How many vent tiles to ensure loft temperature is same as upstairs room temp during a heatwave? Or even better lower?

BluebottleTrap · Tuesday at 5:11 PM

I need to get scaffolding so I don't want to half-arse this. I'd like to be able to open my loft hatch on a hot summer night and feel warm air rushing up into the loft and out through these tiles. Right now I open the loft hatch on a hot day and feel blasted by hot air coming down from the loft! I know 'hot air rises', but I swear I can feel hot air come down when I open the loft hatch (must be higher pressure or something).

I have a 1960s three bed mid terrace with normal tiles. I was thinking 8 ventilating tiles at the top (4 on each side of the roof), and then another 4 on each side lower down.

Or would just getting a single velux window at the top that I can open be simple? Or one of those spinning extractors?

noseall · Tuesday at 6:51 PM

BluebottleTrap said:
I need to get scaffolding so I don't want to half-arse this. I'd like to be able to open my loft hatch on a hot summer night and feel warm air rushing up into the loft and out through these tiles. Right now I open the loft hatch on a hot day and feel blasted by hot air coming down from the loft! I know 'hot air rises', but I swear I can feel hot air come down when I open the loft hatch (must be higher pressure or something).

I have a 1960s three bed mid terrace with normal tiles. I was thinking 8 ventilating tiles at the top (4 on each side of the roof), and then another 4 on each side lower down.

Or would just getting a single velux window at the top that I can open be simple? Or one of those spinning extractors?

Get the loft insulated to within an inch of its life and keep the (insulated) hatch closed. all the will in the world is not going to stop the temperature increasing in there unless you remove all the tiles and membrane.

BluebottleTrap · Tuesday at 8:17 PM

noseall said:
Get the loft insulated to within an inch of its life and keep the (insulated) hatch closed. all the will in the world is not going to stop the temperature increasing in there unless you remove all the tiles and membrane.

So when people say they open the loft hatch during heatwaves thinking they are clever because ‘hot air rises’ are imagining it? I’ve always suspected so, I’m the kind of person who’ll get thermometers, humidity sensors etc and properly test things - and never observed this loft hatch trick working.

Wayners · Tuesday at 8:24 PM

I've plastered and painted upstairs ceilings in heat waves and had problems because the plasterboard ceilings are hot. A lack of insulation is the cause..
Heat travels to cold so you need to try and keep it out with insulation.
Open things up early morning and later evening to cool the property.
Eventually only an air conditioner works as the property warms up

Si_ · 2026-06-03T15:35:07+0100

BluebottleTrap said:
So when people say they open the loft hatch during heatwaves thinking they are clever because ‘hot air rises’ are imagining it? I’ve always suspected so, I’m the kind of person who’ll get thermometers, humidity sensors etc and properly test things - and never observed this loft hatch trick working.

It depends on the temperature difference. If it's small, air will flow upwards for a time and the house will cool. If it's large, air will flow both ways and the house will heat up. I intend to fit an extractor fan in the loft to dispel the nuclear reactor levels of heat we get on hot days.

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How many vent tiles to ensure loft temperature is same as upstairs room temp during a heatwave? Or even better lower?

BluebottleTrap

noseall

BluebottleTrap

Wayners

Si_

DIYnot Local

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