Best sealant for draught proofing a greenhouse

[quanglewangle]

Goal for this winter is to cut down heat loss from the greenhouse.

Ideally should be long-lasting and not damaged by sulphur candle treatment.

Do folks have any recommendations for a mastic type sealant.

[burnie]

I don't have any gaps in the glass or the frames, so have never had to do this, when I tried insulating one years ago with bubblewrap all I got was green mould everywhere from the condensation, so I stopped doing it. What are you trying to grow over the winter, could you not just insulate part of the greenhouse by using a blow away or similar?

[roitelet]

I used a cheap walk in‘Blowaway’ in the tunnel and it was most effective. Thank you L**l! Minimal condensation problems as well. Going to use it again this year perhaps with a fleece jacket on the outside for extra insulation.

[quanglewangle]

burnie
There are 1-2 mm gaps between the panes and also between the panes and the frame members.

I have been able to successfully start tomatoes, aubergines and cucumbers on new year's day but I would like to start earlier.

Although it doesn't (usually) get that cold over winter it does get very windy. So main heat loss from greenhouse is probably draughts.

[Nicos]

Have you thought of getting some sheepswool loft insulation? ( washed not raw!)
You can buy it on rolls or in smaller amounts like joist strips depending on how much you need/ want to pay.

You can poke it into the gaps, it’s flexible, won’t rot, is slightly breathable, and can be removed and washed ( if necessary )and reused for years until you choose to either compost it or use it as mulch.
I imagine it wouldn’t cut out too much light either .

We have used it for insulating our campervan and I was very impressed/pleased with the results and ease of use.

[quanglewangle]

Have you thought of getting some sheepswool loft insulation?...

Thanks for that. In fact since the price of wool has tanked I have been offered fleeces for free for, eg, mulch. Unwashed, but I guess a washing machine would do it.

[Nicos]

^^^ do some research on that first!….it might felt into one solid mass and/or block your filter…..

[quanglewangle]

^^^ do some research on that first!….it might felt into one solid mass and/or block your filter…..

That would get me into big trouble! Reminds me of when I was caught washing my bike in the shower...

[Nicos]

That would get me into big trouble! Reminds me of when I was caught washing my bike in the shower...

Hahaha!…I could see how that would pan out!

[Bren In Pots]

That would get me into big trouble! Reminds me of when I was caught washing my bike in the shower...

Good one QW

QW a clear silicone sealant should work applied from the outside.

[quanglewangle]

QW a clear silicone sealant should work applied from the outside.

From outside - thanks for that tip

[Nicos]

I always thought you needed some through draught to stop the glass from exploding in high wind?
Would sealing it reduce airflow in the summer and help create overheating/ humidity?

Only asking…it’s a long time since I owned a greenhouse!

[quanglewangle]

I always thought you needed some through draught to stop the glass from exploding in high wind?
Would sealing it reduce airflow in the summer and help create overheating/ humidity?

Both objections are very probably valid, but I would rather stop the draughts and then manage wind overpressure, humidity, and overheating separately and in definite ways.

[greenishfing]

I remember when we were sealing the deck on an old wooden boat in Spain in the 90's. At the time sikaflex was the state of the art but very expensive sealant (prohibitally so if you were redecking a 50 foot boat). There were varying cheaper copies. We filled all the gaps with hemp rope, hammering it in tightly into the gaps and then sealing with varying sealants. At that time the only effective sealant proved to be sikaflex because it expanded and contracted more than the others and gave a good seal. We tried them all then and suffered the consequences of a leak ( mouldy shoes and handbags for me!!!!). Maybe technology has moved on, however maybe hemp rope would fill the gaps first.
...

[greenishfing]

That would get me into big trouble! Reminds me of when I was caught washing my bike in the shower...

You must be related to my husband!!!!