Limiting temperature of a conservatory

[Roly]

Summer's here and the conservatory regularly tops 100 degrees even on overcast days.

What are the best ways to keep the temperature within sensible limits ?

I've seen adverts for thermal inserts that are slid into the polycarbonate roofing. The lack of any pricing structure leads me to suspect that it's not cheap and will be a high-pressure sale of a largely ineffective product. Is it worth considering ?

Other obvious solutions might be to use a thermostatically controlled extracor fan or some sort of shading in the roof.

Has anybody any suggestions or observations ?

It's only a small conservatory, less than 3 metres square and south facing.

[mrcheerful]

I thatch mine for the summer using reed stuff on a roll, most garden centres stock it, I got mine from Costco, stapled to a light wooden frame, this stops the sting of the sun, reduces but doesn't black out the light inside and makes the conservatory usable, several friends have copied the idea, all think it works well, it is also very cheap.

mrcheerful

[Ian Stirling]

You'r looking at a solar gain of up to around 10Kw. (need more information about total glass area in the sun direction. for more accuracy) Air absorbs around 1KJ/m^3/C. So, to keep the temperature rise down to 10C, you'r looking at .1m^3/s of airflow. To keep it within a couple of degres, more like half a cubic meter a second.

A 30cm fan should easily do this, requiring only an output speed of

1-5m/s or so.

[Christian McArdle]

Stick reflective insulating foil over the polycarbonate. The same stuff that is used behind radiators or on campervan windscreens. Obviously, the fan can help too. Install an opening roof light near the apex, so hot air can escape through convection.

Christian.

[Mary Hinge]

Very interested in this thread - in a similar position with the house we've just moved into recently. This time a large lean-to conservatory

- 5m wide by 3m deep, east facing against a two-storey house so mostly in shade in the afternoon. Solid walls to south and north sides, fully glazed to the east. Roof is very shallow pitch triple-wall polycarbonate.

I would prefer to avoid air con due to high up-front and running costs. Conservatory blinds seem to cost an awful lot as well. What sort of air extraction rate might be required in this case? Any chance one of those 275m3/hr Xpelair jobs might help, or are we talking major air-shifting?

The inserts for polycarb roofs looking interesting, anyone had these fitted?

TIA.

[Set Square]

I once considered putting solar-powered fans (similar to

but not precisely this) in my conservatory - but never actually pursued it. There seemed to be a certain logic in having a system whose extraction capacity increased in line with the solar input. Don't know how well it would work in practice.

[Andy Hall]

I am not sure which ones you mean here.

Short of fitting air conditioning, there are four main things that can be done:

- Fit roof vents which can be opened to allow the warm air to convect out. This is very effective and also pulls in cooler air through the door, windows or from inside the house.

- Fit fans in the roof. I used two large 54" types which are run at low speed and are hence silent. They can also be run in either direction. In the summer, they further assist the vents and in the winter circulate the warm air.

- Fit blinds. These are not inexpensive if you want good ones. For maximum exclusion of inbound heat, the reflecting type - typically concertina on wires give the best results but are not a thing of beauty. I used pinoleum blinds, which are still quite effective but look a great deal better.

- Fit curtains or window blinds. How useful this is depends on the relative position to the sun.

.andy

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[IMM]

A double negative. An attempt to confuse or make out you are cleverer what your are. I suspect the latter. It should be:

These are expensive

tsk, tsk.

[Christian McArdle]

Actually, "expensive" and "not inexpensive" have subtly different meanings, particularly when regarding any middle ground.

Christian.

[Andy Hall]

Based on your performance in the heatbank thread, that is a truly amazing comment.

Wrong. Something can be inexpensive, of medium price or expensive.

Saying that something is not inexpensive merely indicates that. It could be of medium price or expensive.

All three are ultimately in the opinion of the buyer.

To you, anything that can't be bought on a market stall for a fiver is expensive, and you seem to lack an ability to relate value to price.

.andy

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[IMM]

Sop you are saying he was trying to confuse.

[Christian McArdle]

No. I was saying that your statement equating "not inexpensive" with "expensive" was incorrect. Clearly, he did confuse you, though.

Christian.

[Andy Hall]

There's only one person in this NG who causes confusion....

along with a number of other things of course...... :-)

.andy

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[IMM]

< snip tripe by a snot >

[Nick Brooks]

I know it's a long shot but I'd be really grateful if you stopped doing this as it adds nothing to the conversation and even though I've onbly been reading this group for a few months, it's getting a bid dull and certainly doesn't give an impression of the thoughtful intelligent person I'm sure you are really

Thank you

Nick Brooks (expecting snip tripe by xxxxx)

[IMM]

As you have probably assessed by now, I don't suffer fools gladly.

[Ian Stirling]

That'll explain the attitude.

[bigbria]

Question: On a hot day, with say the vents open but the fans off and the blinds up, what's the internal temperature like?

Brian

[Ian Stirling]

For ballpark use, the total heat gain is 1Kw/m^2. This area is measured at right angles to the sun. As the day goes on, the area rises and falls depending on the angle which the sun is shining onto it.

I'll assume that the 5m is against the house, and that it's 2.5m tall. In the morning, you've got some 5*2.5 = 12.5Kw. As a very rough ballpark, 1Kw raises the temperature of a 1m^3 by 1C in 1 second.

275m^3/h is (/3600) =.08m^3/s. Heated by 20C, this will absorb .08*20 = 1.6Kw, which is about an eighth of what you need.

So, if this was the only means of cooling, it'd heat to some 160C. The polypropylene will probably melt, and let the heat out first :) (or more accurately, it'll simply go out through the walls.

[Andy Hall]

That really is a "how long is a bit of string" question.

A lot depends on how much of the conservatory is in sunlight, for how long and which part of the day. It also varies seasonally of course.

Mine faces north west and so only receives major sun from mid afternoon onwards.

Use of the blinds and vents make a big difference.

I tend to open the doors on particularly hot days which effectively makes the internal temperature virtually the same as outside, under shade.

I would suggest taking it one step at a time and seeing what suits you.

.andy

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