Question Supplying fresh air to a cinema room. Can PC fans do it?

Triggaaar

Distinguished Member
I hope to finish our extension build in a couple of months, and move on to building the cinema room (build thread here: A dreamer stops dreaming)

I'm putting in a single room MVHR (Mechanical Ventilation with Heat Recovery) for the kitchen/living area, but I also need a solution for the cinema room.

I don't want 24/7 MVHR for it, as the kind of unit I'd need would be too costly.
I don't want aircon, as that too will be costly.

Instead, what I'm hoping to do, is simply run some ducting extracting from the cinema room into the utility room (where there is an MVHR extract), and from the kitchen/living space into the cinema room. I'm not worried about cooking smells going into the cinema room, as I'd keep the pipes away from that area. The fans would only really need to be on when using the room.

What I'd like to know is if 120mm/140mm static pressure PC fans are capable of pushing air down a 125mm ish PVC duct, and if so, for how many metres. Any ideas?

Thanks
 

mikeysthoughts

Well-known Member
How big is the room to be ventilated? One fan certainly won't do it as it won't be able to shift the cubic metres you'll need but a few working together might, at a push.

Worth noting that everyone I've seen that has a MVHR regrets it, but that's a separate thread entirely!
 

Triggaaar

Distinguished Member
How big is the room to be ventilated? One fan certainly won't do it as it won't be able to shift the cubic metres you'll need but a few working together might, at a push.
Finished dimensions of about 4.6m x 3.7m (less chimney breast) x 2.6m high (less riser) = about 42 cubic metres. I was thinking of an extract point above the AV equipment and an inlet point at the opposite end of the room, as well as both an extract and inlet to the projector, to help keep it cool. So I was thinking of 4 fans.

Worth noting that everyone I've seen that has a MVHR regrets it, but that's a separate thread entirely!
Oo. Can we make it this thread too please? Why have they regretted it?
 

mikeysthoughts

Well-known Member
Finished dimensions of about 4.6m x 3.7m (less chimney breast) x 2.6m high (less riser) = about 42 cubic metres. I was thinking of an extract point above the AV equipment and an inlet point at the opposite end of the room, as well as both an extract and inlet to the projector, to help keep it cool. So I was thinking of 4 fans.
Interesting concept.

If your primary goal is localised heat extraction away from equipment, plus some oxygenation of the room, you might find it to be successful.

For overall room cooling, I'm extremely doubtful. The incoming air is unlikely to be cool enough to have any meaningful impact on the room. Ambient temperature will rise as heat generated by AV equipment and humans is going to greatly exceed the cooling capabilities of the system.

Oo. Can we make it this thread too please? Why have they regretted it?
Genuinely worth asking this in the relevant subforum. Both here and on self-build home forums I've seen many complaints about the high running costs, poor overall performance and loud operation.

I was initially investigating it for a self build house but discounted it quite quickly.
 

Triggaaar

Distinguished Member
Interesting concept.

If your primary goal is localised heat extraction away from equipment, plus some oxygenation of the room, you might find it to be successful.

For overall room cooling, I'm extremely doubtful. The incoming air is unlikely to be cool enough to have any meaningful impact on the room. Ambient temperature will rise as heat generated by AV equipment and humans is going to greatly exceed the cooling capabilities of the system.
Mmm. Cooling equipment and some oxygenation were the primary objectives. While I'm not trying to make the room cool, I don't want the room getting uncomfortably hot.

Genuinely worth asking this in the relevant subforum. Both here and on self-build home forums I've seen many complaints about the high running costs, poor overall performance and loud operation.
I have posted about it on a build forum, where the units seem popular enough, but then the members there tend to be on the extreme end of insulating and removing air leaks, so MVHR is a necessity. I don't have any choice but to have MVHR for the new kitchen area (I don't have window trickle vents, and the kitchen hood doesn't extrac), but your comments certainly make me cautious about having a larger unit the works for other rooms in the house.
 

Triggaaar

Distinguished Member
What I think I'll do is get some lengths of pipe laid out on the floor, attach a fan or two, and see if there's much airflow at the other end.

140mm static pressure fans seem like the ones I'd want. Any idea if I'd get them to work better with either 125mm or 150mm ducting pipe?
 

mikeysthoughts

Well-known Member
The air transfer system will slow the rate of temperature increase, but without a more active system (Aircon ideally) you'll probably find yourself getting toasty by the end of the film.

The three primary factors in this are the temperature differential, the air flow rate and the heat generation in the room.

Applied to your proposed system, temperature differential will be fairly small... You'll be drawing air into the room at the ambient temperature of your kitchen/living space, say 20C. This wouldn't be low enough to have a proper cooling effect. Contrast that with the air coming from an Aircon on an appropriate setting which would be around 10C.

Regarding airflow, one 140mm fan shifts around 45 CFM or 76 cubic metres per hour. Two working together at each end of a pipe will reduce the load on each fan, but for simplicity sake, your overall air moved will be similar. I'd say 140mm fans on a 125mm duct would be best, to give lower turbulence through the pipe.

So coming into your 42Cu m3 room you'd have 76cu m3 of 20C air per hour. Fair to assume the same going out, so you'd have 'new' air every 35 min or so.

On the face of it you might be ok. What we need to do is understand the heat generated by the AV equipment and your own body, and then whether the cooling effect of that amount of incoming 20C will have enough of an impact. That's trickier!
 

Triggaaar

Distinguished Member
Wow, thank you for your comprehensive thoughts mikey.
The air transfer system will slow the rate of temperature increase, but without a more active system (Aircon ideally) you'll probably find yourself getting toasty by the end of the film.

The three primary factors in this are the temperature differential, the air flow rate and the heat generation in the room.
I understand the 3 factors you've explained, but I have no idea what those numbers will be.

Applied to your proposed system, temperature differential will be fairly small... You'll be drawing air into the room at the ambient temperature of your kitchen/living space, say 20C. This wouldn't be low enough to have a proper cooling effect. Contrast that with the air coming from an Aircon on an appropriate setting which would be around 10C.
If the temperature differential is really small, then the solution must be working :) Obviously it won't cool like aircon. It also won't be able to keep the room as cool as the kitchen space. That's fine, as long as it doesn't get too hot (I don't actually know what 'too hot' is in degrees. Not something we generally have an issue with.

Regarding airflow, one 140mm fan shifts around 45 CFM or 76 cubic metres per hour. Two working together at each end of a pipe will reduce the load on each fan, but for simplicity sake, your overall air moved will be similar. I'd say 140mm fans on a 125mm duct would be best, to give lower turbulence through the pipe.
The fans I'm looking at say 74 CFM, but I imagine that will be at 0pa (pressure). I have no idea how much they'll move in practice, hence thinking I'd try and test before running the pipe. A fan at each end of the pipe sounds ideal, but I'd be concerned about any noise at the cinema end. I wondered about a fan at the end (about 2m outside the room) and another immediately outside the room. Not as good as 1 each end, but no issue with noise. Maybe they're quiet enough that I can have them in the room too?

I'd say 140mm fans on a 125mm duct would be best, to give lower turbulence through the pipe.
Oh, I'd assumed a larger pipe would give less turbulence, as the air will move slower for the same volume/hour.

So coming into your 42Cu m3 room you'd have 76cu m3 of 20C air per hour. Fair to assume the same going out, so you'd have 'new' air every 35 min or so.

On the face of it you might be ok. What we need to do is understand the heat generated by the AV equipment and your own body, and then whether the cooling effect of that amount of incoming 20C will have enough of an impact. That's trickier!
Understood, and thanks again.

I assume the only alternative is to actually fit an aircon unit, and run that through the pipes, and to the outside. Have you any idea how much a suitable unit would cost?
 

mikeysthoughts

Well-known Member
For me too hot would be 26C, but we're all different!

The fans I'm looking at say 74 CFM,
They'll be noisy buggers then to shift that much air at 140mm. I wouldn't want that in the room, but outside should be fine.

Oh, I'd assumed a larger pipe would give less turbulence,
My understanding is that you'd achieve a less turbulent flow with the smaller pipe, because the air wouldn't dissipate outwards from the fan after it has entered the pipe. Very difficult to describe in words, and I could be wrong. Nothing wrong with experimenting and seeing for yourself! The push/pull effect of one fan at each end would reduce turbulence regardless of pipe size.

Fixed Aircon I think you're looking at around £800+ installation.
 

Triggaaar

Distinguished Member
They'll be noisy buggers then to shift that much air at 140mm. I wouldn't want that in the room, but outside should be fine.
This is the fan I'm currently thinking:

Arctic have a table showing the different properties of their fans (noise level, pressure, etc), and this one seems most suitable. Here's the same fan at Amazon, showing Arctic's comparison table:

My understanding is that you'd achieve a less turbulent flow with the smaller pipe, because the air wouldn't dissipate outwards from the fan after it has entered the pipe. Very difficult to describe in words, and I could be wrong.
The words make perfect sense. Arctic have a diagram (in that Amazon link) showing the airflow from their P series, suggesting the air is supposed to concentrate after the fan, so the 125mm could be more suitable.

Nothing wrong with experimenting and seeing for yourself!
The only issue is I can't really buy multiple sizes of pipe, I need to choose and order the whole lot (well, I could if I wanted to order a few, pay the postage, and bin what I don't use, but that doesn't fit the budget).

Fixed Aircon I think you're looking at around £800+ installation.
Excellent, thank you. If I go with my fans, and in the future I decide to add Aircon, do you think it would be able to connect to the ducting I install (with the odd adapter)?
 

Harkon321

Well-known Member
I’ve looked at inline fans for mine. One for extraction in the soffit and then a quiet extractor as an intake from kitchen. This would be ducted through A dead vent surrounded by insulation.
I’m going to wire for air con but try without first.
 

Triggaaar

Distinguished Member
I’ve looked at inline fans for mine. One for extraction in the soffit and then a quiet extractor as an intake from kitchen. This would be ducted through A dead vent surrounded by insulation.
I’m going to wire for air con but try without first.
Sounds like a plan. I was also thinking of just shoving an inline fan near the end of the pipe, but the PC fans might do what I need.

What do you mean by 'a dead vent'?

Thanks
 

Harkon321

Well-known Member
Google sound proofing and dead vent.

It’s basically a cavity stuffed with insulation that the duct pipe snakes through. So my plan is to have extractor fan high on kitchen wall, then down a stud cavity full of insulation and out through the bottom through cinema wall.
 

Triggaaar

Distinguished Member
Google sound proofing and dead vent.

It’s basically a cavity stuffed with insulation that the duct pipe snakes through. So my plan is to have extractor fan high on kitchen wall, then down a stud cavity full of insulation and out through the bottom through cinema wall.
Like this

Great stuff, thank you.

I should be able to do some of that, although I'm not sure where yet (which ends of the pipe etc). My current plan is to have rigid ducting, which would stop me have the S curve in a dead vent, but I may be able to work a solution.
 

Harkon321

Well-known Member
Curve means sound has no direct path. Depends how far you want to go with stuff.
 

ufo550

Well-known Member
Mmm. Cooling equipment and some oxygenation were the primary objectives. While I'm not trying to make the room cool, I don't want the room getting uncomfortably hot.

I have posted about it on a build forum, where the units seem popular enough, but then the members there tend to be on the extreme end of insulating and removing air leaks, so MVHR is a necessity. I don't have any choice but to have MVHR for the new kitchen area (I don't have window trickle vents, and the kitchen hood doesn't extrac), but your comments certainly make me cautious about having a larger unit the works for other rooms in the house.
I might have to have MVHR on my conversion. Seen these two which boast of low(ish) noise levels, but its the noise they'll let out I'm concerned about.


 

mb3195

Distinguished Member
AC if possible should be one of the top priorities of a cinema room. I know of high end installs that don’t have it and 100% regret not going down that route. Everything in a cinema room gets hot, including people. During the winter it’s not an issue, but imagine watching a film with the temps we had last week.

My first ever film I watched in my room before AC was rogue one. 4 of us in the room, temp at the start was 21 degrees. 45 minutes later it went up to 28, 10 minutes after that we stopped the film and left the room as it was too hot.

If you can do it, do it.

Just ask @steelman1991 who has the same current dilemma.
 

Harkon321

Well-known Member
That’s really interesting as I’m trying to wing it without. Do you use it for heating as well? Worried that it’ll take too long to warm up the room and make more noise than the projector when running and be a distraction?
 

mb3195

Distinguished Member
That’s really interesting as I’m trying to wing it without. Do you use it for heating as well? Worried that it’ll take too long to warm up the room and make more noise than the projector when running and be a distraction?
they heat as well. In the winter I just select “cinema pre warm” on my harmony app, wait 5 minutes and go in to a toasty room with all
My equipment all on ready to go.
 

Harkon321

Well-known Member
@mb3195 Do you leave it on whilst watching a film? Just wondered how loud it is?

Only experience of AC being holiday apartments. 🙄
 

mb3195

Distinguished Member
@mb3195 Do you leave it on whilst watching a film? Just wondered how loud it is?

Only experience of AC being holiday apartments. 🙄
on all of the time, you can put it in silent mode where it really it almost it silent. I just leave it in auto, I listen really loud so never notice it.
 

Harkon321

Well-known Member
Don’t suppose you know what unit you have fitted? And then I’ll leave this poor guys thread in peace. 🤔
 

Triggaaar

Distinguished Member
AC if possible should be one of the top priorities of a cinema room. I know of high end installs that don’t have it and 100% regret not going down that route. Everything in a cinema room gets hot, including people. During the winter it’s not an issue, but imagine watching a film with the temps we had last week.
Having not experienced it, it's difficult to imagine. Our house hasn't been too hot anywhere indoors this year. Of course I realise the cinema room will be different, but I don't know whether it'll be quite warm, or too hot.

My first ever film I watched in my room before AC was rogue one. 4 of us in the room, temp at the start was 21 degrees. 45 minutes later it went up to 28, 10 minutes after that we stopped the film and left the room as it was too hot.
Blimey, that's not good. But if that was the case with everyone's cinema room, I imagine we wouldn't see a cinema room here without it.

If you can do it, do it.
Well I don't have the budget for it, but if it's not actually possible to watch a film in there, I'll have to get cheaper AV gear (think 2nd hand Epson instead of 2nd hand JVC) to be able to get it.

How much do you think it could be done for (with 2 pipes 5m to the outside wall)?
 

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