Hi, it's Jason again from Fraser Valley Rose farm here. I am beautiful day mid-January
It's negative 5 degrees outside, but it's beautiful in here
So nice in fact that I have to have the greenhouse door open to keep it working temperatures what I'm working on is
Another thing to do with my greenhouse benches
So I made a video last week where I talking about how to use or why I use greenhouse benches for all my young plants
One thing I left out of that was one special project that a bench is for
And I'll be modifying one of the benches today and design that's using it for greenhouse heating or bench heating for
propagating seeds and the and cuttings more easily
So a little bit of insight here a lot of larger greenhouse operations
They use other systems like a boiler that radiates water underneath the tables try to get heat underneath the table
It's such a benefit to new seedlings and new cuttings
Unfortunately for a small grower like me that doesn't make a lot of sense. I'm not going to have a boiler up my greenhouses
I'm not going to run the risk of freezing
I just don't have enough benches or need enough space
To make that make sense so what I was looking for is a solution that could do that same purpose or function
But do it in a small space where I could do maybe 15 20 trays
Per table and rotate them through to start all my seedling crops
And it's a relatively easy thing to do the main thing you're trying to do is just to have a heat source underneath the plant
problem is you want to do it in as
Efficient a way as you can without wasting a bunch of electricity or heat
And you want to direct it to your seedlings in a way that's controlled so you don't overheat that you don't
Waste a bunch of energy. I'll show you what I'm going to be using for that on this bench
It's slightly different than the other benches, but it's built on the same template, so I'm using same bottom same legs
I still have that copper band across the bottom try to keep slugs off the tables
But I'll be using some other materials on it to try to keep the temperature where I want it to be
okay, I'm speaking of materials these are them or most of what I'll be using to modify my bench, so I'm starting with the
Base of the bench itself you'll notice on this one that I haven't put the wire mesh across the top
It's just open on the top and over here. I have some materials
I'll be using to modify that for my heating bench here across the bottom. I'm going to have
Some plywood just for support on top of that I have this
Insulation with the foil on the one side, so it's got that I don't know if you can see it in the video here
There's got a reflective foil on one side for the sides
I'm going to be using this hard board insulation quite firm so it's not so susceptible to breaking and
I don't know if I'll use this yet or not
But this is a I picked this up the hardware store as well
And it's just a foil that I'm considering wrapping around the inside to try to keep some of that temperature inside
So I actually have one of these
Built in a slightly different fashion in the other greenhouse them not that far away, so maybe I'll sleep over there right now
Show you what I got
Excuse the mess... it's just the way my second greenhouse look in between growing anything
and here's
Version 1.0, and currently. I'm not using it to start seeds or to stick cuttings
It's actually in use right now
Just trying to overwinter some young cuttings from last year that we rooted last year and as you can see
it's base built on the same base as the other benches, but what I've done is I've
put the
Insulation around the outside to try to keep the heat where I want it and underneath. I have one of those foil barriers as well
inside of the bench
And try to raise the temperature what I'm using as a heat source is
Just a heating cable - a soil heating cable, you can get online
Just from Amazon or that kind of thing
It's just a plain heating cable like that the new bench that I'm going to be building will have a cable
It's twice that length and uses twice as much
Electricity, so it should be able to keep that bench a little bit warmer this one here just
manages to keep the temperature of the soil
Above the greenhouse temperature so I don't know if I mentioned, but it's -5 outside right now
the
Plants that I have on this bench over here if I knock them out of their pot
Easily enough done. It's actually solid
I'm going to say it's thawing because it's been warm outside today, or
Warm with the solar gain, but here on this bench
You know I don't know if I can show you that but it's not frozen solid it moves quite easily inside the pot so to
Pop directly across the aisle from each other one on an unheated bench frozen solid one on the heated bench
Still maintaining above zero temperature switch for a lot of plants can make the difference between living and dying
So back to the bench that I'm building now. I just quickly cut it down
The length of the Bench because the bench is 7 feet long whereas the plywood came in an 8 foot section
So now I'm going to pin that down the screws
And I'll be onto the next step just to cut down that first layer of insulation
I've screwed down the plywood now and
It makes a nice firm substrate for the rest of it here the next layer
I'm going to put down is this foam insulation
And it's a light density foam insulation with a foil top on it and before I do that
I guess I'd like to discuss quickly some of my thoughts on why I designed this the way
I did now some people design by placing a light source down here now
The they can either have rope lights strung along on the bottom or they can have
Light bulbs, and there's nothing wrong with too it that way
This is where I fall back on
reading on Wikipedia about how heat moves in things and
it moves three different ways it moves by
conduction convection and radiation
It orders to avoid heat loss or to put it where I wanted the best. I want to have it not go other places
Convection is the main culprit there
so I have light bulbs down here the heated air around it will start to escape and
It will come up and throw onto the bench
But will also do is come out this way it has a way to travel and have some ways to get lost
what some people do is they'll put a skirt on the bench down to the bottom or
Enclose that somehow and that's fine, too
That's just different approach than what I'm doing here second way, you can lose heat there is that radiation and so whenever
Imagine you're looking through an infrared
Camera you see that glow on things. That's
infrared
Radiation moving out from the object and there's very little you can do to stop that except to put up a radiant barrier
that's what this foil is on top of the insulation here is a radiant barrier to stop the heat from moving A
Direction you Don't want it to
but
Limiting down the convection. So I've put the
cables on top of the Bench and by limiting down the radiation
Basically have left only one other method for the heat to move which is direct
Conduction through the soil media through in this case. I'll be using sand and that's the way I've designed it the way that I did
Put the foam trimmed it down to size put it on the top here
I don't really need to hold it down with anything because it'll be held down by the weight of the sand that I put down
On top of it and the next step I'm going to use this
roll insulation go around the outside Edge here and just walk off radiant heat from escaping from the outside here
So just trimming down this final layer of hardboard insulation here and with an exacto knife
you can just trim these to the dimensions you want and
Once you've made a good slice
Down into it
And we've gone deep enough you can just
snap it it's a clean slice where you want it
okay, so you can see that I finished putting the film around the outside here and the final step of building the holder for the
Sand here is to put on this firm board insulation
I just cut and I pinned it in the other side there the screw that I'm using it has a
Washer around it that's going to hold the insulation a little bit tighter
against the the Sidewall and so also now
And not too tight don't want to crush the insulation as we go in now. We've got a nice solid
Outside Margin of the table here I can fill this top portion with sand now
After I received the heater. I'll just put the tables across the top and I'll show you that next step before I proceed
It's a couple days later now and the shipment has arrived from Amazon
This is our soil heating cable reason
I chose to use this instead of say the rope lights that I've seen in other videos is this is
Thermostatically-controlled and it's intended to be carried so I don't know the electrical safety end of things
but I assume that one that's meant to be buried is safer than one that isn't meant to be buried and
The thermostatic thing is important because if it does warm up in the greenhouse here and this gets above the temperatures that's good for my
Plants it's going to shut down. It's not going to overheat or cause a problem
So that's why I've chosen this now the next thing. I'm going to do is I'm going to lay it out on this table and
Take it down into the pattern it's going to be for even heat distribution
as you can see we've taped down the heating cable onto the heating bench now and
The Pattern that I've used just is kind of random in a way
But it's one big loop and you have to make sure that if you can there's no large
Spaces or dead spaces between the table, so obviously the heat will dispersed amongst the sand
But we don't want to leave any dead spots on the on the table for heat try to make it as even as possible
The next thing we're going to do and I've only taped it down
Just using painters tape here because I don't need to actually hold it in place the next thing
I'm going to do is I'm actually gonna scoop some sand on
top of it
and
that's going to hold the table down and
Also create a nice spot where to put down my trays even and it's also going to share the heat amongst itself
So that's the goal now. I'll get that cover for you and
I'll do this one more video here where I show you how it actually heats up with what temperature's it gets to
For the seedlings and cuttings
Here's the completed bench sand in place holding down those cables
And it's been running for in the range of two to three hours now. So it should be starting to heat up inside there
Just to show you what that heating looks like now what I thought. I'd do is. I would take a quick heating measurement and
Just to be fair here. I thought I'd
Compare it to our indoor in sorry in greenhouse beds here the in-ground beds
It's been warm enough in the greenhouse here to get some heating and you'll notice there's some crop residue down here. That's okay
all this is the soil eventual I just want to get down to the basic soil here and
Give you a soil temperature reading so turning this on here
This is just a an infrared thermometer a baby ear thermometer
Ten point eight degrees is what I'm getting which actually isn't bad
considering middle of January and
Just to make a comparison here
To what I'm getting at the heated bench
give myself a
new reading right here and
Almost 22 degrees, that's like a 11 or 12 degree
Difference just over the course of a couple of hours so expect this bench
To bring it up to around 25 degrees pretty consistently and top out around 27 where it'll stop heating now
That's it finished, and you know we built our other
benches
This was built onto the top of one of those and so
excluding those costs if I'm just talking about
The plywood the insulation heating cable sand and all that your total costs for this
We're probably in the range of about $100
Anyway, thank you so much for watching and if you have any comments, please leave them below