ᐅ Who should you entrust with the room-by-room heating load calculation?
Created on: 2 Feb 2020 12:23
A
annab377
Hello everyone,
Do heating system installers know that underfloor heating is best sized and planned using a room-by-room heat load calculation?
Is the room-by-room heat load calculation also important for selecting the heat pump (in our case either water-to-water or ground-to-water), or is the "overall heat load calculation" of the entire building according to DIN 12831 sufficient?
If my architect does not offer this, who should I turn to? What should I look for in the phone directory / on the Internet to find a professional who can assist me with this?
From what I have read here in the past months, a room-by-room heat load calculation is very important. A precise calculation can save money because the heat pump selected accordingly will operate more efficiently, allowing the house to be heated more effectively.
Thank you for your answers,
Greetings from BaWü
Ann.
PS: Am I mistaken, or can the overall heat load calculation according to DIN 12831 really be verified or recalculated by oneself (assuming you have all the U-values of the building envelope, of course)? Are there already ready-made templates available on the Internet for this? Maybe also for the room-by-room heat load calculation, or is that usually too complex for the homeowner?
Do heating system installers know that underfloor heating is best sized and planned using a room-by-room heat load calculation?
Is the room-by-room heat load calculation also important for selecting the heat pump (in our case either water-to-water or ground-to-water), or is the "overall heat load calculation" of the entire building according to DIN 12831 sufficient?
If my architect does not offer this, who should I turn to? What should I look for in the phone directory / on the Internet to find a professional who can assist me with this?
From what I have read here in the past months, a room-by-room heat load calculation is very important. A precise calculation can save money because the heat pump selected accordingly will operate more efficiently, allowing the house to be heated more effectively.
Thank you for your answers,
Greetings from BaWü
Ann.
PS: Am I mistaken, or can the overall heat load calculation according to DIN 12831 really be verified or recalculated by oneself (assuming you have all the U-values of the building envelope, of course)? Are there already ready-made templates available on the Internet for this? Maybe also for the room-by-room heat load calculation, or is that usually too complex for the homeowner?
S
Strahleman3 Feb 2020 09:29It was the first provider. As mentioned, you can use the calculation as a basis, but you need to question some of the values here and there.
You also have ventilation losses without controlled mechanical ventilation, which are then significantly higher. To my knowledge, you can only estimate the actual ventilation losses with reasonable accuracy if you know the n50 value from the blower door test. However, the 1.9/h assumed in the calculation is quite high even without prior testing. For example, a KfW55 house must be below 1.5/h.
You also have ventilation losses without controlled mechanical ventilation, which are then significantly higher. To my knowledge, you can only estimate the actual ventilation losses with reasonable accuracy if you know the n50 value from the blower door test. However, the 1.9/h assumed in the calculation is quite high even without prior testing. For example, a KfW55 house must be below 1.5/h.
IMHO, the Blower Door test measures how "airtight" your house is. That means all windows, doors, and openings are closed, controlled mechanical ventilation is turned off... and then it checks what air escapes.
However, this has nothing to do with the ventilation losses of the controlled mechanical ventilation system (or airing through windows, or window frame leakage, etc.).
The controlled mechanical ventilation system expels warm air from inside and brings in cold air from outside. This incoming air is then reheated using heat recovery. Still, some heat loss occurs. In the room-specific heating load calculation, this varies from room to room depending on room temperature, air exchange rate, supply air temperature, and other factors.
This difference must be compensated by the heating system in addition to the transmission heat loss through the building components.
However, this has nothing to do with the ventilation losses of the controlled mechanical ventilation system (or airing through windows, or window frame leakage, etc.).
The controlled mechanical ventilation system expels warm air from inside and brings in cold air from outside. This incoming air is then reheated using heat recovery. Still, some heat loss occurs. In the room-specific heating load calculation, this varies from room to room depending on room temperature, air exchange rate, supply air temperature, and other factors.
This difference must be compensated by the heating system in addition to the transmission heat loss through the building components.
Yes, in the end, you end up calculating yourself dizzy based on the standard outdoor temperature, which last occurred here in the West about 5 years ago, and conclude that even the smallest heat pump is already oversized for everyday use (you can hardly get anything below 6 kW (20,000 BTU/h)) and that you will install it with a 5-10 cm (2-4 inches) clearance.
But then with proof provided.
However, this does not change the result in practical application.
And don’t come to me with 10 W pump power that can be optimized away. That does not justify the effort.
But then with proof provided.
However, this does not change the result in practical application.
And don’t come to me with 10 W pump power that can be optimized away. That does not justify the effort.
You are confusing two things. It’s not about sizing the heat pump, but about designing the underfloor heating system.
For me, the calculation took two evenings.
You often spend more time on less meaningful tasks in home construction. However, now I can show the builder that, for example, 30/25 works well.
For me, the calculation took two evenings.
You often spend more time on less meaningful tasks in home construction. However, now I can show the builder that, for example, 30/25 works well.
...of course, these things are related. However, for sizing, you don’t necessarily need a room-by-room heating load calculation. The building’s heating load can also be estimated using a few key values during new construction.
Room-by-room heating load calculations are primarily used for the correct sizing of underfloor heating systems.
Sure, you can also estimate or simply decide to install the pipes as closely and extensively as possible.
But it can also work differently. If you say that a design based on a supply/return temperature of 35/30°C (95/86°F) is sufficient for you, then install as much as possible and you will manage with it. That said, as has been mentioned... below 10cm (5 inches), the effect decreases, and installation becomes more difficult depending on the pipe diameter.
If you want lower temperatures, the calculation quickly reveals where the system might fall short, showing you where additional surfaces need to be covered (for example, wall heating), or whether you should consider additional insulation measures (if it’s not too late).
Above all, a room-by-room heating load calculation is especially helpful if you have a somewhat stubborn builder.
Room-by-room heating load calculations are primarily used for the correct sizing of underfloor heating systems.
Sure, you can also estimate or simply decide to install the pipes as closely and extensively as possible.
But it can also work differently. If you say that a design based on a supply/return temperature of 35/30°C (95/86°F) is sufficient for you, then install as much as possible and you will manage with it. That said, as has been mentioned... below 10cm (5 inches), the effect decreases, and installation becomes more difficult depending on the pipe diameter.
If you want lower temperatures, the calculation quickly reveals where the system might fall short, showing you where additional surfaces need to be covered (for example, wall heating), or whether you should consider additional insulation measures (if it’s not too late).
Above all, a room-by-room heating load calculation is especially helpful if you have a somewhat stubborn builder.
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