Colder inside the Greenhouse than out!

[dwrudd]

Hi all,
Just wondering how does the temperature in your greenhouse react at night.
Yes, I know it gets colder but have you campared it to outside.
I have a little weather station which has two radio sensors ( was a good boy last year and Santa was impressed) but every night it gives a max/min for in the house, garden and greenhouse.
Thing is, it is consistantly colder in the greenhouse than outside. Last night it was -4 out but -7.5 in greenhouse and as I type, the temp out is -1.3 but -3.2 in the greenhouse.

I have tried swapping the sensors and running them side by side to check calibration but they are spot on.

Any idea's?
Darren

[Digger-07]

Does the area in the garden where the higher temperature reading come from get warmer during the day and store the heat in some way?

[Alison]

Does seem a little strange, guess that you haven't got your greenhouse insulated at all?

[Alice]

I think you're probably talking about location and aspect Darren. I was trying to take some pics today to illustrate the point but didn't do well. On the north side of the house it was -2 degrees and the frost never lifted all day. On the south side the sun was shining and the thermometer on the wall was at 20 degrees.Much warmer than the greenhouse. I had plants standing out there (didn't get good pics as the sun was too bright) basking in it. I think this is what is going on with your greenhouse.

Above is the frost on the north side BUT
these plants are in the sun

The temperature advantage probably carries on overnight. Have you checked the day time temps in the same locations.

[roitelet]

Hi dwrudd,

I have one of those posh weather stations and the sensor is next to my very old mercury Max.Min. thermometer. The reading from the weather station is always at least 2 or 3 degrees higher than the max/min. so I do wonder just how accurate they are.

Perhaps you should try one of the old steam driven ones in the greenhouse then you can compare the temperature.

[dexterdoglancashire]

Darren, many years ago I went to stay in a friends house which was the old railway station at Penrith - yep, it was colder inside than outside even though the walls were around 4" thick! (He wouldn't turn the heating on in the middle of winter!) We've never let him forget it!

I currently have one of those plastic greenhouse covers set up in the normal greenhouse to provide protection, as well as a couple of those baby plastic greenhouses - seems to be working OK so far - having said that with the way the temperature is going to drop this week, shall wait and see. (Shan't be going outside to check - its too cold!) DDL

[Snadger]

Hi dwrudd,


Perhaps you should try one of the old steam driven ones in the greenhouse then you can compare the temperature.

Do you know of an outlet for one of these 'steam' driven jobbies then roitelet? Lol

[rustylady]

I WANT ONE! I have to walk up to the greenhouse to check the temperature.

Seriously, though - do you open your greenhouse at all during the day, and is it heated at all. If it is well insulated with no heating don't forget that insulation works both ways. It can keep things warm, or it can keep them cold.

[dwrudd]

As far as the old steam driven thermo's go, I have one in there also and used it inside and out to calibrate and double check. The greenhouse is a 6x4 which has twin wall polycarbonate but no further insulation as I have nothing in there yet. I have moved the outside sensor several times and it is consistently warmer outside at night. (Obviousley it is warmer inside during the day) I suppose I will just have to use the heater when I plant up or call in ghostbusters.
Cheers all
Darren

[bubblewrap]

your greenhouse colder inside than it is outside?
Remedy just open the door and warm it up a bit

[dwrudd]

Last time I did that, three windows blew out!

[blackcatlois]

I insulate with bubble wrap round the lower part of my greenhouse, fleece around the roof area, but on the nights I don't use a greenhouse heater I swear it's as cold inside the greenhouse as it is outside (on checking my min max thermometer) - I thought bubble wrap/fleece were supposed to make it warmer by a couple of degrees but it doesn't seem to be working. /

[nick the grief]

I insulate all of my greenhouse with the large Bubble wrap and the unheated one has dropped to -3c this year so I would say it's considerably warmer.

If you just do the sides most of the heat will disappear thru the roof. a better idea would be to put Builders polystyrene round the sides (below bench level - assuming your not growing in the borders) and use bubble wrap on the roof & the sides above bench level