ᐅ Where to install ducts for controlled residential ventilation in the ceiling of the top floor
Created on: 24 Feb 2016 19:21
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world-e
Hello,
can someone briefly explain where the ducts for a mechanical ventilation system with heat recovery can be installed on the upper floor if the house has two full stories, the top ceiling is a beam ceiling, and the roof above is either uninsulated or has only 60mm (2.4 inches) of insulation above the roof deck? If the ducts are installed above the beam ceiling, they are outside the thermal envelope; if installed within the insulation, much of the insulation’s effectiveness is lost. Also, running ducts perpendicular to the beams is difficult. How is this usually done? Thank you.
can someone briefly explain where the ducts for a mechanical ventilation system with heat recovery can be installed on the upper floor if the house has two full stories, the top ceiling is a beam ceiling, and the roof above is either uninsulated or has only 60mm (2.4 inches) of insulation above the roof deck? If the ducts are installed above the beam ceiling, they are outside the thermal envelope; if installed within the insulation, much of the insulation’s effectiveness is lost. Also, running ducts perpendicular to the beams is difficult. How is this usually done? Thank you.
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Sebastian7925 Feb 2016 11:06The installation temperature must be 5 degrees Celsius (41°F), correct – but that’s why I insulate the unit with 5 cm (2 inches), so it will almost certainly never drop below that inside the insulation. The condensate pipe is also located within the insulation. By the way, the gable walls are insulated with 14 cm (6 inches).
@Alexej:
I’ll see how the moisture situation develops – I plan to install a suitable sensor up there. The attic peak isn’t plastered, and the roof isn’t 100% airtight – according to best practice guidelines, the attic peak should be ventilated. So far, it hasn’t been damp or below freezing...
I had considered ventilating the attic through the mechanical ventilation system, but that could cause two problems:
@Alexej:
I’ll see how the moisture situation develops – I plan to install a suitable sensor up there. The attic peak isn’t plastered, and the roof isn’t 100% airtight – according to best practice guidelines, the attic peak should be ventilated. So far, it hasn’t been damp or below freezing...
I had considered ventilating the attic through the mechanical ventilation system, but that could cause two problems:
- You draw in very cold air during winter – although the total volume is small, the exhaust air will cool down.
- You allow warm air into the attic – this can condense on the cold external surfaces, and the vapor permeability of the wood fiber insulation boards might not be sufficient to handle it.
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michisa8688825 Feb 2016 18:53Hello everyone,
we are currently facing the same issue. The mechanical ventilation system is located in the basement in the building services room. The top ceiling, including the collar beam layer, will receive intermediate insulation (h=22cm (9 inches)). Below that is the vapor barrier, followed by the substructure for the drywall panels. My idea now is to make the substructure thick enough to accommodate the ventilation ducts for the mechanical ventilation system. I would then insulate the installation space as well.
Do you have any concerns about mold risk since the vapor barrier is placed beneath the installation space?
we are currently facing the same issue. The mechanical ventilation system is located in the basement in the building services room. The top ceiling, including the collar beam layer, will receive intermediate insulation (h=22cm (9 inches)). Below that is the vapor barrier, followed by the substructure for the drywall panels. My idea now is to make the substructure thick enough to accommodate the ventilation ducts for the mechanical ventilation system. I would then insulate the installation space as well.
Do you have any concerns about mold risk since the vapor barrier is placed beneath the installation space?
S
Sebastian7925 Feb 2016 19:08No, the approach with the installation level is normal, but how much height do you want to lose? That’s about 10cm (4 inches) you need to compensate for – plus drywall.
Also, you might have problems with mold possibly – with that much insulation? It would need to be calculated...
Also, you might have problems with mold possibly – with that much insulation? It would need to be calculated...
I also have the controlled residential ventilation system installed in the attic, with all rooms ventilated through ceiling outlets, and so far no issues. The attic is insulated between the rafters and has consistently maintained temperatures above +5°C (41°F). I also ventilate it with a very low setting. This provides a small, regulated air exchange, but so far no problems with moisture or anything similar.
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Sebastian7925 Feb 2016 21:48Is your ridge beam located within the airtight layer? Is it plastered?
No, but a clipped gable roof, meaning there are no walls on the sides. Otherwise, the insulation also includes a vapor barrier following the principle of increasing tightness from the outside to the inside, and it is quite carefully sealed. Below, towards the upper floor, there is additional insulation, with a vapor barrier above the upper floor.
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