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Harrisville Primary School Greenhouse Donation. More »

A Bit of History

Those of you who know us from the early days know that we initially began Hunkin Garden Products Ltd selling domestic glasshouses imported from Halls in the UK. We stopped selling glasshouses some time ago because we could no longer get glass at a realistic price from NZ suppliers. We looked at importing our own glass, and while we could have done this, freighting glass around the country without breakage seemed impossible. Time has moved on and the kids you see in the picture can now be seen on our Miniature Hereford page 10 years on. The little girl in the purple gumboots has a Bachelor of Social Sciences in psychology degree and is now studying to become a Master of Science. The little boy is a student and the computer Guru at the local college where he sets up and maintains the school's computers and network.

After 19 years we now have our own range of greenhouses. As my father, a retired fitter turner says "there is no substitute for experience" and we have used our experience to design a stronger, higher side-walled greenhouse using 6mm-twin wall polycarbonate. By having these greenhouses made in China for us all these improvements have been made at a very competitive price.

So what are the benefits or polycarbonate over glass? It is a "no brainer" really.

Safety has got to be number one, especially if there are young children playing in your backyard. Polycarbonate is one of the toughest coverings around. Polycarbonate protects against rocks, hail, and can even withstand the impact of a baseball that may have ventured into your yard. It can also withstand a heavy snow load. The safe nature of polycarbonate makes our greenhouses ideal for schools.

Lightweight so we can supply much bigger pieces, which means glazing, for want of a better word, is much easier. Instead of 106 panes of glass that we used to have in a 12 x 8 greenhouse for instance, we now have 36 large pre-cut polycarbonate sheets, meaning fewer air gaps to leak air and less fiddling around fitting little panes. Your greenhouse is assembled in no time at all.

Diffused light every gardener knows plants need light to grow. It is a vital part of the photosynthesis process. What is not so commonly known is that plants often grow better under diffused light because light tends to be scattered and leaves pick up light from all directions. There have been claims of 20% to 30% increases in growth with diffused light. Direct light on the other hand can often cause burning of the leaves, which reduces growth. The twin-wall polycarbonate diffuses the light so your plants are unlikely to get burnt in bright sunlight. No need to paint the outside to prevent scorching or erecting shade cloth in summer.

Energy saving - The more heat the greenhouse retains, the better, especially if you want to heat the greenhouse. (See our comparative table below in the frequently asked questions). There is also less condensation, and little or no dripping from overhead.

Our Guarantee

Every greenhouse comes with a 10-year guarantee on the aluminium frame against faulty workmanship, much more than you will receive from most other manufacturers. The polycarbonate is guaranteed in N.Z. for 7 years against breakdown (going brittle) by U.V degradation. If U.V breakdown occurs, and is confirmed by the manufacture's sample analysis, a pro rata replacement credit will be allowed. A credit will be issued, based on original invoiced value, for the unused period of the warranty. Warranty is to the original purchaser of the greenhouse. The polycarbonate must be installed with the UV coated side to the outside (facing the sun) otherwise the warranty is void.
By purchasing one of our greenhouses you are making a long-term investment that will bring you many years of enjoyment and service.

With unbeatable durability, safety, insulation and pricing, what are you waiting for?

Here is what Marie had to say about our greenhouses

"We have been looking to buy a green house for several years now and finally bought one off you a few months ago. We are extremely happy with the green house. It arrived in perfect condition. We employed our friendly fencer to put up the base, so it was concreted in and extra reinforcing in each of the corners. We completed the rest ourselves (with no building experience). We went to the garden show at Manfield (Manawatu) recently and once again looked at green houses (there were 3 different types). There was no comparison. The green house I bought from you is far superior. The height side walls and strength were very obvious. Thank you for a great product."

Frequently asked questions

What is polycarbonate?
Polycarbonate belongs to the group of plastics called thermoplastic polymers. It is not to be confused with acrylic, which is a much cheaper and inferior product. Polycarbonate is widely used in industry because it has excellent temperature resistance (125 Celsius to minus 40 Celsius), impact resistance (250 times stronger than glass, virtually unbreakable) and optical properties (80% of visible light, glass transmits 89%) which makes it ideal for greenhouse applications. It is non-toxic, stain resistant and weighs six times less than glass.

The use for Polycarbonate is almost endless. Here are a few applications. Bulletproof windows as used in banks, safety glasses, crash helmets and prescription glass lenses. CDs and DVDs are made from polycarbonate. Ever tried to break one?

Will the polycarbonate get brittle after long exposure to sunlight like other plastics?
Don't confuse polycarbonate with the cheaper acrylic plastics that are available. The polycarbonate has a UV treatment on one side that must face the sun. We give it a seven year limited warranty, but polycarbonate products used for roofing in NZ (Laserlite TM corrugated roofing for instance) is advertised with a lifetime warranty. www.laserlite.co.nz.

What is horticultural glass?
Horticultural Glass is made by the rolled glass process and is the cheapest form or glass. A continuous stream of molten glass is forced between water-cooled rollers to get the correct thickness. Horticultural glass often has optical imperfections and sometimes depending on the source, is not as clear as window glass (sometimes a bit green).

When horticultural glass breaks it splinters leaving sharp jagged edges which must be handled with great care. Care must be exercised when handling glass and you should always place a gloved hand under the glass so it can't slip. If glass ever shatters in your garden or on the lawn, that is the last time you will ever be able to run around with bare feet, because you will never get rid of all the glass splinters.

So what's the big deal about insulation?
Greenhouses work by trapping the heat from the sun. If the heat escapes easily through the glazing or air gaps then the whole point of having a greenhouse is lost. The best greenhouses are the ones that can hold the heat for as long as possible. The polycarbonate sheets fit inside the frames so there are no air leaks. These greenhouses are the best-sealed greenhouses I have seen and rivals a tunnel house that has a completely welded skin.

What is 6mm-twin wall polycarbonate?
Two thin sheets of polycarbonate are separated by a 4.5mm still air gap, much like double insulation used on windows in colder climates. The construction is like the coreflute used in plastic real estate signs.

Won't water and bugs get between the twin wall?
The polycarbonate fits inside the frames so bugs and water can't get in.

Doesn't glass insulate?
It does to a point, because infra red (heat) does not transmit through glass very easily. Well that's the theory. However we all know that in order to keep your house warm in winter you pull thermal drapes across your windows, so it is not that good.

Insulation factors R ratings for different greenhouse materials.
Most people will be familiar with the R rating given for insulation. Fibreglass insulation for instance ranges from R1.6 up to R 3.6 and more. The higher the "R" number, the better the insulation. The table shows some comparisons.

Material Insulating "R" number
6mm twin wall polycarbonate 1.5
3mm horticultural glass 0.95
Polythene plastic as used in tunnel houses 0.83

From this table you can see twin wall polycarbonate insulates 50% better than glass traditional 3mm glass and about 72% better than plastic. In a greenhouse situation the use of plastic is a bit better in a tunnel house because it is normally welded so it is quite airtight (no draughts) and glass is a little worse in a glasshouse (more draughts) because of more joins (smaller panes) and unavoidable air leaks. Our greenhouses are so well sealed they rival the tunnel house welded skin for air tightness.

What is best for greenhouse frames, aluminium or steel?
The only reason manufacturers use steel for frames in domestic greenhouses is price. These greenhouses are often made from electroplated galvanised sheet steel that has been cut and folded or rolled to shape. The protection layer is very thin, and the cut edges of course are not galvanised, so though the frames will last quite a long time, eventually they will rust. The sheet steel is also quite thin, so where it has been cut there is often a very sharp edge. The only disadvantage with aluminium is cost. It is a more expensive metal and dies have to be made in order to extrude the product to shape. The frames are much thicker and in most cases have rounded edges from the extrusion process. Aluminium has a thin protective oxide layer on the outside that forms immediately the moment the aluminium is exposed to air. Any damage is instantly sealed off with an oxide layer. Aluminium never rusts and provided compatible materials are used with it, there is virtually no corrosion. Aluminium will last a lifetime, and with the rising cost of raw materials it is false economy to purchase a greenhouse with a steel frame that you will eventually have to replace. We have a 10 year limited warranty on the frame. It is quite conceivable that a steel-framed greenhouse will have started rusting before our guarantee has run out.

Before making a decision to purchase a greenhouse look very closely at the construction so you can make educated comparisons.


New Titan series - Better, stronger, wider

The Titan series are our newly designed greenhouses that we believe are even stronger than our previous series. We have combined a clip and special polycarbonate glue/sealer system in the construction of the Titans. Other systems of fixing polycarbonate to greenhouses have their problems. A clipped system can be prone to panel blow-outs, but they are easy to put back. The insertion system is not a complete cure for blow-outs, as panels amazingly can still blow out in very high winds. The problem with the inserted system is that you have to partially de-construct the greenhouse frame to get the panels back in, and this can be very difficult.

New technology has meant there are now special glues/sealers for polycarbonate that can match the expansion characteristics of the panels. The result is a system that uses full length UV treated PVC capping to clip in the panels, backed up by special polycarbonate glue for added strength. The result is, not only do we have a very strong method of holding in the panels should you need to replace one, the greenhouse does not have to be pulled apart either. Even construction is easier and more relaxed. You can assemble the frame on one day and put the panels in the next. With an insert system once you start assembly you have to get it all done in a day, quite a stress with a large greenhouse.

Other improvements are our alloy base fully powder coated dark green for all models, even if you have a mill finish frame. This ensures durability when in contact with the ground. Bases no longer have joins halfway down the long side, they are once piece with obvious construction and strength benefits.

Added features are a downpipe system as standard so with the high eaves it is possible to collect water in a barrel off the roof. There is nothing like rainwater to get you plants growing. An extension system means you can build a semi commercial greenhouse from day one or at a later date if required. The extension system has the same strength characteristics as the main greenhouse.


Special deals:
Buy any greenhouse and receive some automatic vent openers worth $125.00 each for free. These units are our new double spring models, do not need power to operate and can be a lifesaver if you are frequently away from your property or you just forget to open or close your vents.
This is how it works. We will supply enough autovent openers to automate half the roof vents in your greenhouse:
Titan 79 with 4 roof vents - 2 autovents FREE
Titan 912 with 4 roof vents - 2 autovents FREE
Titan 914 with 6 roof vents - 3 autovents FREE


Titan 97 greenhouseTitan 79 (approx 9 feet long x 7 feet wide)

  • 2849mm L x 2125mmW x 2330mmH. Eave height with base 1653mm
  • 1.3mm thick aluminium extrusions. Heavier profiles for more strength
  • Single door
  • Clip and silicone sealant system for fixing polycarbonate.
  • Glued and clipped polycarbonate act as sheet bracing
  • The polycarbonate glue is supplied
  • 19mm x 19mm x 1.6mm thick angle bracing
  • Braces in eaves and apex
  • Double extrusion across the back wall for extra strength.
  • Stainless steel nuts and bolts
  • PVC capping system
  • 100mm high powder coated aluminium base
  • 4 roof vents standard for better ventilation (twice as many as other brands)
  • Downpipes supplied with the greenhouse for collecting water off the roof.
  • 6mm twin walled polycarbonate
  • 10 year warranty on frame and 7 years polycarbonate
  • 2776mm L x 2125mmW x 2330mm extensions available to make a longer greenhouse. (It can be added at a later date)
  • Extensions are braced the same as the greenhouse
  • 4 roof vents in extensions

Available in powder coated dark green $2240.00, or plain aluminium mill finish $2039.00
Freight Auckland suburbs excluding rural delivery $100 NI $165, SI $220.00

Choose a product and destination:

Titan 7 Series Extension system (approx 9 feet long x 7 feet wide)

  • 2776mmLx2125mmWx 2330mmH.
  • Built to match the main greenhouse
  • 4 roof vents
  • All other specifications the same as the main greenhouse.

Available in powder coated dark green $1598, or plain aluminium mill finish $1427.00
Freight Auckland suburbs excluding rural delivery $80 NI $145, SI $200.00

Choose a product and destination:

If you order an extension with your greenhouse we will give you a quote on freight as it will probably be cheaper because we can combine the freight.

Titan 912 (approx 12 feet long x 9 feet wide)

  • 3543mmL x2751mm W x 2535mmH. Eave height with base 1653mm
  • 1.3mm thick aluminium extrusions. Heavier profiles for more strength
  • Double door
  • Clip and silicone sealant system for fixing polycarbonate.
  • Glued and clipped polycarbonate act as sheet bracing
  • The polycarbonate glue is supplied.
  • 19mm x 19mm x 1.6mm thick angle bracing
  • Braces in eaves and apex
  • Double extrusion across the back wall for extra strength.
  • Stainless steel nuts and bolts
  • PVC capping system
  • 100mm high powder coated aluminium base
  • 4 roof vents standard for better ventilation (twice as many as other brands)
  • Downpipes supplied with the greenhouse for collecting water off the roof.
  • 6mm twin walled polycarbonate
  • 10 year warranty on frame and 7 years polycarbonate
  • 2776mm L x 2751mm W 2535mm L extensions available to make a longer greenhouse. (It can be added at a later date)
  • Extensions are braced the same as the greenhouse
  • 4 roof vents in extensions

Available in powder coated dark green $2769.00, or plain aluminium mill finish $2548.00
Freight Auckland suburbs excluding rural delivery $120, NI $220, SI $270

Choose a product and destination:

Titan 914 (approx 14 feet long x 9 feet wide)

  • All the same features as the Titan 149 except with 6 roof vents as standard
  • 4237mm L x 2751mm W x 2535mm H. Eave height with base 1653mm

Available in powder coated dark green $3088.00, or plain aluminium mill finish $2855.00
Freight Auckland suburbs excluding rural delivery $130, NI $230, SI $285

Choose a product and destination:

Titan 9 Series Extension system (approx 9 feet long x 9 feet wide)

  • 2776mmLx2751mmWx 2535mmH.
  • Built to match the main greenhouse
  • 4 roof vents
  • All other specifications the same as the main greenhouse.

Available in powder coated dark green $1698, or plain aluminium mill finish $1527.00
Freight Auckland suburbs excluding rural delivery $100, NI $200, SI $255

Choose a product and destination:

If you order an extension with your greenhouse ask for a quote on freight as it will probably be cheaper because we can combine the freight.

Accessories

Hanging brackets

These brackets are made of aluminium and can be attached to the framing of your greenhouse without disassembly using the stainless steel rhombus bolt supplied. There are many uses but a typical application is to hang a string from the bracket and wind a tomato up it for support.
Available in powder coated dark green $1.50, or plain aluminium mill finish $1.30
Postage $2.50 any number. Please note when you order the postage will be added for each item, however when we process your order you will only be charged one lot of postage. There will be no postage if ordered with a greenhouse.

Choose a product:

Aluminium shelf with stainless steel bolts

This shelf attaches to the walls of your greenhouse leaving the ground free and is available in powder coated dark green.

  • Size: 1388x650mm (L x W)
  • Height adjustable
  • Solid aluminium frame for easy assembly
  • 6 Aluminium slats.

Available in powder coated dark green $146.75, or plain aluminium mill finish $126.75
Postage NI $16.50 SI $26.00

Choose a product and destination:

Aluminium 2 tier stepped staging

Two tier free standing staging to make maximum use of space and light

  • 1185L x 340/680W x 1050/500H (mm)
  • Solid aluminium frame for easy assembly
  • 9 Aluminium slats.

Available in powder coated dark green $225.40, or plain aluminium mill finish $205.40
Postage NI $16.50 SI $26.00

Choose a product and destination:

Aluminium staging with plastic seed trays (included)

This staging is ideal for germinating seedlings. The 12 removable trays allow you to make maximum use of space.

  • 1010L x 405W x 998H (mm)
  • Solid aluminium frame for easy assembly
  • 12 seeds trays

Available in powder coated dark green $115.40, or plain aluminium mill finish $105.40
Postage NI $16.50 SI $26.00

Choose a product and destination:

Automatic vent opener (two spring) (see our special deal)

Our automatic vent openers are a great accessory to add to you greenhouse, especially if you are working away from home. One of the first things you will notice with a greenhouse is how efficiently it can trap the heat. This is a good thing in winter, but as summer approaches it is very easy to have your greenhouse overheat if you don't have the vents open. The problem is you need to remember to open them, and if you work during the week this can become a bit of a chore. On those frosty days it is very important to close the vents in time otherwise all the heat gathered through the day is rapidly lost.

Fortunately there is a solution. You can install automatic vent openers on your greenhouse vents. These units require no electricity. The mechanism utilises a wax made of plant oils harmless to humans even if licked (though you might need to stock up on toilet rolls) that expands with heat. This expansion pushes a piston rod out of the cylinder that then opens the window. When the temperature falls, the wax retracts and the weight of the window together with the force of the opener's closing spring closes the window again. The opening temperature range is adjustable between 15 and 25 degrees Celsius.
The two spring design holds the lighter polycarbonate vents shut with more force than a single spring design improving their wind resistance.

Automatic vent opener $125.00
Postage NI and SI $10.00

Choose a destination:

Louvre

If you want extra ventilation then a louvre can be fitted to the plain end of the greenhouse to allow fresh air to enter. They are very effective when you have the doors open at the other end because this allows fresh air to pass through the greenhouse. Our louvre blades are made of tempered glass for extra strength with no sharp edges. Louvres can be added at any time to your greenhouse but it is much easier to install them when you first construct it. Please note the louvres will only fit the end wall (plain gable end) of the greenhouse.

Available in powder coated dark green $95.00, or plain aluminium mill finish $85.00
Postage NI $10.00 SI 15.00

Choose a product and destination: