56 replies to this topic

[Gareth Davies]

For at least a year now, I've been debating which way to go with my Nep collection. I've been growing lowlanders from seeds with no real idea what I'm doing or where I'm going, and I've ended up with quite a few seedlings and some useful experience- all gained the hard way. Many plants have bravely given their lives in my quest to learn how to grow these things.

One thing I've learned: in the uk, lowlanders are really, really hard to grow well. It's their demand for excessive heating that's the killer... I used to think I could get away with winter temperatures around 18-20C, but really, it's not enough. Yes, we can drag some lowlanders through at those temperatures, but they look like crap.

So- I've had to think: which way should I go? Give up or take it seriously?  I've had to be honest with myself, ever since I was a teenager- 25 years ago- I've thought of N rafflesiana as the ultimate exotic plant. I know, I know, there's far more worthy species but I just can't get away from this idea that raffs are impossibly exotic. Also, I really, really want a decent size bicalcarata.

So- I've had to face the fact that the current arrangement of small plants in a "hot box" in the highland greenhouse is never going to be satisfactory. These are around a third of my lowlanders, with no pitchers at the end of this winter




What I need is a dedicated lowland house. After taking a pile of advice from folks here, I've had a think and decided that the usual aluminium/ glass greenhouses are impractical. What's needed is a greenhouse based on one concept: multiple layers of insulation. It's either that, giving up lowlanders, or bankruptcy owing to lowland heating bills.

So- this thread is supposed to the story of me trying to build a greenhouse and ultimately grow some nice raffs, amps and a bical or two.

[Gareth Davies]

Let's get started.

Hopefully, with this thread, I can gain motivation by exposing myself to public humiliation if I fail completely.

So- phase one is to find a site in the patch of overgrown shrubs and brambles that passes for my garden.
Here's an old greenhouse that came with the house when I bought it, next to the end of the garage.




This had to be cleared and some room made for the new structure



I'll skip the next bit, which was a couple of weeks of making drawings, doing some research, coming up with a design, and then doing some trigonometry (and some people say that you never use the things that you learn at school! Admittedly, it's been 25 years since I needed to know what a hypotenuse is.)

After that, off to the woodyard, buying some bits of timber, chopping them up and doing some basic joinery

[Gareth Davies]

The plans got changed a bit along the way and what was originally going to be an 8 x 12 foot greenhouse is now going to end up being about 9 x 14.

Some bits of wood have now been joined together

These are the sides



This is the rear gable:



I haven't added any more details since this isn't a woodworking forum. But it's amazing what you can do with a chop-saw, and a hammer and sharp chisel.

Obviously, these seem a bit short. The idea is that these pieces stand on brick walls.... double-skinned brick walls (for insulation), then ultimately, multiwall polycarbonate for glazing.

So- that's where the project stands this week. I'm hoping for a nice Spring so I can get out in the garden digging some foundations and building walls over the next couple of weeks....

Edited by Gareth Davies, 16 March 2012 - 17:13 PM.

[TheInactiveMoth]

Looks good! I wish you luck!

[corky]

looks like you are used to working with wood,is it your own design

[manders]

Look forward to seeing the results with great interest Gareth.  I keep my conservatory at 15C min and heating was substantially higher (at least 2X my greehouse heating (9C Min) would hate to think what a hothouse would cost to heat year round but with wooden frame and lots of polycarb it should be manageable.  Cant wait to see the finished results.  

[Gareth Davies]

Corky, yes, I have to admit I quite like my woodwork. So far, I've built things like wardrobes, dressers, chests of drawers, and what I ought to be doing is making a painted pine kitchen (so far I've done 3 of the 14 units that I need.)  But instead, I decided a greenhouse was far more important.
The idea was to do a classic design, more Victorian style, but within the limits of what's practical.

Mark- as a rule, I read that as a guideline, every 5C we raise the temperature, it doubles heating costs. So- if I want my new greenhouse at 20C, it'll cost at least 8 times as much to heat as a greenhouse kept at 5C. Terrifying.
I'm quite a long way from testing my design.

And I have to apologise for this post being low on Nep content, but here we go, it's been a nice week of warm sunshine (yes, even here in Leeds!) and I've dug out a couple of old trees and shrubs, got the site cleared and put down some concrete footings.

[nadja77]

Fantastic project. Can't wait to see the result! With winter around the corner for us I have also been working on ideas to build an adequately heated green house for my lowlanders (haven't got much further than that). Even here, with temps barely going below 0° its an expensive undertaking. I can't imagine what the costs must be like in your climate! Good luck, and keep the pics coming

[Daniel G]

Hmm, very interesting.
It'll be nice to know what's possible in the North, so i work out my future plans...
I wish you all the best!
Dan

[ada]

Gareth,   Have you thought about lining the brick part of your greenhouse with high density polystyrene to stop heat transfere through the bricks?

ada

[Gareth Davies]

Ada- yes, that would be part of the story in about 2 weeks' time!
I'm taking a lot of the principles from conservatory building and my loft conversion, so it's all about the insulation. Multiple layers of insulation is key.
It's going to be a double skin of bricks (or concrete blocks) with some insulation between the skins.
The weather forecast for next week is glorious- so I might make some decent progress!

[Gareth Davies]

It's been a week of unusually good weather.... July temperatures in March.  It's been hard to stay indoors and work for a living when there's beautiful warm sunshine outside.
So- quite a lot of bricklaying got done this week to make the base of the new greenhouse.



The photo illustrates the nice weather perfectly.

Going back to Ada's point above, the idea with the base is to use "house construction" methods, so this base has a cavity-wall construction which I will fill with insulation.
It's been interesting for me, I've never used these new "aerated concrete" blocks before- they're a type of concrete block with particularly good insulation qualities, but what's interesting from a building point of view is that you simply cut the concrete blocks with a handsaw.
Anyway, pic of the cavity wall:



The pressure is still on- now that the weather has warmed up, the Neps are getting impatient for a new home and are battling for space... the first pitchers for the season are forming and a couple of the EP merrilliana hybrids are becoming real bullies...

[mobile]

Gareth Davies, on 31 March 2012 - 07:19 AM, said:

It's been interesting for me, I've never used these new "aerated concrete" blocks before- they're a type of concrete block with particularly good insulation qualities, but what's interesting from a building point of view is that you simply cut the concrete blocks with a handsaw.

The internal walls of my house are made of some soft grey blocks, which I have always presumed to be aerated concrete. I found that you can drive course drywall screws straight into them and they hold very well... much easier than the plastered brick walls or plasterboard walls of my old house.

[mantrid]

Love this kind of project. Im renovating a house at the moment and am enjoying every minute of it and all the challenges its bringing.
Are you going to insulate the floors? It will probablly be worth it for a relatively small area such as this, and cost of materials will be recouped quickly. I woulddnt make it complex with membranes, concrete slabs etc, keep it simple maybe 100mm Kingspan under a screed would do. I read that upto 15% of heat in a home can be lost through the floor.

[manders]

mantrid, on 31 March 2012 - 09:35 AM, said:

Love this kind of project. Im renovating a house at the moment and am enjoying every minute of it and all the challenges its bringing.
Are you going to insulate the floors? It will probablly be worth it for a relatively small area such as this, and cost of materials will be recouped quickly. I woulddnt make it complex with membranes, concrete slabs etc, keep it simple maybe 100mm Kingspan under a screed would do. I read that upto 15% of heat in a home can be lost through the floor.

I did my greenhouse floor with 2inch polystyrene overlaid with foam matting, not a typical greenhouse floor by any means but very cheap, the foam matting is waterproof and cleanable but does fade in the sunlight (i should have picked white/grey).  I cant say for sure if it helped but my greenhouse heating bill this year was around 60-70£ for the winter (10C minimum).

[Gareth Davies]

Mobile- yes, they're the things.. excellent for insulation, and you and drive screws right into them! Great things to work with.

Mantrid- I'm not going to insulate the floor. My theory is that heat loss to the floor isn't huge... any heat that goes into the floor isn't really lost, it's more like it's stored there.  The problem with heat loss through floors in houses- such as my 1930s semi- is that you have floorboards over joists that are then pretty much exposed to the outside air temperature via airbricks. I've started going round my house putting insulation between joists under my floorboards, and it really does make a difference. Not an easy project, but one that keeps my leaky old house a bit warmer.

Manders- I think your low heating bill might be demonstrating the wonders of multiple layers of glazing insulation... I'm just not convinced that insulating the floor would make much difference... although I'd be happy to be proved wrong.....

[corky]

your making great progress,will be very interested to see it finished

[manders]

Gareth Davies, on 31 March 2012 - 12:02 PM, said:

Manders- I think your low heating bill might be demonstrating the wonders of multiple layers of glazing insulation... I'm just not convinced that insulating the floor would make much difference... although I'd be happy to be proved wrong.....

Your probably right Gareth, a house in general is allready well insulated so the floor there does make a difference, but in a greenhiouse most of the heat goes through the glass / air leaks / aluminium frame.

[Daniel G]

Great Work!
Still following this eagerly. Gutting that the weather's taken a turn for the worse.

What are you going to use in the way of heating?

[Robert]

That was a very nice greenhouse setup, still has space around.