-
Sorry as going to come back to you yesterday...
Opening them when it's hotter outside isn't recommended as I understand it.
Sort of. Firstly, the temps you mention (eg 26 at night) sounds hotter than outside, generally. Secondly - yes sure if you are actively cooling the inside, then don't open the windows. Comfort isn't just temps though, it's a combination of temp, humidity and air movement. So increasing air flow can make it feel more comfortable even if it doesn't change temp.
I don't have expertise on active cooling machines. Nor do I know much about reflective films, sorry. Taping paper on windows works, but you can't see out of them.
If I was to suggest low energy approach - or what you might try while waiting for the active cooling thing to arrive:
Day-time:- Reduce as much solar gain as possible. Daylight is fine, it's sunlight you want to block out.
- Ventilation - In the morning, hopefully the inside is relatively cool, so as it hots up outside you might want to not let too much hot air in. But, once inside is hot too, try to encourage air-flow. One-sided ventilation only really works in a small room. It's much more effective to encourage cross-ventilation. So, you open both windows in your living room. Or open a window there, prop your doors open, open in furthest right bedroom and kitchen too.
Your considerations there are going to be - where is the prevailing wind coming from? Where is the sun coming from? Ideally you want the incoming air to be coming from a shaded part of the building - this will change throughout the day, but it makes a difference. Note that air takes the easiest route, so you can get dead spots. Fans can help with that. South and West-facing windows are the most problematic. - Convection/ stack effect - hot air will naturally try and get out at the top of the room. So try to open windows as high as you can for air to get out (no idea what your windows are like, but trad sash are great for this). This pulls air in from any openings/vents lower down (not good for toddlers) but could also be a consideration when trying to encourage cooler/shaded air in from one place and hot air out from another place. If you only have low down openings, the hot air in the room just stays there, stuck.
- Night-time - open everything up as much as you can and get through flow, try and get rid of that hot air and replace it with cooler. Assuming outside is cooler. At 4th floor you have the benefit of not so many moths/mosquitos/thieves coming in at night, and tend to have some air movement. But not much shade. Do you have any exposed thermal mass - like a concrete floor finish? Unlikely, but if so, cool that down at night as much as you can.
- Reduce as much solar gain as possible. Daylight is fine, it's sunlight you want to block out.
hoefla-
Thanks! This is pretty much what we've been doing for the last couple of years. If you cast your mind back to the summer of 2018 where we had weeks with highs in the 30s and it was very still, passive cooling strategies become ineffective. Our place lingered at the 29-30 degree mark inside, despite our efforts and fans and whatnot. IIRC 2019 wasn't quite so crazy but still a bit wild at times.
10,000 BTU monoblock cooler on the way - I'm thinking of it as £600 of insurance. Hopefully won't have to use it that much.
-
You have, with this post and others, unwittingly become my go-to passive cooling consultant.
Much like @Howard, we have a loft extension heat problem - during the London Summer month, the top bedroom can hit 35+°C, making it impossible to use.
This is in comparison to the first-floor mid bedroom, which is in shadow in the day, and has one external (solid) wall, that maxes out at 23 / 24°C.
It's only this year that I've really started to look at it, as with the house filling up with children, I can't just change rooms to the coolest one any more.
So far, I've been trying to mitigate it with selective window opening, (interior) shutter closing, and door opening / closing, but that only knocks it down a few degrees.
I've just shelled out for external awnings for the Velux windows - per your comment, stopping the sun before it gets to the windows seems smart - and also some more reflective blinds.
I rather feel, though, that the real problem is that the extension was built on the cheap, and the insulation in the roof is well below building regs for extensions (not that it was ever signed off...) - I've chucked a load of PIR between the roof rafters in the eaves (as there was none), and when doing so, could see that there is what looks like a very cheap thermal quilt in the main roof space.
Out options appear limited to:
- Close the door, and give up the room over Summer,
- A split aircon unit, with solar panels powering it so that I don't feel too much like an environmental disaster
- Rebuild the roof with more insulation (the rafters aren't deep enough to have think PIR and adequate ventilation
- Is there such a thing as roof shades?
- Close the door, and give up the room over Summer,
Howard
NotThamesWater
Top of a four story block. Floorplan is here. There's lots of glass (at least for a building of its age) and being quad aspect you get sun all day long somewhere.
I think there’s mileage in ‘reflective’ covering for the windows as user suggested. They open fully inwards so it wouldn’t be difficult to fit them to the exterior.
Are you familiar with solar control film? A quick google indicated that it’s important to get the right variety based on circumstances.
We have blackout blinds and curtains.
We open the windows at night, when the air outside is cooler or similar to that inside. Opening them when it's hotter outside isn't recommended as I understand it.
If you mean how air behaves as it heats and cools, kinda, I guess.