ᐅ Heat Pump Combined with Home Climate Control

Dear community,

My wife and I are currently working with a general contractor to dive into the detailed building planning.
One of our main concerns is a proper air conditioning system for the house.

The project currently includes about 300m2 (3,230 sq ft) of living space plus a basement (ground floor + first floor + attic); KFW 55 standard plus photovoltaic system (sizing still to be decided).

We both have previous negative experience, having lived for over 10 years in apartments where indoor temperatures in summer uncontrollably reached 32-35°C (90-95°F). This has to stop.
Therefore, our original idea was to plan for air conditioning units in the key rooms right from the start (individual air conditioning units). Now I also understand that a heat pump can cool a few degrees below the outdoor temperature. At summer temperatures above 30°C (86°F), that would not be enough for me.

So my question is: do you have any experience with this? Does this thinking make sense, or would you say that a proper heat pump with cooling function is definitely sufficient?

Of course, we are aware that whole-house air conditioning adds extra costs. But is the investment worthwhile?

1. New houses stay cool inside much longer than older buildings. However, once heat gets in, it is also much harder to get out.
2. Because of this, careful consideration is given to sun protection/shading during the house planning process.
3. Yes, a heat pump can provide cooling. But since it only circulates cool water through the underfloor heating system and does not dehumidify, the effect is quite limited. Why? Because with a higher cooling capacity or very low temperatures, condensation would form in the floor (with underfloor heating). Therefore, you might be able to lower the temperature by about 3°C (5°F). Noticeable, but not comparable to an air conditioner. Combined with well-planned sun protection, this can be sufficient. The experience, however, is subjective – some say "great," while others find 22°C (72°F) indoors already too warm. The 32–35°C (90–95°F) you had in your old home will definitely not be reached in the new building.
4. Whether it’s worth it depends on the situation. A heating system is definitely necessary to avoid problems in winter. An air conditioner usually does not make financial sense, but it might improve comfort 😉.

I hope this information helps you a bit. I have not yet used the cooling function of my heat pump because it has not been warm enough.

That said, given your seven-figure investment, I would boldly suggest that spending a few extra dollars on some (partial) air conditioning would suit the property.

Axolotl2022 schrieb:

1. New houses stay cool inside for much longer than older buildings. However, once the heat gets in, it is also much harder to get out.
2. Because of point 1, careful consideration is given to sun protection/shading during house planning.
3. Yes, a heat pump can provide cooling. But since it only circulates cool water through the underfloor heating system and does not dehumidify, the effect is quite limited. Why? Because with higher cooling capacity or very low temperatures, condensation would form in the floor (with underfloor heating). So you might be able to lower the temperature by about 3°C (5°F). Noticeable, but not comparable to an air conditioning system. Combined with well-planned sun protection, this can be sufficient. However, comfort is subjective – some say “great,” while others find 22°C (72°F) indoors too warm. You definitely won’t experience the 32-35°C (90-95°F) of your old home in the new building.
4. Whether it’s worth it is relative. A heating system is necessary, as you would otherwise have problems in winter. An air conditioner is usually not financially worthwhile, but it might improve comfort significantly 😉.

I hope this information helps you a bit. I haven’t used the cooling function of my heat pump yet, as it hasn’t been warm enough.

Given your seven-figure investment, I would boldly say that spending a few extra dollars on (partial) air conditioning would be fitting for the property.

That was a really great and helpful post! Thank you!

At our company, we have an underfloor cooling system. It helps somewhat, but other issues outweigh the benefits. Our problem is that the blinds rise with every breeze, and for large window areas, only two narrow slits can be opened like firing ports. The air exchange is so poor that even on rainy days with 15°C (59°F), you can’t lower the temperature. In two offices, larger windows (emergency exits) are installed, and there it works much better.

The key is to have effective shading to keep the heat out and to be able to ventilate any heat away during cooler outdoor temperatures (evenings, nights). A garden with plenty of greenery and shade in the main wind direction also helps, and it’s best to avoid heat accumulation caused by terraces if possible. (In our current apartment, we have the problem that the balcony faces west, and on hot days it still holds so much heat after sunset that we cannot ventilate through it until 1–2 hours later when the heat finally dissipates.)

The question is, what is your desired temperature, and which rooms would you like to cool?

I generally assume that the ground floor is less affected by heat issues than the upper floors. Therefore, the focus for cooling would be on the following rooms: bedrooms and children’s rooms 1 & 2 on the first floor; two offices and a guest room in the attic; possibly a fitness room in the basement!?

I am excluding the separate apartment, which will be built either as an extension or as a separate building. This could be cooled with a standalone air conditioning unit if necessary, as it will not be occupied continuously.

How the ground floor heats up naturally also depends on the orientation of the house.

The kitchen/dining/living areas can become quite warm, partly due to the sun and partly because we operate several electrical appliances there and spend a lot of time in that space. I would definitely include this in the air conditioning planning.