To vent or not to vent?

[TorontoJoe]

Hi All,

So, it appears my tried and tested method of starting seeds in cups in the windows isn't popular here at home... I'm being told that potting mix sprinkled about the house is frowned upon. As an alternative this year I bought one of these little greenhouses to start my seeds. Something like this one:



Now, it's still quite cold where I am so I built a heating system. It's basically an open top wooden box. Inside is a heater and temperature controller. I plunked the whole greenhouse on top. now I can keep the interior a constant 25C.

It occurred to me that there might need to be some air movement in there. I have a little 8" fan that I can mount to the top to keep air moving around inside but I'm wondering if this is enough?

This is where I'm torn - If I don't bring in fresh air am I asking for mould and other nastiness?

On the other hand - if I pump in fresh air - that air will be very cold. I think it would struggle to maintain an acceptable temperature and the heater would run constantly?

My posted last frost is date is May 9th so I've got to get on it.... but currently the temperature is 2C...

Some practical advice and shared experience would be greatly appreciated.