Is the Aira range available as a monobloc design? (i.e., most of the ‘gubbins’ are within the unit that lives outside) Our Daikin is of the monobloc design so there is very little to cause noise indoors; admittedly we don’t have a conventional DHW tank as we had insufficient space to accommodate more than the existing 99 litre tank so have a Sunamp Thermino ePC210 which runs silently. Our secondary pump is almost silent and with the airing cupboard doors shut, we cannot hear any sound. The pump is a Wilo Pico and runs at a consumption of ~7-9 watts. I don’t suppose any of this is relevant to an Aira system, but I do try!😉 Regards, Toodles.

Thanks @toodles. Just checked and it is indeed a monobloc design. It makes sense to me that the components I'm talking about wouldn't make a lot of noise - as far as I can tell the indoor unit is similar to an unvented hot water cylinder. Useful info that your setup is low noise

I haven't heard any discernible noise from the internal parts of my system, which is a Vaillant. Admittedly, I have no buffer, but I doubt they are noisier. And so far, no noise from radiators and pipes expanding, though perhaps when the water is hotter in winter there will be some expansion noises.

The Aira model is a monobloc, so should be similar. 

@ivanopinion We used to experience expansion / contraction noises and to a lesser extent, the sound of water coursing through the pipes when we had a gas boiler based system. With the lower temperatures used in our ASHP system, we do not hear either noise source now. The system is blissfully silent - and we love it! Regards, Toodles.

The biggest noise impact is that some of our toilet cisterns are noisy when they fill, due to the water being at mains pressure.

Posted by: @ollie

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40L buffer tank

Ask why you need it? You should be running an open system, so just one zone, so no need. No buffer means no secondary internal pump, which could add noise.

Our is completely silent.

Would I install any of it in my bedroom - no chance. 

Can you do loft for cylinder? Could be horizontal or vertical. Can you put it in an insulated shed outside?

Thanks all, very helpful. @johnmo loft would be first choice but because the tank is nearly 400kg when full I'd have to get a structural engineer involved, they'd also need to get the empty tank up there which would at minimum require a bigger loft hatch. Shed outside was also an option but I'd have to run the pipes for some distance outdoors which would be a problem in itself. 

@ollie, @johnmo raises a valid point about buffer tanks, as they can require additional distribution pumps. While it hasn’t been problematic or particularly annoying for us, I know it’s been incredibly frustrating for others, with noise keeping them up at night. The biggest noise we’ve noticed from internal components definitely comes from the distribution pumps that drive the system’s flow. They emit a low hum, and depending on where they’re located in the house, they can be quite distracting.

The other alternative for a cylinder is the heat geek mini store cylinder 

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Heat Geek Mini Store - Newark Cylinders

Newark Cylinders has launched the super-compact, highly efficient Heat Geek Mini Store, designed by leading heating experts, Heat Geek.

@johnmo

The Mini Stores look great and would appear to be the solution to a problem, but would they get past the MCS criteria?

Our old gas system used to wake OH when the heating came on, partly through valves for the hot water coming on and partly through radiator creaking noises as they warmed. For a full year we’ve run the gas central  heating low and continuously so that did  anyway with the creaking. The airing cupboard is in the bedroom and it still has the change over valve in it so it should be no worse.