B
Bauherr3817 Feb 2016 18:58Hello everyone,
for our building project, the Zehnder Comfoair 350 is planned to be installed. The catalog offers two different duct systems to choose from – on one hand, the InFloor system, which uses round flexible ducts integrated into the concrete ceiling, and on the other hand, the OnFloor system, which uses flat-oval flexible ducts installed between the concrete ceiling and the insulation layer.
I once read that the round ducts are the better option because they provide optimal airflow and have the lowest air resistance.
The general contractor initially recommended the round ducts, but now suddenly the flat-oval ducts are supposed to be installed... which seems a bit strange.
Does anyone have experience with this OnFloor system? Are there increased airflow noises during operation of the ventilation system due to higher air resistance, possibly reaching levels that might be perceived as disturbing? Or maybe someone has a different ventilation system with flat ducts and can share their experience?
for our building project, the Zehnder Comfoair 350 is planned to be installed. The catalog offers two different duct systems to choose from – on one hand, the InFloor system, which uses round flexible ducts integrated into the concrete ceiling, and on the other hand, the OnFloor system, which uses flat-oval flexible ducts installed between the concrete ceiling and the insulation layer.
I once read that the round ducts are the better option because they provide optimal airflow and have the lowest air resistance.
The general contractor initially recommended the round ducts, but now suddenly the flat-oval ducts are supposed to be installed... which seems a bit strange.
Does anyone have experience with this OnFloor system? Are there increased airflow noises during operation of the ventilation system due to higher air resistance, possibly reaching levels that might be perceived as disturbing? Or maybe someone has a different ventilation system with flat ducts and can share their experience?
Hi! I don’t have any experience with the system you mentioned.
We have a Pluggit Avent P310, and the flat (“oval”) ducts are installed within the screed.
Under normal operating conditions, I can’t detect any disturbing airflow noise. Only at the highest setting is there a slight humming sound, but just directly at the supply and return outlets.
Every manufacturer has their own systems and duct types. All of this is well tested, and I would almost say that it works perfectly with any manufacturer as long as they have a well-deserved good reputation (which is the case with yours). Additionally, the required and actual air velocities in the ducts for regular air exchange are not high at all.
As far as I remember, round ducts are typically used when ventilation outlets are located in the ceiling or wall rather than on the floor. Oval ducts – partly due to the floor structure height – are usually installed under the screed.
Best regards
Thorsten
We have a Pluggit Avent P310, and the flat (“oval”) ducts are installed within the screed.
Under normal operating conditions, I can’t detect any disturbing airflow noise. Only at the highest setting is there a slight humming sound, but just directly at the supply and return outlets.
Every manufacturer has their own systems and duct types. All of this is well tested, and I would almost say that it works perfectly with any manufacturer as long as they have a well-deserved good reputation (which is the case with yours). Additionally, the required and actual air velocities in the ducts for regular air exchange are not high at all.
As far as I remember, round ducts are typically used when ventilation outlets are located in the ceiling or wall rather than on the floor. Oval ducts – partly due to the floor structure height – are usually installed under the screed.
Best regards
Thorsten
Hello,
the choice between oval and round pipes is less about airflow characteristics and more about the installation method. Yes, theoretically a round pipe has the best ratio between surface area and cross-section, resulting in the lowest wall friction. But unless my fluid dynamics lectures completely fail me, you can safely ignore that with such low speeds and flow rates. Just look in your car’s engine bay: intake ducts use a mix of round, oval, rectangular, and flat cross-sections.
You use the round pipes (usually 75mm (3 inches) diameter) when the pipes need to be installed inside a thin slab ceiling.
Advantage: you often need less additional floor buildup. Also, you avoid penetrating the ceiling, which can be a benefit for upper floors where there is an unfinished or uninsulated attic above, since the vapor barrier remains intact.
Disadvantage: pipe installation must be perfectly coordinated with the concrete pouring of the ceiling—and this applies to every floor. So your pipe installer may need to come three times.
Many structural engineers get stressed over this because the pipes in the ceiling have to be considered for structural calculations. That’s actually nonsense, as the pipes run in the middle of the slab, an area free from shear and tensile stresses. The edges of a beam carry the load, not the center. But on construction sites, calculations are not particularly precise—in my opinion, as a mechanical engineer, please don’t take this the wrong way—the structural design is often just roughly estimated and based on tables. So they can’t properly handle these cases in their calculations. Probably too much effort!
In contrast, oval pipes are installed on top of the finished ceiling, underneath the screed. They are embedded in the screed insulation. To avoid making the insulation unnecessarily thick, the pipes are slightly flattened.
Advantage: the shell construction can be completed first, then the pipe installer comes only once to install all the ducts. This makes site coordination much easier.
Disadvantage: the floor assembly becomes thicker because you need at least 60–70mm (2.5–3 inches) of screed insulation.
For us, the basement ceiling and ground floor ceiling will definitely have oval pipes in the screed. It’s possible that we will use some round pipes in the upper floor ceiling. The system planner is currently working that out.
According to two suppliers who offer both systems, there is no difference in noise. You shouldn’t hear anything at normal low settings.
Best regards,
Andreas
the choice between oval and round pipes is less about airflow characteristics and more about the installation method. Yes, theoretically a round pipe has the best ratio between surface area and cross-section, resulting in the lowest wall friction. But unless my fluid dynamics lectures completely fail me, you can safely ignore that with such low speeds and flow rates. Just look in your car’s engine bay: intake ducts use a mix of round, oval, rectangular, and flat cross-sections.
You use the round pipes (usually 75mm (3 inches) diameter) when the pipes need to be installed inside a thin slab ceiling.
Advantage: you often need less additional floor buildup. Also, you avoid penetrating the ceiling, which can be a benefit for upper floors where there is an unfinished or uninsulated attic above, since the vapor barrier remains intact.
Disadvantage: pipe installation must be perfectly coordinated with the concrete pouring of the ceiling—and this applies to every floor. So your pipe installer may need to come three times.
Many structural engineers get stressed over this because the pipes in the ceiling have to be considered for structural calculations. That’s actually nonsense, as the pipes run in the middle of the slab, an area free from shear and tensile stresses. The edges of a beam carry the load, not the center. But on construction sites, calculations are not particularly precise—in my opinion, as a mechanical engineer, please don’t take this the wrong way—the structural design is often just roughly estimated and based on tables. So they can’t properly handle these cases in their calculations. Probably too much effort!
In contrast, oval pipes are installed on top of the finished ceiling, underneath the screed. They are embedded in the screed insulation. To avoid making the insulation unnecessarily thick, the pipes are slightly flattened.
Advantage: the shell construction can be completed first, then the pipe installer comes only once to install all the ducts. This makes site coordination much easier.
Disadvantage: the floor assembly becomes thicker because you need at least 60–70mm (2.5–3 inches) of screed insulation.
For us, the basement ceiling and ground floor ceiling will definitely have oval pipes in the screed. It’s possible that we will use some round pipes in the upper floor ceiling. The system planner is currently working that out.
According to two suppliers who offer both systems, there is no difference in noise. You shouldn’t hear anything at normal low settings.
Best regards,
Andreas
S
Sebastian7919 Feb 2016 14:26Another disadvantage with the bare concrete floor: you have to coordinate plumbing, heating, and electrical installations to make sure nothing overlaps. That can be really challenging...
I would always install them in the concrete ceilings to avoid any hassle...
I would always install them in the concrete ceilings to avoid any hassle...
Similar topics