Polytunnel questions

redser7

I have my materials for a self-build and have a question on ventilation in hot weather.

I am building this on an allotment so there is just no way I can get up there every morning to open the doors before work. The allotment gates only open at 8am. But I should be able to do it 3 days a week, maybe 4. I should be fine for most of the summer with the doors shut day and night as I will have mesh on the doors permanently. This should be fine for summer night temperature drops. In Winter time I'll place poly covered panels on the doors.
But what can I do about spring when night temps can get very low? I am thinking or putting a separate window in above the gable doors with a greenhouse automatic vent opener. Would this work?

Appreciate any concerns and suggestions as I'd like to get this clear in my head before I start to assemble it.

Thanks

Corsendonk

redser7 wrote: »

I have my materials for a self-build and have a question on ventilation in hot weather.

I am building this on an allotment so there is just no way I can get up there every morning to open the doors before work. The allotment gates only open at 8am. But I should be able to do it 3 days a week, maybe 4. I should be fine for most of the summer with the doors shut day and night as I will have mesh on the doors permanently. This should be fine for summer night temperature drops. In Winter time I'll place poly covered panels on the doors.
But what can I do about spring when night temps can get very low? I am thinking or putting a separate window in above the gable doors with a greenhouse automatic vent opener. Would this work?

Appreciate any concerns and suggestions as I'd like to get this clear in my head before I start to assemble it.

Thanks

Big concern is that you won't be there 7 days a week in the summer, not just to open the doors but to irrigate whatever you plant unless your going with low care crops. Greenhouse/Polytunnel crops require more careful management in my opinion. So if you go ahead make sure you put in a sprayline or something similiar that when you get there in the evenings you can give a 10-15 min shower of water by attacting a hose to the end and go off to do some harvesting or weeding in your outdoor plot.

On warmer sunny days too I struggle to keep the temps contollable, it reaches above 100F in my glasshouse at times and that includes opening the door fully and all the vents(windows) in the roof so a quick spray of water in the early morning can help cool the crop during the hotter part of the day.

You never know you might get friendly with someone in the same allotment that could open up your tunnel the odd morning for you.

What crops do you plan to grow in spring in the polytunnel?

Corsendonk

redser7 wrote: »

I have my materials for a self-build and have a question on ventilation in hot weather.

I am building this on an allotment so there is just no way I can get up there every morning to open the doors before work. The allotment gates only open at 8am. But I should be able to do it 3 days a week, maybe 4. I should be fine for most of the summer with the doors shut day and night as I will have mesh on the doors permanently. This should be fine for summer night temperature drops. In Winter time I'll place poly covered panels on the doors.
But what can I do about spring when night temps can get very low? I am thinking or putting a separate window in above the gable doors with a greenhouse automatic vent opener. Would this work?

Appreciate any concerns and suggestions as I'd like to get this clear in my head before I start to assemble it.

Thanks

Big concern is that you won't be there 7 days a week in the summer, not just to open the doors but to irrigate whatever you plant unless your going with low care crops. Greenhouse/Polytunnel crops require more careful management in my opinion. So if you go ahead make sure you put in a sprayline or something similiar that when you get there in the evenings you can give a 10-15 min shower of water by attacting a hose to the end and go off to do some harvesting or weeding in your outdoor plot.

On warmer sunny days too I struggle to keep the temps contollable, it reaches above 100F in my glasshouse at times and that includes opening the door fully and all the vents(windows) in the roof so a quick spray of water in the early morning can help cool the crop during the hotter part of the day.

What crops do you plan to grow in spring in the polytunnel?

redser7

Thanks Corsendonk. Certainly a lot to consider. The ideal thing would be to come to an arrangement with someone to open the doors on days when I can't and vice versa. I'll ask around and see what turns up.
Havn't decided yet. Probably standard greenhouse fair. Toms will definately feature. As will bedding plants. That will be the main benefit for me. Plus being able to grow out of season stuff.

Nonmonotonic

Or invest in one of these?

redser7

Cheers Nonmonotonic, that's the very thing I was talking about in the OP. Think I'll invest.

Corsendonk

Nonmonotonic wrote: »

Or invest in one of these?

Would do the job but you would need more than one depending on the polytunnel length and on each side of the tunnel roof.

redser7

Cheers. Yeah I'd have one each end built into the doors. Bit like stable doors, one half of each would open and close automatically. And above the door would be a narrow permenant vent to release the hottest air. Can't put anything on the sides unfortunately as I would have the cover stretched down over the hoops. Only place to do the ventilation would be the gable ends.

Nonmonotonic

Apologies Redser, I dident fully read the post ( well past my bedtime! ). Maybe you can orientate your tunnel to create a natural flow of air through your 'gable ends'.

redser7

No worries, that's actually better than the ones I had seen as the temperature sensor arm is in the main arm, whereas the other ones have a long sensor arm sticking out.
Yes I'll orientate it with the prevailing wind, problem is not being able to get up to it every day to open and close the doors to let the wind through. Hopefully a mixture of a small permenant vent plus the auto opener will see me through on days when I can't get up there.