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I am looking in to upgrading the heating system in my house, and I am surprised that I can hardly find any systems that heat up the house by blowing hot air in to the desired areas, as is standard for office building etc. I prefer this system because I also have a wood burning stove and would like to install a ventilation system anyway so I can distribute the heat through the house and make better use if it. A ventilator and some piping seem like a low cost way of improving the heating in the house.

I would like to use a heat pump for warming the air and I can only find two types of systems:

  1. Air to water systems. These warm up water and the water then needs to be pumped through a piping system in the floor or through a piping system with radiators. I don't want to replace all the floors in the house and I don't want ugly pipes and expensive radiators in the whole house.
  2. Air to air systems. These warm up air, which is what I want, but they all work through big "indoor units" that need to be placed in every room where heating is required.

What I would like is one big "indoor unit" on the attic, and a piping system with valves that distributes the warm air to where it is needed. That way I can keep my floors and don't need to install any pipes or radiators in my living area. Do systems like this exist for a reasonable price, and if not, why?

Edit to provide additional information:

I live in Denmark and centrally heated forced air is nearly nonexistant here. The electricity price here is about 2.5 Danish Krone (0.37 USD about 3 times US price). About 70% of this amount are taxes. I am close to buying a house which has the following heating system. 1 times 4KW heat pump with 2 indoor units, one in the living room and one in the entrance on the other side of the house. Electric heaters in every room and a wood-burning stove in the living room. It has an electric heater for hot water. I see the following problems with this system:

  1. Heating hot water will be very expensive.
  2. The bedrooms are only heated with electric heaters if the door is closed, which is expensive.
  3. If it gets very cold the efficiency of the heat pump will go down and electric heaters need to be used to keep the house warm
  4. The warmth of the wood-burning stove does not reach far enough to heat the rest of the house

I am considering to buy an additional heat pump and a ventilation system to fix most of these issues. The additional heat pump should provide hot water, but I believe it can also provide extra heating with little additional cost. The ventilation system can spread the heat of the stove to the rest of the house. It would be very nice if I could also use the ventilation system to distribute heat from the additional heat pump through the house, because I would like to avoid placing pipes and radiators or additional indoor units in the whole house.

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  • What is a reasonable price? There are systems like this and you can find an installer to fit one. But in a residential setting it can be the cause of drafts. – Solar Mike Jun 21 '20 at 13:34
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    What you describe is standard for those of us in the South where A/C is primary and heating is secondary. @SolarMike is correct, though, that this may result in drafts. What you will need is a central outdoor heat pump unit and an indoor air handler with a dual-use (A/C or heat pump) coil and backup electric heat for those days when it's too cold for a heat pump to operate efficiently. Alternatively you could use a gas furnace with the appropriate coil. You'll need to run air ducts; research the literature for tips on avoiding drafts. – ehbowen Jun 21 '20 at 13:52
  • Thank you for pointing out the draft issue, that is very good to keep in mind. – Orbit Jun 21 '20 at 15:30
  • In a comment on an answer, you indicate that you have a wood burning stove as your primary means of heating? Is your question really about how to use this existing stove to more evenly heat your house by distributing the heat produced by the existing stove as opposed to installing a whole new furnace system? If that's the case, please edit your question to include this very vital additional info! If not, please edit to provide some additional detail on what you currently have for heat generation and distribution. – FreeMan Jun 21 '20 at 16:36
  • What country do you line in? As already answered, forced air is very common in North America so I assume you live somewhere else. – DoxyLover Jun 21 '20 at 17:30
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They already have that. It's the dominant system in use in North America... but I don't think you want it. The problem is, the pipes are enormous. - like 4" x 12" (100 x 300mm) per duct, with a dozen ducts.

We joke, and call that thing a "duct-o-pus".

That is why businesses have drop ceilings — to hide the monstrosity of ducts above.

Fat pipes

Now, the traditional North American approach was to have a fuel furnace with an air-air heat exchanger, then a powered "air handler" blower to force air through the heat exchanger and ductopus. When air conditioning was added, its evaporator (cold side) coil was added just above the furnace heat exchanger. With "traditional" heat pump systems, the fuel pump coil replaces the air conditioner, and emergency electric heat strips replace the fuel furnace (or not). But we still have the duct-o-pus.

That system is exactly what you say you want: a heat pump in a central location that uses air as the distribution medium.

Thin pipes

In North America, the new trend is to "slay the duct-o-pus", stop using air as a distribution medium, and use freon itself. Those units are called "mini-splits", and simply require a 1” hole for the Freon lines. They use a central compressor and have a heat/cool unit in each room.

Water interchange

Another method seen commercially (think: hotels) is to plumb service water around the complex. Then have standalone heat pump units which interchange heat with the service water. The heat pump units can be either per-room, or per apartment and have their own ductopus. Then, a central facility at the complex has some mechanical plant to return the water to a "normal" temperature of around 30C, either by running through cooling towers, or heating it with fuel. As an alternative, it can have a "ground-source” for temperate water all year; a running stream, seawater (this works for boats, obviously), or favorable aquifer conditions. That is the only way water interchange makes sense for small operations.

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  • Thanks for the answer, a duct-o-pus sounds pretty good to me. I have a huge attic that is only used for storage, so I can easily hide the monster there. An additional advantage of such a system is that it can also be used to distribute the heat of my wood-burner to the rest of the house. It is really bugging me that I have to open the windows in the living room to get rid of the heat, and at the same time spend of lot of money to electrically heat the rest of the house. – Orbit Jun 21 '20 at 15:39
  • Do you know of a commercial solution to heat the air in the pus with freon? Or should I buy a system intended for floor/radiator heating and use the hot water it produces in a coil in the system? – Orbit Jun 21 '20 at 15:42

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