Jaslyn
Newly Registered
Posts: 3
Joined: Thu Sep 04, 2014 11:58 pm
Location: Italy

Greenhouse heating and overwintering pot plants

Hi

I'm hoping to build a greenhouse (8 m x 4 m) from hard plastic sheeting, lined with plastic bottles. This year it will mostly be to overwinter my plants and then start seedlings, next year a few veggies. I live in Northern Italy near the pre Alps. Low temps are -14 C (7 F).

We have a wood burning heating system for our home and the green house will be within a few meters of the boiler room. I'm lucky enough to have unused/spare radiator and underfloor heating connections which I can run pipes from.

So...would I have a soil heated system (using underfloor heating pipe) and radiators? What should the temperatures be for each system used in conjunction with each other?

For my pot plants I'm thinking of building a large wooden crate, lining with polystyrene wall insulation, plastic sheeting
and then filling the empty spaces between pots with something... sawdust, builder's sand or soil????. Is this sufficient
insulation or would this box benefit from base heating as well? Or better to use base heating and no sawdust? We have loads of sawdust which I thought would create some extra heat but a bit concerned about attracting mice and other unwelcome guests.

Not sure if these ideas are hair-brained or overkill! Just trying to use materials that we have available. Go easy o.k

tomc
Super Green Thumb
Posts: 2661
Joined: Sun Apr 10, 2011 2:52 am
Location: SE-OH USA Zone 6-A

Welcome Jas,

American is a funny language. An' american might see a question about "pot" and infer you meant reefer, instead of a potted plant.

If you can get a copy from your local library of Four Season gardening, by Elliot Coleman, it might answer a whole lot of your questions.

I found a minimum--maximum thermometer very helpful to my winter garden space. Knowing how cold it got, and how hot it got was central to knowing how much to heat the space. Both digital and analog examples existed when I needed one.

Jaslyn
Newly Registered
Posts: 3
Joined: Thu Sep 04, 2014 11:58 pm
Location: Italy

Definitely not THAT kind of pot! Thanks for the reply but our library doesn't have English books besides the classics. Guess I will have to do more research or order the book online... it's a big wide google out there. From the research I've done, heated water pipes should be sufficient to grow and start seedlings... the radiators were also for me! As for the potted plants... I'm hoping with the warmer air and insulation will keep them from freezing, but still in a dormant stage.? ... or soil heat and keep them growing all year round.

tomc
Super Green Thumb
Posts: 2661
Joined: Sun Apr 10, 2011 2:52 am
Location: SE-OH USA Zone 6-A

Elliot Coleman carried on the work Helen & Scott Nearing started when they went rustic. he (Elliot) lives still in Maine.

To oversimplify they built a greenhouse inside a greenhouse. Gaining as a result about 10°F with each shelter in a shelter.

Most beds with under-heat get used to boost heat for germination. IE warm soil, faster germination.

In a buried cold frame or greenhouse it takes little past a blanket and a kerosene lantern to warm things up to keep already growing plants going.

I'd be inclined to still rely on a min-max thermometer to dictate what your shelter (and plants need).

A radiator of some kind will work best with some kind of fan to move heated air around. But I'm wondering if anywhere south of the frost line you'll need that agressive of a heater. Italy after all does encompass a space running from the alps to olive country.



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