On my first chicken shed conversion,I have used felt but bonded it down with the tar glue stuff,I also used fabric glue and stuck loft insulation on the roof inside and then covered it-(applied with glue again) with heavy duty plastic sheeting.The floor is bonded laminate which I bought from the tip and has lasted 3 years with no problems,I even jet wash it all out. I have also used sealant in all the gaps.
I did have red mite last year,but the source was from another shed which for some reason is not as far to go to lay an egg and I did not creosote this one as was new-and I was made aware that you are not allowed to creosote new sheds-only those which have been done before?!
The main coop was re-creosoted-(not creocote) from the start and I have not found any red mite.I do however get vent lice (well my hens do!)occasionally but only on the largest fluffy birds like my orps a cross orps...strange that!
I wish to stress that I am not advising to use the real creosote in case of repercussions and all the story which comes with it.I do have to say though that I was raised on a very old farm and all the buildings were thick tarry creosote which went sticky in the hot sun

. However,none of the chickens had bugs back then,I have no idea why,the eggs were fine and the chooks were healthy..