Here is what dlhunicorn posted in the other thread: Illness quite often occurs with environmental stress (i.e. HEAT and COLD stress) therefore insulation as well as proper/sufficient ventilation (particularly with you using cedar which may have negative impact when ventilation is inadequate >fumes are toxic) ... now re this and my suggestion for insulation as well as being able to keep the infirmary temp stable and draft free (yet well ventilated) which is crucial for an infirmary as well as being able to clean/sanitize/disinfect: For two of those things (cleaning/disinfect and insulation) I would suggest that you try and find a package of priced down PVC plastic wall/ceiling paneling (I got a package of five four-yard plus lengths priced down from fifty to five bucks because one of the panels in the package was damaged) http://img.alibaba.com/photo/50447886/PVC_Wall___Ceiling_Panels.jpg (this is the plastic hollow type I mean) >will automatically provide insulation (see link with photo) and the plastic will not only allow for easy disinfection/sanitization but will also keep the mites/lice down (which tend to attack weak birds >>>any with a well established flock at a certain point find their (wood) coops next to impossible to rid of mite problem which keeps reinfesting the birds >the plastic interior suface resolves this.) ...these panels have a tongue and groove interlocking system and is super simple to install I am sure they have cheap similar substitutes (look at your local DIY) but here is the US website of the brand I use (might give them a call and explain it is for your chicken coops and ask about purchasing damaged panels >they probably throw them away) http://www.dumaplast.us/ (at the bottom is telephone number) It sure makes cleaning the coop easy! So I'm not sure you'll need the PVC if you aren't planning on using your playhouses as a chicken hospital, but sealing the wood is probably a really really good idea. And since the PVC would make it easier to clean, I'm all for that!