[brownp]

After looking at the different options, I have bought a (relatively cheap) low wattage tube heater to help protect seedlings in my potting shed once sowing season starts.
I wondered about the best place to install it….
The main thing I’m not sure about is the height…is it better to put it lower on the basis that heat rises (ie below the wooden staging) or more on a level of the seeds (around waist height)….and is the proximity to the perspex window relevant?
Hope someone practically minded can help - thanks in advance
Phil

[JayG]

I'd say underneath the staging is the best place - as you say warm air rises so this would provide the maximum benefit to the seedlings above given that you can't hope to heat the entire potting shed with a low wattage heater.

If it proves necessary, you could raise the heater about a foot from the floor if it can be done safely, and no nearer to any window than is practically possible (sheets of expanded white polystyrene sheets can be used to reflect heat (and light) back to where you want it if you have any - mine was part of the packaging used when I bought a new fridge-freezer.)

[steven c]

we make a temperary propagator across width of greenhouse 6 feet, under a ply board we have a tubular heater wired to a roomstat [seemed pretty easy to do] this is then in a sort of tent of glass and bubblewrap
when the sun hits the greenhouse can rise quickly hence the stat we finish off lots of our veg in this prior to going outside then this is dismantled when tomatoes etc need the space.  i have seen minigreenhouses used
inside a main greenhouse perhaps that may suit you   good luck