Jump to content
IMPORTANT ANNOUNCEMENT ABOUT LOGGING IN ×
  • WELCOME GUEST

    It looks as if you are viewing PalmTalk as an unregistered Guest.

    Please consider registering so as to take better advantage of our vast knowledge base and friendly community.  By registering you will gain access to many features - among them are our powerful Search feature, the ability to Private Message other Users, and be able to post and/or answer questions from all over the world. It is completely free, no “catches,” and you will have complete control over how you wish to use this site.

    PalmTalk is sponsored by the International Palm Society. - an organization dedicated to learning everything about and enjoying palm trees (and their companion plants) while conserving endangered palm species and habitat worldwide. Please take the time to know us all better and register.

    guest Renda04.jpg

Greenhouse Heating


bgifford

Recommended Posts

Hello everyone.

I have a problem. I have built a Greenhouse this year to put all my palms and other tropicals in. It's about 16ft wide, 20ft long and 10ft high.  I am planning on installing eventually a 220/240V line or Natural Gas line but will not be able to get that done this year. So I will need to use 110V Heaters. Has anyone had experience and/or has some recommendations as to which heaters I should get? planning on keeping temps around 50-55F at night if possible. Greenhouse is insulated well especially around the End walls. The coldest it got here in Central KY last year was about 5F but only for a few nights. Most of the time the lows were in the mid 20's and often above freezing temps.

Thanks.

Brian

Link to comment
Share on other sites

Welcome to the show!  I commandeered this heater calculation from another website but it will give you an idea of how many BTU's you will need to heat a greenhouse.

SIZING A GREENHOUSE HEATING SYSTEM
To find the right size heater, follow this step by step guide to calculate the amount of BTUH the heater needs to generate for the greenhouse. As an example, let’s use a GrowSpan Series 2000 Commercial Greenhouse that measures 35 ft wide by 96 ft long.

CALCULATE THE TOTAL SURFACE AREA
First measure the end wall: 35 ft width x 14 ft (average wall height) = 490 (one end)
490 x 2 = 980 sq ft (both ends)

Next measure the roof. Each side of the roof measures: 18’ x 96’ = 1,728

1,728 x 2 = 3,456 sq ft total roof surface area

MULTIPLY THE SQUARE FEET BY THE U-FACTOR
 GrowSpan’s S2000 Greenhouse is covered with 8 mm polycarbonate, which has a U-factor of .62  

490 (one end wall) x .62 = 304

3,456 (roof surface area) x .62 = 2,143

ADD THE NUMBERS
304 + 2,142 = 2,447

MULTIPLY BY DELTA T (THE AMOUNT OF HEAT LOSS OVER THE LENGTH OF THE HOUSE.) WE WILL USE THE HIGHEST DELTA T NUMBER OF 70 TO ENSURE MAXIMUM HEAT CAPABILITY.
2,447 x 70 = 171,290

CALCULATE THE AMOUNT OF BTUH
With GrowSpan’s 93% efficiency heater: 171,290 divided by .93 = 184,183. This is how many BTUH are needed to heat the GrowSpan S2000 Greenhouse.

You can find greenhouse heater calculators all over the web. Do a google search.

I have a greenhouse too and I have used electric heaters, portable kerosene and portable propane heaters, and now a fixed propane heater.  The 120V electrics will work but will probably take several and they will run constantly just to keep the temp near 40 F.  At one point I had 4 running in my 30' x 48' x 12' greenhouse.  They could not keep it above freezing when the outside temp went into the low 20's (Zn 8b).  These were the typical Big Box store home electric fan forced floor heaters(1500 Watt).  I then turned to portable propane heaters which are far more efficient and supply higher BTU output.  I do not have natural gas supply as I am outside the city limits so I had to turn to fixed propane.  I have a 150,000 BTU ceiling fixed hard plumbed propane heater now and it will easily heat the greehouse.  For emergencies(such as running out of Propane in the big tank I now use a torpedo style kerosene/diesel fuel fan forced 80,00/120,000 BTU thermostat controlled rolling heater as a backup.  It can run up to 10 hr continuous and heats well, and does not put out significant fumes.  I would have bought this before the electric heaters if I had known then.  If you have 240V supply then your electric heater options increase greatly. 

jimmyt

Edited by jimmyt
syntax
  • Like 5
  • Upvote 1
Link to comment
Share on other sites

Also factor in the greenhouse material double wall,  glass, polycarbonate, polyethylene, as they all have different heat loss characteristics.  

jimmyt again!

  • Like 1
Link to comment
Share on other sites

It's going to take a LOT of energy to sustain 50-55 degrees with outside temps below freezing using electric heaters. I used a medium sized single electric for example in my insulated garage to overwinter plants the last two seasons where outside temps rarely fell below freezing and could barely sustain low 50's.  Granted single heater, but also I'd venture far better insulated and generally warmer sharing walls with the house plus far less severe temperatures being a full climate zone warmer in 7b. This was with it running 24/7 for several months in an area similar in size to your greenhouse. I'd probably recommend 3-4 of the large HD or Lowe's heaters and expect to see a noticeable spike in your electric bill.

  • Like 1
Link to comment
Share on other sites

4 hours ago, Trent said:

It's going to take a LOT of energy to sustain 50-55 degrees with outside temps below freezing using electric heaters. I used a medium sized single electric for example in my insulated garage to overwinter plants the last two seasons where outside temps rarely fell below freezing and could barely sustain low 50's.  Granted single heater, but also I'd venture far better insulated and generally warmer sharing walls with the house plus far less severe temperatures being a full climate zone warmer in 7b. This was with it running 24/7 for several months in an area similar in size to your greenhouse. I'd probably recommend 3-4 of the large HD or Lowe's heaters and expect to see a noticeable spike in your electric bill.

Absolutely Trent!  

Link to comment
Share on other sites

Thanks everyone. I figured that it would take quiet a bit of energy to heat my Greenhouse if I would only use 110V heaters. I have been looking really hard at some things and what it would cost me to get a Natural Gas line run from the House to the Greenhouse. And will go with that. Might just have to find a way short term until the Guy gets out there to install it. 

Last winter I stuck a lot of my plants in my attached garage and it stayed always above 40 without running extra heaters. So if push comes to shove I do that again until I get the Gas line installed.

Thanks again everyone.

Link to comment
Share on other sites

I definitely would commandeer the garage again - You do not need the headache and huge bills that come with heating a (plastic) greenhouse. 

The money you would spend in heating it would serve you much better going towards the new heating system. Save your thousands (not pennies.) 

Additionally, when all is said and done, I would love to hear what system you end up putting in, and what the real cost is to heat it, when that time comes. 

Edited by The Silent Seed
Link to comment
Share on other sites

On 10/2/2019 at 9:48 AM, The Silent Seed said:

I definitely would commandeer the garage again -

I might actually have to do that since I will be gone on vacation in November and don't want to worry about my plants being possibly exposed to temperatures that might be harmful without me being able to intervene.

I will use this winter to get everything organized so that I can operate the greenhouse for the next winter.

 

Link to comment
Share on other sites

what you can also do is have a compost bin in there and really step up the composting. the heat generated can keep it above freezing. my grandfather has a decent sized greenhouse and keeps it above freezing year round in our zone 8b climate just by composting. he keeps jade plants and aloe vera and various frost sensitive plants in there all year. 

Link to comment
Share on other sites

  • 2 weeks later...

So I moved everything in the Garage these last few days since we will be running more and more risk of frost and freezing temps. I figured I would use this winter to make sure everything in the greenhouse is ready for next winter. Now I have a lot more stuff in the Garage this year than I have ever had. I guess I let everything go dormant. Reduce watering to a minimum I guess.

Does anyone have any tips for Garage storage? Last year all I had in the Garage were my Banana plants. Kept the Palms in the house but I added a lot this year to my inventory. So no real experience here with keeping Palms in the Garage. 

Link to comment
Share on other sites

Can you keep the temp above freezing in the garage?  Does the garage have natural lighting?   Those will be your 2 main hurdles for overwintering.  Yes you would have to significantly cut back on watering during the winter.  Depending on your plants some do not like temps even into the low 40's for any significant period of time.   I assume you dug the banana plants and just overwintered the corms.

Link to comment
Share on other sites

Yes. Temps never get below 45 really in the Garage. There are two south facing windows but and I keep the Lights in the Garage on during the Day to help and was thinking about spot grow lights for the ones the might not get enough light. Hope that helps. Plus on nice days I was thinking about keeping the Garage door open on nice days to get Sunlight in there.

Link to comment
Share on other sites

I don't know the combined wattage of your grow lights. That said I would invest in a 120 watt LED 5000-6500k "corn" bulb with an e39/e26 adapter.  That's all the light the palms would need.

Like this:

https://www.amazon.com/dp/B07MC8PV4K/ref=cm_sw_r_cp_awdb_t1_g6mQDb1BED4HN

Heat is a different matter...

 

5 year high 42.2C/108F (07/06/2018)--5 year low 4.6C/40.3F (1/19/2023)--Lowest recent/current winter: 4.6C/40.3F (1/19/2023)

 

Link to comment
Share on other sites

On 10/17/2019 at 4:27 PM, GottmitAlex said:

I don't know the combined wattage of your grow lights. That said I would invest in a 120 watt LED 5000-6500k "corn" bulb with an e39/e26 adapter.  That's all the light the palms would need.

Like this:

https://www.amazon.com/dp/B07MC8PV4K/ref=cm_sw_r_cp_awdb_t1_g6mQDb1BED4HN

Heat is a different matter...

 

I have two of these already. Will put those in there and put on a timer. 

Thanks for all of the advice on this.

Link to comment
Share on other sites

  • 2 weeks later...

I would just like to share what I've done to keep my tropical plants happy in my greenhouse. I'm in zone 8b (Belgium). I use the chinese greenhouse concept, where the northside if fully insulated. I use pir insulation on the back and northside of the roof. The south side, back and front are open. The whole greenhouse is insulated on the inside for winter with bubble wrap insulation (you need the one with the big bubbles not the small ones). The plants are on raised beds halfway from floor to roof. The raised beds consist of closed plastic containers filled with water (110L). There are eight in total. These have to be as dark as possible in order to absord heat. These serve as thermal mass to store heat accumulated during the day, which is gradually released overnight. The primary effect is to stabilize them termperature night and day, to avoid heat cold spike which tropical plants hate. I keep the greenhouse heated to a minimum of 12C using an electric heater (2000w) and a sepparate thermostat. As the thermal mass provides an additional 7C heat on most days, the heater doesn't come on all that often. Generally during the early hours of the day when the heat thermal mass as dissipated. The larger palms are ok without extra heat, but the smaller seedlinds need more. So what I did was place very large trays on top of the water barrels, filled them with sand and placed a heating cable inside the sand (60w-100w). On top of this goes another tray where the seedlings and sensitive palms go. You need to keep some water in that tray at all times, else the seedlings will dry up overnight from the bottom heat. This setup provides a lot of moisture throughout the greenhouse which helps to distribute the heat further. In future, I plan to use a coil ground heat exchanger and a small heat pump to replace the electric heater.

Other things I've read about are replacing your greenhouse glass with K Glass (costly but effective), using induction heating which is 99% efficient, using compost (already mentioned above I believe) which I've also done and is very effective but I just don't have the room anymore. Also using phase change materials: costly but totally replaces electric heating. And finally, if you have the room and are home all the time, install a diy rocket mass heater. With this you can turn your greenhouse into a steaming hot tropical jungle in any climate ;)

Some pics of my setup...

 

 

IMG_20191014_140544_gh.jpg

IMG_20191014_140611_gh.jpg

  • Like 5
  • Upvote 1
Link to comment
Share on other sites

  • 2 years later...
On 10/17/2019 at 4:27 PM, GottmitAlex said:

I don't know the combined wattage of your grow lights. That said I would invest in a 120 watt LED 5000-6500k "corn" bulb with an e39/e26 adapter.  That's all the light the palms would need.

Like this:

https://www.amazon.com/dp/B07MC8PV4K/ref=cm_sw_r_cp_awdb_t1_g6mQDb1BED4HN

Heat is a different matter...

 

Does this still hold up? 100 watt LED lights of many kinds are pretty cheap now including actual grow lights, but I didn't think they were practical for many large plants such as tall palms especially given the small 'focal length' of the light intensity sweet spot PAR/lux etc. 

Link to comment
Share on other sites

17 hours ago, Aceraceae said:

Does this still hold up? 100 watt LED lights of many kinds are pretty cheap now including actual grow lights, but I didn't think they were practical for many large plants such as tall palms especially given the small 'focal length' of the light intensity sweet spot PAR/lux etc. 

As a grow light, yes. 

 

5 year high 42.2C/108F (07/06/2018)--5 year low 4.6C/40.3F (1/19/2023)--Lowest recent/current winter: 4.6C/40.3F (1/19/2023)

 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Recently Browsing

    • No registered users viewing this page.
×
×
  • Create New...