ᐅ KfW 70 House: Gas Consumption Too High, What Solar Panel Output Is Needed?
Created on: 22 Jan 2016 10:16
A
aytex
Hello everyone,
We moved into our newly built home about a year ago, and now we can finally assess our energy costs. We have a strong feeling that they are definitely too high. We have already discussed this with our builder and are investigating the causes. However, I would like to get your opinions as well. Here are some key details:
Our first annual statement shows an energy consumption of 28,500 kWh. Our online research indicates that this is significantly too high for a KfW70 house. On average, about 60 kWh/m² per year is expected. Even if you double this value, our consumption would still be 8,000 kWh higher. Also, we cannot understand how the solar system is contributing to the total energy balance, as our consumption remains very high.
I would appreciate any feedback. Perhaps we can exchange comparison values so we can better understand how our numbers compare on average.
We moved into our newly built home about a year ago, and now we can finally assess our energy costs. We have a strong feeling that they are definitely too high. We have already discussed this with our builder and are investigating the causes. However, I would like to get your opinions as well. Here are some key details:
- KfW70 standard
- 180m² (1,938 sq ft) living area
- External thermal insulation composite system (ETICS)
- Triple glazing
- Underfloor heating
- Solar thermal system for hot water and heating support (approx. 12m² (130 sq ft) on the roof) from COSMO
- 750-liter (198-gallon) tank
- 3-person household (our youngest is 4 years old)
Our first annual statement shows an energy consumption of 28,500 kWh. Our online research indicates that this is significantly too high for a KfW70 house. On average, about 60 kWh/m² per year is expected. Even if you double this value, our consumption would still be 8,000 kWh higher. Also, we cannot understand how the solar system is contributing to the total energy balance, as our consumption remains very high.
I would appreciate any feedback. Perhaps we can exchange comparison values so we can better understand how our numbers compare on average.
Is building drying or screed drying still included here? It’s common for up to 6000 kWh to be lost to the environment during this phase.
In the first year, experience shows that energy consumption is usually somewhat higher overall.
Is it possible that your 750-liter (200-gallon) tank is being poorly controlled?
A heat loss of 28,500 kWh is quite significant. Do you have a mechanical ventilation system with heat recovery? If not, losses can typically be around 14,000 kWh or less, depending also on individual habits like showering, bathing, and leaving windows open for continuous ventilation because of feeling warm.
In the first year, experience shows that energy consumption is usually somewhat higher overall.
Is it possible that your 750-liter (200-gallon) tank is being poorly controlled?
A heat loss of 28,500 kWh is quite significant. Do you have a mechanical ventilation system with heat recovery? If not, losses can typically be around 14,000 kWh or less, depending also on individual habits like showering, bathing, and leaving windows open for continuous ventilation because of feeling warm.
Hi,
28,500 kWh??? Do you have a sauna club or belong to a nudist group that sits naked in the house at 35°C (95°F)?
Seriously, there must be more to this than just carelessness. Are you sure there isn’t a meter reading error?
For comparison, our current house (first occupied at the end of 2011) has
135 sqm (1453 sq ft) plus a basement
Gas heating with 5 sqm (54 sq ft) of solar thermal for domestic hot water and standard radiators
14 cm (5.5 inches) insulation,
triple glazing,
probably didn’t quite meet the KfW 70 standard.
No mechanical ventilation with heat recovery, so it’s more like very generous airing out, sometimes forgetting to close the bathroom window for hours.
Two adults and, since November 2014, one child.
Last year’s consumption was almost exactly 7,500 kWh, in previous years between just under 8,000 and 8,500. The first year was slightly higher.
Your house is larger, so let’s add 50% for that and maybe another 50% for extended drying out after construction. That puts you somewhere around 15,000 to 18,000 kWh as a possible extreme value.
You really shouldn’t have used more than that in this house!
Have your heating system checked urgently—is it venting gas unburned up the chimney? I had that problem many years ago in a rental apartment. We noticed a constant noise from the boiler even when it was off. It turned out a bimetallic safety switch was broken and never shut off the gas supply. Fortunately, the gas went straight up the chimney, otherwise I wouldn’t be typing this now...
Best regards,
Andreas
28,500 kWh??? Do you have a sauna club or belong to a nudist group that sits naked in the house at 35°C (95°F)?
Seriously, there must be more to this than just carelessness. Are you sure there isn’t a meter reading error?
For comparison, our current house (first occupied at the end of 2011) has
135 sqm (1453 sq ft) plus a basement
Gas heating with 5 sqm (54 sq ft) of solar thermal for domestic hot water and standard radiators
14 cm (5.5 inches) insulation,
triple glazing,
probably didn’t quite meet the KfW 70 standard.
No mechanical ventilation with heat recovery, so it’s more like very generous airing out, sometimes forgetting to close the bathroom window for hours.
Two adults and, since November 2014, one child.
Last year’s consumption was almost exactly 7,500 kWh, in previous years between just under 8,000 and 8,500. The first year was slightly higher.
Your house is larger, so let’s add 50% for that and maybe another 50% for extended drying out after construction. That puts you somewhere around 15,000 to 18,000 kWh as a possible extreme value.
You really shouldn’t have used more than that in this house!
Have your heating system checked urgently—is it venting gas unburned up the chimney? I had that problem many years ago in a rental apartment. We noticed a constant noise from the boiler even when it was off. It turned out a bimetallic safety switch was broken and never shut off the gas supply. Fortunately, the gas went straight up the chimney, otherwise I wouldn’t be typing this now...
Best regards,
Andreas
Umbau-Susi22 Jan 2016 11:18We used exactly the same amount last year
in a 230 m2 (2,475 sq ft) house from 1936 with reasonably insulated attic, uninsulated exterior walls, mostly double-glazed windows from 1996, and a solar system for hot water. Oh, and we have thermostat-controlled wall radiators.
However, in the evenings, the wood stove is often running on one floor for additional heating.
Mhhhhhh, it’s somehow really quite shocking.
in a 230 m2 (2,475 sq ft) house from 1936 with reasonably insulated attic, uninsulated exterior walls, mostly double-glazed windows from 1996, and a solar system for hot water. Oh, and we have thermostat-controlled wall radiators.
However, in the evenings, the wood stove is often running on one floor for additional heating.
Mhhhhhh, it’s somehow really quite shocking.
H
HilfeHilfe22 Jan 2016 12:18andimann schrieb:
Hi,
28,500 kWh??? Do you have a sauna club or belong to a nudist association that sits naked in the house at 35°C (95°F)?
Very cool! You just saved my weekend :-)
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