ᐅ Controlled Residential Ventilation: Integrating an Insulated Attic into a Mechanical Ventilation System
Created on: 4 Nov 2025 13:07
K
kletterbuxeK
kletterbuxe4 Nov 2025 13:07Hello everyone,
I am building a passive house, so a controlled mechanical ventilation system is a given.
I am building with a vapor-open construction method, so humidity is not an issue that needs to be considered.
I have an attic space (1.2 m high [4 feet]) that is located within the insulation layer.
Unfortunately, my planner is no help on this, so here is my question: Does the attic space need to be included in the ventilation concept? What are the arguments for doing so? Are there any mandatory reasons that I might be overlooking?
Thanks in advance for your responses.
I am building a passive house, so a controlled mechanical ventilation system is a given.
I am building with a vapor-open construction method, so humidity is not an issue that needs to be considered.
I have an attic space (1.2 m high [4 feet]) that is located within the insulation layer.
Unfortunately, my planner is no help on this, so here is my question: Does the attic space need to be included in the ventilation concept? What are the arguments for doing so? Are there any mandatory reasons that I might be overlooking?
Thanks in advance for your responses.
Are you sure the attic is insulated? In well-insulated houses, I’ve seen that the exterior roof insulation runs above the attic, while the insulation between the rafters follows along the ceiling or collar beams to minimize the surface area. This means the pitched roof is neither fully outside nor truly within the thermal envelope.
I wouldn’t include that in the mechanical ventilation with heat recovery system, since the air quality there is basically irrelevant.
I wouldn’t include that in the mechanical ventilation with heat recovery system, since the air quality there is basically irrelevant.
K
kletterbuxe5 Nov 2025 06:27Hello Gerald,
yes – your option was also an idea, but in the upper ceiling I only have 22 cm (9 inches), which is not enough with natural building materials. For the cavity insulation between the rafters, I have well over 30 cm (12 inches) of blown-in insulation.
Currently, the plan is to place the hybrid inverter and the battery in the attic. And they do produce quite a lot of heat. I just remembered that this was one reason to ventilate the attic – to get the heat out of there. But maybe I’ll test it first to see if it can work without ventilation.
yes – your option was also an idea, but in the upper ceiling I only have 22 cm (9 inches), which is not enough with natural building materials. For the cavity insulation between the rafters, I have well over 30 cm (12 inches) of blown-in insulation.
Currently, the plan is to place the hybrid inverter and the battery in the attic. And they do produce quite a lot of heat. I just remembered that this was one reason to ventilate the attic – to get the heat out of there. But maybe I’ll test it first to see if it can work without ventilation.
If the attic only contains technical equipment/heat sources (hybrid inverter/battery), do not include it in the mechanical ventilation system; air quality there is hardly relevant. It is better to keep it sealed, possibly vent waste heat through a small exhaust point/overflow vent, and ensure airtightness; no supply or exhaust air in the attic.
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