cross-posted from: https://lemmy.world/post/19705740

In my post earlier today, I commented that I saw bird houses made of composite material (such as Trex) and was curious as to their thermal properties, since climate change is making many traditional house designs dangerous due to higher average temperatures.

After reading the articles below, it sounds as though composite lumber heats up faster, retains heat longer reaches higher temperatures, and also loses heat faster than traditional, unfinished softwood.

Article from Trex

Article from a deck builder

Even if the heat differential won’t kill the birds, it seems to have greater potential to stunt nestling growth and to increase dehydration risk.

I didn’t find any articles from birding groups about them being dangerous, but it seems very recent that they have been taking note of increased nest box death, so it may not have much research into it yet.

While the initial thought was something like this should last longer, stay prettier, and be easy to maintain sounded great, seeing it both holds more heat during the day and loses more at night sounds like a negative in both directions. It may be best to stick with unfinished wood.

I’m curious to hear anyone’s thoughts on this. Don’t take my hour of research as gospel. It just came up in conversation and I haven’t seen this discussed.

  • @voleEnglish
    3•6 days ago

    retains heat longer, and also loses heat faster

    These two points are contradictory. Something either holds heat longer or loses it faster.

    I read your second link and it seems that color matters way more than composite vs real wood. Though in any case they were measuring the upward-facing surface temperature of the decking material, not the inside temperature of a structure made from the material.

    I’m no bird building engineer, but here is what I’d consider if I was worried about bird house temperatures:

    • ventilation: helps bring the temperature down/up to the ambient air temperature
    • solar absorption: lighter colors tend to absorb less warmth from sunlight
    • insulation: more insulation means less heat/cold will transfer from the outside surface in, and will make the temperature inside more stable throughout the day/night

    And addressing each point in terms of composite vs real wood:

    • ventilation: same for both composite and real wood
    • solar absorption: unpainted light-colored wood appears to be fairly cool, but if it’s painted/stained then it doesn’t matter
    • insulation: I can’t find a good source, but it seems like real wood is a better insulator than composite. You can use thicker boards to increase insulation.

    So, if you make a bird house with unstained unpainted untreated wood and the exact same bird house design with composite wood, I think it’s reasonable to assume that the composite one will get a little warmer on a hot day. If the bird house has some ventilation, I don’t think there will be much of a difference.

    • anon6789OPEnglish
      1•6 days ago

      I went back and reread what I wrote and I think I meant it reached higher temps. Good catch.

      A lot of your points get elaborated on in the links. You did a better job summing up a number of them.