On Sat, 13 Jan 2007 05:32:04 +0000, Les Hemmings wrote
(in article ):

wrote:
Greenhouses do sometimes get Damaged from Strong winds & Gales , Today
we have had very Strong winds , it looks like the Weather is getting a
lot worse , today we have had very Strong Gales & I would suggest
anybody who has a Greenhouse that they secure all there Vents & make
sure all Doors are closed

Sealing a structure in very high winds has the opposite effect. As the
pressure drops outside (moving air, lower pressure) the high pressure inside
the structure causes it to explode. It's the major cause of building loss in
hurricanes, all those people you see in those pre-hurricane news reports
boarding up their homes to make them airtight are also the ones whos houses
star in those spectacular "expoding house" shots during the storm.

snip

Your advice seems consistant with your job. More damaged greenhouses equals
more money for yourself. If everyone were to button up their brand spanky
new greenhouse all nice and tight you'd be quids in! So perhaps you knew all
about the pressure effects after all? Or is that just my cynical, black
heart?

I agree with Les's advice. During the 1987 hurricane in the UK, a friend had
recently had their large greenhouse professionally cleaned and it was shut up
tight while they were away. Result: it imploded fairly spectacularly. We,
more by accident than design g, had left vents slightly open. Result: no
damage. One example doesn't prove anything, but I have always remembered
this and always leave a gap. It so happens we have an unheated greenhouse
which is not used during the winter, so nothing is likely to be damaged by
the open vents.




--
Sally in Shropshire, UK
bed and breakfast near Ludlow: http://www.stonybrook-ludlow.co.uk
Burne-Jones/William Morris window in Shropshire church:
http://www.whitton-stmarys.org.uk