Post #G21-018: Radiant barrier for keeping a raised bed warm at night, final post.

 

I’ve been looking into simple ways to keep to keep a raised garden bed warm at night.  So far, I’ve figured out the following:

  • What doesn’t work:  Floating row cover (Post #G21-012)
  • What does work:  Space blanket plus “passive solar” (Post #G21-014)
  • Why that works:  The math behind the space blanket (Post #G21-015)
  • You need the extra heat input from passive solar:  (Post#G21-017).

I have now learned one two more things. 

First, space blankets are too fragile to be used on a windy day.  That’s unfortunate, because they are cheap and easy to store.  But the windy conditions two days ago showed me that they just aren’t strong enough.  I had to cover the space blankets with a tarp to keep them from being shredded.

Second, actual radiant barrier, made for use in construction, works better than space blankets.  This is material sold for use in home construction.  This isn’t the the bubble-wrap-type Reflectix (r) insulation.  This is more-or-less a piece of aluminum-coated Tyvek (r), and so it’s a heavy, stiff, strong fabric.  I had a roll left over from a prior project and tried it last night, as the weather report called for near-freezing temperatures. Continue reading Post #G21-018: Radiant barrier for keeping a raised bed warm at night, final post.

Post G21-015: The math behind the space blanket

 

Background.

Fair warning:  This is a technical post.  It wanders off into a discussion of heat content, conduction, radiation, and so on.  Calculations will be openly displayed, without apology.

If that’s not your thing, then skip it.  Sometimes the juice is not worth the squeeze. Continue reading Post G21-015: The math behind the space blanket