kevinm

If you run at above dew point, you wont dehumidify. Also the dew point inside the floor structure is likely to be higher than in a room, especially with steam/humid air rising from the ground floor. Both my wife and I struggle to sleep if the bedroom in our current house is above 22/23C. We want carpet in our bedroom which would render ufh cooling useless. My preference was for ufh cooling starting out, but once I dug into it, fan coils made more sense. EDIT: I should have also said that we are only putting fan coils in bedrooms, kitchen and sitting room.

We did but there were a few reasons that we decided not to. With the house being timber frame, there were concerns from the architect with regards to hidden condensation (particularly on the undserside of the screed upstairs) With the ufh pipes in the insulated raft (no screed downstairs). Response times would be very slow. We want the fan coils as much for humidity reduction as cooling, cooling the ufh provides no dehumidification. Running the fancoils at low water flow temp and low fan speed will dehumdify the air without cooling the room excessivly. We are ~25km from the Atlantic, and 150m from a 3 km2 lake, so high humidity is an issue with warm weather.

We are in the final design stages of a passive-certified timber frame house. Cooling was a big focus for us. All south and west windows have external venetian blinds. This will cut the solar gain. We looked at mhrv cooling but concluded it was a waste of time. You would do well to get 800w of cooling without running your fan at a noisy speed. If you cool your mhrv aggressively, you then have to insulate your mhrv ducts, or you will get condensation on the outside. Also with most mhrv systems, you dont have individual room control. This is important, as rooms' cooling demand changes throughut the day, especially without external shading. We are going with fancoil units made by systemair. They have a large range of fancoils. We are going with a combination of ceiling casettes, hidden ducted and wall mounted units. This gives individual room control of the cooling. https://www.systemair.com/en-ie/products/air-conditioning/fan-coil-units I cant see them on the UK website for some reason. SystemAir Ireland have said they can order whatever fancoil I want on a supply-only basis. One consideration with active cooling the house is that you will want to close the mhrv summer bypass once the house gets cooler than ambient so that you are not dunmping all your nice cold air outside. It will also help to dehumidify the air coming in by pre-cooling it.

Are you sure it's R290 (Propane)? I was not aware that R290 split systems existed.

I interviewed for a position as a Site Engineer with the OPW 13/14 years ago. I have never come across such a group of ignorant and arrogant civil servants. Totally aloof, and out of touch, most joined straight out of Uni, and had zero private sector experience.

I would say zero difference. I doubt I will ever get the extra money spent on PH certification back.

Heat recovery drops with increased capacity, there is a strong trend to support this, look at the Zehnder/Helios/Brink units. The bigger units in a product family have lower heat recovery efficiency. The SB-350 achieves 79% heat recovery. The bigger SB-550 would be very close to the 75% minimum heat recovery requirement for PH certification. Maybe they dont want to risk the cost if they are not certain that it will pass? The PH-crtified Titon looks different to all the other HRV3 machines, the filter access is different. That suggests there is more than just the cost of certification at play, looks to me like they made a special unit targeting high efficiency.

I am going block and EWI, so cant comment on ICF. Most high-performimg MHRV units have PH certification now, I would be skeptical of any unit making big claims and not getting PH certification.

If you build the house to PH spec (use PHPP etc), the main extra cost is the external validation, which I have been quoted £2300.

He is travelling to me in Ennis, so I assume so.

Hillard Tanner He is doing the design for my passive-certified masonry build (insulated raft and EWI). He has a lot of experience in insulated rafts. He is based in Fermoy.

It's not just a lack of storage capacity but grid stability. Grids need the inertia form large spinning turbines to balance the grid as supply and demand fluctuates. PV inverters, dont have any inertia, and they also track the grid frequency, so they dont resist any frequency deviation. For this reason most grids need a mininum number of thermal plants to remain in production to provide inertia to the grid. There are now devices called synchronous condensors, which are basically enourmous flywheels connected to a motor/generator, that provide grid inertia for times of high renewables production. Google synchronous condensors.

I considered the same idea but decided against it. Air has such a low heat capacity, you need to move a lot of air (noisy) to get a decent cooling effect. Also any cooled ducts will need to be insulated to stop condensation forming in the void spaces (potential for mould of drips staining ceilings. I'm still waiting for the phpp calcs to be done, but I'll most likely be going independant MHRV and a few hidden splits in ceilings where needed.