ᐅ Heat Load Calculation: Heating Demand Assessment according to DIN 12831 or DIN 4708?
Created on: 19 Mar 2014 11:14
L
LacosHello everyone,
we are building a detached house (10.50m x 9m (34.4 ft x 29.5 ft)) and have received the energy demand calculation.
Since I am a complete beginner, I would like to ask for your help because the energy calculation seems a bit odd to me. Here are some details for better assessment:
- Gable roof, living area approx. 139m² (1495 ft²) (attic not developed)
- KfW 70 standard, cavity wall construction (total 46cm (18 inches)) with stagnant air layer
(sand-lime brick, insulation, air layer, facing brick)
- South-West orientation (no trees etc.)
- no mechanical ventilation system
- underfloor heating, geothermal energy (brine-water // deep drilling, Waterkotte Eco Touch B0/35=4.4)
Now to my questions:
1) It seems that the energy calculation was done according to DIN 4708.
Isn’t DIN 12831 already mandatory? Or optional? Can it be required for a new build?
What are roughly the differences between these standards?
2)
Calculated values:
Heating and cooling energy demand = 2.9 (domestic hot water) + 9.1 (heating) = 12 kWh/year
HT’ value W/(m²K) 0.30
QP kWh/(m²a) 38.9
-> The calculated heat demand seems a bit high for 139m² (1495 ft²) of heated area
(the attic, as mentioned, will not be developed). Do you see it the same way?
I would really appreciate your comments/feedback!
Thank you,
Lacos
we are building a detached house (10.50m x 9m (34.4 ft x 29.5 ft)) and have received the energy demand calculation.
Since I am a complete beginner, I would like to ask for your help because the energy calculation seems a bit odd to me. Here are some details for better assessment:
- Gable roof, living area approx. 139m² (1495 ft²) (attic not developed)
- KfW 70 standard, cavity wall construction (total 46cm (18 inches)) with stagnant air layer
(sand-lime brick, insulation, air layer, facing brick)
- South-West orientation (no trees etc.)
- no mechanical ventilation system
- underfloor heating, geothermal energy (brine-water // deep drilling, Waterkotte Eco Touch B0/35=4.4)
Now to my questions:
1) It seems that the energy calculation was done according to DIN 4708.
Isn’t DIN 12831 already mandatory? Or optional? Can it be required for a new build?
What are roughly the differences between these standards?
2)
Calculated values:
Heating and cooling energy demand = 2.9 (domestic hot water) + 9.1 (heating) = 12 kWh/year
HT’ value W/(m²K) 0.30
QP kWh/(m²a) 38.9
-> The calculated heat demand seems a bit high for 139m² (1495 ft²) of heated area
(the attic, as mentioned, will not be developed). Do you see it the same way?
I would really appreciate your comments/feedback!
Thank you,
Lacos
Hello,
In most cases, power surcharges for the combined heat generator for heating and hot water (bivalent, alternative) are not necessary and can even be detrimental (oversizing)! This depends on the local climate parameters!
These are at best verification results that have nothing to do with actual demands or consumption (heating, hot water)!!! The latter are usually more or less significantly higher, depending on the planned heat generator!!!
Apparently, no solid fundamental assessment has been carried out here—rather, a sales pitch to inexperienced customers!
12 kWh/year for heating and hot water is almost worthy of a Nobel Prize or a perpetual motion machine by itself and I would immediately insist on this in the contract!
Best regards
Lacos schrieb:First, thermal energy (kWh) is not the same as power (kW). For the latter, DIN 12831 applies as the standard in the design case (heating operation)! The DIN 4708 standard is initially not related to this at all. DIN 4708 only applies to domestic hot water!
....Now to my questions:...
In most cases, power surcharges for the combined heat generator for heating and hot water (bivalent, alternative) are not necessary and can even be detrimental (oversizing)! This depends on the local climate parameters!
Lacos schrieb:
...
2)
Calculated values:
Thermal energy demand for heating and cooling = 2.9 (hot water) + 9.1 (heating) = 12 kWh/year...
These are at best verification results that have nothing to do with actual demands or consumption (heating, hot water)!!! The latter are usually more or less significantly higher, depending on the planned heat generator!!!
Apparently, no solid fundamental assessment has been carried out here—rather, a sales pitch to inexperienced customers!
12 kWh/year for heating and hot water is almost worthy of a Nobel Prize or a perpetual motion machine by itself and I would immediately insist on this in the contract!
Best regards
Hello,
Apparently, my post did go through after all—my apologies!
In my opinion, your AW structure is excellent and aligns well with my philosophy of “separation of powers” due to competing demands. Regarding the building body, you have done everything right at first glance—hardly better possible! Congratulations!
Ground source heat pump: Instead of the costly deep drilling, much more affordable surface or trench collectors could be interesting here! However, this requires appropriate energy extraction areas.
If you have specific questions in this regard, feel free to ask directly or via private message!
Best regards
Lacos schrieb:
....
Thank you very much for the initial feedback. I will review it again and possibly share excerpts. I might have also misunderstood or incorrectly selected something in my haste.
Apparently, my post did go through after all—my apologies!
In my opinion, your AW structure is excellent and aligns well with my philosophy of “separation of powers” due to competing demands. Regarding the building body, you have done everything right at first glance—hardly better possible! Congratulations!
Ground source heat pump: Instead of the costly deep drilling, much more affordable surface or trench collectors could be interesting here! However, this requires appropriate energy extraction areas.
If you have specific questions in this regard, feel free to ask directly or via private message!
Best regards
Hello everyone,
I wanted to ask for your opinion on the following values:
Qp value: 38.9 kWh/(m²a)
H'T value: 0.301 W/(m²K)
Calculated U-values:
Exterior wall: 0.19
Roof: 0.16
Floor slab: 0.32
Calculations are based on a target temperature of 19°C (66°F).
Best regards,
Lacos
I wanted to ask for your opinion on the following values:
Qp value: 38.9 kWh/(m²a)
H'T value: 0.301 W/(m²K)
Calculated U-values:
Exterior wall: 0.19
Roof: 0.16
Floor slab: 0.32
Calculations are based on a target temperature of 19°C (66°F).
Best regards,
Lacos
A quick question regarding this. If I want to have the sizing of my heating system planned properly, I need to consult a qualified energy consultant / building services engineer, right?
What data do they use as a basis? Do I give them the energy demand from my previous utility bills, how often I use the bathtub, and the preferred temperature in my rooms?
What data do they use as a basis? Do I give them the energy demand from my previous utility bills, how often I use the bathtub, and the preferred temperature in my rooms?
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