Hello,
I am planning a renovation in Athens, Greece of a 95 square meter apartment that I will use intermittently 3 months a year (fall/spring). For a variety of reasons, my preference is underfloor heating / cooling using a Vaillant Arotherm heatpump and hydronic/pex tubing underfoot. My understanding is that underfloor cooling will provide “X” degrees of cooling, and that fan coils will be installed as a “booster” to achieve the desired cooling temperature of 22 Celsius.
I am seeking advice as to:
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A reasonable expectation of how many degrees cooling (from outside air temperature) the Arotherm can achieve before limitations are reached (is this a result of mechanical limitations, and dew point limitations?). The salesperson said I could expect up to 12 degrees Celsius cooling from the outside air, but a brochure I found online by a NZ HVAC company said the expected cooling range for a Vaillant Arotherm with radiant cooling was 3-5 Celsius from outside air temperature. (I would so appreciate anyone’s direct experience with the Arotherm on this specific question).
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Is there technology that can be installed alongside the radiant floor to detect condensation or leaks onto the slab? (and notify us remotely as we are 7 times zones away for 9 months a year). I asked the Vaillant salesperson if dew point sensors could be placed on the slab, but he said there was no way for those sensors to feed that information back to the heat pump, and that “it’s not necessary”… but I didn’t completely follow why…
Some facts:
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Athens is pretty much 30 - 41+ degrees Celsius in the summer months, and with climate change 45 degree Celsius days could become more frequent. The salesperson disclosed that the unit will not start if the internal temperature is > 46 degrees, but that applies to almost all heat pumps on the market.
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Of the 95 SM of floor space, 80 SM will be stone (or tile) floors, and the remaining 15 SM in the living room will be engineered wood.
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Ceiling height is 2.95 M but will be dropped to 2.7 M for recessed lighting and to hide some fan coils. Fan coils will be used to boost cooling to the desired 22 Celsius range. Salesperson suggested hiding the 3 fancoils in the hallway ceiling from where it could help cool the 2 bedrooms and open concept LR/DR/Kitchen.
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Hot water will provided by a Vaillant gas boiler (instant-hot). Space is limited for a water tank, and as part time residents we want to avoid the leakage risk that comes with a water tank.
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Currently considering Vaillant as there are only 3-4 reputable brands that can provide excellent after-service and support to their product in Athens Greece. I believe Vaillent is the best among those few but open to feedback on their Arotherm product. I know they are using a new refrigerant and don’t know if this poses a mechanical/technology risk.
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The “Athenian way” to heat cool this apartment would be to use gas heated radiators and electric mini splits. While attractive from a cost perspective, I am trying to avoiding the dust and visual noise of radiators and mini-split wall units (allergies and central Athens has a high dust factor).
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An “American way” of a ducted HVAC system is not possible due to the ceiling beams in the unit (standard for Athens due to earthquake risk). We would have to drop the ceiling down below the beams to 2.4 M which would make resale difficult later in life (Athenians consider 2.4 M unbearably low).
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I am told there might be cost savings in the winter with a heat pump (50%?), but less to almost none in the summer because of the temperature differential. If anyone could point me to an online calculator that could help me estimate this, that would be great. I don’t expect a huge difference in energy bills, but would be nice to know.
Please know that this is my first foray into considering a heat pump (but I have radiant in the US) - so apologies if I am missing any pieces of the Heat Pump/Radiant puzzle. I am doing my best to educate myself before I decide how to heat and cool this apartment, and greatly appreciate any advice or thoughts from the community!
