Heating system air-water heat pump + underfloor heating - offer evaluation

Hello everyone,

we are currently in the process of obtaining quotes for our construction project, a single-family house 230 sqm city villa without a basement.

I received the offer for the air-to-water heat pump and underfloor heating today. Since I have absolutely no experience in this area so far, I wanted to ask about your experience. The item for the heat pump with installation seems quite high to me when I compare the few prices for the heat pump I find online.

Our builder, who is doing the shell construction for us, indicated that the capacity for the heat pump should be around 7 kW. Nothing else has been calculated or considered so far.

I hope you can make something of these statements.

Regards

We have 190 sqm heating, 1800m pipe, 3 distribution cabinets for 9300 net.

is way too expensive and have a heat load calculation including the design of the underfloor heating done by an engineering office. Then you have a comparison.

I completely agree. Within that price range, all the building services (i.e., heating, [Kontrollierte-Wohnraumlüftung], cooling, etc.) were included for me. Not just a heat pump + underfloor heating.

First have the heating load calculated, including the room-by-room heating load! Then choose the heat pump. Not larger than the calculated heating load! Make sure the heat pump can modulate down to a very low level. Have the underfloor heating designed based on the room-by-room heating load calculation. Specify the target temperatures as well as the desired maximum flow temperature (goal 30°C or lower). If necessary, consider wall heating in the bathroom to achieve the desired temperature. No chicken ladder in the heating circuit; if desired, have an electric heating cartridge installed. Specify maximum heating circuit lengths, not over 100m, preferably around 80m. Better to have more short heating circuits than one excessively long heating circuit. You need a lot of flow in the underfloor heating with a heat pump! This is easier to achieve with several shorter heating circuits than with a few overly long ones. Find out what the selected heat pump specifies. Do not install pipes that are too thin. Then have the offer prepared. No buffer tank in the heating circuit, and if any, only connected in series in the return flow and kept as small as possible! No mixing groups, separation storage tanks, etc. Read up on the "meaningfulness" of ERR in a highly insulated new building with low heating load! Do you really want surface-mounted heating circuit distributors? Now you are probably overwhelmed and discouraged... It doesn’t help. Better to educate yourself now than to have a poorly dimensioned system later.

For the sizing of the heating pipe of the underfloor heating, 17x2 should be the minimum to prevent the resistance/pressure drop from rising to an unmanageable level. Otherwise, it costs pump energy. It is not specified at all in the offer!