Hello everyone,
We just had a conversation with the company responsible for our heating and plumbing installation.
First of all – we are building a large single-family house with a basement, two full floors, and a hipped roof with a 22° (22 degrees) pitch. Wall construction is 17.5 cm (7 inches) sand-lime brick, insulation with mineral wool, plus a brick façade.
We are building according to the 2012 Energy Saving Ordinance (EnEV 2012) and are not aiming to achieve a higher standard.
Our original plan was:
- Gas heating with underfloor heating on all levels, no wall-mounted radiators, and a central mechanical ventilation system with heat recovery.
Now, after the discussion, I’m totally confused. The company recommends:
- Heating via an air-to-air heat pump, solar thermal for hot water, plus gas to support hot water
- Underfloor heating only on the ground floor and first floor, excluding children’s rooms and bedrooms (to avoid overheating during sleep), with the rest heated by wall-mounted radiators on a second heating circuit
- No mechanical ventilation system with heat recovery due to noise issues
I can understand reconsidering the mechanical ventilation system because of potential constant noise and airflow, so we might want to think that over.
But I’ve never heard of combining a heat pump, gas, and solar thermal in one system!
Solar thermal is said to be uneconomical anyway, especially with a roof pitch of only 22° (22 degrees), right? We also don’t have a direct south-facing roof orientation. Does anyone have links or information about the economic viability?
Our main priorities are comfort; cost and economic efficiency are not the primary focus, but I don’t want to end up building something completely pointless either. The problem is, we need some sort of renewable energy source to comply with the Energy Saving Ordinance. The thermal protection report is not available yet, but I definitely need some concrete information for the next meeting. It would be great if someone could help!
We just had a conversation with the company responsible for our heating and plumbing installation.
First of all – we are building a large single-family house with a basement, two full floors, and a hipped roof with a 22° (22 degrees) pitch. Wall construction is 17.5 cm (7 inches) sand-lime brick, insulation with mineral wool, plus a brick façade.
We are building according to the 2012 Energy Saving Ordinance (EnEV 2012) and are not aiming to achieve a higher standard.
Our original plan was:
- Gas heating with underfloor heating on all levels, no wall-mounted radiators, and a central mechanical ventilation system with heat recovery.
Now, after the discussion, I’m totally confused. The company recommends:
- Heating via an air-to-air heat pump, solar thermal for hot water, plus gas to support hot water
- Underfloor heating only on the ground floor and first floor, excluding children’s rooms and bedrooms (to avoid overheating during sleep), with the rest heated by wall-mounted radiators on a second heating circuit
- No mechanical ventilation system with heat recovery due to noise issues
I can understand reconsidering the mechanical ventilation system because of potential constant noise and airflow, so we might want to think that over.
But I’ve never heard of combining a heat pump, gas, and solar thermal in one system!
Solar thermal is said to be uneconomical anyway, especially with a roof pitch of only 22° (22 degrees), right? We also don’t have a direct south-facing roof orientation. Does anyone have links or information about the economic viability?
Our main priorities are comfort; cost and economic efficiency are not the primary focus, but I don’t want to end up building something completely pointless either. The problem is, we need some sort of renewable energy source to comply with the Energy Saving Ordinance. The thermal protection report is not available yet, but I definitely need some concrete information for the next meeting. It would be great if someone could help!
B
Bauexperte13 May 2015 09:50bortel schrieb:
What do you mean by that? That a domestic hot water heat pump is not suitable for a new build in my opinion.
bortel schrieb:
So would you prefer a solar system to an air-to-water heat pump? That can’t be answered in general terms! There are good reasons to use gas as an energy source, just as there are for heat pumps. It always depends on the specific case, the particular building, and the future occupants.
Regards, Bauexperte
A mechanical ventilation system with heat recovery also provides increased comfort. With a ground heat exchanger, moderate cooling in summer is possible (though it is not a miracle solution).
I once slept directly on the floor heating surface for a while. It was great (I kept the heating completely off during the day). And if you have the comfort of a bed, I don’t see an issue. Besides, the heating output and floor temperature depend on the insulation. A well-insulated house with mechanical ventilation and heat recovery requires less heating power. You hardly notice if the heating is completely off for a few hours. You can easily lower the heating at night if a warm floor under the bed is a problem.
With underfloor heating, the response time depends on the overall construction. I don’t think it makes sense to combine underfloor heating (low flow temperature) with wall radiators (high flow temperature). The possibility to reduce the temperature at night also depends on the building method. A well-insulated solid construction cools down slowly.
@Bauexperte: The keyword here is entropy. Strictly speaking, it initially takes more energy to cool an unused room. With electric heating, this would be the cheapest option. Only when flow temperature, temperature gradients, and optimal system performance come into play does it become more cost-effective to maintain a room at a constant moderate temperature rather than heating it on demand.
I once slept directly on the floor heating surface for a while. It was great (I kept the heating completely off during the day). And if you have the comfort of a bed, I don’t see an issue. Besides, the heating output and floor temperature depend on the insulation. A well-insulated house with mechanical ventilation and heat recovery requires less heating power. You hardly notice if the heating is completely off for a few hours. You can easily lower the heating at night if a warm floor under the bed is a problem.
With underfloor heating, the response time depends on the overall construction. I don’t think it makes sense to combine underfloor heating (low flow temperature) with wall radiators (high flow temperature). The possibility to reduce the temperature at night also depends on the building method. A well-insulated solid construction cools down slowly.
@Bauexperte: The keyword here is entropy. Strictly speaking, it initially takes more energy to cool an unused room. With electric heating, this would be the cheapest option. Only when flow temperature, temperature gradients, and optimal system performance come into play does it become more cost-effective to maintain a room at a constant moderate temperature rather than heating it on demand.
B
Bauexperte14 May 2015 00:28Good evening,
Best regards, Bauexperte
maximax schrieb:I like the explanation: "A measure of disorder in a closed system that increases in all naturally occurring processes."
@Bauexperte: The keyword is entropy.
Best regards, Bauexperte
Bauexperte schrieb:
"Measure of disorder in a closed system that increases in all naturally occurring processes" OK, here’s the simplified version: Entropy can never decrease, only increase (2nd law of thermodynamics). That’s why, for example, I can convert electrical energy to heat energy with 100% efficiency, but not the other way around. It’s also why additional energy is required to raise a certain amount of heat from, say, 10°C (50°F) to 30°C (86°F) with a heat pump, or why most heating systems do not achieve 100% efficiency (or more generally, why a perpetual motion machine is impossible).Bauexperte schrieb:
I have to disagree with the previous poster – "22°C (72°F) and evaporate" was not meant as a joke. With tightly wound coils, that’s already quite a lot. You will notice it yourself; at the supply temperature, it is too warm for your heating needs. As mentioned, today’s situation is not comparable to yesterday.
@Bauexperte – I need to ask again. Why do you think 22°C (72°F) feels different or warmer in a new build than 24°C (75°F) with underfloor heating and tiles heated to over 30°C (86°F)? By the way, I’m sitting at 22.8°C (73°F) right now on my laptop and feeling cold.
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