My mania for A2A heat pumps is well known on this forum. I've a few questions.

1. Is the controllability they offer a significant benefit?

I'm looking forward to the controllability they offer. I intend to have three indoor units. Each will be independently controllable and programmable via the handset or an app on my phone. That's significantly better than my current radiator TRV based system. Even a tree hugger like myself can't be bothered to switch off TRVs that I don't need to be on, and so I often heat areas that don't need to be. I think the independent controllability will reduce this.

2. Is their ability to dehumidify a significant benefit?

Secondly, modern air conditioners appear to be able to dehumidify, if necessary, without lowering the indoor temperature much. Given I try to keep air leakage down, and do suffer from humidity in some areas, this feels useful. Would probably mean I would need to worry less about, for example, drying laundry in the house, or humidity from cooking and showers etc.

3. Is a unit that can also ventilate a good idea?

Finally, there are some units (like the ururu sarara one in catalogues available here: http://tinyurl.com/zlmmbrs) that can bring in fresh air at the same time. Feels sensible. As long as you are knocking a hole in the wall for these things, might as well add a channel for fresh air. Which feels like it can kind of provide MHRV in to the bargain.

This last one is basically me trying to justify buying the ururu sarara unit to myself. The claimed COPs are stratospheric (well over 5), but it's twice the price of a high performing R401a unit. I'm trying to persuade myself that the added ventilation provided, in addition to slightly higher COP, makes it worth it.

Incidentally, more manufacturers are rolling out the new, higher performing R32 refrigerant across their range. Reckon it gives a 10% boost to COPs for all types of heat pump, a good thing.

Posted By: GarethC2. Is their ability to dehumidify a significant benefit?

3. Is a unit that can also ventilate a good idea?

I think that in general if you have good ventilation, you don't need dehumidification, at least in our climate.

And the consideration with ventilation is of course heat recovery. Does it do heat recovery, or is it always using a heat pump to make the full temperature adjustment?

<blockquote><cite>Posted By: djh</cite>
I think that in general if you have good ventilation, you don't need dehumidification, at least in our climate.</blockquote>

I first discovered the virtues of dehumidifiers in western Ireland. For the first half of this winter, much of southern England has experienced a western Irish climate

I wonder if there is some metric (COP, SEER, efficiency, efficacy etc) that can be modified to give a sensible comparison of heat pumps that also ventilate and also against combinations of separate systems?