How to stay warm in small shed in late autumn with low temperatures of 30-40 degrees F?

Question

A small (8 by 14 foot) shed is setup for field work at a remote site. The shed can be accessed by truck as it is next to a dirt road. In this shed is just a shelf bed and some camping basics. It is a 3-season shed and is poorly insulated, but it is dry and solid.

For field work on the edges of "3-season" weather, when it is very cold in early spring or late autumn, how could this shed safely be warmed? Expected daily temperatures would range from 40-60F with extremes as high as 80F and as low as 26F (below freezing). Field work is mostly manual labor but could require some dexterity, and field visits would range in duration from 3 to 10 days.

Some options I am considering: There is no wood stove in place but that is an option, though given the shed size it would need to be a very small stove. There will be a 100Ah 12V deep cycle battery available, but at least 20Ah of that will be used for other purposes and given electric heating uses a lot of power I am not sure that is a good option. Camp stoves seem like a dangerous option, but what about smaller and lower-tech options such as the small dishes of high-proof alcohol which are burned for cooking?

Some additional context: This shed is already equipped with a battery powered smoke and CO detector along with a fire extinguisher. A propane cooking stove is used in the shed with windows and doors open for ventilation. Warm, dry clothes, adequate sleeping bags, and plenty of food and exercise are part of these work visits, so I am not worried about hypothermia, but I am asking about additional warming options for comfort and morale. A 4wd vehicle can pull up pretty close to the shed, making propane or a wood stove install an option.

Answer 1

If it's not practical to install an actual heater, then your situation is basically like the one found in alpine climbing huts. The shed protects you from the wind and the rain, but that's about it. You want lots of warm down, including a high-quality down sleeping bag and a thick down puffy jacket. Wool long underwear, thick wool socks, wool hat, wool gloves.

As long as you're outdoors for most of the day staying active, it's not that unpleasant to hunker down in the evening with all your layers on, and climb into the sleeping bag to read a book or eat your food. 26 F really isn't that cold, as long as you have all the insulation.

Since you have the shed for storing stuff, you have some good options for staying comfortable. Keep a set of all the wool items that is only used at night, so that it stays clean and doesn't get smelly. Find some insulated booties.

Answer 2

The best option is a flued fuel-based heating system, such as a wood fire (depending on fuel availability). All the other options require you to either have open burning of fuel in the shed, which is a no-no for reasons of flame and CO production, or to use electricity, which as you mentioned is a precious resource. With a flue, gas (propane or methane) and liquid fuel (ethanol, kerosene) fires become an option too.

New Zealand has standard 4-bed hiking huts that are not much bigger than yours - they are 3.6 x 3 m (9.8 x 11.8 feet = 115 sq foot, yours is 112). All the ones that are within forests are heated solely by wood fires and those that are above the tree line are unheated (I believe, some may have fuel burners of some sort). However, these are largely intended for temporary stays of overnight to a week or two (depending on person and activity). Generally people just wear more clothes and make hot food/drinks to keep warm. However, as you mention, for extended stays this is not ideal for morale and comfort, especially if the occupants are having to do work that requires fine motor skills (e.g. writing, typing, dissection etc) where you can't wear gloves.

In all of these huts there are large signs alerting to the dangers of CO poisoning and saying to open windows when cooking.