coldframe construction question

[fruit&vegvirgin]

is there any reason why the roofs of coldframes slope? I have commandeered a couple of old wooden crates and an old glass window, and have got some pots of summer bulbs in there. but the crates are the same height all the way round, so the light only comes in from the top - will it still do the same protection job? or will they be deprived of light? the spot they are in, if we ever get any sun it will be from early morning to about 2pm.

[Jaxom]

I’m not so good on the science bit by my hair is wonderful.

If I understand it correctly sloping sides allow the inside to heat up easier.
Rather than cut your crates you could slope the ground they are on. Take a little earth from the front edge and put it at the back edge. Volla.... Sloping cold frame facing the sun.
Jax

[Nicos]

never would have thought that one up!! Must be all the Brains

[eskymo]

I think they are also sloped so as to stop rain water gathering in a big puddle on the top of them. I made a coldframe last year to over winter crop in and left it with a flat roof and the water ended up collecting in a big puddle and stretching my polythene. I ended up having to burst holes in it to let the water out as it was too heavy to lift.

So I now have a sloping roof on it which works a lot better. Water still collects, but not as much as before - I never replaced the polythene so it still sags a little...must get round to that!

[eskymo]

It's also a good idea to line the inside walls of the coldframe with silver foil to reflect more light inside!

[nick the grief]

The angle allows more light in F&V if its straight sided the sun being low at this time of year sees a smaller area to hit. It's all to do with some old greek chap called pythagoras I guess & allows rain (and snow as its forecast) to run off

[fruit&vegvirgin]

cool, so tomorrow I will chuck a couple of bricks under the back of my crates, thus creating a slope, and staplegun tinfoil to the inside!
fantastic, I'd never have thought of that! cheers.

[nick the grief]

Make sure there's no gaps round the sides F&V else you'll loose all the heat

[sewer rat]

On the subject of flat topped cold frames - the huge long one I built for my boss had to have a flat top - his idea, not mine - and I can vouch for the fact that this holds water, ice and snow - as can his jeans and boots as he discovered when he showed me his trick new rope handles for opening the lids - he got wet but I got muddy - rolling about on the ground laughing .
I swear the man has no sense!
Rat

[fruit&vegvirgin]

the other half had a good idea last night - staple gun bubblewrap in first, and then add the tinfoil - insulation and illumination!

[eskymo]

I like the sond of that. I'm making a new cold frame this week to start off my onion sets. I meant to do it last month, but didn't have any time due to work commitments - I think I will definitely put in some bubble wrap for insulation as we're bound to get another cold spell of frost before March.

[nick the grief]

You can buy stuff that goes behind your radiators that is silver foil with a bubble back & some has a polystyrene backing as well. try the local DIY store & save your bublewrap to put over the top in case of frost.

[andrewo]

I just threw a load of bubble wrap away!

[nick the grief]

you should know better Andrew, why do you think I've got two sheds

[andrewo]

I have no shed! Boo-hoo