What is the ceiling like, all one level up to the stairwell? If so, creating a false transom to block the flow along the ceiling can help reduce heat migration upstairs. I did this in our house with good success. The ceiling was flat before I added this and the wood stove heat would head right up the stairs. With this block, it has more resident time in the living and dining rooms.
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Also, check upstairs closely for air leaks. If air is leaking through poorly sealed windows, attic vents or stairs, etc., then that will create a chimney effect, pulling the heat upstairs.
Thanks. It's completely open plan (downstairs has a kitchen/diner and living room, partially separated by an interior wall but with no door between the two rooms. The living room has the stairs in it, leading directly up to a small landing where the bathroom and 3 bedrooms are located, all with doors thankfully so I can at least close them off) so I am not sure a false transom would work (nowhere to reasonably put it!). Good to know that blocking air flow across the top of the room might help, maybe I can come up with some way of thinking that through...
Regarding leaks almost definitely - I need to weatherproof the window at the top of the stairs (which is great for light, but probably not so great for avoiding a chimney effect) and change the hatch to the attic (also at the top of the stairs) to one that's insulated I think.
You or someone else can n your family may not like this solution but I will throat out there. Clear vinyl strip door and clear shower curtains. They do not meet to go all the way down but far enough to keep a decent layer of warm air from going up the stairs.
Might end up feeling a bit like an abattoir! But thanks for the suggestion. What other kinds of materials might work? I am guessing thermal cloth curtains might do the job, would a bedsheet or something less permanent have a noticeable effect do you think?
The air "stratifies" (layers) in the warm room, with indeed the warm air at the top. So the hottest air is the air that goes up first, because it moves easiest (least dense) and because it's first in line to get there.
Therefore, one step that may help is to mix the air (decrease its stratification) in the warm room. That is best done with a ceiling fan.
A curtains to somewhat close off the path to upstairs might be considered if possible.
If you have multiple rooms upstairs, keep all the doors closed (so that only the landing gets the heat).
Blowing down warm air from upstairs is likely going to be least effective, because it won't be as hot anymore, and making it flow is going to make people feel colder. (I.e. it has cooled down to a few degrees above what you want downstairs, so you'd have to blow a *whole lot* of air down the stairs to move enough BTUs down the stairs because the heat content of "slightly warmer" air is not so high - and blowing a whole lot means people will feel the wind, making it actually feel less comfortable. That's the same reasoning as putting your AC to a bit higher temp and adding a fan in summer.)
So, prevention is the key, not mitigation of heat that has escaped upstairs.
Better suggestions might (...) be possible if the layout of the spaces is provided.
Begreen's suggestions are very helpful too in preventing this from happening.
Thanks for the explanation of air stratification. I suspected when posting this that prevention might end up being the answer, but good to have it confirmed (and some tips provided by you and others). I could feasibly put some kind of curtain on/around the stairs, not sure my partner would go for that though.
How are you heating the house? If forced hot air, do you have returns? Keeping the fan running can help circulate the air. With a boiler, are you on a single zone? Do you have a gravity fed system or a circulation pump? A ball valve can sometimes be installed to control how much hot water flows through a loop. Part of your issue could be simply too much heat being directed upstairs.
Could changing the thermostat location(s) help by running the heat less?
I am in the UK where we don't tend to have any kinds of fancy heat circulatory systems in our homes - it's a classic steel radiator in each room powered by a gas condensing boiler. Excluding the landing at the top of the stairs which has no radiator. I could certainly move the thermostat up into that space and maybe set it at slightly higher than I would want downstairs to be and see if that makes a noticeable difference? I suspect it would just mean the heating cuts out around the same time though. In all honesty I find downstairs being too cold worse than upstairs being too warm.
Lots of valuable info above. As EatenByLimestone said, if you have any type of heating which can be 'zoned' - that certainly helps. I used to live in a 2-story town home and it was a bi-annual task to open all the air vents upstairs / close all vents downstairs so the air conditioner could keep the upstairs cool and the downstairs naturally stayed cool. Then reverse for the winter so the furnace could heat the downstairs and the upstairs stayed naturally warm.
If you don't have that, then as stoveliker said anything which can help break up the 'hot' air stream, or even things like closing doors upstairs can help stop the hot air from rising up there.
As above, sadly no vents whatsoever in this home (unless you count the leaky windows and walls...). As you and others have said, I think maybe the 'breaking up of air flow' is gonna be the best option. Thanks for the suggestions though!