OV9

That had crossed my mind

mik wrote: Tue Jun 23, 2026 4:55 pm So what do they do? Sink heat into water that you throw out? Seeking education.

you stick a big hose out of the window!

mik wrote: Tue Jun 23, 2026 4:55 pm So what do they do? Sink heat into water that you throw out? Seeking education.

I think you're thinking of an air cooler there - those are fans with a tank you fill with water/ice which communicates with the fan via a radiator so you remove some of the heat from the air into the water (and then, yes, throw out*). I haven't tried one but from what I have read they don't do a lot in terms of cooling the room down but are nice to have blowing in your face.

The portable AC units suck in air and use a refrigerant to transfer heat from one stream to another, blowing the cold air out into your room and have a long tube that you point out of a window (like a tumble drier) to vent the hot air. These will cool down a room, but can struggle with bigger rooms depending on the power (ours is 9000 BTU which is enough for a medium sized room but struggles with a large room). Also unless you have a sash window, sealing the window shut around the vent pipe is frustrating. Also they are damn noisy.

*in theory you could save money on water heating costs by using this warmed water to make tea, cook pasta or run a bath but while this is not specifically prohibited by the handbook I would not recommend it

Thanks both - that was my first assumption (on previous page) but nobody answered

Yes it's unfortunate that we have primarily casement style windows which are the worst for this application. Amazon sell cheap sealing kits, fiddly to fit but more effective. Also there are 3 types of portable AC units. Single hose outlet (least efficient), double hose (so pulls air from outside and expels air outside) - way more efficient and then you have split systems which are almost as efficient as the professionally installed units and much more quiet as the noisy bit goes outside and you just have the fan bit inside. But they have limitations such as only suitable for the ground floor but they're quiet.

I made this from a bit of hardboard and some velcro to hold it to the window frame. Our AC unit came with an adaptor which I think was to use on brickwork but it did the job

Rich B wrote: Tue Jun 23, 2026 4:48 pm Yeah, we bought one a few years back - they’re great for small/medium rooms - we tend to put it in my boys room for an hour before he goes to bed before moving it into our room. It struggles a bit in the big lounge area, but it still is worth it! Moving it up and down the stairs each day is a bit of a ballache though - they’re heavy!

We’ve set up ours today. Yes, a ballache. We’re leaving it upstairs and moving from the lad’s bedroom to ours later on. CBA to move it downstairs and have to reattach the hose, I can see the appeal of a fully integrated system but guessing they’re ££££

We just bought one and have been poking it out of a window opened as little as possible, which is obviously less efficient but still does a decent job. Shame the hoses are quite short, < 2m, so it can only really cool the room it's in. Also the one we bought doesn't seem to want to turn off, as advertised and as you'd expect, when the room temperature is lower than the cooling set temperature. Might have to send it back as faulty... once this week has passed.

I have an outdoor 5 a side match tomorrow. The met office app reckons it’ll be 37deg at our kickoff time of 7pm

JonMad wrote: Tue Jun 23, 2026 6:51 pm Shame the hoses are quite short, < 2m, so it can only really cool the room it's in.

You can get longer, we bought a 5m one

I had a look a while ago, probably a couple of years, and couldn’t find any two pipe systems for sale in the uk.

Single pipe ones work, but the air they’re pulling through to cool the condenser and throwing outside has to come from inside the room, using the air it’s cooled, which then has to be replaced by warm outside air. Unless your house is perfectly sealed and you eventually end up in a vacuum chamber

A twin pipe system should be a lot more efficient, like a car system, keeping the hot side completely separate from the cold room side.

Evaporative coolers do work, work have just bought some huge ones which get plumbed into the water supply to keep the membrane damp. I’m always a bit sceptical about how well they work because surely the cooling effect is counteracted by increasing the humidity of the space? It’s been too long since I did thermodynamics to try and work any of it out.

>> 5m one

ahh, thanks. If we keep it I may well invest in one of those. UK uPVC casement windows are a pain though aren't they, for these. And that would stop me moving it from room to room if I had to set up another one of those flappy cover things to seal a different window. John's DIY option above looks much better.

240PP wrote: Tue Jun 23, 2026 6:48 pm

Rich B wrote: Tue Jun 23, 2026 4:48 pm Yeah, we bought one a few years back - they’re great for small/medium rooms - we tend to put it in my boys room for an hour before he goes to bed before moving it into our room. It struggles a bit in the big lounge area, but it still is worth it! Moving it up and down the stairs each day is a bit of a ballache though - they’re heavy!

We’ve set up ours today. Yes, a ballache. We’re leaving it upstairs and moving from the lad’s bedroom to ours later on. CBA to move it downstairs and have to reattach the hose, I can see the appeal of a fully integrated system but guessing they’re ££££

I heard of someone have an upstairs and downstairs system fitted and was surprised at how reasonable the price sounded. I’d always assumed it would be £10k plus but was more like 3.5. Not cheap, but if we keep having long hot summers I’d start to consider it!

You’d hope as it becomes more common and popular in domestic settings the price would start to come down too.

240PP wrote: Tue Jun 23, 2026 6:51 pm I have an outdoor 5 a side match tomorrow. The met office app reckons it’ll be 37deg at our kickoff time of 7pm

That's savage make sure you drink insane amounts of water. I did a sweat measurement while zone 2 running a few weeks ago, when we had that 35ºC day and at that kind of temperature I lose 2 litres of fluids per hour

JonMad wrote: Tue Jun 23, 2026 6:56 pm >> 5m one

ahh, thanks. If we keep it I may well invest in one of those. UK uPVC casement windows are a pain though aren't they, for these. And that would stop me moving it from room to room if I had to set up another one of those flappy cover things to seal a different window. John's DIY option above looks much better.

I bought one of these sealing kits last month and it's dead easy to fit, plus doesn't block all the light out. Fits with velcro so easily removed and stored ready when the hot weather disappears.

https://amzn.to/4uX5YTD

I went mountain biking when it was 30+ a few weeks back, the second my water was gone i had to give up. there was shade under the trees too.

My dad wanted to do some forestry on Father’s Day. It was “only” 26 degrees. This was me after an hour in the morning when it was much cooler

It got to the point where I was wringing out my T-shirt every 20 minutes by lunch time.
In the end it wasn’t the dehydration that got me but being covered in sweat, sawdust and being feasted upon by insects.

pleasant

I'm particularly looking forward to Thursday night where the forecast says the overnight low is going to be 23ºC as much as I love this weather, sleeping in a bedroom that will probably stay at 30ºC+ all night isn't conducive to a decent night of kip.

mik wrote: Tue Jun 23, 2026 4:55 pm So what do they do? Sink heat into water that you throw out? Seeking education.

Heat exchanger, basically the same as the AC on a car. Pulls air in, removes the heat and pumps the hot air out one way, puts the cooled air out the other way.

Need an outlet for the hot (air) hose, ideally out a window, ideally one that will work with whatever sealing kit they provide (AFAIK mostly works best on sash windows, you're fucked if you have side opening ones).

So if you can't seal the window, you can't let it 'condition' a room (cos warm air will get in from outside) but you can still point it at your balls (or your face, I guess?) and cool down that way with just cool air hitting you.

Edit: Didn't notice the additional page, arf, but I'm leaving it here because I like my point about ball chilling.