Who's in the UK and has caved in and bought air conditioning?

I am in the process of watching Run Away on Netflix.  It is set in the UK and filmed there as well.  I am not sure what specific region though.  Anyway while the shots of the country side are beautiful and green they seem less green than I remember from previous trips I've taken to England... so a question for those in the UK... with the recent rise in temperatures during the last few summers are things less green now?  Or am I remembering things through 'emerald green' tinted glasses?

The UK is consistently Grey and overcast as a general rule. Except 5-8 weeks in the summer where our insulated miserable weather houses struggle with 30C and we all think about getting aircon.  The hard bit is our walls are solid with no space for ducting of any kind, so if you have the money some people end up with free standing units.  Still rare. 

e14phil said:

The hard bit is our walls are solid with no space for ducting of any kind

I'm planning on ducting through an existing window vent (or two) 

Have just acquired a 6" duct fan that can move up to 402cfm, so hoping I can tap into some of the cooler evening air to help with night time sleeping, without going to full-on aircon at this stage.

Although, I suspect that the solid walls / roof space act as a storage heaters to some extent.

For a dual 9" that is quite a low flow rate and a lot of noise. The AC Infinity 8" duct fans are rated at 807 CFM and 10" fans at 1201 CFM in comparison. The 32 dBA of the 6" on minimum was attractive for sleep though.

Visualising what is actually going on with airflow throughout the house is the tricky bit. Not sure if there is a low cost practical sensor solution that could be used to log it alongside multiple temperature sensors.

I recall the cheap 4" duct fans that I was experimenting with twenty years ago in the office, playing all sorts of tunes with the wind loading on them.

I'm using a generic fan from Amazon Comfort-CZ319WT-Reversible-Auto-Locking-Expanders.  Fairly wimpy Air Flow Capacity 272 cfm.  Speed 2884 rpm.  Noise Level 53.3 db.  So, not that quiet.  I run the higher speed which is what I think the specs apply to.  It is quieter at the lower speed, but I haven't tried measuring the impact to cooldown time.  I do run one on the first floor too, but the results seem to  superpose - so I imagine having intake and exhaust on the same level provides some degree of isolation.  I should do a smoke test to view the airflow .  One humorous note, we sleep in a downstairs bedroom with the doors closed and I don't notice the sound of the fans, but one night I realized that I could hear what is apparently the beat frequency of the two fans.

A great party trick, just remember your long bag.

I notice though that a number of cooling fans appear to tend to push air out more to the sides rather than directly to the front, in which case the further they are placed back may reduce the amount actually making it through the window opening. In which case they may benefit from some sort of cowling.

This has all to do with the Bernoulli effect where nearby air is "sucked" along the one blown by the fan. 

Look for videos with Bernoulli and bag as keywords for quite graphic display of the principle.

For more practical applications, this same principle is used by "fanless" fans sold by a famous UK vacuum cleaner manufacturer. 

ralphjy said:

I’m not sure I understand the effect of spacing the fan a meter from the window.

Is the spacing to prevent the air from being drawn in from the window then pushed straight back out ?
You won't have that issue with the fan fitted into the window though. 

ralphjy said:

When I lived in California we had high volume whole house fans that drew air from the house through the attic and out the side of the attic.

I saw these when looking at 6" - 8" duct fans.

Looks like 10" - 12" in size and 1201 - 1604 CFM 

https://acinfinity.com/whole-house-fan-systems/ 

I’m not sure I understand the effect of spacing the fan a meter from the window.  Do you have a link to this study?  Like Dave, I tried exhausting air from the upstairs window (I had the fan physically in the window with the sash down).  I think I agree with Dave that this would work if a large volume of air was moving.

When I lived in California we had high volume whole house fans that drew air from the house through the attic and out the side of the attic.  Those were very effective.  I don’t remember what they were rated, but you definitely knew when they were operating.

https://www.bbc.co.uk/news/articles/cly76jlxljlo

"...Placing the fan next to the open window and pointing it inwards, towards the rest of the room, can help.

But pointing the fan towards the window - to try and blow the hot air in your home outwards, as some social media posts advise - isn't particularly useful as you would not get the cooling benefits of having it pointed towards you..."

That was my original thought as well but it wasn't working in actual practise.

Lower kitchen window open and mechanical venting out of upstairs bedroom window.

The downstairs kitchen appeared to be benefiting but not the upstairs bedroom.

I think the reason is a large volume of air needs to be moved through the entire house before the exit point starts to get the benefit. At the same time trapped building heat upstairs is heating any cooler air being drawn up through it.

Thanks for this, it is really useful info.

To solve the casement window issue, I'm kind of thinking of a rectangular board that fits over the window opening then quarter turn latches to lock it in place (or alternatively hinge it from the ceiling). Then fit fans / duct flanges to the board.

The upper vent windows in the bedroom are around a 19" x 10" opening, so could perhaps take up to two 8" side-by-side, or one 10", or one 12"+ with a round to oblong/rectangular manifold.

What sort of fans are you using and are you running both at full speed ? My 6" duct fan at full speed moves a lot of air (402 CFM) but at the expense of a lot of noise. On minimum setting though it's very quiet.

However I think the bigger issue here is that I'm hitting a plateau long before reaching outside temperature. I'm not getting that same cooling overnight that you are seeing without ventilation. (26°C is around 79°F). 

Some mornings this year I've been waking up to 30.0°C (86°F) even though overnight temperature outside has been forecast at around 20°C.

I was wondering if a push-pull arrangement in the one room might work with cooler outside air being pulled in through one window vent and pushing warm air out of the other.

beacon_dave said:

I found that by pulling the cooler evening outside air into the room lowered the room temperature much quicker than pushing the hot room air out.

A university in the Netherlands had the opposite finding during a study:

Putting a fan pointing outward , a meter in front of an open window, while having another window open at the other side of your house, was the post efficient to lower temp.

If you have several floors, put the fan upstairs, and open the opposite window downstairs.

That seems to generate the mos efficient heat exchange draft inside.

beacon_dave said:

I found that by pulling the cooler evening outside air into the room lowered the room temperature much quicker than pushing the hot room air out.

A university in the Netherlands had the opposite finding during a study:

Putting a fan pointing outward , a meter in front of an open window, while having another window open at the other side of your house, was the post efficient to lower temp.

If you have several floors, put the fan upstairs, and open the opposite window downstairs.

That seems to generate the mos efficient heat exchange draft inside.

I understand the Bernoulli effect, but as Dave has mentioned there is a lot of more going on with the dynamics of airflow in a house that can cause it to be not effective.  Unfortunately, without doing quite a bit of experimentation/measurement I don't think that it will work for me.  Suffice to say, air intake with a low velocity fan with an outside to inside temperature differential and airflow to an open window in a second room works well and reversing the airflow does not.  In the intake scenario I have the fan mounted in the window and in the exhaust scenario I positioned the fan 1 m from the open window.  Unfortunately, this room does not have multiple windows so the airflow path is not straightforward and the air intake velocity at the remote window will be very low. With both windows in the same room exhaust might work better.  Pulling cold air from a second room's window through to the room you are trying to cool will work but with a lot longer time constant. 

A great party trick, just remember your long bag.

I notice though that a number of cooling fans appear to tend to push air out more to the sides rather than directly to the front, in which case the further they are placed back may reduce the amount actually making it through the window opening. In which case they may benefit from some sort of cowling.

This has all to do with the Bernoulli effect where nearby air is "sucked" along the one blown by the fan. 

Look for videos with Bernoulli and bag as keywords for quite graphic display of the principle.

For more practical applications, this same principle is used by "fanless" fans sold by a famous UK vacuum cleaner manufacturer. 

ralphjy said:

I’m not sure I understand the effect of spacing the fan a meter from the window.

Is the spacing to prevent the air from being drawn in from the window then pushed straight back out ?
You won't have that issue with the fan fitted into the window though. 

ralphjy said:

When I lived in California we had high volume whole house fans that drew air from the house through the attic and out the side of the attic.

I saw these when looking at 6" - 8" duct fans.

Looks like 10" - 12" in size and 1201 - 1604 CFM 

https://acinfinity.com/whole-house-fan-systems/ 

I’m not sure I understand the effect of spacing the fan a meter from the window.  Do you have a link to this study?  Like Dave, I tried exhausting air from the upstairs window (I had the fan physically in the window with the sash down).  I think I agree with Dave that this would work if a large volume of air was moving.

When I lived in California we had high volume whole house fans that drew air from the house through the attic and out the side of the attic.  Those were very effective.  I don’t remember what they were rated, but you definitely knew when they were operating.

https://www.bbc.co.uk/news/articles/cly76jlxljlo

"...Placing the fan next to the open window and pointing it inwards, towards the rest of the room, can help.

But pointing the fan towards the window - to try and blow the hot air in your home outwards, as some social media posts advise - isn't particularly useful as you would not get the cooling benefits of having it pointed towards you..."

That was my original thought as well but it wasn't working in actual practise.

Lower kitchen window open and mechanical venting out of upstairs bedroom window.

The downstairs kitchen appeared to be benefiting but not the upstairs bedroom.

I think the reason is a large volume of air needs to be moved through the entire house before the exit point starts to get the benefit. At the same time trapped building heat upstairs is heating any cooler air being drawn up through it.