If you used a dryer hose, it would not keep the air warm, it could even cause you more problems.
Poultry do not need to be "kept" warm. If you allow them to grow feathers according to the climate, use the deep litter method for organic heat (composting) and keeping a layer of 2" or so of fresh litter over that, they should be fine.
You can use card board for insulation on the ceiling as that is where heat escapes, heat rises, it will help out.
Hope this helps you out a bit, but keeping them fed with healthy foods, cracked corn at bedtime- keeps them warm from their body grinding it up over night. Also, make sure that whatever you are using for roosts allows them enough toe coverage with their feathers.
They will be fine!