Strategies for staying cool

[Martin Brown]

You have to open the windows at night to gain some headroom as well.

It will eventually reach the same temperature of the air outside if there is any exchange of air going on. The point is that it doesn't get significantly hotter than the air outside like it would in a greenhouse!

Your only other option then is a fan to move what air there is around a bit and aid evaporation from your skin. That will feel cooler. My office fan has three settings low, medium and high. They should more properly be called gale, storm force and hurricane. None of them are compatible with having any loose paperwork on my desk.

So far it hasn't been hot enough to merit using it provided I do most of my office work provided I give up mid afternoon.

You are not doing it right then or your expectations are completely unreasonable (probably both). You cannot expect to cool something in direct sunlight using any sort of conventional material all you can do is slow its rise in temperature.

If you really want to cool something in direct sunlight then you need expensive metamaterials which are mirror finish or white for visible and near IR radiation and black in the 10um thermal band.

It doesn't come cheap.

Some progress has been made with mass producing metamaterials. I am a bit sceptical how well they work with grime and bird lime on them.

[Tim Streater]

It keeps a lot of it out. I agree that hot curtains will heat the inside air, but thass why the curtains need to be thick.

[Harry Bloomfield, Esq.]

tim... formulated the question :

Blinds and curtains drawn against direct sun, do work - they stop the IR landing on you, furniture, walls and floors. In Italy and other hot countries, they often fit roller blinds to the outside, operated by a strap inside. Often they are horizontal wooden slats.

[Martin Brown]

If you are serious about the optimum thermal performance then you want the most brilliant white that you can find on the sun facing side, a thin layer of insulator and then a mirror metallic finish on the inside.

If you are really serious then you have a second layer behind that to trap the warm air against the sun facing curtain.

My workshop uses the stuff intended for putting behind radiators to decouple the interior from the sun drenched roof and main door. It makes a huge different to the interior temperature this time of year.

It can only slow down the ingress of heat it cannot prevent it, but the temperature never gets higher than the free air temperature and stay below it until quite late in the afternoon.

The mirror mylar solution I suggested elsewhere also works reasonably well at reflecting heat and light back outside without making the room too dark. External shutters or sunshades trump any internal solution.

It is the visible light as well that is being thermalised in the room. Reflecting as much as possible back is the first line of defence but it must be by a material that still looks black in the 10um thermal band.

Aluminium foil gets mad hot in direct sunlight. Brilliant matt white doesn't. MgO was the preferred super white for observatory domes back in the days before they had air conditioning. TiO2 isn't a bad choice for a white pigment matt consumer paint.

[nightjar]

Drive around in the car with the air conditioning on :-)

[R D S]

That.

A lad was doing some plastering for me in blistering heat, I was suffering but couldn't complain as he'd been grafting in it for hours while i'd been sat on my arse.

I could have kissed the bastard when he announced he was running low and might need another bag!

[RJH]

Mmm, - surely curtains closed, windows open will help?

[David]

Just adding to the discussion that you can get double glazing with micro blinds between the panes. This solves some of the inside/outside problem and does slow down the heating effect of the sun.

Shadow side doors/ground floor windows open and sunny side upstairs windows open also seems to work for cooling air flow.

Cheers

Dave R

[Brian Gaff (Sofa]

Fit outside shutters to windows and only open windows on the non sunny side. Change the config as the sun moves around, but beware if you have concrete outside as that stays radiating heat long after the sun has gone. Obviously most of the problem we have is not that its hot, but that it is extremely humid because the hot air can lold a lot of moisture. If you can cool the aire the moisture is released and with it the heat allowing the colder air if directed on you to take more of the sweat away. Its them there thermodynamics. I guess you have not got a mountain nearby which you could drive up and the air is coller up there of course. grin. Brian

[tim...]

but from the pov of cooling in summer it's not - we have windows which are deliberately designed to let in the thermal energy of the sun, only restricted by whatever blinds you put up behind that window. We have houses like that because we have cold winters and want that warming effect in the winter, suffering the problems it creates for the summer.

I can tell you with 100% certainly (because I have been trying it all week),

There is no temporary structure that you can use to block off this window that will stop this thermal energy heating up the inside of the room to the same temp as we currently have outside.

Most people don't have that possibility

but it's not hotter outside than in.

and presumably houses designed with better shaded windows because of it

come on the clever clogs tell me what I have to do *inside* my house that will stop this

I have spent the week trying the suggestions from last time, and they haven't worked.

we've been round that discussion - Oh no I don't

Even if it were financially cost effective, my building owner would not allow it

[tim...]

well of course

room 29 degrees at bedtime - down to 26 degrees by morning

not exactly a useful reduction, but it is what it is

I have no way of creating a through draft.

It will only equalise very slowly.

agreed

daytime it's 29 degrees outside

but overnight it's 18 (so the weather report tells me). It never cools close to that.

I never really thought otherwise

but last discussion other people assured me that this *was* possible

that's not going to be an issue because whatever I use has to go temporarily on the inside.

and putting temporary stuff on the inside always leaves scope for a pocket of air between the window and the material, to warm up and convect heat into the room

[Max Demian]

Not practical for a bungalow or ground floor flat.

[Tim Streater]

So how do you open or indeed close them from inside the house? You'd have to go outside to do that.

[The Natural Philosopher]

Wrong

an insulated curtain will stop the incoming radiant heat. After that you have to rely on thermal mass to keep indoors cool

Draw curtains and close windows by day Open windows and curtains at night

[Theo]

35C upstairs here...

Did you try the 'emergency blanket' idea I posted a while back?

I've got some up - it and the window gets quite hot so it seems to make a difference, but I've not attached it flat against the glass so a lot of the heat isn't being reflected outside. The old one I had that's foiled paper works better than the new one I bought which is just slightly aluminized plastic (you can see through it).

I'm currently looking at honeycomb blinds that have a foil centre:

can fit flush to the glass. Although I don't know how much difference they will make.

I notice quite a difference between white roller blinds and coloured blinds

- behind the white it feels a lot cooler.

It is tricky, I agree :(

Theo

[Theo]

On roller shutters there's usually a belt through the wall you can pull, or they can be motorised.

For pocket sliding doors/windows you can also get sliding shutters that go outside the door. You slide one, other or both depending on what you want.

For folding shutters you just open the window and lean out.

Theo

[tim...]

they have remote ways of opening and closing them

[Chris Hogg]

Not with sash windows, and many windows open inwards, particularly on the continent IIRC. But it's a bit much to expect in the UK for just a few days per year, as is air conditioning. Grin and bear it, or should that be bare it!

[tim...]

but the air gap between the window and the curtain will heat up

and that will transfer to the room because the curtain can't possible be

100% efficient

The theory is not in doubt

what I am telling you is that it doesn't work

[tim...]

yup

these wont fit my window (I have looked at more than one supplier)

I don't have a wide enough frame