ᐅ Setting up a mechanical ventilation system with heat recovery for an energy-efficient home (KfW 70 standard) combined with underfloor heating
Created on: 30 Nov 2014 12:03
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PhoenixDH
Hello everyone,
after living in our new house for a few days now, I’m wondering if our heating system is set up optimally.
It consists of a gas boiler with a 100-liter (26-gallon) hot water tank and a mechanical ventilation system with heat recovery.
The entire ground floor has underfloor heating, while upstairs only the bathroom does.
The other rooms are equipped with panel radiators.
My friends and I both work and leave the house early, around 7:00 a.m., returning only around 6:00 p.m.
Currently, we have the system programmed so that the heating/ventilation system/pump/hot water start about one hour before we’re home and turn off when we leave, or at 10:00 p.m. in the evening, except on weekends.
Does it make sense to set the system up this way?
Considering that underfloor heating is quite slow to react.
The question is, what is more efficient: generating energy only when needed, taking into account that the system cools down in between, or maintaining a constant temperature and using just one time window per day.
Some practical experience would be helpful, thanks!
after living in our new house for a few days now, I’m wondering if our heating system is set up optimally.
It consists of a gas boiler with a 100-liter (26-gallon) hot water tank and a mechanical ventilation system with heat recovery.
The entire ground floor has underfloor heating, while upstairs only the bathroom does.
The other rooms are equipped with panel radiators.
My friends and I both work and leave the house early, around 7:00 a.m., returning only around 6:00 p.m.
Currently, we have the system programmed so that the heating/ventilation system/pump/hot water start about one hour before we’re home and turn off when we leave, or at 10:00 p.m. in the evening, except on weekends.
Does it make sense to set the system up this way?
Considering that underfloor heating is quite slow to react.
The question is, what is more efficient: generating energy only when needed, taking into account that the system cools down in between, or maintaining a constant temperature and using just one time window per day.
Some practical experience would be helpful, thanks!
P
PhoenixDH13 Jan 2015 09:01Thanks to you! In December, the two of us had about 120m³ (4,239 ft³) with roughly the same values.
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DerBjoern13 Jan 2015 09:14By the way, we also use nighttime setback, even though the entire house has underfloor heating. The temperatures don’t really drop much overnight. Whether setback directly saves energy is certainly questionable, but I experience another positive effect. At these mild temperatures around 0°C (32°F), my gas boiler can’t modulate down low enough and starts short cycling. This is probably not as inefficient for a condensing gas boiler as it is for a heat pump, but it still likely costs a few percent in efficiency. With setback, the heating system can run continuously for about 30-45 minutes in the morning instead of short cycling throughout the night. This also helps to make better use of the condensing effect.
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PhoenixDH18 Jan 2015 14:48So, for the record.
The stove is installed and running.
It fits exactly as we had envisioned.
Heating during the day with the stove, all doors open, and the whole house warms up nicely—works well.
The gas meter barely moved.
It was different at night:
From 11 PM to 9 AM, about 2 kW were wasted.
I think this is because during the day, when the thermostat senses the temperature is sufficient and turns off the underfloor heating, the floor hasn’t warmed up enough yet.
Well, let’s wait and see...
The stove is installed and running.
It fits exactly as we had envisioned.
Heating during the day with the stove, all doors open, and the whole house warms up nicely—works well.
The gas meter barely moved.
It was different at night:
From 11 PM to 9 AM, about 2 kW were wasted.
I think this is because during the day, when the thermostat senses the temperature is sufficient and turns off the underfloor heating, the floor hasn’t warmed up enough yet.
Well, let’s wait and see...
P
PhoenixDH26 Jan 2015 17:15I’m going to run another test now:
Until now, we had two time windows: 5-7 and 14-21, with temperatures set to 22°C (72°F) and 18°C (64°F) during the setback.
I’m switching to a single time window from 5 am to 9 pm, keeping the temperatures at 22°C (72°F) and 18°C (64°F).
I plan to run this for 30 days and then draw some conclusions.
One clarification question:
When we talk about the night setback, does that refer to the period when the heating runs at the lower temperature? Basically, the time between two daytime windows, right?
So if someone says “we don’t have a night setback,” does that mean the heating runs continuously?
I think I’m a bit confused.
Until now, we had two time windows: 5-7 and 14-21, with temperatures set to 22°C (72°F) and 18°C (64°F) during the setback.
I’m switching to a single time window from 5 am to 9 pm, keeping the temperatures at 22°C (72°F) and 18°C (64°F).
I plan to run this for 30 days and then draw some conclusions.
One clarification question:
When we talk about the night setback, does that refer to the period when the heating runs at the lower temperature? Basically, the time between two daytime windows, right?
So if someone says “we don’t have a night setback,” does that mean the heating runs continuously?
I think I’m a bit confused.
D
DerBjoern26 Jan 2015 17:25PhoenixDH schrieb:
When we talk about night setback, we mean the period during which the heating runs at a lower temperature, right? Like also between two time slots during the day, correct?
So if you read "we don’t have night setback," does that mean the heating runs continuously?
I think I’m a bit confused.You need to distinguish what is meant by setback. Usually, it refers to maintaining a temperature of, for example, only 18°C (64°F) during the setback period. In a well-insulated new building, this often means the heating is completely off during that time because the temperature doesn’t drop that quickly at night. In an uninsulated older building, the heating would run at a low level, just enough to maintain the setback temperature.
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PhoenixDH26 Jan 2015 17:31Okay, thanks, then I was on the right track.
Yes, of course, that would mean our KfW70 standard is not met, because the temperature only drops by 1 degree when I set the heating to night setback from 9 p.m. to 5 a.m.
I’m looking forward to the new results.
After that, we will run the heating continuously, basically from 0 to 0, and then decide how to adjust it.
Because if the consumption is not higher, it can run continuously, which also ensures comfortable conditions if you come home earlier.
Yes, of course, that would mean our KfW70 standard is not met, because the temperature only drops by 1 degree when I set the heating to night setback from 9 p.m. to 5 a.m.
I’m looking forward to the new results.
After that, we will run the heating continuously, basically from 0 to 0, and then decide how to adjust it.
Because if the consumption is not higher, it can run continuously, which also ensures comfortable conditions if you come home earlier.
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