How to make the most out of insulating a
Greenhouse.
Introduction
OK just a very short science lesson here.
Greenhouses are heated by solar energy.
Heat energy can be reflected by white or silver surfaces.
Bubble wrap traps small pockets of air that are heated, but still let some
light through.
Plants need heat and light to grow.
The north side of a greenhouse will get no direct sunlight.
Foil Insulation
OK so now we have sorted out the science bit lets work out how we can use
these facts to our advantage. Firstly almost everyone knows they need to
install bubble wrap in the winter to reduce the heat loss from a greenhouse
(if you don't instructions can be found
here). If we use silver reflective foil (the equivalent of using 55mm of
loft insulation!!) on the north side of the greenhouse we will further
reduce the heat loss and due to the lack of direct light from that side the
light reflected from the foil there will be no ill effect to the plants.
Lining with the foil is slightly different to the installation of bubble
wrap in that it is best fitted horizontally (bubble wrap you normally work
between the supports in vertical strips). Each strip should then be stuck to
the next with a clear sticky tape, this will prevent any heat being lost
behind the lining or possibly more importantly will prevent any cold drafts
from coming down on to the plants.
   
In the winter months the sun is lower and so there maybe some benefit in
extending the foil to the north side of the roof area in order to reflect
the solar energy down into the greenhouse. (It's not shown here because we
ran out of foil)
You'll notice that we used Greenhouse shading clips to attach the foil to
the greenhouse. A word of warning here, the clips won't got through the foil
you need to make a hole first. A pair of sharp scissors or a large nail will
work fine. The clips also quickly fall off of the frame, it maybe an idea to
use a hot glue gun to secure them, we didn't as benches were to be fitted
and these will help keep everything in place.
Foil insulation is available from
Screwfix.com
Bubble wrap in greenhouses traps small pockets of air that
are heated, but still let some light through. It's easy to install. Here the
bubble wrap is pushed into the gap between the glass and the frame and then
taped in place. This also helps to cut down on drafts, air can move between
the frame and the glass unless the glass has been sealed in. The
disadvantage of sealing the glass to the frame is that in the summer it's
harder to keep the greenhouse cool and air circulation is reduced. Bubble
wrap should last three or four seasons so is a very cost effective method of
insulation the greenhouse. !!!See
Supplier
On a really bright winters day you may find that the greenhouse gets too hot
and the vents need to open. Here the bottom part of the vent is covered as
it opens outwards, but the bubble wrap is taped so that it won't get trapped
in the auto opener.
Around the door is an issue on this Greenhouse as for some reason the door
and the frame refuse to meet. The door itself is insulated as can be seen,
but a second piece is dropped across the doorway to limit the extent of cold
wind drafts.
I prefer to have the bubbles against the glass with the smooth side facing
inwards, however I'm starting to rethink this on. Whilst you potentially
trap more air and increase the thermal properties a little using my method
I'm wondering if the condensation would not help the smooth side to stick to
the glass and make it easier to install and tape. I guess there's only one
way to find out and that's to try.
If you find that tape won't stick to the frame or glass then clean with
white spirit, this will remove the dirt and allow the tape to stick.
Whilst we've gone through this topic please remember that drawing fresh air
into the greenhouse is no bad thing, but a cold draft is not good. Always
check that auto openers are able to work correctly. On any warm day open the
doors and the vents in order to replace the air.
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