ᐅ Which combination of heat pump and supplementary heating system is recommended?
Created on: 14 Oct 2015 07:42
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daytonaHello everyone,
The floor plan design is almost finished, and there is already a proposal from the general contractor (GC) regarding the heating system. Now I am trying to learn more about the topic myself in order to critically question it, as I suspect the GC wants to sell their “favorite” solution.
The house will be built to KfW 70 standard with underfloor heating, covering about 179m² (1,925 sq ft) of living space without mechanical ventilation. The plot is 1,100m² (11,840 sq ft) in total, planted along the property boundaries with tall conifer trees, and about 40% of it will be built on by the house, garage, and terrace. The south-facing roof has a slope of 22°, providing enough space for a photovoltaic system with approximately 5 kWp output.
Gas boilers are completely out of the question!
The GC’s proposal is for an air-to-water heat pump combined with solar thermal (4m² (43 sq ft) of vacuum tube collectors). The outdoor unit of the heat pump would be placed facing the street (neighbor >15m (50 ft) away) and approximately 7m (23 ft) from our bedroom window.
Here are my questions:
Would it make more sense to combine a heat pump with photovoltaic panels instead of solar thermal? How do you roughly estimate the costs for photovoltaic? (My rough calculation: €1,700/kWp = around €9,000)
Would you prefer a ground-source heat pump over an air-to-water heat pump? I have read quite a bit about trench collectors, which seem reasonably priced and don’t require excavating the entire plot, but most information is anecdotal experience.
Any suggestions are welcome.
The floor plan design is almost finished, and there is already a proposal from the general contractor (GC) regarding the heating system. Now I am trying to learn more about the topic myself in order to critically question it, as I suspect the GC wants to sell their “favorite” solution.
The house will be built to KfW 70 standard with underfloor heating, covering about 179m² (1,925 sq ft) of living space without mechanical ventilation. The plot is 1,100m² (11,840 sq ft) in total, planted along the property boundaries with tall conifer trees, and about 40% of it will be built on by the house, garage, and terrace. The south-facing roof has a slope of 22°, providing enough space for a photovoltaic system with approximately 5 kWp output.
Gas boilers are completely out of the question!
The GC’s proposal is for an air-to-water heat pump combined with solar thermal (4m² (43 sq ft) of vacuum tube collectors). The outdoor unit of the heat pump would be placed facing the street (neighbor >15m (50 ft) away) and approximately 7m (23 ft) from our bedroom window.
Here are my questions:
Would it make more sense to combine a heat pump with photovoltaic panels instead of solar thermal? How do you roughly estimate the costs for photovoltaic? (My rough calculation: €1,700/kWp = around €9,000)
Would you prefer a ground-source heat pump over an air-to-water heat pump? I have read quite a bit about trench collectors, which seem reasonably priced and don’t require excavating the entire plot, but most information is anecdotal experience.
Any suggestions are welcome.
As far as I know, a heat pump combined with solar thermal systems usually doesn’t make much sense.
With heat pumps, you no longer need a large buffer tank because the pumps are designed to heat the tank intermittently. If the tank is too large, you end up losing energy through constant reheating.
For solar thermal systems, it is very useful to install the largest possible buffer tank (proportional to the number of solar collectors) so that as much water as possible is heated during full-day sunlight, maximizing the amount of solar energy captured.
Gas boilers have so far been among the cheapest heating systems to install. An air-source heat pump is roughly comparable in cost. However, both usually have somewhat higher ongoing energy costs in comparison.
A geothermal heat pump, or brine heat pump, has a higher efficiency, which reduces the monthly electricity bill for heating. If your plot allows it, I would consider this option further. We originally wanted this type of system, but it was not feasible on our property. Large trees can especially be a problem...
However, I have only come across this "trench collector" method as a DIY solution in the pink forum, which seems too risky for my taste. There are also other geothermal providers who, for example, bury cylindrical baskets in the ground. (This way, the entire property doesn’t need to be excavated.)
With heat pumps, you no longer need a large buffer tank because the pumps are designed to heat the tank intermittently. If the tank is too large, you end up losing energy through constant reheating.
For solar thermal systems, it is very useful to install the largest possible buffer tank (proportional to the number of solar collectors) so that as much water as possible is heated during full-day sunlight, maximizing the amount of solar energy captured.
Gas boilers have so far been among the cheapest heating systems to install. An air-source heat pump is roughly comparable in cost. However, both usually have somewhat higher ongoing energy costs in comparison.
A geothermal heat pump, or brine heat pump, has a higher efficiency, which reduces the monthly electricity bill for heating. If your plot allows it, I would consider this option further. We originally wanted this type of system, but it was not feasible on our property. Large trees can especially be a problem...
However, I have only come across this "trench collector" method as a DIY solution in the pink forum, which seems too risky for my taste. There are also other geothermal providers who, for example, bury cylindrical baskets in the ground. (This way, the entire property doesn’t need to be excavated.)
daytona schrieb:
Would you prefer a ground-source heat pump over an air-to-water heat pump? I’ve read quite a bit about trench collectors since the costs are more manageable and you don’t have to excavate the entire property, but most experiences and explanations seem to be based on anecdotal evidence...?Definitely, as long as the property allows it.
The calculations done in the pink forum are certainly more reliable than the rough rule of thumb (installing double the floor area) used by a typical heating contractor when sizing a ground collector.
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