ᐅ New Construction: Floor Structure / Ceiling Thickness for Ductwork of Mechanical Ventilation Systems
Created on: 11 Aug 2020 20:08
M
Martial.white
Good evening,
we are building a house (currently in the preliminary design phase) and I am currently sorting out an issue between the architect (who has never installed a mechanical ventilation system with heat recovery but is otherwise excellent) and the heating engineer. I have a question about the floor construction with mechanical ventilation:
As I understood from the heating engineer, there are three options:
Option 1: With a 20cm (8 inch) concrete slab, the 63mm (2.5 inch) duct is completely embedded within the concrete slab. On top of that comes a 15cm (6 inch) floor build-up as planned by the architect, including impact sound insulation, underfloor heating, etc.
Option 2: Concrete slab (20cm / 8 inch), and then within the 20cm (8 inch) space above it (instead of the 15cm / 6 inch build-up as planned), the 63mm (2.5 inch) ducts plus underfloor heating and other layers.
Option 3: Too expensive because of shallow ducts, so not an option.
Or are options 1 and 2 actually the same, meaning I definitely need a 20cm (8 inch) concrete slab plus a 20cm (8 inch) floor build-up?
Additional question/comment: At the end of the day, because the ground floor has large rooms, it makes sense to increase the story height (floor to floor level) by 275cm (108 inches) to be on the safe side...
Thank you very much
we are building a house (currently in the preliminary design phase) and I am currently sorting out an issue between the architect (who has never installed a mechanical ventilation system with heat recovery but is otherwise excellent) and the heating engineer. I have a question about the floor construction with mechanical ventilation:
As I understood from the heating engineer, there are three options:
Option 1: With a 20cm (8 inch) concrete slab, the 63mm (2.5 inch) duct is completely embedded within the concrete slab. On top of that comes a 15cm (6 inch) floor build-up as planned by the architect, including impact sound insulation, underfloor heating, etc.
Option 2: Concrete slab (20cm / 8 inch), and then within the 20cm (8 inch) space above it (instead of the 15cm / 6 inch build-up as planned), the 63mm (2.5 inch) ducts plus underfloor heating and other layers.
Option 3: Too expensive because of shallow ducts, so not an option.
Or are options 1 and 2 actually the same, meaning I definitely need a 20cm (8 inch) concrete slab plus a 20cm (8 inch) floor build-up?
Additional question/comment: At the end of the day, because the ground floor has large rooms, it makes sense to increase the story height (floor to floor level) by 275cm (108 inches) to be on the safe side...
Thank you very much
Lumpi_LE schrieb:
For round flexible ducts, the distributors are usually located under the ceiling or on the wall—right where the ducts come out. Ah, okay. I think I understand now. In our case, they all lead into the technical room in the basement (the unit is not installed yet). So I assume that a distributor box like that will be mounted on the wall next to the ventilation unit.
With standard round ducts, the air is distributed via the manifold boxes. These can be hidden in the crawl space (which is very inconvenient), mounted on the ceiling or walls, or placed behind bulkheads.
Just like in your case. All ducts come together in the utility room and are connected to the manifold boxes.
With sheet metal ducts, this is not necessary because the airflow can be very effectively regulated by adjusting the cross-sectional area of the ducts. This is not possible with round ducts since they always have a fixed diameter of 63mm (2.5 inches) or 75mm (3 inches).
Just like in your case. All ducts come together in the utility room and are connected to the manifold boxes.
With sheet metal ducts, this is not necessary because the airflow can be very effectively regulated by adjusting the cross-sectional area of the ducts. This is not possible with round ducts since they always have a fixed diameter of 63mm (2.5 inches) or 75mm (3 inches).
For our ventilation system, 75mm (3 inches) round ducts were installed in the concrete ceiling. This required the structural builder to increase the ceiling thickness to 22cm (9 inches).
We were specifically advised against using flat ducts—poor cleanability was the main argument. Whether that is accurate, I cannot say, as we trusted their statements and went with round ducts...
We were specifically advised against using flat ducts—poor cleanability was the main argument. Whether that is accurate, I cannot say, as we trusted their statements and went with round ducts...
Martial.white schrieb:
Good evening,
We are building a house (currently in the preliminary design phase) and I’m caught between the architect (who has never installed a mechanical ventilation system with heat recovery but is otherwise great) and the HVAC specialist. I have a question regarding the floor construction with mechanical ventilation:
As I understood from the HVAC expert, there are three options:
Option 1: With a 20cm (8 inch) concrete slab, the 63mm (2.5 inch) duct is fully embedded within the slab. On top of that comes a 15cm (6 inch) floor build-up as planned by the architect, including impact sound insulation, underfloor heating, etc.
Option 2: 20cm (8 inch) concrete slab and then within the 20cm (8 inch) space above it (instead of the planned 15cm (6 inch) build-up), the 63mm (2.5 inch) ducts are installed, plus underfloor heating, etc.
Option 3: too expensive because of flat ducts – not an option.
Or are options 1 and 2 actually the same, meaning I definitely need a 20cm (8 inch) concrete slab plus 20cm (8 inch) build-up?
Additional question/comment: At the end of the day, since the ground floor has large rooms, it makes sense to increase the floor-to-floor height (top of floor to top of floor) to 275cm (108 inch) to be safe…
Thank you very much I had similar questions in the beginning. Are you working with an energy consultant? The energy consultant will specify how thick the insulation layer in your floor should be. However, they usually do not calculate for intermediate floors; for that, you’ll need to ask your plumber or HVAC specialist. Regarding the slab thickness: you can bring in a structural engineer already during the preliminary design phase. They can perform a quick preliminary calculation and thus provide you with early certainty for your planning, which is what you need right now.
By the way, the architect should know this and, based on experience, be able to assume the correct floor structure. Structural engineering is also part of their studies.
M
Martial.white15 Oct 2020 13:32Thank you very much,
however, for me this comes a bit too late. The building permit / planning permission application has already been submitted and the construction drawings have been prepared.
The architect was no help in this particular case. He has always installed single-family houses with window trickle vents until now but made that clear from the beginning.
So, as you said, the route was to go to the heating specialist and their technical advisor.
Before that, however, we had already decided to increase the clear height of the ground floor due to the "large" rooms. With that, we are now on the safe side.
however, for me this comes a bit too late. The building permit / planning permission application has already been submitted and the construction drawings have been prepared.
The architect was no help in this particular case. He has always installed single-family houses with window trickle vents until now but made that clear from the beginning.
So, as you said, the route was to go to the heating specialist and their technical advisor.
Before that, however, we had already decided to increase the clear height of the ground floor due to the "large" rooms. With that, we are now on the safe side.
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