Welcome to BYC. Did I count right that you have about 20 birds right now?
@3KillerBs is great with coop dimensions. They should be able to tell you for sure!
Thank you for the vote of confidence.
Here are The Usual Guidelines.
For each adult, standard-sized hen you need:
- 4 square feet in the coop (.37 square meters)
- 10 square feet in the run (.93 square meters),
- 1 linear foot of roost (.3 meters),
- 1/4 of a nest box,
- And 1 square foot of permanent, 24/7/365 ventilation, preferably located over the birds' heads when they're sitting on the roost.
For 20 birds you need:
- 80 square feet in the coop. 8'x10' is the most practical because 7'x12' or 6'x14' require a lot of weird cuts.
- 20 feet of roost
- 200 square feet in the run. 10'x20', 12'x16' or 8'x25' as suits the land available.
- 20 square feet of ventilation.
- 5 nest boxes.
I'm not sure if I understand what you mean by "coop" and "henhouse". The normal definition of the terms is that the coop is the enclosed shelter where the roosts are and the run is the outdoor fenced area. Henhouse and coop are usually considered the same thing -- the enclosed section where the roosts are.
Your 40 square foot area is half the coop space you need for 20 birds.
Your 76 square foot area is about 1/3 of the run space you need for 20 birds.
This article explains why these numbers are guidelines rather than hard-and-fast rules,
https://www.backyardchickens.com/articles/how-much-room-do-chickens-need.66180/ but given that you're having significant behavior problems there is a very good chance that the behavior is related to the over-crowding.
We're getting insulation but that's how it's been.
As for lighting those two heatlamps go all night.
If you said where, in general, you're located I missed it. Climate matters a great deal, especially when it comes to housing.
Here in the US Southeast, uninsulated metal roofing and siding are very common for animal housing and present no problems as long as there is abundant ventilation. The most common reason to insulate a metal roof is to prevent condensation from forming on underside of the roof in cold weather and dripping on the birds. It is completely unnecessary to insulate in order to keep a coop warm.
Speaking of warm,
Why are you running heat lamps for fully-feathered, 24-week-old pullets? Depending on various circumstances, the usual time to wean chickens completely off heat is between 4 and 8 weeks. Chickens tolerate cold much better than they tolerate heat because they have built-in down parkas.
A well-acclimated chicken doesn't even notice the cold until it gets down near 0F. Here's a useful article for you if you're in a cold-winter area:
https://www.backyardchickens.com/articles/cold-weather-poultry-housing-and-care.72010/
Looks like the run has very little shelter to help a low pecking order hen escape the notice of the bullies.
Clutter in the run is important. A chicken shows it's acceptance of another chicken's dominance by moving away from the dominant chicken and breaking line-of-sight. In a barren rectangle the subordinate bird can't break line of sight so the dominant bird interprets that as a challenge that calls for discipline.
This is what my former run looked like before I moved the chickens to the new coop:
There was nowhere in the run where I could stand and see the entire thing and I'm a lot taller than a chicken.
