demanded the battery be at 70%! (not realistic after about 1 year.)
Test work was performed at a facility in Canada that was the furthest northern city accessible by car. A WWI prisoner of war camp was located there because of its remote location. .
I will not mention the name for privacy reasons. PM me if you want to know.

Here is a list of the heating system design temperatures for major cities in the US.

It’s difficult to say since cold is simply means a lack of heat, and unlike heat ‘cold’ has a limit to how extreme it can get. I’ll go as far as saying that at around -78 degrees fahrenheit carbon dioxide freezes, so at that temperature or lower clothing with electronic heating would be required to be outside in.
Also, at that temperature you would need a breathing medium of some type since breathing temperatures that low directly could be fatal. The coldest bases at the Antarctica many times are not inhabited during the winter due to temperatures dropping too low, though one could still stay inside.

My brother in law just told me that phone infrastructure electronics are spec’ed to -40°F. Below that, they will not start – so no phone or internet below -40°C unless there is some heat source to warm the electronics.

It all depends on the air cushion above your skin, so the key factor is wind. Once you are inside an intact building there’s no wind. Crawling into bed with clothes and ski mask you could survive temperatures far below -40 C.

@RocketGuy Hmm. I’ve lived in regions where the temperature goes below -40 on maybe 8–10 days in a year, and never had my phone or internet service cut out for that reason.

Must have gotten Mil Spec’ed to -65 F. This was in Alaska?

No, western interior of Canada.

Then it was expected to be really cold. I don’t think most cities in the US regularly get that cold.

My mistake, I had meant minus 78 degrees centigrade (-109 degrees Fahrenheit).

@mattbrowne: I would think that even with proper clothes on, indoors with a temp of 40 F below, the body would have trouble maintaining its temperature.

@jca – I was talking about clothes plus being in bed. It’s all about insulation. A human being is a 100 watt heater. We just have to trap part of that body heat to survive.