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4 years on... Finally have planning and hope to build this autumn. The plan is still to sit the MVHR I'm the eaves. We'll use ended joists to convert the loft and run ducts through those.

Resurrecting an old thread... this is copied from the PAUL guide referenced. The internal RH of the summer daytime normal heat exchange is 74%. The internal RH of the enthalpy setup is 60%. So I'm not sure it's a like for like comparison? Also wondering if the enthalpy exchanger would help with dehumidification if the house is being cooled in summer?

Great thread I'm a little late to. If trenching anyway, wouldn't it make sense to duct refrigerant lines through solid pipe e.g. 110mm soil pipe, and insulate around the soil pipe e.g. with a combination of XPS and spray foam? That would allow changing out the lines if needed, and minimise losses. I presume the air held in the soil pipe would be static and a reasonable insulator. I wonder if pre-insulated refrigerant lines could be run through the soil pipe, and if that would make much difference vs just insulating outside the soil pipe.

https://mhclgmedia.blog.gov.uk/2024/11/21/warm-homes-plan-and-heat-pumps/ Great news, the 1m from a boundary requirement for PD is to be scrapped. In worse news we didn't know this when we submitted our planning application in Dec 2024, to include a heat pump down the garden and by the boundary (mid- terrace). So we've now poked the planning and noise assessment bear. Any idea when this will actually come into force? I can only see references to early 2025.

I realise this is the wrong time of year to ask...but what have people's experiences been of cooling at temperatures above the dew point? This will surely increase humidity, and actually get below the dew point in a controlled manner would be beneficial for the humidity. Was there any need to run a separate dehumidifier? If you had MVHR, what settings did you have to mitigate this? We would have upstairs UFH in P5 chipboard, so moisture control is critical, downstairs TBC. I feel like I might end up 2 loops with the option to set them at different flow temperatures: (Loop 1) UFH and (Loop 2) insulated pipework with FCUs. I have a decent Home Assistant automation setup and independent control of each would be really useful. Running both loops at the same temperature would allow a minimised flow temp and maximised COP. If we want a rapid warmup we can run the FCUs at a higher temp than the UFH. If we want a rapid cool down we can run the FCUs lower than the UFH. To dehumidify when cooling we can drop the FCU temperatures below dewpoint and/or increase their fan speed. We could even increase the UFH flow temperature accordingly to prevent overcooling. This does beg the question of why not purely fan coil units. It's not a gigantic property (160sqm after extension). We'll be fitting new flooring to much of it anyway e.g. for the kitchen & bathrooms I think there's a clear benefit to UFH above FCUs.

Do you then have two loops, one for the fan coil+buffer and one for the UFH? How do you control this? The Panasonic (I think) heat pumps allow two zones at different temperatures. I wondered if there was an easier way of achieving this with other models.

I can see that if you bring in warm air into the cool house the relative humidity will increase- so in this instance reducing airflow through an MVHR would be beneficial. They may reduce a little of the incoming air's moisture as it is cooled by exhaust air but I doubt I huge amount. Perhaps the main pitch for the comfopost should instead be for dehumidification as part of a larger cooling setup.

I'd see the ability from fancoils added to UFH to preferentially cool certain rooms (e.g bedrooms) handy. Without UFH too, I'd go below the dew point using insulated pipe and condensate drains. With the UFH, taking the fan coils below dew point would I think require two loops, a diverter, and a volumiser for the fan coils loop? Unless you can run one coming loop at 7 degrees C supplied in insulated pipe, then blend the UFH to a temperature above dew point? I can see the argument for just adding AC, but as additional outdoor unit wouldn't suit our property (mid-terrace).

So all of this has confirmed for me that a comfopost isn't worth it for us. If you're running fancoils on the same loop as UFH, presumably that gives plenty of circulating volume. It would then run offset above the dew point, accepting achieving less than maximal cooling/heating output from the fan coils. It seems to me there's little point in running insulated pipe to supply the fan coils? And is there any need then to provide a condensate drain for the fan coils?

I initially thought 3 fan speeds seems a little basic, however the panasonic FCUs are only 4 speed https://www.bpcventilation.com/panasonic-fan-coil-unit

is the summer house also UFH? How do you take the water loop from your house to the summer house, and how far is it?

Thanks Dan, your comments on that other thread I linked were very helpful. My understanding is that if you have active cooling, the MVHR should cool intake air using exhaust air if you disable the summer bypass? Are there any benefits you can see you the comfopost additional to fancoils +/or UFH at all? I.e. if money were no object (unfortunately not the case) then could you argue for both comfopost plus the UFH/fancoils?

Hi John, what's the floor area and the floor construction inc covering your UFH is in? Was this ground floor only, or upper floors? That's superb efficiency and personally I'd see the money as well-spent to maintain a comfortable temperature. I still come across lots of people who happily burn oil to heat their house to 25 degrees but think it's unacceptably wasteful to apply cooling using (renewable or even self-generated) electricity.

Yeah I had looked at the datasheets- the largest comfopost can do 2.8kw cooling (ERV MVHR) with 600m^3/hr air flow. So noisy and limited cooling- but I think it's useful to get actual experience of that too. There's another useful thread on here from someone who decided against heat battery/cooling in the end.

Exactly the clear answer I needed! Out of interest though, have you got any data through HA about it? What size heat battery have you got, and what flow temp and air flow were you using?