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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?

I forgot to include the link to the product I was referring to- these are what I spotted https://aerfor.com/en/reverso

I've also spotted these recently. I don't love the look personally but appreciate the price and flexible mounting options. I presume these would also give the option for some individual room control of cooling (for examples different preferences for bedroom temperature), although with the small buffer volume issue that's been already mentioned. It also strikes me that the optimal positioning and airflow direction does vary between heating and cooling applications, but I don't know how much difference that would actually make.

Dave, how has the heat/cool battery attached to the MVHR performed over the summer?

Hi all, I came across this post on another forum about reducing the cold bridging across sash boxes. I wanted to see if there was any experience on here. https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=16668 I am refurbing my old sash windows in a 1905 mid-terrace. The main plan is retrofitting vacuum insulated glazing, draft stripping, and replacing the mastic joints. We'll be adding internal wall insulation, either Thermactive plaster or PIR, with a plan to boost ventilation (MVHR) for moisture control within a major refurb. We have a single storey bay window with 3 sashes in. I was putting expanding foam behind the mastic where the joint was large, and it seemed to be an endless void. Turns out the boxes aren't complete and are open to the stone on the external face. This is a big cold bridge, with only 20mm window frame and ~100mm stone between inside and out. Obviously foam in here could bust out the boxes and would definitely stop the weights running. I was wondering however about sheathing the weights in plastic pipe e.g. 40mm waste pipe, and filling the remaining cavity with loose fill insulation. Any experience with this/recommendations/cautions?

Thanks Dave, this is fantastic to see and very interesting. What period is that cooling accumulated consumption over? Or do you have a measure for how much heat you've been able to extract over a day? And could you share your approx. floor space? Do you have data for your dew point in the summer? I presume when it's hotter, with incoming air being cooled as it passes through the MVHR, you'll have a high relative humidity and a higher dew point, so the flow temp to the underfloor heating will have to be substantially higher than the 13.3+2 celsius dew point offset above?