Roof Vents vs Exhaust Fan

[MoonShadows]

I have a high peak greenhouse with two roof vents that open with paraffin vent openers. You can see one of them open in the upper right side of this pic.

I also have a couple of fans to keep the air moving. To get better air flow, circulation and venting, I am thinking of putting in a louvered exhaust fan with thermostat high up on the peaked wall and a motorized intake louver low down on the north wall. If I do this, do I really need the roof vents...I guess I am thinking more for the cooler/colder weather. The paraffin controlled vents are slow to react, and I don't want to lose all my heat. I'm thinking of sealing them for the winter and dropping the ceiling somewhat using bubble wrap to preserve as much warmth as possible. Any thoughts?

 

[alp]

Roof vents or openable roof panels. Exhaust fan costs money and is not an organic solution.

 

[MoonShadows]

Yes, an exhaust fan is not organic and costs money in electricity, but I am trying to discern what would be best for a winter greenhouse.

 

[Greenhorn]

That is a great looking greenhouse.

I'm only modedestly knowledgeable as I only use a small fan and manual vents, mostly for getting hot air out as my greenhouse is quite small. I have read up a little on it. Would also be good to understand the seasons (tempatures) you will be using the greenhouse. Also are you using a heater at times, any cooling?

What I'm thinking about is the potential negitve impact of fans and louvers on internal greenhouse tempature. Unless your internal tempature is at balance with the external tempature it seems using an intake or exhaust fan could negitively affect the greenhouse internal tempature (by drawing in external air) all for the need of circulation. Any air removed from the greenhouse will generally be replaced by outside air.

How would circulation be handled when there is no desire, or there would be negitive consequences to exchanging temperate inside air with less temperate ouside air?

From what you have suggested I think a circulation fan setup might be the best option?

https://www.growerssupply.com/farm/supplies/ExternalPageView?pageKey=EXTERNAL_PAGE_3008

Alp - can you please advise to the details or strategy of an organic solution? Just saying "venting" and "be organic" is not really a helpful or useful response.

 

[MoonShadows]

I would like to use it all year, but would settle for 9-10 months out of the year. Winter temps in Jan-Feb can go as low as -10F, but that is unusual. Average winter temps here are usually no lower than 0F at night. No cooling in the summer, but I would use heating in the coldest times. I understand what you are saying about a fan negatively affecting the internal temps, but from what I have read...unless I am wrong...exhaust and circulation are crucial to avoid too high levels of humidity and moisture. At other times, I would use fans to keep the internal air circulating without bringing any fresh air in. Let me take a look at that link you provided. Thanks!

 

[specalk]

You can get one of those solar exhaust fans like people install on roof houses and have a speed controller setup on it with a temp meter. When it gets to hot the brushless motor pulls out hot air until it gets to the perfect temp zone. You will also want to build flaps so you have a intake for air so pressure does not build up and allows the fan to pull air.

 

[MoonShadows]

That is a great looking greenhouse.

I'm only modedestly knowledgeable as I only use a small fan and manual vents, mostly for getting hot air out as my greenhouse is quite small. I have read up a little on it. Would also be good to understand the seasons (tempatures) you will be using the greenhouse. Also are you using a heater at times, any cooling?

What I'm thinking about is the potential negitve impact of fans and louvers on internal greenhouse tempature. Unless your internal tempature is at balance with the external tempature it seems using an intake or exhaust fan could negitively affect the greenhouse internal tempature (by drawing in external air) all for the need of circulation. Any air removed from the greenhouse will generally be replaced by outside air.

How would circulation be handled when there is no desire, or there would be negitive consequences to exchanging temperate inside air with less temperate ouside air?

From what you have suggested I think a circulation fan setup might be the best option?

https://www.growerssupply.com/farm/supplies/ExternalPageView?pageKey=EXTERNAL_PAGE_3008

Alp - can you please advise to the details or strategy of an organic solution? Just saying "venting" and "be organic" is not really a helpful or useful response.

Thanks for the advice @Greenhorn . The more I read about winter greenhouses, the more I am learning that circulation is more crucial than ventilation. I know a winter greenhouse is subject to condensation; that is why I was thinking more about ventilation, but exhausting warm are for cold air seems counterproductive. My thinking now is to concentrate on circulation with a passive vent if the green house gets too warm during the day. Thanks for the link, too.

 

[BigC]

These are not hard to make yourself

 

[Greenhorn]

I'm glad you have come up with a plan. Good luck and let us know what you come up with.

 

[MoonShadows]

I would like to detail this further as my plan comes together. Any/all feedback or advice is welcomed!

I bought two Western Red Cedar Raised 3' x 6' Garden Bed Kits from Home Depot to put in my greenhouse. At $68.97 each, it was actually cheaper to buy these than buy the cedar wood and make them myself. They go together with 3" deck screws, but I also added 3" Zinc-Plated Heavy Duty Corner Braces to strengthen them up a bit more.

I am going to use some Redwood 2x4's and 1 x 4's from my old greenhouse benches to build a bottom for these. Then, I am going to place them on concrete block bases (for a comfortable working height and to keep them off the floor), and make 1' high frames that I will cover with a 6 mil thermal anti-condensate "clear" (91%) greenhouse film to create a cold frame within my greenhouse. The frame will hinged for ease of working in the beds and adjustable ventilation when needed. These beds will give me a second barrier from the cold weather.

I have a bunch of 5 gal white buckets with snap on lids from supplies we buy for our home business. I bought black paint made by Krylon that is supposed to adhere well to plastic. I am going to fill these with water to use as heat sinks. I am also going to cover the North and East walls with Reflectix® Insulation.

With these measures I am hoping to gain an increase of 2-3 zones. I also have an oil filled radiator heater if needed.

I just put the raised beds together. I will post pics as I move forward.

 

[Greenhorn]

I enjoyed your follow up next steps. It's Interesting that your doing raised beds in a sense, I pretty much only do germination in 1020 trays and small pots, because of GH size and climate. I really like you heat sinks for warmth. I use a small oil filled radiator type heater for the rare clod nights, the work well and are fairly cost effective in an appropriate size space. Just reread, cold frames in the GH, that is interesting too. I can see the value based on where your at. Thanks for the update

 

[MoonShadows]

I'll have more this week and post some pics.

 

[MoonShadows]

I went to Lowes today and bought the Reflectix Insulation for the East and North walls and 10 tubes of elastomeric caulking for the panels.

 

[MoonShadows]

Here's a pic of one of the western red cedar raised beds I bought.

I put 4 - 2x4 runners, one on each of the outside long walls and two spaced further in, that will hold the "floor" of the raised beds which will be made up of 1 x 4 redwood slats that I had from dismantling my greenhouse benches. They are only 24" long, so I'll have to cut a bunch of them smaller, and I'll alternate them as I put in the bottom. I'm going to wait until I have the boxes in my greenhouse before I add the slats.

Yesterday and today, I finally got around to caulking and covering the north wall and part of the east wall with the Reflectix insulation. The insulation goes up rather easy; the caulking is another story! I hate caulking. Hot day! You might be able to see the thermometer reads 100 F in the greenhouse.

Next step will be to put in the concrete block bases for the 2 raised beds. Hopefully, I can find some time tomorrow to start on that.

 

[Greenhorn]

That's quite nice, not just a nice greenhouse, but good construction too. I really like how your using the black buckets and the reflective material. Making use of the natural. I feel guilty as I didn't even seal the ends of my polycarbonate sheets no caulking to be found. I actually use shade cloth almost as your using the reflective material. I have an east facing house wall and one side of my green house is only a few feet away, so I use shade cloth to block some of the reflective heat. With that I like your open space too

Is the floor sand or dg or something? Looking forward to seeing the raised beds up.